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Commissioning a new treatment planning system (TPS) involves many time-consuming tasks. We investigated the role that knowledge-based planning (KBP) can play in aiding a clinic's transition to a new TPS. Sixty clinically treated prostate/prostate bed intensity-modulated radiation therapy (IMRT) plans were exported from an in-house TPS and were used to create a KBP model in a newly implemented commercial application. To determine the benefit that KBP may have in a TPS transition, the model was tested on 2 groups of patients. Group 1 consisted of the first 10 prostate/prostate bed patients treated in the commercial TPS after the transition from the in-house TPS. Group 2 consisted of 10 patients planned in the commercial TPS after 8 months of clinical use. The KBP-generated plan was compared with the clinically used plan in terms of plan quality (ability to meet planning objectives and overall dose metrics) and planning efficiency (time required to generate clinically acceptable plans). The KBP-generated plans provided a significantly improved target coverage (p = 0.01) compared with the clinically used plans for Group 1, but yielded plans of comparable target coverage to the clinically used plans for Group 2. For the organs at risk, the KBP-generated plans produced lower doses, on average, for every normal-tissue objective except for the maximum dose to 0.1 cc of rectum. The time needed for the KBP-generated plans ranged from 6 to 15 minutes compared to 30 to 150 and 15 to 60 minutes for manual planning in Groups 1 and 2, respectively. KBP is a promising tool to aid in the transition to a new TPS. Our study indicates that high-quality treatment plans could have been generated in the newly implemented TPS more efficiently compared with not using KBP. Even after 8 months of the clinical use, KBP still showed an increase in plan quality and planning efficiency compared with manual planning.

Background Underestimation of the spinal cord's volume or position during spine stereotactic radiosurgery can lead to severe myelopathy, whereas overestimation can lead to tumor underdosage. Spinal cord delineation is commonly achieved by registering a magnetic resonance imaging (MRI) study with a computed tomography (CT) simulation scan or by performing myelography during CT simulation (myelosim). We compared treatment planning outcomes for these 2 techniques. Methods Twenty-three cases of spine stereotactic radiosurgery were analyzed that had both a myelosim and corresponding MRI study for registration. The spinal cord was contoured on both imaging data sets by 2 independent blinded physicians, and Dice similarity coefficients were calculated to compare their spatial overlap. Two treatment plans (16 Gy and 18 Gy) were created using the MRI and CT contours (92 plans total). Dosimetric parameters were extracted and compared by modality to assess tumor coverage and spinal cord dose. Results No differences were found in the partial spinal cord volumes contoured on MRI versus myelosim (4.71 ± 1.09 vs. 4.55 ± 1.03 cm3; P = 0.34) despite imperfect spatial agreement (mean Dice similarity coefficient, 0.68 ± 0.05). When the registered MRI contours were used for treatment planning, significantly worse tumor coverage and greater spinal cord doses were found compared with myelosim planning. For the 18-Gy plans, 10 of 23 MRI cases (43%) exceeded the spinal cord or cauda dose constraints when using myelosim as the reference standard. Conclusions Significant spatial, rather than volumetric, differences were found between the MRI- and myelosim-defined spinal cord structures. Tumor coverage was compromised with MRI-based planning, and the high spinal cord doses were a concern. Future work is necessary to compare thin-cut, volumetric MRI registration or MRI simulation with myelosim.

Investigate the impact on prostate orientation caused by use and removal of a Foley catheter, and the dosimetric impact on men prospectively treated with prostate stereotactic body radiotherapy (SBRT).Twenty-two men underwent a CT simulation with a Foley in place (FCT), followed immediately by a second treatment planning simulation without the Foley (TPCT). The change in prostate orientation was determined by rigid registration of three implanted transponders between FCT and TPCT and compared to measured orientation changes during treatment. The impact on treatment planning and delivery was investigated by analyzing the measured rotations during treatment relative to both CT scans, and introducing rotations of ±15° in the treatment plan to determine the maximum impact of allowed rotations.Removing the Foley caused a statistically significant prostate rotation (P 0.0028) compared to normal biological motion in 60% of patients. The largest change in rotation due to removing a Foley occurs about the left-right axis (tilt) which has a standard deviation two to five times larger than changes in rotation about the Sup-Inf (roll) and Ant-Post (yaw) axes. The change in tilt due to removing a Foley for prone and supine patients was -1.1° ± 6.0° and 0.3° ± 7.4°, showing no strong directional bias. The average tilt during treatment was -1.6° ± 7.1° compared to the TPCT and would have been -2.0° ± 7.1° had the FCT been used as the reference. The TPCT was a better or equivalent representation of prostate tilt in 82% of patients, vs 50% had the FCT been used for treatment planning. However, 92.7% of fractions would still have been within the ±15° rotation limit if only the FCT were used for treatment planning. When rotated ±15°, urethra VRemoving a Foley catheter can cause large prostate rotations. There does not appear to be a clear dosimetric benefit to obtaining the CT scan with a Foley catheter to define the urethra given the changes in urethral position from removing the Foley catheter. If urethral sparing is desired without the use of a Foley, utilization of an MRI to define the urethra may be necessary, or a pseudo-urethral planning organ at risk volume (PRV) may be used to limit dosimetric hot spots.

After radiosurgery of malignant tumors, it can be difficult to discriminate between transient treatment effects, radiation necrosis, and tumor progression on post-treatment imaging. Misinterpretation of an enlarging lesion may lead to inappropriate treatment and contribute to disagreements about treatment efficacy. In an effort to clarify this problem, we reviewed our experience with interpreting post-radiosurgical imaging in patients with malignant primary and secondary brain tumors. We reviewed results of radiosurgery of 30 malignant gliomas and 35 metastatic brain tumors with minimum follow up of 1 year or until death. Of 30 gliomas, 73% were larger a mean of 13 weeks after radiosurgery. Of 35 metatstatic tumors, 22% were larger a mean of 10 weeks after radiosurgery. Eleven had 18F-fluorodeoxyglucose-positron emission tomography (FDG-PET) of enlarging lesions. Eight showed increased activity with respect to brain; three decreased activity. Of the eight, six predicted incorrectly based upon the patients' subsequent courses (all alive, mean follow up of 27 months), and two correctly, with the patients dying from the imaged lesions 8 and 13 months later. Of the three with FDG uptake less than brain, one patient was alive with 32 weeks of follow up, and two patients died from the imaged lesion 13 and 21 months later. Radiographic enlargement after radiosurgery is common, especially for gliomas. Physicians caring for these patients should be aware of this phenomenon and be cautious in interpreting post-treatment images. MRI appearance may be useful for metastases. FDG-PET seems unreliable. Further evaluation of Tl-201 and HMPAO SPECT or MRS is warranted.

Purpose: There is potentially a wide variation in plan quality for a certain disease site, even for clinics located in the same system of hospitals. We have used a prostate-specific knowledge-based planning (KBP) model as a quality control tool to investigate the variation in prostate treatment planning across a network of affiliated radiation oncology departments. Methods: A previously created KBP model was applied to 10 patients each from 4 community-based clinics (Clinics A, B, C, and D). The KBP model was developed using RapidPlan (Eclipse v13.5, Varian Medical Systems) from 60 prostate/prostate bed IMRT plans that were originally planned using an in-house treatment planning system at the central institution of the community-based clinics. The dosimetric plan quality (target coverage and normal-tissue sparing) of each model-generated plan was compared to the respective clinically-used plan. Each community-based clinic utilized the same planning goals to develop the clinically-used plans that were used at the main institution. Results: Across all 4 clinics, the model-generated plans decreased the mean dose to the rectum by varying amounts (on average, 12.5, 2.6, 4.5, and 2.7 Gy for Clinics A, B, C, and D, respectively). The mean dose to the bladder also decreased with the model-generated plans (5.4, 2.3, 3.0, and 4.1 Gy, respectively). The KBP model also identified that target coverage (D95%) improvements were possible for for Clinics A, B, and D (0.12, 1.65, and 2.75%) while target coverage decreased by 0.72% for Clinic C, demonstrating potentially different trade-offs made in clinical plans at different institutions. Conclusion: Quality control of dosimetric plan quality across a system of radiation oncology practices is possible with knowledge-based planning. By using a quality KBP model, smaller community-based clinics can potentially identify the areas of their treatment plans that may be improved, whether it be in normal-tissue sparing or improved target coverage. M. Matuszak has research funding for KBP from Varian Medical Systems

This article reviews the indications for radiotherapy in advanced stage disease and discusses the recent prospective trials demonstrating a survival benefit by the addition of radiotherapy. Various treatment plans are reviewed with and without internal mammary node coverage. Although it is not clear whether internal mammary node irradiation can have a favorable impact on survival, it is clear that inadequate treatment planning of the parasternal region can result in excess cardiac morbidity and mortality. Careful planning using computed tomographic systems is required to optimize chest wall planning. With individualized treatment planning, it is hoped that the next generation of trials will show improved survival from further reduction in breast cancer deaths and significantly decreased cardiac toxicity.

Purpose: Commissioning a treatment planning system (TPS) involves many tasks, including making sure users have sufficient training and experience to create quality plans. We investigated the role that knowledge-based planning (KBP) can play in aiding a clinic’s transition to a new TPS. Methods: 60 clinically treated prostate and prostate bed IMRT plans were exported from an in-house TPS and used to create a KBP-model in a newly introduced commercial TPS (Eclipse v13.5, Varian Medical Systems). To determine the benefit that KBP may have in a TPS transition, the model was tested on two groups. Group 1 consisted of the first 10 patients treated in the commercial TPS after the transition from the in-house TPS, Group 2 consisted of 10 patients planned in the commercial TPS, but without the KBP model, after 8 months of clinical use. The KBP-generated plan for each patient was compared to the clinically-used plan in terms of quality and planning efficiency. Results: On average, the KBP-generated plans provided better target coverage for group 1 than the clinical plans,and about equivalent coverage for group 2. The average absolute difference (KBP-clinical) for D95 for the PTV was 0.48±0.49% and −0.11±0.48% for groups 1 and 2, respectively. For the OARs, the KBP-generated plans produced lower doses for every normal tissue objective except the maximum dose to 0.1cc of rectum (0.50±0.27Gy and 0.22±0.17Gy for groups 1 and 2, respectively). The time needed for KBP-generated plans ranged from 6– 15min compared to 30–150 and 15–60min for groups 1 and 2, respectively. Conclusion: Knowledge-based planning is a promising tool to aid in transitions to new TPSs. Our study indicates that high-quality treatment plans could have been generated in the new TPS more efficiently compared to not using KBP. Even after 8 months of clinical use, KBP still showed a quality and efficiency increase compared to manual planning. Partially supported by Varian Medical Systems

After radiosurgery of malignant tumors, it can be difficult to discriminate between transient treatment effects, radiation necrosis, and tumor progression on post-treatment imaging. Misinterpretation of an enlarging lesion may lead to inappropriate treatment and contribute to disagreements about treatment efficacy. In an effort to clarify this problem, we reviewed our experience with interpreting post-radiosurgical imaging in patients with malignant primary and secondary brain tumors. We reviewed results of radiosurgery of 30 malignant gliomas and 35 metastatic brain tumors with minimum follow up of 1 year or until death. Of 30 gliomas, 73% were larger a mean of 13 weeks after radiosurgery. Of 35 metatstatic tumors, 22% were larger a mean of 10 weeks after radiosurgery. Eleven had 18F-fluorodeoxyglucose-positron emission tomography (FDG-PET) of enlarging lesions. Eight showed increased activity with respect to brain; three decreased activity. Of the eight, six predicted incorrectly based upon the patients' subsequent courses (all alive, mean follow up of 27 months), and two correctly, with the patients dying from the imaged lesions 8 and 13 months later. Of the three with FDG uptake less than brain, one patient was alive with 32 weeks of follow up, and two patients died from the imaged lesion 13 and 21 months later. Radiographic enlargement after radiosurgery is common, especially for gliomas. Physicians caring for these patients should be aware of this phenomenon and be cautious in interpreting post-treatment images. MRI appearance may be useful for metastases. FDG-PET seems unreliable. Further evaluation of Tl-201 and HMPAO SPECT or MRS is warranted.

In this paper we describe the clinical use of an in-house mutual information-based image registration system for improving target volume definition in conformal radiotherapy treatment planning. This system enables a clinician to delineate clinical and anatomic structures on magnetic resonance and nuclear medicine imaging studies and have these structures geometrically mapped to the x-ray CT study used for treatment planning. This system requires very little user interaction and can accommodate a wide range of anatomic sites. These factors combined with consistent accuracy at the sub-voxel to voxel level have improved the overall quality and physician confidence in the delineation of target volumes and surrounding healthy tissues.

Over a period of approximately 3 years, our institution has implemented and refined a system of Stereotactic Radiosurgery (SRS) which utilizes the standard multi leaf collimator (MLC) of the Scanditronix MM50 Racetrack Microtron and treats in an arrangement of segmental “pseudo-arcs.” This system employs a commercial BRW-based stereotactic frame which is mounted to the treatment table. With the exception of the table-mounted frame hardware there have been no modifications to the treatment machine to accommodate these treatments. By use of standard evaluation parameters (e.g., treatment time, planning time, dose conformance and dose heterogeneity ratios) this system compares quite favorably with reported data from institutions treating SRS with either a GammaKnife or a standard linear accelerator with tertiary collimators.