Image Guidance

Purpose: External beam accelerated partial breast irradiation requires accurate localization of the target volume for each treatment fraction. Using the concept of target registration error (TRE), the performance of several methods of target localization was compared. Methods and Materials: Twelve patients who underwent external beam accelerated partial breast irradiation were included in this study. TRE was quantified for four methods of image guidance: standard laser-based setup, kilovoltage imaging of the chest wall, kilovoltage imaging of surgically implanted clips, and three-dimensional surface imaging of the breast. The use of a reference surface created from a free-breathing computed tomography scan and a reference surface directly captured with three-dimensional video imaging were compared. The effects of respiratory motion were also considered, and gating was used for 8 of 12 patients. Results: The median value of the TRE for the laser, chest wall, and clip alignment was 7.1 mm (n = 94), 5.4 mm (n = 81), and 2.4 mm (n = 93), respectively. The median TRE for gated surface imaging based on the first fraction reference surface was 3.2 mm (n = 49), and the TRE for gated surface imaging using the computed tomographybased reference surface was 4.9 mm (n = 56). The TRE for nongated surface imaging using the first fraction reference surface was 6.2 mm (n = 25). Conclusions: The TRE of surface imaging using a reference surface directly captured with three-dimensional video and the TRE for clip-based setup were within 1 mm. Gated capture is important for surface imaging to reduce the effects of respiratory motion in accelerated partial breast irradiation. Ó 2008 Elsevier Inc.

CT-guided percutaneous biopsy is a widely accepted practice in the medical field. Because efficient and safe CT-guided percutaneous interventions require accurate needle placement, there are limitations to the accuracy obtainable using free-hand techniques, particularly for small or deeply situated target areas. In addition, CT-directed percutaneous biopsy can be tedious and time consuming, since frequent re-imaging may be required. As a demonstration platform, we are developing a robotic biopsy testbed incorporating a mobile CT scanner, a small ''needle driver'' robot, and a localizer. This testbed will be used to compare robotically assisted biopsy to the current manual technique. The testbed will also allow us to investigate software architectures for integrating various hardware and software components. This testbed is the first step in developing the robotically assisted biopsy system of the future. In this paper, we present the overall concept and then provide details about the user interface and coordinate transformations.

Angesichts der zunehmenden strukturellen Verschaltung von Mensch und Maschine in der chirurgischen Praxis selbst genügt es nicht mehr, pathologische Veränderungen auf der Basis eines entsprechend theoriegeleiteten Bildwissensauf in medizinischen Visualisierung „lediglich“ zu erkennen. Bildkompetent müss ChirurgInnen inzwischen nicht mehr nur als DiagnostikerInnen sein, sondern Bilder gestalten zunehmend auch die Therapie. Visualisierungspraktiken lenken, steuern, führen und gestalten inwischen auch den Behandlungsprozess und etablieren ein verändertes Verhältnis zwischen ChirurgIn und PatientIn, zwischen Körper und Bild, zwischen Mensch und Maschine. Der Beitrag untersucht dieses Gefüge von Anschauung, Operativität und Bildlichkeit in der minimal-invasiven Chrirurgie anhand der medialen Produktionsbedingungen des roboter-assistierten Operationssystems Da Vinci. Dabei wird anhand konkreter Fallbeispiele der Architektur, Navigation und Steuerung des Systems gezeigt, dass dem Herstellerversprechen erhöhter medizinischer Effizienz und Präzision bildgeführter Operationssysteme eine praktische Kenntnis der Differenz zwischen Körper und Bild entgegenstehen muss, die nicht in Abrenzung zum Maschinellen verhandelt werden kann, sondern als Synthese von Chirurg und Operationssystem gedacht werden muss.

Three-dimensional (3D) ultrasound (US) is increasingly being introduced in the clinic, both for diagnostics and image guidance. Although dedicated 3D US probes exist, 3D US can also be acquired with the still frequently used two-dimensional (2D) US probes. Obtaining 3D volumes with 2D US probes is a two-step process. First, a positioning sensor must be attached to the probe; second, a reconstruction of a 3D volume can be performed into a regular voxel grid. Various algorithms have been used for performing 3D reconstruction based on 2D images. Up till now, a complete overview of the algorithms, the way they work and their benefits and drawbacks due to various applications has been missing. The lack of an overview is made clear by confusions about algorithm and group names in the existing literature. This article is a review aimed at explaining and categorizing the various algorithms into groups, according to algorithm implementation. The algorithms are compared based on published data and our own laboratory results. Positive and practical uses of the various algorithms for different applications are discussed, with a focus on image guidance.

Percutaneous cholecystostomy (PC), a technique that consists of percutaneous catheter placement in the gallbladder lumen under imaging guidance, has become an alternative to surgical cholecystostomy in recent years. Indications of PC include calculous or acalculous cholecystitis, cholangitis, biliary obstruction and opacification of biliary ducts. It also provides a potential route for stone dissolution therapy and stone extraction. Under aseptic conditions

Three-dimensional (3D) ultrasound (US) is increasingly being introduced in the clinic, both for diagnostics and image guidance. Although dedicated 3D US probes exist, 3D US can also be acquired with the still frequently used two-dimensional (2D) US probes. Obtaining 3D volumes with 2D US probes is a two-step process.

Background: Computed tomography (CT) has revolutionized noninvasive cardiovascular evaluations. Complicated percutaneous procedures require precise imaging guidance that conventional X-ray is often unable to provide. By combining X-ray imaging with real-time, interactive, CT-based landmarks, interventional procedures could be facilitated. We describe two cases using the first CT/Live X-ray overlay in which this technology shows its potential. Case reports: A 31-year-old male with an anatomically complicated atrial septal defect (ASD) was referred for percutaneous closure. Transesophageal echocardiography (TEE) revealed an inferior location of the ASD complicated by it's proximity to a prominent Eustachian ridge. The CT was used to create a patient-specific physical model in preparation for the procedure and an in-lab real-time CT overlay allowing successful closure. A second case of a 41-year-old male with coronary artery disease status-post coronary artery bypass, aortic valve replacement (AVR), and aortic root replacement with an abnormal coronary computed tomography angiogram (CTA). In a prior procedure years ago the saphenous vein graft (SVG) to the left anterior descending artery (LAD) could not be cannulated during invasive angiography, given the patient's complicated and unusual anatomy. Using CT overlay, the superiorly and anteriorly located SVG was cannulated successfully. Discussion: CT/Live X-ray overlay provided an adequate anatomical intra-procedural ASD evaluation, defect sizing, and guidance in one case and localization of an anatomically challenging graft ostium in the other case. Adding the CT landmarks as an overlay to traditional X-ray techniques provides a revolutionary and advanced imaging fusion concept that should improve procedural success.

Intensity-modulated radiation therapy (IMRT) is a revolutionary new paradigm that aims at improving the therapeutic ratio by increasing the dosegradient between target tissues and surrounding normal structures thereby offering probability of better loco-regional control with decreased risk of complications. IMRT is relatively intolerant to set-up uncertainties, warranting periodic image-guidance, making Image-Guided Radiation Therapy (IGRT) a natural corollary to IMRT. There are several challenges associated with the planning, delivery, and quality assurance of the IMRT and IGRT processes that must be addressed to realize the full potential of such exciting and promising technology. Given the complexities involved, it is quite intuitive to understand that IMRT and IGRT are resource-intensive, demanding increased labor, rigour, and expenses too. Other disadvantages associated with high-precision techniques include potentially increased risk of marginal failures, decreased dose homogeneity, and an increase in total body dose with increased risk of secondary carcinogenesis. The aim of this review is to define the role of IMRT and IGRT in contemporary head and neck oncologic practice through a critical appraisal of pertinent literature. Despite relatively short follow-up and limited clinical outcomes data, the weight of evidence suggests that loco-regional control is not inferior (either comparable or even better) and toxicity lesser with IMRT resulting in potentially improved quality-oflife, prompting the widespread adoption of such technology in community practice. Ongoing clinical trials in head and neck IMRT are currently addressing issues to optimize the IMRT process, adopting functional imaging for dose-painting, and incorporating adaptive re-planning strategies to further improve outcomes.

Progress in radiotherapy is guided by the need to realize improved dose distributions, i.e. the ability to reduce the treatment volume toward the target volume and still ensuring coverage of that target volume in all dimensions. Poor ability to control the tumour's location limits the accuracy with which radiation can be delivered to tumour-bearing tissue. Image-guided radiation therapy (IGRT) aims at in-room imaging guiding the radiation delivery based on instant knowledge of the target location and changes in tumour volume during treatment. Advancements are usually not to be attributed to a single event, but rather a combination of many small improvements that together enable a superior result. Image-guidance is an important link in the treatment chain and as such a major factor in this synergetic process. A historic review shows that many of the so-called new developments are not so new at all, but did not make it into mainstream radiotherapy practice at that time. Recent developments in improved IT infrastructures, novel irradiation techniques, and better knowledge of functional and morphologic information may have created the need and optimal environment to revive the interest in IGRT.

Radiation therapy has gone through a series of revolutions in the last few decades and it is now possible to produce highly conformal radiation dose distribution by using techniques such as intensity-modulated radiation therapy (IMRT). The improved dose conformity and steep dose gradients have necessitated enhanced patient localization and beam targeting techniques for radiotherapy treatments. Components affecting the reproducibility of target position during and between subsequent fractions of radiation therapy include the displacement of internal organs between fractions and internal organ motion within a fraction. Image-guided radiation therapy (IGRT) uses advanced imaging technology to better define the tumor target and is the key to reducing and ultimately eliminating the uncertainties. The purpose of this article is to summarize recent advancements in IGRT and discussed various practical issues related to the implementation of the new imaging techniques available to radiation ...

The development of computer-based image guidance has allowed stereotactic radiosurgery and radiotherapy to be freed from the constraints imposed by the stereotactic frames once required for intracranial radiosurgery. This freedom has led to the application of radiosurgery to targets outside the brain. In this paper, we briefly review the technologies, treatment parameters, and clinical outcomes of radiosurgical treatment for spinal pathology, including metastatic tumors and rare but challenging lesions such as arteriovenous malformations and benign tumors. A special emphasis is put on the newest development, fiducial-less robotic radiosurgery. Spinal radiosurgery is associated with excellent rates of tumor control and pain relief with a good dose sparing of the highly sensitive spinal cord. Further research is required to optimize treatment strategies and to assess clinical benefits and toxicity in the long term.

The goal of this work was to evaluate the efficacy of various image-guided adaptive radiation therapy ͑IGART͒ techniques to deliver and escalate dose to the prostate in the presence of geometric uncertainties. Five prostate patients with 15-16 treatment CT studies each were retrospectively analyzed. All patients were planned with an 18 MV, six-field conformal technique with a 10 mm margin size and an initial prescription of 70 Gy in 35 fractions. The adaptive strategy employed in this work for patient-specific dose escalation was to increase the prescription dose in 2 Gy-perfraction increments until the rectum normal tissue complication probability ͑NTCP͒ reached a level equal to that of the nominal plan NTCP ͑i.e., iso-NTCP dose escalation͒. The various target localization techniques simulated were: ͑1͒ daily laser-guided alignment to skin tattoo marks that represents treatment without image-guidance, ͑2͒ alignment to bony landmarks with daily portal images, and ͑3͒ alignment to the clinical target volume ͑CTV͒ with daily CT images. Techniques ͑1͒ and ͑3͒ were resimulated with a reduced margin size of 5 mm to investigate further dose escalation. When delivering the original clinical prescription dose of 70 Gy in 35 fractions, the "CTV registration" technique yielded the highest tumor control probability ͑TCP͒ most frequently, followed by the "bone registration" and "tattoo registration" techniques. However, the differences in TCP among the three techniques were minor when the margin size was 10 mm ͑ഛ1.1% ͒. Reducing the margin size to 5 mm significantly degraded the TCP values of the "tattoo registration" technique in two of the five patients, where a large difference was found compared to the other techniques ͑ഛ11.8% ͒. The "CTV registration" technique, however, did maintain similar TCP values compared to their 10 mm margin counterpart. In terms of normal tissue sparing, the technique producing the lowest NTCP varied from patient to patient. Reducing the margin size seemed the only sure way to reduce the NTCP significantly, irrespective of the IGART technique employed. In escalating the dose with the iso-NTCP constraint, the largest average gain in dose was observed with the "tattoo registration" technique, followed by the "CTV registration" and "bone registration" techniques. This is attributed to the fact that in three of the five patients, the "tattoo registration" technique yielded the lowest NTCP, hence a greater window of opportunity to escalate the dose was possible with this technique. However, the variation among the five patients was also largest with the "tattoo registration" technique where, in the case of one patient, the required dose actually needed to be below the original prescription dose of 70 Gy to satisfy the iso-NTCP constraint. This was not the case with the "CTV registration" technique where positive and similar dose escalation was allowed on all five patients. Based on these data, an attractive dose escalation strategy may be to implement the "CTV registration" technique ͑for consistent dosimetric coverage͒ for daily target localization in combination with a margin reduction ͑for increased normal tissue sparing͒.

Background and Objective: In the last decade, the field of medicine has ingressed into a new era of technological advancements, driven by an ever increasing demand to reduce patient costs and risks, improve patient safety, efficiency, and surgical outcomes. The need for alternative ways of training and surgery is stronger than ever. Virtual reality based training and surgery systems hold significant promise in this direction. However, development of realistic virtual surgery systems for invasive orthopaedic surgical procedures remains one of the most challenging problems in the field of virtual reality based surgery and training because of the involvement of complex musculoskeletal structures and surgical tools. In recent years, some advances have been made in this area but they have limited practical scope because of their support for small range of procedures and training scenarios. The tools developed so far are either restricted in their ability or follow non patient-centric approaches and hence, cannot be considered viable alternatives to the conventional techniques for invasive orthopaedic surgery and training. In this paper, we discuss the challenges and complexities associated with the development of a virtual reality based system for orthopaedic training and surgery, and present our image guidance based navigation system, developed as part of our ongoing research initiative to build a comprehensive tool for realistic virtual orthopedic surgery and training.

Advances in conformal radiation therapy and advancements in pre-clinical radiotherapy research have recently stimulated the development of precise micro-irradiators for small animals such as mice and rats. These devices are often kilovolt x-ray radiation sources combined with high-resolution CT imaging equipment for image guidance, as the latter allows precise and accurate beam positioning. This is similar to modern human radiotherapy practice. These devices are considered a major step forward compared to the current standard of animal experimentation in cancer radiobiology research. The availability of this novel equipment enables a wide variety of pre-clinical experiments on the synergy of radiation with other therapies, complex radiation schemes, sub-target boost studies, hypofractionated radiotherapy, contrast-enhanced radiotherapy and studies of relative biological effectiveness, to name just a few examples. In this review we discuss the required irradiation and imaging capabilities of small animal radiation research platforms. We describe the need for improved small animal radiotherapy research and highlight pioneering efforts, some of which led recently to commercially available prototypes. From this, it will be clear that much further development is still needed, on both the irradiation side and imaging side. We discuss at length the need for improved treatment planning tools for small animal platforms, and the current lack of a standard therein. Finally, we mention some recent experimental work using the early animal radiation research platforms, and the potential they offer for advancing radiobiology research.

Objective. – Percutaneous drainage of pelvic abscesses may be challenging using a conventional anterior route because of overlying intestinal or vascular structures. Although, the posterior transgluteal route is not commonly performed, it may provide a safer approach when the conventional anterior route is not feasible. We retrospectively analyzed our experience in transgluteal percutaneous drainage of pelvic abscesses in 21 patients

Brachytherapy has consistently provided a very conformal radiation therapy modality. Over the last two decades this has been associated with significant improvements in imaging for brachytherapy applications (prostate, gynecology), resulting in many positive advances in treatment planning, application techniques and clinical outcome. This is emphasized by the increased use of brachytherapy in Europe with gynecology as continuous basis and prostate and breast as more recently growing fields. Image guidance enables exact knowledge of the applicator together with improved visualization of tumor and target volumes as well as of organs at risk providing the basis for very individualized 3D and 4D treatment planning. In this commentary the most important recent developments in prostate, gynecological and breast brachytherapy are reviewed, with a focus on European recent and current research aiming at the definition of areas for important future research. Moreover the positive impact of GE...

Computer-aided implant dentistry (CAID), the direct translation of preoperative prosthetic planning to the operating theater by means of image guidance technologies, is a novel application of computer aided surgery (CAS). This work deals with the application of a modular software system for computer-aided interventions to CAID. The system is based on AVW-2.5, a software library dedicated to biomedical image processing, and a custom interface for communication with an optical tracker. A specific CAID toolset was also manufactured. We assessed the performance of two different point-based registration algorithms for this specific application of computer-aided preprosthetic surgery on several jaw models. The fiducial localization error (FLE) achievable with our system was found to be 0.7 mm, the fiducial registration error (FRE) accounted for 0.7 mm, and the target registration error TRE (the overall navigation accuracy) was found to be 1.3 mm. Since these results compare well to the resolution of the high-resolution computed tomography scan used we consider the precision of our system to be sufficient. Future enhancements of our system include the implementation of a medical augmented reality display system and the customization of the software package for exploration of other clinical applications of CAS.

Traditional oncology distinguishes between two separate and incommensurable states in the evolution of solid malignancies: the localized disease, which is curable; and the disseminated status, which is per se palliative. Recently, a huge body of evidence suggests a fundamental change in the understanding of cancer, indicating an intermediate state in the trajectory of solid malignancies: the oligometastatic state. The following review will critically analyse existing hypotheses and facts from the basic sciences and try to contextualize it in regard to the clinical evidence available to date. Consecutively, it will try to draw possible clinical consequences for application of radiotherapy in this specific clinical scenario.

Background and purpose: X-ray volumetric imaging system (XVI) mounted on a linear accelerator is available for image guidance applications. In preparation for clinical implementation, phantom and patient imaging studies were conducted to determine the irradiation parameters that would trade-off image quality, patient dose and scanning time.

Occipital condyle (OC) screws are an alternative cephalad fixation point in occipitocervical fusion. Safe placement of occipital, C1 lateral mass, and C2 pars screws have been described previously, but not OC screws. The craniocervical junction is complex, and a thorough understanding of the anatomy is needed.

To compare the residual setup errors measured with ExacTrac X-ray 6 degree-of-freedom (6D) and cone-beam computed tomography (CBCT) for a head phantom and patients receiving intracranial non-invasive fractionated stereotactic radiotherapy (SRT).Setup data were collected on a Novalis Tx treatment unit for an anthropomorphic head phantom and 18 patients with intracranial tumors. Initial corrections were determined and corrected with the ExacTrac system only, and then the residual setup error was determined by means of three different procedures. These procedures included registrations of ExacTrac X-ray images with the corresponding digitally reconstructed radiographs (DRRs) using the ExacTrac 6D fusion, and registrations of CBCT images with the planning CT using both online 3D fusion and offline 6D fusion. The difference in residual setup errors between ExacTrac system and CBCT was computed. The impact of rotations on the difference was evaluated.A modest difference in residual setup errors was found between ExacTrac system and CBCT. The root-mean-square (RMS) of the differences observed for translations was typically <0.5 mm for phantom, and <1.5 mm for patients, respectively. The RMS of the differences for rotation(s) was however <0.2 degree for phantom, and <1.0 degree for patients, respectively. The impact of rotation on the setup difference was minor but not negligible.This study indicates that there is a general agreement between ExacTrac system and CBCT.

Based on case studies in minimally invasive surgery, the paper investigates how head-mounted displays (HMDs) transform action and perception in the operating theater. In particular, it discusses the methods and addresses the obstacles that are linked to the attempt to eliminate the divide between vision and visualization by augmenting the surgeon’s field of view with images. Firstly, it analyzes how HMDs change the way images are integrated into the surgical workflow by looking at the modalities of image production, transmission, and reception of HMDs. Secondly, it examines how HMDs change where and in which situations images are used by looking at screen architectures in minimally invasive surgery. Thirdly, it discusses the impact of HMD-based practice on action, perception, and decision-making, by examining how HMDs challenge the existing techniques and routines of surgical practice and, therefore, call for a new type of image and application-based expertise.

Image-guided interventional pain procedures are one of the keystones of pain medicine. The choice of the most appropriate imaging technique is pivotal to ensure both technique's success and patients safety. Aim of this review is to present and discuss published evidence on the best imaging guidance technology for those procedures where more than one imaging option is available. Peer reviewed published evidence on the use of fluoroscopy, ultrasound, and computer tomography to perform epidural injections, facetjoints injections, medial branch RF denervations and stellate ganglion block will be presented, and advantages and disadvantages for each technique will be discussed.

Summary Cerebrospinal fluid rhinorrhea occurs as a result of abnormal communication between the subarachnoid space and the pneumatized portion of the skull base, the paranasal sinuses and the middle ear. Conservative measures may be sufficient in the management of cerebrospinal fluid rhin- orrhea, but, in some cases, surgical treatment may be required. Transnasal endoscopic techniques are constantly being used in

Minimally invasive techniques for the treatment of some spinal diseases are percutaneous treatments, proposed before classic surgery. By using imaging guidance, one can significantly increase accuracy and decrease complication rates. This review report physiopathology and discusses indications, methods, complications and results of performing these techniques on the spine, including different level (cervical, thoracic, lumbar and sacroiliac) and different kind of treatments (nerve block, disc treatment and bone treatment). Finally the present article also reviews current literature on the controversial issues involved.

In liver stereotactic body radiotherapy, reduction of normal tissue irradiation requires daily image guidance. This is typically accomplished by imaging a surrogate to the tumor. The surrogate is often an implanted metal fiducial marker. There are few reports addressing the specific risks of hepatic fiducial marker implantation. These risks are assumed to be similar to percutaneous liver biopsies which are associated with a 1-4% complication rate -almost always pain or bleeding. To the best of our knowledge, we present the first case of such a fiducial marker migrating to the heart.

Image guidance promises to improve targeting accuracy and broaden the scope of medical procedures performed with needles. This paper takes a step toward automating the guidance of a flexible tipsteerable needle as it is inserted into human tissue. We build upon a previously proposed nonholonomic model of needles that derive steering from asymmetric bevel forces at the tip. The bevel-tip needle is inserted and rotated at its base in order to steer it in six degrees of freedom. As a first step for control, we show that the needle tip can be automatically guided to a planar slice of tissue as it is inserted. Our approach keeps the physician in the loop to control insertion speed. The distance of the needle tip position from the plane of interest is used to drive an observer-based feedback controller which we prove is locally asymptotically stable. Numerical simulations demonstrate a large domain of attraction and robustness of the controller in the face of parametric uncertainty and measurement noise. Physical experiments with tip-steerable Nitinol needles inserted into a transparent plastisol tissue phantom under stereo image guidance validate the effectiveness of our approach.

Background Image-guidance systems allow accurate interfractional repositioning of IMRT treatments, however, these may require up to 15 minutes. Therefore intrafraction motion might have an impact on treatment precision. 3D geometric data regarding intrafraction prostate motion are rare; we therefore assessed its magnitude with pre- and post-treatment fiducial-based imaging with cone-beam-CT (CBCT). Methods 39 IMRT fractions in 5 prostate cancer patients after125I-seed implantation were evaluated. Patient position was corrected based on the125I-seeds after pre-treatment CBCT. Immediately after treatment delivery, a second CBCT was performed. Differences in bone- and fiducial position were measured by seed-based grey-value matching. Results Fraction time was 13.6 ± 1.6 minutes. Median overall displacement vector length of125I-seeds was 3 mm (M = 3 mm, Σ = 0.9 mm, σ = 1.7 mm; M: group systematic error, Σ: SD of systematic error, σ: SD of random error). Median displacement vector of bony structures was 1.84 mm (M = 2.9 mm, Σ = 1 mm, σ = 3.2 mm). Median displacement vector length of the prostate relative to bony structures was 1.9 mm (M = 3 mm, Σ = 1.3 mm, σ = 2.6 mm). Conclusion Overall displacement vector length during an IMRT session is Positioning devices reducing intrafraction bony displacements can further reduce overall intrafraction motion. Intrafraction prostate motion relative to bony structures is IMRT duration.

Background: Extrapulmonary tuberculosis is one of the great mimickers of medicine, and often masquerades as malignancy. As a result, patients may be referred to oncologists and surgeons for further evaluation and management, delaying the institution of appropriate anti-tuberculous drug therapy.

Stereotaxy is a neurosurgical technique that can take several hours to reach a specific target, typically utilizing a mechanical frame and guided by preoperative imaging. An error in any one of the numerous steps or deviations of the target anatomy from the preoperative plan such as brain shift (up to 20 mm), may affect the targeting accuracy and thus the treatment effectiveness. Moreover, because the procedure is typically performed through a small burr hole opening in the skull that prevents tissue visualization, the intervention is basically "blind" for the operator with limited means of intraoperative confirmation that may result in reduced accuracy and safety. The presented system is intended to address the clinical needs for enhanced efficiency, accuracy, and safety of image-guided stereotactic neurosurgery for Deep Brain Stimulation (DBS) lead placement. The work describes a magnetic resonance imaging (MRI)-guided, robotically actuated stereotactic neural intervention system for deep brain stimulation procedure, which offers the potential of reducing procedure duration while improving targeting accuracy and enhancing safety. This is achieved through simultaneous robotic manipulation of the instrument and interactively updated in situ MRI guidance that enables visualization of the anatomy and interventional instrument. During simultaneous actuation and imaging, the system has demonstrated less than 15% signalto-noise ratio (SNR) variation and less than 0.20% geometric distortion artifact without affecting the imaging usability to visualize and guide the procedure. Optical tracking and MRI phantom experiments streamline the clinical workflow of the prototype system, corroborating targeting accuracy with 3-axis root mean square error 1.38 ± 0.45 mm in tip position and 2.03 ± 0.58 • in insertion angle.

The development of the CyberKnife technology, a combination of image guidance and industrial robotics, led to a paradigm shift in radiosurgery. Materials and methods The CyberKnife Robotic Radiosurgery System consists of a 6-MV compact LINAC mounted on a computer-controlled robotic manipulator capable of 6 degrees of freedom, with a dedicated image-guidance system which acquires X-ray images during treatment. Apart from standard neurosurgical indications (i.e., acoustic neurinomas, meningiomas, brain metastases, etc.) radiosurgical applications are currently evolving to include extracranial indications such as tumors of the spine, pancreas, lung, and liver. We reviewed the indications and outcomes in the first 1,000 patients treated in the CyberKnife Center Munich. Singledose treatment was chosen because published clinical studies have demonstrated high efficacy and low morbidity for intracranial and spinal tumors. A recent development in radiosurgery is breathing-triggered real-time correction for respiratory motion of tumors, which makes it possible to apply radiosurgical doses to moving targets. CyberKnife treatment is designed to be delivered on an outpatient basis, mostly consisting of a single treatment session lasting between 60 and 90 min. High quality imaging is of utmost importance for successful radiosurgical applications. For example, highfield MRI, multislice CT's, PET and PET-CT imaging data must be integrated in the planning phase for optimal target definition.

The work presented herein describes our methods and results for predicting, measuring and correcting geometric distortions in a 3 T clinical magnetic resonance ͑MR͒ scanner for the purpose of image guidance in radiation treatment planning. Geometric inaccuracies due to both inhomogeneities in the background field and nonlinearities in the applied gradients were easily visualized on the MR images of a regularly structured three-dimensional ͑3D͒ grid phantom. From a computed tomography scan, the locations of just under 10 000 control points within the phantom were accurately determined in three dimensions using a MATLAB-based computer program. MR distortion was then determined by measuring the corresponding locations of the control points when the phantom was imaged using the MR scanner. Using a reversed gradient method, distortions due to gradient nonlinearities were separated from distortions due to inhomogeneities in the background B 0 field. Because the various sources of machine-related distortions can be individually characterized, distortions present in other imaging sequences ͑for which 3D distortion cannot accurately be measured using phantom methods͒ can be predicted negating the need for individual distortion calculation for a variety of other imaging sequences. Distortions were found to be primarily caused by gradient nonlinearities and maximum image distortions were reported to be less than those previously found by other researchers at 1.5 T. Finally, the image slices were corrected for distortion in order to provide geometrically accurate phantom images.

Kilovoltage cone-beam computerized tomography ͑kV-CBCT͒ systems integrated into the gantry of linear accelerators can be used to acquire high-resolution volumetric images of the patient in the treatment position. Using on-line software and hardware, patient position can be determined accurately with a high degree of precision and, subsequently, set-up parameters can be adjusted to deliver the intended treatment. While the patient dose due to a single volumetric imaging acquisition is small compared to the therapy dose, repeated and daily image guidance procedures can lead to substantial dose to normal tissue. The dosimetric properties of a clinical CBCT system have been studied on an Elekta linear accelerator ͑Synergy ® RP, XVI system͒ and additional measurements performed on a laboratory system with identical geometry. Dose measurements were performed with an ion chamber and MOSFET detectors at the center, periphery, and surface of 30 and 16-cm-diam cylindrical shaped water phantoms, as a function of x-ray energy and longitudinal field-of-view ͑FOV͒ settings of 5,10,15, and 26 cm. The measurements were performed for full 360°CBCT acquisition as well as for half-rotation scans for 120 kVp beams using the 30-cm-diam phantom. The dose at the center and surface of the body phantom were determined to be 1.6 and 2.3 cGy for a typical imaging protocol, using full rotation scan, with a technique setting of 120 kVp and 660 mAs. The results of our measurements have been presented in terms of a dose conversion factor f CBCT , expressed in cGy/ R. These factors depend on beam quality and phantom size as well as on scan geometry and can be utilized to estimate dose for any arbitrary mAs setting and reference exposure rate of the x-ray tube at standard distance. The results demonstrate the opportunity to manipulate the scanning parameters to reduce the dose to the patient by employing lower energy ͑kVp͒ beams, smaller FOV, or by using half-rotation scan.

Methods and Materials: Image-guided stereotactic body radiotherapy was performed in 28 patients (89 fractions) with medically inoperable Stage T1-T2 non-small-cell lung carcinoma. The targets from the CBCT and planning data set (helical or four-dimensional CT) were matched on-line to determine the couch shift required for target localization. Matching based on the bony anatomy was also performed retrospectively. Verification of target localization was done using either megavoltage portal imaging or CBCT imaging; repeat CBCT imaging was used to assess the intrafraction tumor position. Results: The mean three-dimensional tumor motion for patients with upper lesions (n ‫؍‬ 21) and mid-lobe or lower lobe lesions (n ‫؍‬ 7) was 4.2 and 6.7 mm, respectively. The mean difference between the target and bony anatomy matching using CBCT was 6.8 mm (SD, 4.9, maximum, 30.3); the difference exceeded 13.9 mm in 10% of the treatment fractions. The mean residual error after target localization using CBCT imaging was 1.9 mm . The mean intrafraction tumor deviation was significantly greater (5.3 mm vs. 2.2 mm) when the interval between localization and repeat CBCT imaging (n ‫؍‬ 8) exceeded 34 min. Conclusion: In-room volumetric imaging, such as CBCT, is essential for target localization accuracy in lung stereotactic body radiotherapy. Imaging that relies on bony anatomy as a surrogate of the target may provide erroneous results in both localization and verification.

Purpose: To determine whether prostate cancer local recurrence after radiation therapy (RT) occurs at the site of primary tumor by retrospectively comparing the tumor location on pre-RT and post-RT magnetic resonance imaging (MRI) and using step-section pathology after salvage radical prostatectomy (SRP) as the reference standard. Methods and Materials: Nine patients with localized prostate cancer were treated with intensity modulated RT (69-86.4 Gy), and had pre-RT and post-RT prostate MRI, biopsy-proven local recurrence, and SRP. The location and volume of lesions on pre-RT and post-RT MRI were correlated with step-section pathology findings. Tumor foci >0.2 cm 3 and/or resulting in extraprostatic disease on pathology were considered clinically significant. Results: All nine significant tumor foci (one in each patient; volume range, 0.22-8.63 cm 3 ) were detected both on pre-RT and post-RT MRI and displayed strikingly similar appearances on pre-RT and post-RT MRI and stepsection pathology. Two clinically insignificant tumor foci (#0.06 cm 3 ) were not detected on imaging. The ratios between tumor volumes on pathology and on post-RT MRI ranged from 0.52 to 2.80. Conclusions: Our study provides a direct visual confirmation that clinically significant post-RT local recurrence occurs at the site of primary tumor. Our results are in agreement with reported clinical and pathologic results and support the current practice of boosting the radiation dose within the primary tumor using imaging guidance. They also suggest that monitoring of primary tumor with pre-RT and post-RT MRI could lead to early detection of local recurrence amenable to salvage treatment. Ó 2007 Elsevier Inc.

Parapneumonic effusions continue to be a significant source of morbidity and mortality. Treatment at earlier stages before fibrous peel and loculations occur has a much better prognosis. Using image guidance, addition of intracavitary fibrinolytic instillation, close follow-up with drainage of residual or new collections are some of the other factors that improve prognosis. In this article, we discussed treatment strategies, percutaneous management of parapneumonic effusions, its alternatives and results.

Bilder zeigen nicht nur, sondern fordern zu Handlungen auf und bedingen diese. Die zunehmende Verschaltung von Technologien, Körpern und Objekten durch visuelle Schnittstellen wie Graphical User Interfaces, Touchscreens oder Augmented-Reality-Anwendungen macht Betrachtende zuallererst zu Benutzerinnen und Benutzern. Derartige Verknüpfungen von Bildmedium und Operation finden sich etwa in medizinischer Planungssoftware, visuell navigierten Drohneneinsätzen und Rapid-Manufacturing-Verfahren in Architektur und Produktentwicklung. Planen, Navigieren und Intervenieren sind nur mehr in Kenntnis eines entsprechenden handlungsbezogenen Bildwissens durchführbar. Um die untrennbare Einheit von Darstellungs- und Handlungslogik in bildgeführten Operationen aufzuzeigen, bedarf es einer disziplinenübergreifenden Reflexion. Unter dem Begriff ›image guidance‹ diskutiert der vorliegende Band die ästhetischen, operationalen und epistemischen Bedingungen, unter denen Visualisierungen zu Medien der Steuerung und Handlungsanleitung werden. Die Beiträge analysieren ›image guidance‹ als Darstellungs-, Wahrnehmungs- und Handlungsprinzip in Architektur, Gestaltung, Medizin, Computerspiel, Militär, Kulturgeschichte und Raumfahrt. Mit Beiträgen von Aud Sissel Hoel, Sabine Ammon, Helena Mentis, Derek Gregory, Pasi Väliaho und Anderen.

Purpose: To determine the total setup error and the required planning target volume (PTV) margin for prostate bed without image guided radiotherapy (IGRT), and to demonstrate the feasibility and dosimetric benefit of IGRT post prostatectomy using surgical clips. Materials and methods: Seventeen patients were treated with intensity modulated radiotherapy (IMRT) to the prostate bed with a 1 cm PTV margin. Three-dimensional shifts of the surgical clips inside the prostate bed were measured with respect to the isocenter from 364 orthogonal kV image pairs, and the total setup error was calculated to determine the required PTV margin. Alternative IMRT plans using 5 mm or 1 cm PTV expansion were generated and compared for rectal and bladder sparing. Results: Surgical clips were reproducibly and reliably identified. The mean (standard deviation) shifts in the left-right (LR), superior-inferior (SI), and anterior-posterior (AP), axes were: À0.1 mm (1.7 mm), 0.6 mm (2.4 mm), and À2.1 mm (2.6 mm), respectively. The required PTV margins were calculated to be 6, 8, and 9 mm in the LR, AP, and SI axis, respectively. A PTV expansion of 5 mm, compared to 1 cm, significantly reduced V65 Gy to the rectum by 10%. Conclusions: In the absence of IGRT, a non-uniform PTV margin of 6 mm LR, 8 mm AP, and 9 mm SI should be considered. Use of clips as fiducial markers can decrease the total setup error, enable a smaller PTV margin, and improve rectal sparing.

Purpose: Magnetic resonance imaging (MRI) provides superior visualization of the prostate and surrounding anatomy, making it the modality of choice for imaging the prostate gland. This pilot study was performed to determine the feasibility and dosimetric quality achieved when placing high-dose-rate prostate brachytherapy catheters under MRI guidance in a standard "closed-bore" 1.5T scanner.

The conventional method of inserting pedicle screws (ie, plain radiography, standard 2D fluoroscopy, direct palpation) was found to be less accurate with cortical violation ranging from 10 to 50%. Small and variable anatomy of the cervical and thoracic spine poses a particular challenge, and it can lead to a devastating neurovascular complication. With recent advances in imaging technologies, such as computed tomography-based image guidance and isocentric C-arm fluoroscopy, surgeons are now able to visualize hidden pedicles and reduce screw misplacement. Using these various navigation systems, the rate of pedicle screw perforation can be decreased to less than 10% and potentially eliminate clinically significant complications and revision surgeries. Semin Spine Surg 19:78-86

Background and Objective: In the last decade, the field of medicine has ingressed into a new era of technological advancements, driven by an ever increasing demand to reduce patient costs and risks, improve patient safety, efficiency, and surgical outcomes. The need for alternative ways of training and surgery is stronger than ever. Virtual reality based training and surgery systems hold significant promise in this direction. However, development of realistic virtual surgery systems for invasive orthopaedic surgical procedures remains one of the most challenging problems in the field of virtual reality based surgery and training because of the involvement of complex musculoskeletal structures and surgical tools. In recent years, some advances have been made in this area but they have limited practical scope because of their support for small range of procedures and training scenarios. The tools developed so far are either restricted in their ability or follow non patient-centric approaches and hence, cannot be considered viable alternatives to the conventional techniques for invasive orthopaedic surgery and training. In this paper, we discuss the challenges and complexities associated with the development of a virtual reality based system for orthopaedic training and surgery, and present our image guidance based navigation system, developed as part of our ongoing research initiative to build a comprehensive tool for realistic virtual orthopedic surgery and training.

Ultrasound (US) image guidance systems used in radiotherapy are typically calibrated for soft tissue applications, thus introducing errors in depth-from-transducer representation when used in media with a different speed of sound propagation (e.g. fat). This error is commonly referred to as the speed artifact. In this study we utilized a standard US phantom to demonstrate the existence of the speed

Background: Image-guidance systems allow accurate interfractional repositioning of IMRT treatments, however, these may require up to 15 minutes. Therefore intrafraction motion might have an impact on treatment precision. 3D geometric data regarding intrafraction prostate motion are rare; we therefore assessed its magnitude with pre-and post-treatment fiducial-based imaging with cone-beam-CT (CBCT).

Minimally invasive techniques for the treatment of some spinal diseases are percutaneous treatments, proposed before classic surgery. By using imaging guidance, one can significantly increase accuracy and decrease complication rates. This review report physiopathology and discusses indications, methods, complications and results of performing these techniques on the spine, including different level (cervical, thoracic, lumbar and sacroiliac) and different kind of treatments (nerve block, disc treatment and bone treatment). Finally the present article also reviews current literature on the controversial issues involved.