Background To evaluate the effect of the 3D radiation field design on normal tissues compared with commonly used appositional fields in patients with lumbar spine metastases. Methods and materials Ten comparative treatment plans for radiation of lumbar spine metastases were compared for posterior and anterior- posterior fields with 3D plans. Results The PTV coverage in all comparative plans was similar. V 15 of the bowel in 3D, AP-PA and PA plans was 6.7 Gy (SD 6.47), 39.8 Gy (SD 11.4) and 37.3 Gy (SD15.7), respectively (p < 0.0001). The mean dose to both kidneys was 9.6 Gy (SD 4.8), 4.1 Gy (SD 3.9) and 4.6 Gy (SD 4.4) for appropriate plans (p = 0.002). Maximal dose to the spinal cord was 30.6 Gy (SD 2.1), 33.1 Gy (SD 9.8) and 37.7 Gy (SD 2) for 3D, AP-PA and PA plans. Conclusion 3D conformal treatment planning of lumbar vertebral metastases was significantly better in term of bowel and spinal cord exposure compared to AP-PA and PA techniques. The exposure of the kidneys in 3D plans, while greater than in the comparative plans, did not violate accepted dose-volume thresholds.

Little attention has been paid to the fact that intensity modulated radiation therapy (IMRT) techniques do not easily enable treatment with opposed beams. Three treatment plans (3 D conformal, IMRT, and combined (anterior-posterior-posterio-anterior (AP-PA) + IMRT) of 7 patients with centrally-located lung cancer were compared for exposure of lung, spinal cord and esophagus. Combined IMRT and AP-PA techniques offer better lung tissue sparing compared to plans predicated solely on IMRT for centrally-located lung tumors.

Extracting structure of interest from medical images is an important yet tedious work. Due to the image quality, the shape knowledge is widely used for assisting and constraining the segmentation process. In many previous works, shape knowledge was incorporated by first constructing a shape space from training cases, and then constraining the segmentation process to be within the learned shape space. However, such an approach has certain limitations due to the number of variations, eigen-shapemodes, that can be captured in the learned shape space. Moreover, small scale shape variances are usually overwhelmed by those in the large scale, and therefore the local shape information is lost. In this work, we present a multiscale representation for shapes with arbitrary topology, and a fully automatic method to segment the target organ/tissue from medical images using such multiscale shape information and local image features. First, we handle the problem of lacking eigen-shapemodes by providing a multiscale shape representation using the wavelet transform. Consequently, the shape variances existing in the training shapes captured by the statistical learning step are also represented at various scales. Note that by doing so, one can greatly enrich the eigen-shapemodes as well as capture small scale shape changes. Furthermore, in order to make full use of the training information, not only the shape but also the grayscale training images are utilized in a multi-atlas initialization procedure. By combining such initialization with the multiscale shape knowledge, we perform segmentation tests for challenging medical data sets where the target objects have low contrast and sharp corner structures, and demonstrate the statistically significant improvement obtained by employing such multiscale representation, in representing shapes as well as the overall shape based segmentation tasks.

In breast cancer, nodal irradiation has become routine, but adds time and creates concerns for field overlap if the "match" is not accurate. We developed a technique to address these issues by using only one isocenter for both areas. Tangents are designed at simulation. The isocenter is then shifted to the upper border of the breast using a straightforward geometrical calculation. After determining the new isocenter, fields are recreated wherein the tangents are treated with a quarter beam and the supraclavicular field fashioned with a half-beam block. The gantry, collimator, and couch angles of the supraclavicular field are adjusted to achieve an accurate match. Ten patients were evaluated. Doses to the spinal cord and brachial plexus were lowered relative to conventional techniques. The hot spots were not augmented. In comparison with standard arrangements, setup time decreased. Accurate matching was consistently achieved and verified by portal imaging. A new approach for treating the supraclavicular fossa is easily executed. Advantages include negligible doses to the critical neural structures (i.e., spinal cord and brachial plexus), optimized matchline, and reduced setup time.

Treatment of arteriovenous malformations (AVM) of the brain is challenging due to the size and location of the nidus-proper and its proximity to the cerebrovascular circulation. Recent advances in catheter techniques and new embolization materials such as Onyx (a liquid agent that is less adhesive and slowly polymerizing) have increased the probability of achieving obliteration. When planning radiosurgical cases following such embolization, however, one must be cognizant of the distortions introduced by this novel substance on imaging studies. A sample of Onyx was irradiated to define the attenuation per mm thickness. The difference in attenuation compared to water was determined. Dose calculations were performed using 3 methods of inhomogeneity corrections. Homogeneous calculations were compared to "standard'' heterogeneity corrections and to "modified'' heterogeneity corrections by assigning individual electron densities to the normal brain and the Onyx. The difference between the attenuation of water in comparison to the Onyx was approximately 3% for beam energy of 6 MV. Best calculation results were achieved when using the modified inhomogeneity corrections which were based on the actual attenuation of the Onyx. The use of Onyx caused significant image artifact on MR and especially CT. As such, a correction must be manually introduced into the planning system to account for this potential error. Otherwise, dose calculation may be unreliable and could have dire consequences for patients receiving high doses of radiotherapy.

Background: Local control of brain metastasis (BM) is increased by whole-brain irradiation (WBI) with or without resection. However, patients who have new or recurrent BM after WBI and undergo resection are left without adjuvant therapy options. Methods: We performed a retrospective analysis evaluating the addition of a stereotactic radiosurgery (SRS) boost to the resection cavity both as an adjuvant and salvage procedure. Results: For the period from May 2005 to March 2007, we identified 16 patients. Nine patients were female and the median age for the entire group was 59.6 years (range 33.5-73.5) and median KPS 90(60-100) at the time of SRS. Time to SRS after surgical removal was 2-16.9 weeks (median 6.5) and the overall median follow-up was 7.6 months (3.0-26.2). During the follow-up period, 1 patient recurred locally and was referred for additional surgery. Two patients with primary breast cancer developed leptomeningeal spread. Both of these patients as well as all other patients have remained free of local recurrence thus far. No treatment-related toxicity (as defined by imaging or clinical criteria) has been observed. Distant metastases occurred in 3 patients. Conclusion: These preliminary results demonstrate feasibility of post-resection SRS in selected patients with outstanding local tumor control. Larger prospective BM studies and longer follow-up are needed to determine the role of post-resection SRS (to the cavity) as salvage therapy in patients with BM. Copyright (C) 2010 S. Karger AG, Basel

Purpose: In radiation therapy there is a need to accurately know the location of the target in real time. A novel radioactive tracking technology has been developed to answer this need. The technology consists of a radioactive implanted fiducial marker designed to minimize migration and a linac mounted tracking device. This study measured the static and dynamic accuracy of the new tracking technology in a clinical radiation therapy environment.Methods and Materials: The tracking device was installed on the linac gantry. The radioactive marker was located in a tissue equivalent phantom. Marker location was measured simultaneously by the radioactive tracking system and by a Microscribe G2 coordinate measuring machine (certified spatial accuracy of 0.38 mm). Localization consistency throughout a volume and absolute accuracy in the Fixed coordinate system were measured at multiple gantry angles over volumes of at least 10 cm in diameter centered at isocenter. Dynamic accuracy was measured with the marker located inside a breathing phantom.Results: The mean consistency for the static source was 0.58 mm throughout the tested region at all measured gantry angles. The mean absolute position error in the Fixed coordinate system for all gantry angles was 0.97 mm. The mean real-time tracking error for the dynamic source within the breathing phantom was less than 1 mm.Conclusions: This novel radioactive tracking technology has the potential to be useful in accurate target localization and real-time monitoring for radiation therapy. (C) 2010 Elsevier Inc.

During the past half-century, the cornerstone of treatment for brain metastases has been whole brain irradiation (WBI). WBI has multiple salutary effects including rapid relief of neurological signs and symptoms as well as enhanced local control. Unfortunately, WBI may also engender side effects including memory deficits and decrements in quality of life. Since memory control is thought to be mediated by the hippocampus, attention has been turned to whole brain radiotherapeutic techniques that allow sparing of the hippocampus. In order to be able to minimize dose deposition within the hippocampus, clinicians must be able to confidently identify that structure. However, manually tracing out the hippocampus for each patient is time consuming and subject to individual bias. To this end, an automated method can be very useful for such a task. In this paper, we present a method for extracting the hippocampus from magnetic resonance imaging (MRI) data. Our method is based on a multi-scale shape representation using statistical learning in conjunction with spherical wavelets for shape representation. Indeed, the hippocampus shape information is statistically learned by the algorithm and is further utilized to extract a hippocampus from the given 3D MR image. Results are shown on data-sets provided by Brigham and Women's Hospital.

PURPOSE:Although chemoradiotherapy was considered the standard adjuvant treatment for gastric cancer, a recent Phase III trial (Medical Research Council Adjuvant Gastric Infusional Chemotherapy [MAGIC]) did not include radiotherapy in the randomization scheme because it was considered expendable. Given radiotherapy's potential, efforts needed to be made to optimize its use for treating gastric cancer. We assessed whether intensity-modulated radiotherapy (IMRT) could improve upon our published results in patients treated with three-dimensional (3D) conformal therapy. METHODS AND MATERIALS:Fourteen patients with adenocarcinoma of the stomach were treated with adjuvant chemoradiotherapy using a noncoplanar four-field arrangement. Subsequently, a nine-field IMRT plan was designed using a CMS Xio IMRT version 4.3.3 module. Two IMRT beam arrangements were evaluated: beam arrangement 1 consisted of gantry angles of 0 degrees , 53 degrees , 107 degrees , 158 degrees , 204 degrees , 255 degrees , and 306 degrees . Beam arrangement 2 consisted of gantry angles of 30 degrees , 90 degrees , 315 degrees , and 345 degrees ; a gantry angle of 320 degrees /couch, 30 degrees ; and a gantry angle of 35 degrees /couch, 312 degrees . Both the target volume coverage and the dose deposition in adjacent critical organs were assessed in the plans. Dose-volume histograms were generated for the clinical target volume, kidneys, spine, and liver. RESULTS:Comparison of the clinical target volumes revealed satisfactory coverage by the 95% isodose envelope using either IMRT or 3D conformal therapy. However, IMRT was only marginally better than 3D conformal therapy at protecting the spine and kidneys from radiation. CONCLUSIONS:IMRT confers only a marginal benefit in the adjuvant treatment of gastric cancer and should be used only in the small subset of patients with risk factors for kidney disease or those with a preexisting nephropathy.

To the Editor: We would like to thank Lohr et al. for their insightful response to our recent article ( 1 Alani S. Soyfer V. Strauss N. et al. Limited advantages of intensity-modulated radiotherapy over 3D conformal radiation therapy in the adjuvant management of gastric cancer. Int J Radiat Oncol Biol Phys. 2009; 74: 562-566 Abstract Full Text Full Text PDF PubMed Scopus (37) Google Scholar ). They are correct in surmising that we used relatively smaller target volumes as a starting point. In general, we did not try to encompass the peritoneum despite the knowledge that this is a documented pattern of failure. Instead, we chose to comport with the guidelines of the Intergroup Study (INT) 0116 investigators in defining at-risk regions ( 2 Macdonald J.S. Smalley S.R. Benedetti J. et al. Chemoradiotherapy after surgery compared with surgery alone for adenocarcinoma of the stomach or gastroesophageal junction. N Engl J Med. 2001; 345: 725-730 Crossref PubMed Scopus (3108) Google Scholar ). IMRT for Gastric Cancer: What is its Full Potential? In Regard to Alani et al. (Int J Radiat Oncol Biol Phys 2009;74:562–566)International Journal of Radiation Oncology, Biology, PhysicsVol. 75Issue 2PreviewTo the Editor: With great interest have we read the article on intensity-modulated radiotherapy (IMRT) for gastric cancer (GC) by Alani et al.(1), and we appreciate the cautious approach, expanding the foundation for adjuvant radiochemotherapy of GC. Although we concur that the benefits of IMRT are far from being proven clinically despite a favorable view of IMRT dose-distribution characteristics (2–4) and encouraging results having been published (3, 5), we would like to draw attention to a few issues that also have to be regarded when drawing conclusions from plan-comparison studies. Full-Text PDF