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K Schupak

Publications and source records attributed to K Schupak.

6 recordsLinked to original sources
PubMed2002

A parameter optimization algorithm for intensity-modulated radiotherapy prostate treatment planning.

An iterative algorithm has been developed to analytically determine patient specific input parameters for intensity-modulated radiotherapy prostate treatment planning. The algorithm starts with a generic set of inverse planning parameters that include dose and volume constraints for the target and surrounding critical structures. The overlap region between the target volume and the rectum is used to determine the optimized target volume coverage goal. Sequential iterations are performed to vary the numerous parameters individually or in sets while other parameters remain fixed. A coarse grid search is first used to avoid convergence on a local maximum. Linear interpolation is then used to define a region for a fine grid search. Selected parameters are also tested for possible improvements in target coverage. In several representative test cases investigated the coverage of the planning target volume improved with the use of the algorithm while still meeting the clinical acceptability criteria for critical structures. The algorithm avoids time-consuming random trial and error variations that are often associated with difficult cases and also eliminates lengthy user learning curves. The methodology described in this paper can be applied to any treatment planning system that requires the user to select the input optimization parameters.

Algorithms↗
PubMed2001

The treatment of large extraskeletal chondrosarcoma of the leg: comparison of IMRT and conformal radiotherapy techniques.

Extraskeletal chondrosarcoma of the leg is a rare, malignant neoplasm with very few cases having been reported in the literature. In this study we investigate the possibility of using intensity modulated radiotherapy (IMRT) for this type of disease and demonstrate its advantages over conventional three-dimensional (3D) conformal treatment. A case was presented of a patient with extraskeletal chondrosarcoma of the lateral compartment of the leg in which the target volume was 50 cm in length and twisted around the surrounding bones. Both the 3D conformal plan and IMRT plan were designed using the Memorial Sloan-Kettering Cancer Center planning system. The IMRT plan produced a superior dose distribution to the patient as compared to the 3D conformal plan both in terms of dose conformity and homogeneity in the target volumes, and reduction of the maximum dose to the bone. The planning time of the IMRT plan was about 3-5 times shorter than that of the 3D conformal plan. It was demonstrated that the IMRT technique can be used not just for small tumors, but also for large and spiral-shaped tumors close to critical organs. The IMRT method requires less planning time, and provides better target coverage with more sparing of critical structures. When planning patients with multiple target volumes receiving different prescribed doses, the IMRT technique can more easily meet this requirement.

Adult↗
PubMed1995

The relationship between the technical accuracy of stereotactic interstitial implantation for high grade gliomas and the pattern of tumor recurrence.

PURPOSE: To correlate the pattern of failure and subsequent survival with the technical accuracy of stereotactic brain tumor implantation. METHODS AND MATERIALS: The patterns of failure of 47 consecutive patients with primary or recurrent gliomas after stereotactic implantation delivering 60 Gy via removable high activity 125I sources were reviewed. When the tumor was covered at all levels by the chosen isodose distribution, the implant was considered to be "ideal." If the coverage was not complete, a numerical description of the volume of tumor outside the isodose was assigned. Criteria for "adequate" and "inadequate" implants were defined. Standard radiographic criteria, with pathologic confirmation in 26 cases, were used to categorize the patterns of failure into the following components: central, peripheral, distant (within the brain parenchyma), leptomeningeal, and spinal. A peripheral failure was scored as being in the "direction of error" when the prescribed isodose did not cover the tumor volume and the subsequent tumor progression was in this region. Survival was calculated from the date of implantation. RESULTS: Of 47 cases examined, 72% had an element of central and/or peripheral failure and 23% had a component of distant or meningeal failure. Among the patients with "adequate" or "inadequate" ("nonideal") implants who had a component of peripheral failure, only 19% were in the "direction of error." All patients with technically "inadequate" implants progressed in both the central and peripheral region. Among the groups who had "ideal," "adequate," and "inadequate" implants; 37%, 70%, and 75%, respectively, underwent reoperation [p = not significant (NS)]. Patients who underwent reoperation had a longer median survival than those who did not; 521 days vs. 298 days, respectively (p = 0.035). For patients with "nonideal" implants, a median survival of 470 days was found for patients undergoing reoperation vs. 184 days for those who did not (p = 0.016). CONCLUSIONS: (a) Patients with "inadequate" implants failed in both the central and peripheral region in all cases. This pattern, while less common in those with "ideal" or "adequate" implants, occurred in the majority of cases. (b) The technical excellence of the implant had no impact on survival. (c) Patients with "nonideal" implants were more likely to have reoperation than those with "ideal" implants, and this intervention was associated with a significant survival advantage.

Adult↗
PubMed1995

Palliation of irresectable hilar cholangiocarcinoma with biliary drainage and radiotherapy.

Twelve patients with irresectable or recurrent hilar cholangiocarcinoma were treated with internal biliary drainage followed by intraluminal (iridium-192) and external-beam radiotherapy. Biliary drainage was accomplished by means of a combined surgical and interventional radiological approach. Initial biliary decompression was performed surgically by tumour resection, intrahepatic biliary enteric bypass or distal biliary-enteric anastomosis with a temporary stent. Maintenance of internal biliary drainage and application of intraluminal radiotherapy were accomplished radiologically with the use of percutaneous dilatation and metallic expandable biliary endoprostheses. Median survival was 14.5 months; all 12 patients survived for at least 6 months. Early complications during radiotherapy were minor and included two patients with cholangitis and one with transient haemobilia. Jaundice was relieved in ten of 12 patients, while episodes of cholangitis were seen during long-term follow-up in 11 (median 1.5 episodes per patient). Internal biliary drainage, in conjunction with radiotherapy, appears to be safe and effective palliation of irresectable or recurrent hilar cholangiocarcinoma. Patients can maintain a reasonable quality of life with an acceptable incidence of cholangitis, without the hindrance of external drainage devices.

Aged↗
PubMed1991

Role of brachytherapy in recurrent extremity sarcoma in patients treated with prior surgery and irradiation.

The treatment options for recurrent extremity sarcoma following conservative surgery and irradiation are limited. Amputation is the treatment of choice offered for the majority of these patients. In a selected group of patients with recurrent sarcoma, we have investigated the role of brachytherapy along with function-preserving resection. From 1979 to 1988, 40 patients underwent resection and brachytherapy for recurrent extremity sarcoma. There were 23 males and 17 females. All of the patients received function-preserving resection and an afterloading temporary tumor bed implant. A median dose of 4500 cGy was delivered with a range from 3000 to 4800 cGy. The median follow-up was 36 months with a range of 12 to 120 months. The actuarial local control at 5 years is 68%. Five patients (12.5%) developed complications such as wound ulceration (4) and femoral fracture (1) requiring surgery. Five patients developed local failure and an additional two patients had both local and distant failure. All of the failures occurred in patients with more than two prior recurrences. This review suggests that brachytherapy can be used as an effective treatment option in selected patients with recurrent extremity sarcoma following prior surgery and irradiation with satisfactory limb preservation. The data also suggest that higher local control rates can be achieved with early brachytherapeutic intervention.

Adult↗