Image guided radiotherapy

This report presents the methods and results of the Thoracic Auto-Segmentation Challenge organized at the 2017 Annual Meeting of American Association of Physicists in Medicine. The purpose of the challenge was to provide a benchmark dataset and platform for evaluating performance of auto-segmentation methods of organs at risk (OARs) in thoracic CT images. Sixty thoracic CT scans provided by three different institutions were separated into 36 training, 12 offline testing, and 12 online testing scans. Eleven participants completed the offline challenge, and seven completed the online challenge. The OARs were left and right lungs, heart, esophagus and spinal cord. Clinical contours used for treatment planning were quality checked and edited to adhere to the RTOG 1106 contouring guidelines. Algorithms were evaluated using the Dice coefficient, Hausdorff distance, and mean surface distance. A consolidated score was computed by normalizing the metrics against inter-rater variability and a...

Advanced model-based iterative reconstruction algorithms in quantitative computed tomography perform automatic segmentation of tissues to estimate material properties of the imaged object. Compared to conventional methods, these algorithms may improve quality of reconstructed images and accuracy of radiation treatment planning. Automatic segmentation of tissues is, however, a difficult task. The aim of this work is to develop and evaluate an algorithm that automatically segments tissues in CT images of the male pelvis. The newly developed algorithm (MK2014) combines histogram matching, thresholding, region growing, deformable model and atlas based registration techniques for the segmentation of bones, adipose tissue, prostate and muscles in CT images. Visual inspection of segmented images showed that the algorithm performed well for the five analysed images. The tissues were identified and outlined with accuracy sufficient for the dual-energy iterative reconstruction algorithm (DIRA) whose aim is to improve the accuracy of radiation treatment planning in brachytherapy of the prostate.

Purpose: This study introduces a probabilistic nonrigid registration method for use in image-guided prostate brachytherapy. Intraoperative imaging for prostate procedures, usually transrectal ultrasound (TRUS), is typically inferior to diagnostic-quality imaging of the pelvis such as endorectal magnetic resonance imaging (MRI). MR images contain superior detail of the prostate boundaries and provide substructure features not otherwise visible. Previous efforts to register diagnostic prostate images with the intraoperative coordinate system have been deterministic and did not offer a measure of the registration uncertainty. The authors developed a Bayesian registration method to estimate the posterior distribution on deformations and provide a case-specific measure of the associated registration uncertainty. The authors adapted a biomechanical-based probabilistic nonrigid method to register diagnostic to intraoperative images by aligning a physician's segmentations of the prostate in the two images. The posterior distribution was characterized with a Markov Chain Monte Carlo method; the maximum a posteriori deformation and the associated uncertainty were estimated from the collection of deformation samples drawn from the posterior distribution. The authors validated the registration method using a dataset created from ten patients with MRI-guided prostate biopsies who had both diagnostic and intraprocedural 3 Tesla MRI scans. The accuracy and precision of the estimated posterior distribution on deformations were evaluated from two predictive distance distributions: between the deformed central zone-peripheral zone (CZ-PZ) interface and the physician-labeled interface, and based on physician-defined landmarks. Geometric margins on the registration of the prostate's peripheral zone were determined from the posterior predictive distance to the CZ-PZ interface separately for the base, mid-gland, and apical regions of the prostate. The authors observed variation in the shape and volume of the segmented prostate in diagnostic and intraprocedural images. The probabilistic method allowed us to convey registration results in terms of posterior distributions, with the dispersion providing a patient-specific estimate of the registration uncertainty. The median of the predictive distance distribution between the deformed prostate boundary and the segmented boundary was ≤3 mm (95th percentiles within ±4 mm) for all ten patients. The accuracy and precision of the internal deformation was evaluated by comparing the posterior predictive distance distribution for the CZ-PZ interface for each patient, with the median distance ranging from -0.6 to 2.4 mm. Posterior predictive distances between naturally occurring landmarks showed registration errors of ≤5 mm in any direction. The uncertainty was not a global measure, but instead was local and varied throughout the registration region. Registration uncertainties were largest in the apical region of the prostate. Conclusions: Using a Bayesian nonrigid registration method, the authors determined the posterior distribution on deformations between diagnostic and intraprocedural MR images and quantified the uncertainty in the registration results. The feasibility of this approach was tested and results were positive. The probabilistic framework allows us to evaluate both patient-specific and location-specific estimates of the uncertainty in the registration result. Although the framework was tested on MRguided procedures, the preliminary results suggest that it may be applied to TRUS-guided procedures 6858 Med. Phys. 39 (11), November 2012

Purpose: This study introduces a probabilistic nonrigid registration method for use in image-guided prostate brachytherapy. Intraoperative imaging for prostate procedures, usually transrectal ultrasound (TRUS), is typically inferior to diagnostic-quality imaging of the pelvis such as endorectal magnetic resonance imaging (MRI). MR images contain superior detail of the prostate boundaries and provide substructure features not otherwise visible. Previous efforts to register diagnostic prostate images with the intraoperative coordinate system have been deterministic and did not offer a measure of the registration uncertainty. The authors developed a Bayesian registration method to estimate the posterior distribution on deformations and provide a case-specific measure of the associated registration uncertainty. The authors adapted a biomechanical-based probabilistic nonrigid method to register diagnostic to intraoperative images by aligning a physician's segmentations of the prostate in the two images. The posterior distribution was characterized with a Markov Chain Monte Carlo method; the maximum a posteriori deformation and the associated uncertainty were estimated from the collection of deformation samples drawn from the posterior distribution. The authors validated the registration method using a dataset created from ten patients with MRI-guided prostate biopsies who had both diagnostic and intraprocedural 3 Tesla MRI scans. The accuracy and precision of the estimated posterior distribution on deformations were evaluated from two predictive distance distributions: between the deformed central zone-peripheral zone (CZ-PZ) interface and the physician-labeled interface, and based on physician-defined landmarks. Geometric margins on the registration of the prostate's peripheral zone were determined from the posterior predictive distance to the CZ-PZ interface separately for the base, mid-gland, and apical regions of the prostate. The authors observed variation in the shape and volume of the segmented prostate in diagnostic and intraprocedural images. The probabilistic method allowed us to convey registration results in terms of posterior distributions, with the dispersion providing a patient-specific estimate of the registration uncertainty. The median of the predictive distance distribution between the deformed prostate boundary and the segmented boundary was ≤3 mm (95th percentiles within ±4 mm) for all ten patients. The accuracy and precision of the internal deformation was evaluated by comparing the posterior predictive distance distribution for the CZ-PZ interface for each patient, with the median distance ranging from -0.6 to 2.4 mm. Posterior predictive distances between naturally occurring landmarks showed registration errors of ≤5 mm in any direction. The uncertainty was not a global measure, but instead was local and varied throughout the registration region. Registration uncertainties were largest in the apical region of the prostate. Conclusions: Using a Bayesian nonrigid registration method, the authors determined the posterior distribution on deformations between diagnostic and intraprocedural MR images and quantified the uncertainty in the registration results. The feasibility of this approach was tested and results were positive. The probabilistic framework allows us to evaluate both patient-specific and location-specific estimates of the uncertainty in the registration result. Although the framework was tested on MRguided procedures, the preliminary results suggest that it may be applied to TRUS-guided procedures 6858 Med. Phys. 39 (11), November 2012

Objective: Compared to dynamic contrast enhanced MRI (DCE-MRI), image quality in diffusion-weighted MR imaging (DW-MRI) is generally poor because of low image spatial resolution and distortion. Readout-segmented EPI (RS-EPI) is a recently-developed technique to obtain high resolution DW-MRI with less distortion. The study aimed to evaluate the feasibility of high-resolution DW-MRI of the breast, using RS-EPI and single-shot EPI (SS-EPI). Methods: With IRB approval, 26 patients with clinically suspected breast cancer were prospectively enrolled. Breast MRI was performed on a 3.0 T scanner using a 16-channel breast coil. Sequences include T2-weighted imaging (T2WI) with fat saturation, a 3D DCE-MRI series and DW-MRI (b values of 0 and 850 s/mm2 for RS-EPI and SS-EPI). To evaluate image distortion, the antero-posterior (AP) extent of the mammary gland on DW-MRI with RS-EPI and SS-EPI were measured and differences from values obtained from T2WI were calculated. The artefacts on both sequences were scored. Diagnostic performance of lesions on both sequences was assessed using BI-RADS classification and the category was compared to that determined by DCE-MRI. The average difference in the measured AP extent on DW-MRI with RS-EPI was significantly less than that on DW-MRI with SS-EPI (2.3 ± 2.0 versus 12.5 ± 4.7 mm, respectively, p<0.01). Distortion artefacts were significantly lower on DW-MRI with RS-EPI than that with SS-EPI in all cases. The sensitivity of DW-MRI with RS-EPI was higher than that with SS-EPI (88.9 and 77.8%, respectively). DW-MRI with RS-EPI has an advantage of less distortion compared to that with SS-EPI.

Medical physics plays a crucial role in the field of cancer treatment, encompassing various techniques and technologies that aid in diagnosis, treatment planning, and delivery. This comprehensive review aims to provide a thorough examination of the innovations, challenges, and future directions in medical physics as it pertains to cancer treatment. The review begins by discussing the fundamental principles and concepts of medical physics relevant to cancer treatment. It explores the use of radiation therapy, imaging techniques, and other medical physics technologies that contribute to accurate diagnosis and effective treatment. Key advancements in medical physics for cancer treatment are then examined, including the development of intensity-modulated radiation therapy (IMRT), image-guided radiation therapy (IGRT), and proton therapy. These innovations have significantly improved treatment precision, reduced side effects, and enhanced patient outcomes. However, along with these advancements come challenges that need to be addressed. The review identifies challenges such as the need for improved radiation dose calculation algorithms, optimization techniques for treatment planning, and quality assurance protocols to ensure patient safety. Additionally, issues related to cost-effectiveness, access to advanced medical physics technologies, and training of medical physicists are discussed. Thus, this comprehensive review underscores the pivotal role of medical physics in cancer treatment. By examining innovations, challenges, and future directions, it provides valuable insights into the advancements that have revolutionized cancer care, the hurdles that need to be overcome, and the potential for further advancements in the field of medical physics. Understanding and addressing these aspects will lead to improved cancer treatment outcomes and enhanced patient care.

Background/Aim: We experienced an unexpected high incidence of gastrointestinal (GI) toxicity in patients undergoing image-guided intensity-modulated radiotherapy (IG-IMRT) using helical tomotherapy in our initial 2.2 Gy/fraction schedule for prostate cancer; hence, a dosereduction trial from 2.2 Gy to 2 Gy/fraction was conducted using modified planning target volume (PTV) contouring. Patients and Methods: We compared 130 patients treated using 2.2 Gy/fraction (Group A) and 144 treated using the 2 Gy/fraction (Group B) with modified PTV (excluding rectal volume) with a median follow-up period of 62 months. Prescribed dose was 72.6-74.8 Gy in 33-34 fractions (Group A) and 72-74 Gy in 36-37 fractions (Group B). Results: Patients in Group B had a reduced rectal and bladder V10-V70 and were irradiated at the maximal dose. Their cumulative incidence of grade ≤2 GI toxicity at 5 years improved from 10.1% [95% confidence interval (CI), 4.9-15.3%] to 1.4% (0-3.3%). Grade 2≤ urinary toxicity also decreased from 5.5% (1.5-9.4%) in Group A to 1.4% (0-3.3%, p=0.0167) in Group B. The biochemical failure-free 5-year survival rate was 89.1% (95%CI=83.6-95.4%) and 87. 5% (82.0-92.9%, p=0.75) in groups A and B, respectively. Conclusion: The reduced dose fraction schedule decreased the incidence of late GI toxicity without compromising prostate-specific antigen control. Careful target volume definition and fraction size are important even for IG-IMRT.

Introduction: Radiotherapy is a standard treatment for prostate cancer, and image-guided radiotherapy is increasingly being used to aid precision of dose delivery to targeted tissues. However, precision during radiotherapy cannot be maintained when unexpected intrafraction organ motion occurs. Case presentation: We report our experience of internal organ motion caused by persistent gas production in a patient taking an alpha-glucosidase inhibitor. A 68-year-old Japanese man with prostate cancer visited our institution for treatment with helical tomotherapy. He suffered from diabetes mellitus and took an alpha-glucosidase inhibitor. Routine treatment planning computed tomography showed a large volume of rectal gas; an enema was given to void the rectum. Subsequent treatment planning computed tomography again showed a large volume of gas. After exercise (walking) to remove the intestinal gas, a third scan was performed as a test scan without tight fixation, which showed a sufficiently empty rectum for planning. However, after only a few minutes, treatment planning computed tomography again showed extreme accumulation of gas. Therefore, we postponed treatment planning computed tomography and consulted his doctor to suspend the alpha-glucosidase inhibitor, which was the expected cause of his persistent gas. Four days after the alpha-glucosidase inhibitor regimen was suspended, we took a fourth treatment planning computed tomography and made a treatment plan without gas accumulation. Thereafter, the absence of rectal gas accumulation was confirmed using daily megavolt computed tomography before treatment, and the patient received 37 fractions of intensity-modified radiotherapy at 74Gy without rectal gas complications. In this case study, the alpha-glucosidase inhibitor induced the accumulation of intestinal gas, which may have caused unexpected organ motion, untoward reactions, and insufficient doses to clinical targets. Conclusions: We suggest that patients who are taking an alpha-glucosidase inhibitor for diabetes should discontinue use of that particular medicine prior to beginning radiotherapy.

PURPOSE-To test whether iron oxide-containing yttrium aluminosilicate microparticles (IO-YAS MPs) can generate localized therapeutic hyperthermia (≥43°C) when injected intra-tumorally in an animal model of liver cancer and whether MP distributions could be visualized with MR imaging. Sprague-Dawley rats implanted with N1-S1 liver tumors were assigned to alternating magnetic field (AMF) exposure following intra-tumoral injection with IO-YAS MPs (n=7), sham surgery (n=7), or baseline iron quantitation (n=7). Three fiber optic probes allowed spatial and temporal monitoring of temperatures during 24 minutes of AMF. T2-weighted turbo spin echo magnetic resonance imaging was performed within 1 hour post-procedure to detect signal voids due to IO-YAS deposition. Hematoxylin and eosin-stained

Background: To evaluate the feasibility of image-guided radiotherapy based on helical Tomotherapy to spare the contralateral parotid gland in head and neck cancer patients with unilateral or no neck node metastases. Methods: A retrospective review of 52 patients undergoing radiotherapy for head and neck cancers with image guidance based on daily megavoltage CT imaging with helical tomotherapy was performed. Results: Mean contralateral parotid dose and the volume of the contralateral parotid receiving 40 Gy or more were compared between radiotherapy plans with significant constraint (SC) of less than 20 Gy on parotid dose (23 patients) and the conventional constraint (CC) of 26 Gy (29 patients). All patients had PTV coverage of at least 95% to the contralateral elective neck nodes. Mean contralateral parotid dose was, respectively, 14.1 Gy and 24.7 Gy for the SC and CC plans (p < 0.0001). The volume of contralateral parotid receiving 40 Gy or more was respectively 5.3% and 18.2% (p < 0.0001) Conclusion: Tomotherapy for head and neck cancer minimized radiotherapy dose to the contralateral parotid gland in patients undergoing elective node irradiation without sacrificing target coverage.

Purpose:Electronic portal imagers (EPIDs) with high detective quantum efficiencies (DQEs) are sought to facilitate the use of the megavoltage (MV) radiotherapy treatment beam for image guidance. Potential advantages include high quality (treatment) beam&#39;s eye view imaging, and improved cone‐beam computed tomography (CBCT) generating images with more accurate electron density maps with immunity to metal artifacts. One approach to increasing detector sensitivity is to couple a thick pixelated scintillator array to an active matrix flat panel imager (AMFPI) incorporating amorphous silicon thin film electronics. Cadmium tungstate (CWO) has many desirable scintillation properties including good light output, a high index of refraction, high optical transparency, and reasonable cost. However, due to the cleave plane inherent in its crystalline structure, the difficulty of cutting and polishing CWO has, in part, limited its study relative to other scintillators such as cesium iodide an...

Background: Traditional CTV-PTV margin recipes are not generally applicable in the situation of stereotactic ablative radiotherapy (SABR) treatments of multiple target volumes with a single isocentre. In this work, we present a novel geometric method of margin derivation based on CBCT-derived anatomical data. Methods: Twenty patients with high-risk localized prostate cancer were selected for retrospective review. Individual volumes of interest (prostate, prostate and seminal vesicles and pelvic lymph nodes) were delineated on five representative CBCTs and registered to the planning CT using two registration protocols: bone match or prostate-based soft tissue match. Margins were incrementally expanded around composite CTV structures until 95% overlap was achieved. Results: CTV-PTV margins of 5.2, 6.5 and 7.6 mm were required for prostate, prostate and seminal vesicles and pelvic lymph nodes respectively using a prostate matching protocol. For the prostate and seminal vesicle structures, margins calculated using our method displayed good agreement with a conventional margin recipe (within ±1.0 mm). Conclusions: We have presented an alternative method of CTV-PTV margin derivation that is applicable to SABR treatments with more than one isocentric target. These results have informed an institutional trial of prostate and pelvic nodal SABR in men with high-risk localized prostate cancer.

and 0.9916. The values of R 2 and l i were found to be 0.9867 & 0.0316 for V 100 ; 0.9988 & 0.0148 for V 150 ; 0.9958 & 0.00148 for V 200 , respectively. The values of l i are a function of T 1/2edema , hence the increase in V i with time is less pronounced when T 1/2edema changes from 4 to 30 days. Using the values of a=0.04 Gy -1 , b=0.027 Gy -2 and Tr = 1.9 hr (half repair time of sublethal damage in the prostate cells) at the 4 th week, the SF for D 90 and D 100 changes from 4.96Â10 -4 to 12.82Â10 -4 and 6.11Â10 -2 to 8.84Â10 -2 for change in T 1/2edema from 4 days to 30 days. This corresponds with a change in BED from 195.5 Gy to 171.87 Gy and 75.7 Gy to 66.6 Gy, respectively. Conclusions: Values of various dosimetric parameters investigated in this study increased with increasing post-implant time and attains optimal values in 4 weeks. But due to the short half life of 131 Cs seeds and longer T 1/2edema the improvement in dosimetric and radiobiological parameter is less. Therefore it is important to account for the effect of edema at the time of implant by defining seed positions by using post-needle volumes or by compensating for this edema on preplans.

Background: The efficacy of single-session stereotactic radiosurgery (sSRS) for the treatment of intracranial meningioma is widely recognized. However, sSRS is not always feasible in cases of large tumors and those lying close to critically radiation-sensitive structures. When surgery is not recommended, multi-session stereotactic radiosurgery (mSRS) can be applied. Even so, the efficacy and best treatment schedule of mSRS are not yet established. The aim of this study is to validate the role of mSRS in the treatment of skull base meningiomas. Methods: A retrospective analysis of patients with skull base meningiomas treated with mSRS (two to five fractions) at the University of Messina, Italy, from 2008 to 2018, was conducted. Results: 156 patients met the inclusion criteria. The median follow-up period was 36.2 ± 29.3 months. Progression-free survival at 2-, 5-, and 10- years was 95%, 90%, and 80.8%, respectively. There were no new visual or motor deficits, nor cranial nerves impai...

A summary of the results for all fields tested can be seen in figure . The range of calculated minimum distances between the gantry and the patient or the treatment couch is shown for each couch angle. The average minimum distance was 16.6 cm and the median was 15.8 cm. One colliding field, using a 5 cm patient expansion zone, was detected by the software out of a total of 148 fields tested for 36 patients. This field was treatment simulated on a Linac and confirmed to be a collision risk. No undetected collisions occurred clinically during the implementation phase.

Radiation therapy is an effective cancer treatment that is constantly being transformed by technological innovation. Dedicated devices for fraction-by-fraction imaging and guidance within the treatment room have enabled image guided radiation therapy (IGRT) allowing clinicians to pursue highly conformal dose distributions, higher dose prescriptions, and shorter fractionation schedules. Capitalizing on IGRT-enabled accuracy and precision requires a strong link between IGRT practices and planning target volume (PTV) design. This is clearly central to high quality, safe radiation therapy. Failure to properly apply IGRT methods or to coordinate their use with an appropriate PTV margin can result in a treatment that is 'precisely wrong'. The white paper summarized in this executive summary recommends foundational elements and specific activities to maximize the safety and effectiveness of IGRT.

Résultats. -L'analyse de 501 évènements inhabituels rapportés au cours des dix dernières années a montré une diminution substantielle du nombre d'erreurs significatives observées. En tout, 57 % des évènements inhabituels ont été signalés par les manipulateurs en radiothérapie, y compris au cours de la préparation du traitement. La surveillance est censée être la cause la plus fréquente d'évènements inhabituels. Conclusion. -Cette étude sur dix ans de déclaration et de documentation d'évènements inhabituels a abouti à une culture de la sécurité où chaque individu est disposé à partager tout type d'incident avec un accès libre. Notre expérience à l'hôpital universitaire Aga Khan (AKUH) montre que la raison principale de la survenue d'incidents était la surveillance ; la majorité des évènements inhabituels a été signalée par des manipulateurs en radiothérapie, comme prévu, puisqu'ils gèrent l'essentiel du processus de planification des traitements.

The prostatic apex is often radiographically indistinct from the urogenital diaphragm and difficult to identify with certainty using Computed tomography (CT) scans. Autopsy and pathology studies have shown that the caudal portion of the prostate gland harbors tumor in 64-75% of specimens examined. The optimal method of localizing the prostatic apex is still controversial. Yet the prostatic apex can be easily identified on the sagittal images of Trans Rectal Ultrasound(TRUS). The purpose of this study is to evaluate the position of the lowest part of the prostate gland in relation to the tip of the uretherogram. Materials and Methods: 25 consecutive patients with prostate cancer who were undergoing a volume study (TRUS) for prostate seed implant were enrolled in this study. After each volume study a uretherogram was done using hypaque mixed with gel rich in small air bubbles. The mixture was designed to work as a contrast for ultrasound and X-rays. Ultrasound sagittal views were obtained and the distance between the tip of the uretherogram and the prostate apex was measured. Ultrasound view prints were compared to lateral simulation films. The prostatic apex was clearly identified in all 25 patients using ultrasound images in the mid sagittal plan. The apex was seen abutting the pointing tip of the uretherogram in 16 patients (64%), in 6 patients (24%) the distance was 5mm or less, and in 3 patients (12%) the distance was 10 mm or less. Prostatic apex is much closer to the uretherogram tip than what is usually conceptualized. Caution should be applied in designing the lower border of the radiation therapy field. Ultrasound sagittal views are a reliable and accurate tool to identify the prostatic apex with high accuracy.

Adjuvant RT after quadrantectomy or lumpectomy plays an essential role in breast conserving therapy for early stage carcinoma and 60 Gy delivered in 30 fractions in 6 weeks is generally considered the standard dose. The present study aims to evaluate acute, sub-acute and short term late side effects in patients with early stage breast cancer treated with adjuvant radiotherapy (RT) using concomitant boost. Materials and Methods: Between June 2010 and October 2013, 586 patients (median age 60 years, range 27-96 years) with early-stage breast cancer were treated with a hypofractionated schedule of external beam RT after conserving surgery; 143 patients underwent post-operative chemotherapy before starting RT. RT was delivered as follow: 45 Gy in 20 fractions (225 cGy/fr) in 4 weeks to the whole breast and a daily concomitant boost dose (5Gy) to the lumpectomy cavity (25 cGy/fr). The cumulative nominal dose was 50 Gy. The technique used was 3D-conformational RT with 2 tangential fields for the whole breast and 2 oblique fields for the boost. The surgical bed was primarily defined with clips. Toxicity was scored according to LENT-SOMA scale. Results: Twenty-five patients experienced grade 3 skin toxicity within one week from the end of the RT course (eight after adjuvant chemotherapy administered before breast RT). After 19-month median follow-up (range 12-52 months), no grade 4 toxicity were detected; only 5 patients experienced grade 3 skin toxicity and thirty-nine patients reported grade 2 breast pain. Concerning cosmetic results, one patients developed scar retraction; the others 585 patients showed excellent or good cosmetic results. Disease recurrences were recorded in 4 patients: one of them with local relapse, the others three with systemic spread. Conclusions: The explored regimen seems to be feasible providing consistent clinical results with excellent toxicity profile.

Background and purpose: The clinical feasibility of synthetic computed tomography (sCT) images derived from magnetic resonance imaging (MRI) images for external beam radiation therapy (EBRT) planning have been studied and adopted into clinical use recently. This paper evaluates the dosimetric and positioning performance of a sCT approach for different pelvic cancers. Materials and methods: Seventy-five patients receiving EBRT at Turku University Hospital (Turku, Finland) were enrolled in the study. The sCT images were generated as part of a clinical MRI-simulation procedure. Dose calculation accuracy was assessed by comparing the sCT-based calculation with a CT-based calculation. In addition, we evaluated the patient position verification accuracy for both digitally reconstructed radiograph (DRR) and cone beam computed tomography (CBCT) -based image guidance using a subset of the cohort. Furthermore, the relevance of using continuous Hounsfield unit values was assessed. Results: The mean (standard deviation) relative dose difference in the planning target volume mean dose computed over various cancer groups was less than 0.2 (0.4)% between sCT and CT. Among all groups, the average minimum gamma-index pass-rates were better than 95% with a 2%/2mm gamma-criteria. The difference between sCT-and CT-DRR-based patient positioning was less than 0.3 (1.4) mm in all directions. The registrations of sCT to CBCT produced similar results as compared with CT to CBCT registrations. Conclusions: The use of sCT for clinical EBRT dose calculation and patient positioning in the investigated types of pelvic cancers was dosimetrically and geometrically accurate for clinical use.

The aim of this study is to calculate setup margin based on six-dimensional (6D) corrected residual positional errors from kV cone beam computed tomography (CBCT) and from intrafraction projection kV imaging in coplanar and in noncoplanar couch positions in stereotactic radiotherapy. Methods: Six dimensional positional corrections were carried out before patient treatments, using a robotic couch and CBCT matching. A CBCT and stereoscopic ExacTrac image were acquired posttable position correction. Further, a series of intrafraction ExacTrac images were obtained for the variable couch position. Translational and rotational errors were identified as lateral (X), longitudinal (Y), vertical (Z); roll (Ɵ°), pitch (Φ°) and yaw (Ψ°). A total of 699 intrafraction image sets (361 coplanar and 338 noncoplanar) for 51 SRS/SRT patients were analysed. Rotational errors were corrected in terms of translational coordinates. Residual set-up margins were calculated from CBCT shifts. ExacTrac shifts give residual + intrafraction setup margins as a function of coplanar and noncoplanar couch positions. Results: The average residual positional error obtained from CBCT in X, Y, Z, Ɵ, Φ, Ψ were 0.

Introduction: Verifying the patient position is always an essential part of the treatment process, especially in hypofractionated treatments such as accelerated partial breast irradiation (APBI). The purpose of the study was to compare five image guidance techniques with respect to imaging dose and image quality. Methods and materials: We chose five types of imaging methods applicable for APBI and measured their dose exposure on four different accelerators (Synergy, TrueBeam, Artiste and CyberKnife). Absorbed dose was measured with ionization chamber in thorax phantom. Besides dose exposure image quality was also compared. Results: The lowest dose exposure was measured with kV-kV planar imaging followed by kV-CBCT, MV-MV pair and MV-CBCT in ascending order. Average phantom dose with kV-kV image pair on CyberKnife was 0.01 cGy as the lowest and with MV-CBCT on Artiste was 7.11 cGy as the highest. Average dose exposures of MV-MV images with TrueBeam, Synergy and Artiste were 1.18 cGy, 2.13 cGy and 1.61 cGy, respectively, with similar image quality. For the same machines the doses of kV-CT imaging were comparable: 0.65 cGy, 0.65 cGy and 0.52 cGy, with some differences in image quality. MV-CBCT technique resulted in the highest dose and poorest image quality. Conclusions: In APBI the position of the patient and tumour bed can be verified with many tools. When fiducials are available, often 2D imaging is enough to achieve appropriate positioning and the kV-kV method is recommended. Imaging with 2.5MV can also be a good solution instead of 6MV. Without fiducials 3D images should be acquired and the recommended method is the kV-CBCT.

Purpose/Objective: We report the initial results of a prospective study in which patients undergoing radical prostatectomy at the Shands Teaching Hospital or Gainesville VA Hospital who were staged pT3N0 were offered adjuvant irradiation. In this report biochemical relapse-free survival is analyzed for all patients with 2 or more years of follow-up. Materials & Methods: During the period 1988-1995, 77 patients received adjuvant irradiation after radical prostatectemy. Of these, 75 were staged pT3N0. Two patients who underwent orchiectomy prior to irradiation treatment, and two patients staged pT2N0 were eliminated from this analysis. Median follow-up was 46 months, while the minimum was 24 months. PSA values were available for greater than 24 months of follow-up for 66 patients. External beam treatment was delivered to the surgical bed with no attempt to include regional lymph nodes. Patients routinely received 60 Gy delivered in a four-field arrangement. Based upon the surgeon's preference, some patients (26 out of 77) received adjuvant androgen suppression therapy during the interval between surgery and irradiation. The average length of the interval was 115 days. Comparison of the group receiving hormone treatment with the group treated with radiation alone demonstrated no significant differences in pre-operative serum PSA values, or the per cent of patients with positive margins or positive seminal vesicles. Results: Overall survival for the entire group was 93% and the crude distant metastasis rate was 9.2%. Biochemical relapsefree survival (BRFS) after 5 years was 69% for the entire group. Five-year BRFS was 82% for patients receiving androgen suppression and 64% for patients receiving radiation alone. BRFS was significantly improved for patients presenting with preoperative PSA less than or equal to 10 ng/ml (p=0.01); or post-operative PSA less than 1.0 ng/ml (p=O.05); but unaffected by positive seminal vesicles, 5-yr BRFS 62% (p=0.26), positive margins, 5-yr BRFS 73% (p=0.95), or extra-capsular extension, 5-yr BRFS 67% (p=0.67). Post-operative PSA was also a significant predictor after multivariate analysis (p=0.012). Post-operative and pre-operative PSA values were highly correlated. When patients were stratified by their pre-operative PSA values, a possible impact of androgen suppression was apparent. For patients with low pre-operative PSA values (<10 ng/ml), the 5-year BRFS was unaffected, 100% with hormone treatment and 93% without hormones. For patients presenting with intermediate PSA values (>10 ng/ml and <20 ng/ml), however, the 5-year BRFS was improved for patients with androgen suppression, 72% vs. 53%, respectively. Finally, when the presenting PSA value was greater than 20 ng/ml androgen suppression resulted in an eady improvement in BRFS, which disappeared in the fifth year of follow-up. Conclusion: Following irradiation in the adjuvant setting, patients with post-prostatectomy PSA values > 1 .O ng/ml, or preoperative PSA values greater than 15 ng/ml are at high risk for biochemical failure. High-risk patients may be more frequently controlled, however, when androgen suppressive therapy is employed during the interval between surgery and irradiation.

Fluorine-18-fluorodeoxyglucose-positron emission tomography ( 18 F-FDG-PET)-guided focal dose escalation in oropharyngeal cancer may potentially improve local control. We evaluated the feasibility of this approach using volumetric-modulated arc therapy (RapidArc) and compared these plans with fixed-field intensitymodulated radiotherapy (IMRT) focal dose escalation plans. Materials and methods: An initial study of 20 patients compared RapidArc with fixed-field IMRT using standard dose prescriptions. From this cohort, 10 were included in a dose escalation planning study. Dose escalation was applied to 18 F-FDG-PET-positive regions in the primary tumor at dose levels of 5% (DL1), 10% (DL2), and 15% (DL3) above standard radical dose (65 Gy in 30 fractions). Fixed-field IMRT and double-arc RapidArc plans were generated for each dataset. Dose-volume histograms were used for plan evaluation and comparison. The Paddick conformity index (CI Paddick ) and monitor units (MU) for each plan were recorded and compared. Both IMRT and RapidArc produced clinically acceptable plans and achieved planning objectives for target volumes. Dose conformity was significantly better in the RapidArc plans, with lower CI Paddick scores in both primary (PTV1) and elective (PTV2) planning target volumes (largest difference in PTV1 at DL3; 0.81 Ϯ 0.03 [RapidArc] vs. 0.77 Ϯ 0.07 [IMRT], p ϭ 0.04). Maximum dose constraints for spinal cord and brainstem were not exceeded in both RapidArc and IMRT plans, but mean doses were higher with RapidArc (by 2.7 Ϯ 1 Gy for spinal cord and 1.9 Ϯ 1 Gy for brainstem). Contralateral parotid mean dose was lower with RapidArc, which was statistically significant at DL1 (29.0 vs. 29.9 Gy, p ϭ 0.01) and DL2 (29.3 vs. 30.3 Gy, p ϭ 0.03). MU were reduced by 39.8 -49.2% with RapidArc (largest difference at DL3, 641 Ϯ 94 vs. 1261 Ϯ 118, p Ͻ 0.01). 18 F-FDG-PET-guided focal dose escalation in oropharyngeal cancer is feasible with RapidArc. Compared with conventional fixed-field IMRT, RapidArc can achieve better dose conformity, improve contralateral parotid sparing, and uses fewer MU.

Silently asymptomatic at an early stage and often painless, requiring only active surveillance, Prostate Cancer (PCa) is traditionally diagnosed by a Digital Rectal Examination (DRE) and a Prostate Specific Antigen (PSA) blood test. A histological examination, searching for pattern irregularities on the prostate glandular tissue, is performed to quantify the aggressiveness of PCa. The assigned Gleason Score (GS), usually combined with Transrectal Ultrasound Guided Biopsy (TRUS), allows the stratification of patients according to their risk group. Intermediate-risk patients may have a favourable (GS = 3 + 4) or unfavourable (GS = 4 + 3) prognosis. This borderline is critical for defining treatments and possible outcomes, while External Beam Radiotherapy (EBRT) is a curative option for localised and locally advanced disease and as a palliative option for metastatic low-volume disease; active surveillance or watchful waiting can also be an option for patients with a favourable prognosis. With radiomics, quantifying phenotypic characteristics in medical imaging is now possible. In the EBRT workflow, there are several imaging modalities, such as Magnetic Ressonance Imaging (MRI), Computed Tomography (CT), Positron Emission Tomography (PET), Ultrasound and Cone Beam Computed Tomography (CBCT). Most radiomic PCa studies focused on MRI and addressed tumour staging, GS, PSA or Biochemical Recurrence (BCR). This study intends to use CBCT radiomics to distinguish between favourable and unfavourable cases, with the potential of evaluating an ongoing treatment. Seven of the most used feature selection methods, combined with 14 different classifiers, were evaluated in a total of 98 pipelines. From those, six stood out with Area Under the Receiver Operating Characteristic (AUROC) values ≥ 0.79. To the best of our knowledge, this is the first work to evaluate a PCa favourable vs. unfavourable prognosis model based on CBCT radiomics.

Purpose-To develop a novel 4-dimensional computed tomography (4D-CT) technique that exploits standard fast helical acquisition, a simultaneous breathing surrogate measurement, deformable image registration, and a breathing motion model to remove sorting artifacts. Methods and Materials-Ten patients were imaged under free-breathing conditions 25 successive times in alternating directions with a 64-slice CT scanner using a low-dose fast helical protocol. An abdominal bellows was used as a breathing surrogate. Deformable registration was used to register the first image (defined as the reference image) to the subsequent 24 segmented images. Voxel-specific motion model parameters were determined using a breathing motion model. The tissue locations predicted by the motion model in the 25 images were compared against the deformably registered tissue locations, allowing a model prediction error to be evaluated. A low-noise image was created by averaging the 25 images deformed to the first image geometry, reducing statistical image noise by a factor of 5. The motion model was used to deform the low-noise reference image to any user-selected breathing phase. A voxel-specific correction was applied to correct the Hounsfield units for lung parenchyma density as a function of lung air filling. Results-Images produced using the model at user-selected breathing phases did not suffer from sorting artifacts common to conventional 4D-CT protocols. The mean prediction error across all patients between the breathing motion model predictions and the measured lung tissue positions was determined to be 1.19 ± 0.37 mm. The proposed technique can be used as a clinical 4D-CT technique. It is robust in the presence of irregular breathing and allows the entire imaging dose to contribute to the resulting

In the past few years, innovations such as on-board imaging have made it possible to adjust each radiation beam on a daily basis to account for any changes in anatomical positions of target and normal tissues. This "adaptive radiotherapy" has made it possible to reduce margins so as to decrease the risk of normal tissue damage, enabling safe and effective delivery of higher doses/fraction (hypofractionation). It has been proposed that such technological advances will allow adaptive hypofractionation to become the most common form of radiotherapy within the next five years. This is the claim debated in this month's Point/Counterpoint.

In the past few years, innovations such as on-board imaging have made it possible to adjust each radiation beam on a daily basis to account for any changes in anatomical positions of target and normal tissues. This "adaptive radiotherapy" has made it possible to reduce margins so as to decrease the risk of normal tissue damage, enabling safe and effective delivery of higher doses/fraction (hypofractionation). It has been proposed that such technological advances will allow adaptive hypofractionation to become the most common form of radiotherapy within the next five years. This is the claim debated in this month's Point/Counterpoint.

To compare the accuracy of 2D algorithm with an established 3D algorithm, and to define the number of CT-slices needed for treatment planning of intact breast irradiation. Twenty patients with breast cancer treated with conservative surgery were included in this study, ten of them had right breast cancer and the other 10 patients had cancer of the left breast. For each patient, 3-D calculations (HeLax-TMS) were performed using one CT-slice (central), 3 CT-slices (central, caudal, and cephalic) and full set CT-slices in addition to 2D calculations (Multidata System) on the digitized central cut. All calculations were done using 6MV-photon. When using 2D planning with lung correction, a large hot area of 105% was found at the medial and lateral subcutaneous (SC) regions. Comparison of 2D-treatment planning using Multidata System (2D-physics) and 2D-planning using HeLax System (3D-physics) showed that the 2D planning using Multidata System gave a large hot area of 105% compared with He...

To evaluate long-term radiation toxicity and biochemical control of two moderately hypofractionated radiotherapy regimens for prostate cancer. Eligible men with localized prostate cancer received image-guided intensity modulated radiotherapy (IG-IMRT) to a dose of 60 or 66Gy in 3Gy fractions in a phase II trial. Endpoints included late gastrointestinal (GI) and genitourinary (GU) toxicity and biochemical failure (FFBF). Ninety-six men received 60Gy and 27 received 66Gy. Accrual to the 66Gy cohort terminated early due to excessive Grade 3-4 late toxicity. Median follow-up was 128months (60Gy) and 108months (66Gy). In the 60Gy cohort, cumulative late Grade ⩾2 GI and GU toxicity at 8years was 4% and 12% respectively. In the 66Gy cohort, late Grade ⩾2 GI and GU toxicity was 21% and 4% respectively at 8years. The 5- and 8-year FFBF for 60Gy was 81% and 66%, and for 66Gy was 88% and 80%. Moderate hypofractionation with IG-IMRT to 60Gy was associated with favorable late toxicity although l...

Background: A subset of patients experience a biochemical recurrence following radical prostatectomy. Radiotherapy can salvage those patients, provided that all disease is encompassed within the target volume. We hypothesized that this can be achieved more adequately with magnetic resonance imaging (MRI)-guided treatment planning. Material and methods: From January 2009 to April 2014, 183 patients were referred to our department for salvage radiotherapy (SRT). According to protocol, patients received a planning computed tomography (CT) as well as an MRI in treatment position. All MRI scans were retrospectively reviewed by an experienced uro-radiologist. Results: Median prostate-specific antigen (PSA) value at time of referral was 0.3 ng/ml (range 0.02-4.7 ng/ml). MRI did not show any suspected macroscopic disease in 137 patients (75%). In 46 (25%) patients, MRI did indicate a pelvic recurrence. The mean PSA level was significantly higher in patients with a suspected recurrence on MRI (0.4 vs. 1.4 ng/ml, p < .001) on a Student's t-test. The mean follow-up was 33 months (range 5-69 months). Biochemical disease-free survival (bDFS) was significantly worse in patients with suspected disease on MRI [hazard ratio (HR) 2.9, p < .0001]. bDFS was significantly worse in the subgroup where the macroscopic recurrences on MRI received a lower radiation dose (HR 3.4, p ¼ .01). Conclusion: MRI detects loco-regional disease in a substantial subset of patients with a biochemical recurrence after prostatectomy, especially in a PSA above 0.5 lg/l. Lack of MRI-based dose escalation on these macroscopic recurrences could explain some of the biochemical progression observed after SRT.

This study investigates the use a 2D normalized cross-correlation (NCC)-based algorithm to estimate in vivo motion of liver features in 2D Bmode ultrasound (US) images. Datasets included 23 volunteer imaging sequences, each containing first frame annotated points of interest (POI). Images had a range of spatial (0.28 – 0.71 mm) and temporal (11 – 25 Hz) resolution. Image quality was also highly variable. A 2D block-matching algorithm was developed to track POI motion throughout the imaging sequence. A correlation and displacement thresholding tracking approach, which used knowledge of previous displacement and (1) linear extrapolation, (2) a regularizing sinusoidal breathing model or (3) hybrid fixed-reference / incremental tracking was use to account for potential tracking errors. The overall mean error in vessel tracking was 2.15 ± 2.7 mm. This approach to motion estimation shows promise for applications such as radiation therapy tumor tracking.

New technologies continue to be developed to improve the practice of radiation therapy. As several of these technologies have been implemented clinically, the Therapy Committee and the Quality Assurance and Outcomes Improvement Subcommittee of the American Association of Physicists in Medicine commissioned Task Group 147 to review the current nonradiographic technologies used for localization and tracking in radiotherapy. The specific charge of this task group was to make recommendations about the use of nonradiographic methods of localization, specifically; radiofrequency, infrared, laser, and video based patient localization and monitoring systems. The charge of this task group was to review the current use of these technologies and to write quality assurance guidelines for the use of these technologies in the clinical setting. Recommendations include testing of equipment for initial installation as well as ongoing quality assurance. As the equipment included in this task group continues to evolve, both in the type and sophistication of technology and in level of integration with treatment devices, some of the details of how one would conduct such testing will also continue to evolve. This task group, therefore, is focused on providing recommendations on the use of this equipment rather than on the equipment itself, and should be adaptable to each user's situation in helping develop a comprehensive quality assurance program.

Aims and background. To evaluate the feasibility, toxicity and patient outcome of hypofractionated 3-dimensional conformal radiotherapy for low-and intermediate-risk prostate cancer, using daily an ultrasound targeting system (BAT TM ). Between May 2005 and October 2006, 25 patients (cT1-T2, GS ≤7, mean initial PSA = 7.06 ng/ml) received a dose of 72 Gy in 30 fractions. Only the prostate was included in the clinical target volume. Immediately before each radiotherapy session, BAT TM ultrasound alignment was performed. Acute and late toxicity was evaluated according to the Radiation Therapy Oncology Group criteria; the Phoenix definition (PSA = nadir + 2 ng/ml) was applied to define biochemical failure. BAT TM localization data were provided for 300 out of 750 procedures. No interruptions in 3-dimensional conformal radiotherapy due to toxicity were registered. There was no acute rectal toxicity in 52% of patients; 28% had G1, 16% had G2, and 1 patient had a G3 event. No acute urinary toxicity was observed in 28% of the patients. G1 toxicity occurred in 40%, G2 in 28%, and G3 in 1 patient; no G4 event was observed. With an average follow-up of 45 months, one biochemical relapse was observed; late toxicity showed an excellent profile: 78% of the patients had no rectal toxicity, 16% had G1, and 1 patient had G2 toxicity. Most of the patients (68%) had no late urinary complications, whereas 32% had G1 toxicity. Localization data showed systematic and random errors in relation to some procedure biases. Promising tumor control and toxicity profile were observed with this mildly hypofractionated BAT-based 3-dimensional conformal radiotherapy. Free full text available at www.tumorionline.it

Objectives: In radiotherapy, delineation uncertainties are important as they contribute to systematic errors and can lead to geographical miss of the target. For margin computation, standard deviations (SDs) of all uncertainties must be included as SDs. The aim of this study was to quantify the interobserver delineation variation for stereotactic body radiotherapy (SBRT) of peripheral lung tumours using a crosssectional study design. Methods: 22 consecutive patients with 26 tumours were included. Positron emission tomography/CT scans were acquired for planning of SBRT. Three oncologists and three radiologists independently delineated the gross tumour volume. The interobserver variation was calculated as a mean of multiple SDs of distances to a reference contour, and calculated for the transversal plane (SD trans ) and craniocaudal (CC) direction (SD cc ) separately. Concordance indexes and volume deviations were also calculated. Results: Median tumour volume was 13.0 cm 3 , ranging from 0.3 to 60.4 cm 3 . The mean SD trans was 0.15 cm (SD 0.08 cm) and the overall mean SD cc was 0.26 cm (SD 0.15 cm). Tumours with pleural contact had a significantly larger SD trans than tumours surrounded by lung tissue. Conclusions: The interobserver delineation variation was very small in this systematic cross-sectional analysis, although significantly larger in the CC direction than in the transversal plane, stressing that anisotropic margins should be applied. This study is the first to make a systematic cross-sectional analysis of delineation variation for peripheral lung tumours referred for SBRT, establishing the evidence that interobserver variation is very small for these tumours.

This work investigates the possibility of combining Monte Carlo (MC) simulations to a denoising algorithm for the accurate prediction of images acquired using amorphous silicon (a-Si) electronic portal imaging devices (EPIDs). An accurate MC model of the Siemens OptiVue1000 EPID was first developed using the PENELOPE code, integrating a non-uniform backscatter modelling. Two already existing denoising algorithms were then applied on simulated portal images, namely the iterative reduction of noise (IRON) method and the locally adaptive Savitzky-Golay (LASG) method. A third denoising method, based on a nonparametric Bayesian framework and called DPGLM (for Dirichlet Process Generalized Linear Model) was also developed. Performances of the IRON, LASG and DPGLM methods, in terms of smoothing capabilities and computation time, were compared for portal images computed for different values of the RMS pixel noise (up to 10%) in three different configurations, a heterogeneous phantom irradiated by a non-conformal 15 × 15 cm² field, a conformal beam from a pelvis treatment plan, and an IMRT beam from a prostate treatment plan. For all configurations, DPGLM outperforms both IRON and LASG by providing better smoothing performances and demonstrating a better robustness with respect to noise. Additionally, no parameter tuning is required by DPGLM, which makes the denoising step very generic and easy to handle for any portal image. Concerning the computation time, the denoising of 1024 × 1024 images takes about 1 h 30, 2 h and 5 min using DPGLM, IRON, and LASG, respectively. This paper shows the feasibility to predict within a few hours and with the same resolution as real images accurate portal images, combining MC simulations with the DPGLM denoising algorithm.

Background Although moderate hypofractionated radiotherapy were one of standard regimens for localized prostate cancer, the e cacy of moderated hypofractionated regimens has not been well validated in Asian countries. The aim of this multi-institutional phase II study was to con rm the safety and the potential e cacy of moderately hypofractionated intensity-modulated radiotherapy (IMRT) with prostate-based image-guidance for Japanese patients. Methods Patients with low-or intermediate-risk localized prostate cancer were eligible. Patients with a part of high risk (having only one of the following factors, cT3a, 20 < PSA ≤ 30, or GS = 8 or 9) were also included in this trial. Hypofractionated IMRT using daily image-guided technique with prostate matching was performed with a total dose of 70 Gy in 28 fractions. Neoadjuvant hormonal therapy for 4-8 months was mandatory for patients with intermediate or high-risk prostate cancer. The number of patients with low, intermediate, and high-risk prostate cancer was 20, 80, and 34, respectively. The 5-year overall, biochemical failure-free, and clinical failure-free survival was 94.5%, 96.0%, and 99.2%, respectively. The 5-year biochemical failure-free survival for patients with low-, intermediate-, and high-risk disease was 94.1%, 97.4%, and 93.9%, respectively. The incidences of grade 2 gastrointestinal and genitourinary late toxicities at 5 years were 5.3% and 5.3%, respectively. There are no acute or late toxicities ≥ grade 3. The safety and e cacy of moderately hypofractionated IMRT was con rmed in this trial among Japanese patients with prostate cancer.

To evaluate Lipiodol as a liquid, radio-opaque fiducial marker for image--guided radiation therapy (IGRT) for bladder cancer. Materials and Methods: Between 2011 and 2012, 5 clinical T2a-T3b N0 M0 stage II-III bladder cancer patients were treated with maximal transurethral resection of a bladder tumor (TURBT) and image-guided radiation therapy (IGRT) to 64.8 Gy in 36 fractions ± concurrent weekly cisplatin-based or gemcitabine chemotherapy. Ten to 15mL Lipiodol, using 0.5mL per injection, was injected into bladder submucosa circumferentially around the entire periphery of the tumor bed immediately following maximal TURBT. The authors looked at inter-observer variability regarding the size and location of the tumor bed (CTV boost ) on computed tomography scans with versus without Lipiodol. Results: Median follow-up was 18 months. Lipiodol was visible on every orthogonal two-dimensional kV portal image throughout the entire, 7-week course of IGRT. There was a trend towards improved inter-observer agreement on the CTV boost with Lipiodol (p = 0.06). In 2 of 5 patients, the tumor bed based upon Lipiodol extended outside a planning target volume that would have been treated with a radiation boost based upon a cystoscopy report and an enhanced computed tomography (CT) scan for staging. There was no toxicity attributable to Lipiodol. Conclusions: Lipiodol constitutes a safe and effective fiducial marker that an urologist can use to demarcate a tumor bed immediately following maximal TURBT. Lipiodol decreases inter-observer variability in the definition of the extent and location of a tumor bed on a treatment planning CT scan for a radiation boost.

Background.-Surgery is the only definitive therapy for gastro-entero-pancreatic neuroendocrine tumors (GEP-NETs), and achieving complete tumor resection is an important prognostic factor. Radiopharmaceuticals such as 68 Ga-DOTA peptides have been developed that offer superior accuracy for localization of GEPNETs. The study aim was to determine the feasibility of radio-guided surgery (RGS) using 68 Ga-DOTATATE in patients with primary and recurrent GEPNETs. Methods.-Fourteen patients with GEPNETs were enrolled onto a prospective study to determine the feasibility of RGS with 68 Ga-DOTATATE. Findings from preoperative imaging, intraoperative exploration, RGS, and pathology were analyzed. Results.-The median decay corrected target count rate was 172.6 (range 28.15-2341) for tumors, with a tumor-to-background ratio (TBR) of 4.46 (range 1.6-43.56). The median lesion size was 1.55 (range 0.5-15) cm. There was no significant correlation between preoperative imaging maximum standardized uptake value (SUV max ) of the lesions and TBR (Spearman r = -0.01, p = 0.9), TBR and tumor size (Spearman r = 0.29, p = 0.14), and SUV max and tumor size (Spearman r = 0.22, p = 0.28). The probe showed correct identification for gastric and small intestine neuroendocrine tumor (NET), including lymph node metastasis in 17 (81.0 %) of 21 cases, with a median TBR of 3.5 (1.6-40.2). For pancreatic NETs and lymph node metastasis, 16 (66.7 %) of 24 were correctly identified by RGS. Conclusions.-Our study shows that RGS with 68 Ga-DOTATATE is feasible and correctly confirms bowel NETs and metastatic mesenteric lymph nodes. Further studies are needed to determine the benefit of RGS with 68 Ga-DOTATATE.

Image-guided external beam radiotherapy (EBRT) allows radiation dose deposition with a high degree of accuracy and precision. Guidance is usually achieved by estimating the displacements, via image registration, between cone beam computed tomography (CBCT) and computed tomography (CT) images acquired at different stages of the therapy. The resulting displacements are then used to reposition the patient such that the location of the tumor at the time of treatment matches its position during planning. Moreover, ongoing research aims to use CBCT-CT image registration for online plan adaptation. However, CBCT images are usually acquired using a small number of x-ray projections and/or low beam intensities. This often leads to the images being subject to low contrast, low signal-to-noise ratio and artifacts, which ends-up hampering the image registration process. Previous studies addressed this by integrating additional image processing steps into the registration procedure. However, the...

Background: Prostate cancer remains a major health concern worldwide, and postoperative recurrences are a significant challenge in its treatment. Various treatment modalities have been studied, but consensus on optimal strategies has not yet been established. This case report examines the feasibility and toxicity of Stereotactic Body Radiation Therapy (SBRT) as a therapeutic option for postoperative recurrences of prostate cancer. Case presentation: A 68-year-old man with a history of prostate cancer, initially treated with radical prostatectomy, who presented biochemical recurrence. Diagnostic imaging revealed a 9 mm nodule in the prostate bed, which was treated by SBRT guided by ultrasound visualization. The patient tolerated the treatment well, experiencing minimal genitourinary and gastrointestinal discomfort. Discussion: Multiple treatment alternatives exist for post-prostatectomy recurrence. Retrospective studies have suggested the efficacy of SBRT, although they lack robust empirical evidence. Recent investigations have highlighted the safety profile of SBRT, emphasizing the need for further exploration, particularly in image-guided radiotherapy. Conclusion: SBRT guided by ultrasound visualization emerges as a promising option for ablative treatment of postprostatectomy recurrence, offering a favorable safety profile and encouraging oncologic outcomes. Further research is needed to further clarify its role in salvage radiotherapy for localized recurrences.

Objectives: To explore a simple and effective way to determine the total scatter of a C- Series linear accelerator.Methodology: Measurements for this study were acquired using a Varian C-Series linear accelerator, with a 6MV photon beam, a Blue water phantom, 2 IBA CC13 ion chambers and an IBA CCU electrometer. Measurements were acquired for field sizes ranging from 5cm x 5cm to 40cm x 40cm, increasing field size by an increment of 5cm. Three readings were collected for each field size and averaged. All readings were done at a depth of 10cm to reduce the probability of measuring electron contamination in the photon beam. Measurements for Sc calculation were acquired in air using a build-up cap with a 3cm diameter.Results: The average radiation dose measured increased as the field sizes increased. The maximum dose recorded for Sc was 2.33cGy while that for Scp was7.96cGy. There was a non-linear direct relationship between radiation dose measured, Scp and Sc calculated and field size....

Purpose: There are no international guidelines for optimal needle insertion during interstitial intracavitary brachytherapy (IS-ICBT) for cervical cancer. We aimed to investigate the clinical feasibility and added value of computed to mography (CT) guidance to optimize needle insertion in IS-ICBT using the Utrecht appli cator and to evaluate needle shifts. Methods and Materials: We enrolled 24 patients who were treated with IS-BT . Two CT scans each were performed for every patient: 1) aft er applicator insertion without needles (CTpreneedle ); 2) after needle insertion (CT postneedle ). In addition to magnetic resonance imaging (MRI) after external-beam radiotherapy, CT preneedle was used to determine optimal needle locations and insertion lengths based on applicator nd organs at risk positioning on the day of treatment; CTpostneedle was used for IS-ICBT planning. The needle-channel axis was used as a reference to determine needle-shift evolution. Results: A total of 266 interstiti...

New linear accelerators can be equipped with a 6D robotic couch, providing two additional rotational motion axes: pitch and roll. These shifts in kV-CBCT image-guided radiotherapy (IGRT) were evaluated over the first 6 months usage of a 6D Robotic couch-top, ranking the treatment sites for which the two compensations are larger for patient setup. The couch compensations of 2945 fractions for 376 consecutive patients treated on the PerfectPitch™ 6D couch (Varian Medical System) were analyzed. Among these patients, 169 were treated for brain, 111 lung, 54 liver, 26 pancreas, and 16 prostate. During the setup, patient anatomy from planning CT was aligned to kV-CBCT and 6D movements were executed. Information related to pitch and roll were extracted by proper querying of the Microsoft SQL server ARIA database (Varian). Mean values and standard deviations were calculated for all sites. Kolmogorov-Smirnov (KS) test was performed. Considering all the data, mean pitch and roll adjustments w...

The development of targeted anti-cancer therapies through the study of cancer genomes is intended to increase survival rates and decrease treatment-related toxicity. We treated a transposon-driven, functional genomic mouse model of medulloblastoma with…

The case of a 50-year-old man affected by a rhabdomiosarcoma metastatic lesion in the left flank Is reported. The patient was addressed to 50.4 Gy radiotherapy with concomitant chemotherapy in order to locally control the lesion. A Tri-60-Co magnetic resonance hybrid radiotherapy unit was used for treatment delivery and a respiratory gating protocol was applied for the different breathing phases (Free Breathing, Deep Inspiration Breath Hold and Final Expiration Breath Hold). Three intensity modulated radiation therapy (IMRT) plans were calculated and Final Expiration Breath Hold plan was finally selected due to the absence of PTV coverage differences and better organs at risk sparing (i.e. kidneys). This case report suggests that organs at risk avoidance with MRI-guided respiratory-gated Radiotherapy is feasible and particularly advantageous whenever sparing the organs at risk is of utmost dosimetric or clinical importance. adaptive radiotherapy, hybrid radiotherapy, MRI guided radiotherapy, respiratory gating ing (MRI) offers the unique possibility to directly detect and gate the treatment to a particular condition of the respiratory cycle eliminating the need for surrogate-based systems and imaging dose to patient. MRI-guided gated treatments can be performed during