Variability in computed tomography/magnetic resonance imaging (CT/MR) cranial image registration was assessed using a benchmark case developed by the Quality Assurance Review Center to credential ...institutions for participation in Children's Oncology Group Protocol ACNS0221 for treatment of pediatric low-grade glioma.
Two DICOM image sets, an MR and a CT of the same patient, were provided to each institution. A small target in the posterior occipital lobe was readily visible on two slices of the MR scan and not visible on the CT scan. Each institution registered the two scans using whatever software system and method it ordinarily uses for such a case. The target volume was then contoured on the two MR slices, and the coordinates of the center of the corresponding target in the CT coordinate system were reported. The average of all submissions was used to determine the true center of the target.
Results are reported from 51 submissions representing 45 institutions and 11 software systems. The average error in the position of the center of the target was 1.8 mm (1 standard deviation = 2.2 mm). The least variation in position was in the lateral direction. Manual registration gave significantly better results than did automatic registration (p = 0.02).
When MR and CT scans of the head are registered with currently available software, there is inherent uncertainty of approximately 2 mm (1 standard deviation), which should be considered when defining planning target volumes and PRVs for organs at risk on registered image sets.
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To evaluate a hybrid intensity modulated radiation therapy (IMRT) technique as a class solution for treatment of the intact breast.
The following five plan techniques were compared for 10 breast ...patients using dose-volume histogram analysis: conventional wedged-field tangents (Tangents), forward-planned field-within-a-field tangents (FIF), IMRT-only tangents (IMRT tangents), conventional open plus IMRT tangents (4-field hybrid), and conventional open plus IMRT tangents with 2 anterior oblique IMRT beams (6-field hybrid).
The 4-field hybrid and FIF achieved dose distributions better than Tangents and IMRT tangents. The volume of tissue outside the planning target volume receiving > or =110% of prescribed dose was largest for IMRT tangents (average 158 cc) and least for 6-field hybrid (average 1 cc); the FIF and 4-field hybrid were comparable (average 15 cc). Heart volume > or =30 Gy averaged 13 cc for all techniques, except Tangents, for which it was 32 cc. Average total lung volume > or =20 Gy was 7% for all. Contralateral breast doses were < 3% for all. Planning time for hybrid techniques was significantly less than for conventional FIF technique.
The 4-field hybrid technique is a viable class solution. The 6-field hybrid technique creates the most conformal dose distribution at the expense of more normal tissue receiving low dose.
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To report on a hybrid intensity-modulated radiation therapy (IMRT; static plus IMRT beams treated concurrently) technique for lung and esophageal patients to reduce the volume of lung treated to low ...doses while delivering a conformal dose distribution.
Treatment plans were analyzed for 18 patients (12 lung and 6 esophageal). Patients were treated with a hybrid technique that concurrently combines static (approximately two-thirds dose) and IMRT (approximately one-third dose) beams. These plans were compared with conventional three-dimensional (3D; non-IMRT) plans and all IMRT plans using custom four- and five-field arrangements and nine equally spaced coplanar beams. Plans were optimized to reduce V13 and V5 values. Dose-volume histograms were calculated for the planning target volume, heart, and the ipsilateral, contralateral, and total lung. Lung volumes V5, V13, V20, V30; mean lung dose (MLD); and the generalized equivalent uniform dose (gEUD) were calculated for each plan.
Hybrid plans treated significantly smaller total and contralateral lung volumes with low doses than nine-field IMRT plans. Largest reductions were for contralateral lung V5, V13, and V20 values for lung (-11%, -15%, -7%) and esophageal (-16%, -20%, -7%) patients. Smaller reductions were found also for 3D and four- and five-field IMRT plans. MLD and gEUDs were similar for all plan types. The 3D plans treated much larger extra planning target volumes to prescribed dose levels.
Hybrid IMRT demonstrated advantages for reduction of low-dose lung volumes in the thorax for reducing low dose to lung while also reducing the potential magnitude of dose deviations due to intrafraction motion and small field calculation accuracy.
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Purpose: To achieve more uniform dose distributions in breast cancer treatment using multiple sets of multi-leaf collimator (MLC) defined fields. Dose uniformity for many breast cancer patients can ...be significantly improved by using two or more sets of portals and the “hot” regions of a traditional treatment can be significantly reduced.
Methods and Materials: Patients for breast cancer treatment are immobilized with alpha cradle in the traditional arm-up position and have a CT scan in the treatment position. The target volume is delineated on the 5-mm thick CT slices that are obtained from the lower neck to well below the breast target volume. Medial and lateral tangential fields at conventional gantry angles are designed with the aid of digitally reconstructed radiographs (DRRs). The MLC, without collimator rotation, is used to shape the field to spare as much lung as possible. The wedges and relative weights of the beams are optimized to provide the best dose uniformity. For the patients with large dose inhomogeneity, a second set of fields is designed. The weight of the original set of fields is reduced (usually to ∼90%) so that the “original hot” regions receive the prescription dose; the second set of fields delivers a supplemental dose to the “cold” region, typically ∼10% of the total dose. The second set of fields has the same beam parameters but “treat” only the part of breast tissue that is “cool.” Presently, the design of the reduced field is an iterative process. The process can be extended to more than two sets of portals to obtain the desired dose uniformity.
Results: With 3D planning and multiple MLC fields, dose uniformity in the treatment of breast patients was improved from 7%–22% to ∼7%–15%. The volume receiving these high doses decreased significantly and shifted from the lung to the target. By keeping the gantry angles and wedges the same for the multiple fields, treatments can be delivered quickly and reliably. The internal mammary nodes (IM) can also be treated without including significant amount of lung or heart in the field.
Conclusion: Dose uniformity can be significantly improved by using this intensity modulation technique to treat certain breast patients. With these static MLC fields creating the intensity modulation, the dose uniformity to the breast can be significantly improved and the hot region in lung reduced. There is no increase in setup complexity. The small increase in treatment time is insignificant.
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The National Cancer Institute clinical cooperative groups have been instrumental over the past 50 years in developing clinical trials and evidence-based process improvements for clinical oncology ...patient care. The cooperative groups are undergoing a transformation process as we further integrate molecular biology into personalized patient care and move to incorporate international partners in clinical trials. To support this vision, data acquisition and data management informatics tools must become both nimble and robust to support transformational research at an enterprise level. Information, including imaging, pathology, molecular biology, radiation oncology, surgery, systemic therapy, and patient outcome data needs to be integrated into the clinical trial charter using adaptive clinical trial mechanisms for design of the trial. This information needs to be made available to investigators using digital processes for real-time data analysis. Future clinical trials will need to be designed and completed in a timely manner facilitated by nimble informatics processes for data management. This paper discusses both past experience and future vision for clinical trials as we move to develop data management and quality assurance processes to meet the needs of the modern trial.
Quality assurance in radiotherapy (RT) has been an integral aspect of cooperative group clinical trials since 1970. In early clinical trials, data acquisition was nonuniform and inconsistent and ...computational models for radiation dose calculation varied significantly. Process improvements developed for data acquisition, credentialing, and data management have provided the necessary infrastructure for uniform data. With continued improvement in the technology and delivery of RT, evaluation processes for target definition, RT planning, and execution undergo constant review. As we move to multimodality image-based definitions of target volumes for protocols, future clinical trials will require near real-time image analysis and feedback to field investigators. The ability of quality assurance centers to meet these real-time challenges with robust electronic interaction platforms for imaging acquisition, review, archiving, and quantitative review of volumetric RT plans will be the primary challenge for future successful clinical trials.
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Credentialing of institutions for IMRT in clinical trials Palta, Jatinder R.; Deye, James A.; Ibbott, Geoffrey S. ...
International journal of radiation oncology, biology, physics,
07/2004, Volume:
59, Issue:
4
Journal Article, Conference Proceeding
Peer reviewed
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The National Cancer Institute (NCI) clinical cooperative groups have been instrumental over the past 50 years in developing clinical trials and evidence-based clinical trial processes for ...improvements in patient care. The cooperative groups are undergoing a transformation process to launch, conduct, and publish clinical trials more rapidly. Institutional participation in clinical trials can be made more efficient and include the expansion of relationships with international partners. This paper reviews the current processes that are in use in radiation therapy trials and the importance of maintaining effective credentialing strategies to assure the quality of the outcomes of clinical trials. The paper offers strategies to streamline and harmonize credentialing tools and processes moving forward as the NCI undergoes transformative change in the conduct of clinical trials.
Radiation therapy has been integral to cancer patient care. The skin is an intentional and unintentional target of therapy, and is sensitive to the volume of normal tissue in the radiation therapy ...treatment field, daily treatment dose (fractionation), and total treatment dose. We must understand the relationship of these factors to patient outcome as we move toward hypofractionation treatment strategies (radiosurgery). Chemotherapy agents and prescription medications may influence therapy-associated sequelae. Understanding this may prevent significant injury and discomfort. This article reviews established platforms of radiation therapy and sequelae associated with skin therapy. Interactions with other agents and possible predisposition to sequelae are reviewed. Skin cancer resulting from treatment and disease processes associated with possible limited outcome are also reviewed.
Tools and procedures for evaluating and comparing different intensity-modulated radiation therapy (IMRT) systems are presented. IMRT is increasingly in demand and there are numerous systems available ...commercially. These programs introduce significantly different software to dosimetrists and physicists than conventional planning systems, and the options often seem initially overwhelmingly complex to the user. By creating geometric target volumes and critical normal tissues, the characteristics of the algorithms may be investigated, and the influence of the different parameters explored. Overall optimization strategies of the algorithm may be characterized by treating a square target volume (TV) with 2 perpendicular beams, with and without heterogeneities. A half-donut (hemi-annulus) TV with a “donut hole” (central cylinder) critical normal tissue (CNT) on a CT of a simulated quality assurance phantom is suggested as a good geometry to explore the IMRT algorithm parameters. Using this geometry, the order of varying parameters is suggested. First is to determine the effects of the number of stratifications of optimized intensity fluence on the resulting dose distribution, and selecting a fixed number of stratifications for further studies. To characterize the dose distributions, a dose-homogeneity index (DHI) is defined as the ratio of the dose received by 90% of the volume to the minimum dose received by the “hottest” 10% of the volume. The next step is to explore the effects of priority and penalty on both the TV and the CNT. Then, choosing and fixing these parameters, the effects of varying the number of beams can be looked at. As well as evaluating the dose distributions (and DHI), the number of subfields and the number of monitor units required for different numbers of stratifications and beams can be evaluated.
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