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194 Intensity modulated radiation therapy for pediatric patients: Initial experience in 6 patients
CARO 2004
September 9-12 $59
lung window and level settings. Adding a 10 mm uniform margin defines the P-IV. Breathing movement is assessed using '4DCT' technology available with the CT scanner. A 3 mm margin should bound the extent of any GTV movement to allow for setup uncertainties. Noncoplanar beams (7 to 12) are arranged and weighted to meet dose-volume constraints in adjacent organs. These constraints restrict protocol eligibility and guide the total dose prescribed. Total dose includes tissue density corrections, and ranges from 45 to 60 Gy. Treatment is administered in three fractions over 2 weeks using a linear accelerator equipped with a megavoitage (MV) portal imaging device, and kilovoltage (kV) x-ray imaging system. The technical characteristics and validation of this system have been described previously. 1, 2 For each fraction, orthogonal MV images are acquired, along with a volumetric cone-beam dataset. The cone-beam dataset is loaded into a treatment planning system, and fused with the planning CT to assess and correct target position relative to the machine isocentre. Our experience indicates cone-beam CT permits definitive softtissue targeting for extracranial radiosurgery of lung cancer. Future work will incorporate respiration correlated cone-beam reconstruction to verify breathing movement with each fraction. 194 Intensity Modulated Radiation Therapy Patients: Initial Experience in 6 Patients.
for
Pediatric
T. Lam 1, R. Ramaniz, N. Laperriere3, D. Hodgson3. ~Radiation Therapy, Princess Margaret Hospital, Toronto, Ontario; 2Clinical Physics, Princess Margaret Hospital, Toronto, Ontario; 3Radiation Oncology, Princess Margaret Hospital, Toronto, Ontario Objective: There are very few reports of the use of Intensity Modulated Radiation Therapy (IMRT) in pediatric patients. Children in particular may benefit from reduced radiation dose to developing normal tissues. In this report, we explore the potential benefit of IMRT in 6 pediatric patients with rhabdomyosarcoma of the abdomen, pelvis, and lower limb. Methods: An IMRT program has been established at Princess Margaret Hospital based on a CadPlan/Helios calculation engine and a Varian dynamic MLC (dMLC) treatment delivery system. Our IMRT delivery system is based on a sliding window technique. All patients were immobilized on a BodyFix and were under anaesthesia during CT scan as well as during irradiation. Targets and critical structures were drawn on ACQSIM and transferred to a CADPLAN workstation for planning. All critical structure volumes incorporated a margin of 3-5 ram. The patient set-up was verified using portal imaging for the first three days to evaluate any systematic errors and subsequently twice a week for the rest of the treatment. In this report, we are presenting our initial clinical experience in treating these patients with IMRT. Results: We have treated 6 pediatric patients under the age of 10 years. The first 3 patients received systemic chemotherapy as part of their management plan. The first patient was a 28 month old female diagnosed with a group III retroperitoneal embryonal rhabdomyosarcoma involving the celiac axis, pancreas and liver. The second patient was originally diagnosed at age 2 with a group III alveolar rhabdomyosarcoma involving the thigh, left pelvic lymph nodes and para-aortic lymph nodes. She was initially treated with intensive chemotherapy including stem cell transplant, but relapsed in all originally involved sites and received salvage chemotherapy, excision of the thigh mass and radiotherapy to the thigh, ipsilateral pelvic nodes and para-aortic nodes. The third case was a 17-month-old male who underwent a gross total excision of a pelvic embryonal rhabdomyosarcoma that was adjacent to the superior aspect of the bladder and had positive microscopic margins. In all first 3 cases IMRT was able to achieve a
superior dose distritbution to the P-IV and reduce the dose to adjacent normal tissues. IMRT achieved excellent PTV coverage by the 95% isodose while delivering an average 11 Gy less to the vertebral bodies, and reducing dose to the femoral heads by a range of 2-14 Gy. The bowel dose received approximately 4 Gy less with IMRT. In general critical structures doses were less and a superior target coverage was achieved with IMRT compared to conventional conformal plans. Remaining 3 patients are being studied currently and the preliminary results were similar as the first 3 patients. Detailed analysis will be presented. Conclusions: IMRT in these selected pediatric patients resulted in a superior PTV coverage and significant reduction in dose to normal tissues. Pediatric patients particularly stand to benefit from the use of IMRT in view of growth related issues. 195 A New Accurate and Robust Method for Three-Dimensional Definition of Target Volumes Based on a Fuzzy Logic Method.
J.M. Caudre/ier1, M. Vermandef, /. Cameron~, B. Nyin~, M. Coulanges5, J. Rousseau~. ~Ottawa Regional Cancer Centre, University of Ottawa, Ottawa, Ontario; ZUPRES EA 1049, ERT 23-Radioth~rapie Conformationnelle et Imagerie Multimodalite, CHU, Lille, France; 3Department of Radiology, MRI Unit, Ottawa Hospital, University of Ottawa, Ottawa, Ontario; 4Ottawa Regional Cancer Centre, University of Ottawa, Ottawa, Ontario; 5UPRES EA 1049, ERT 23-Radioth~rapie Confonnationnelle et Imagerie Multimodalit~, CHU, Lille, France; 6UPRES EA 1049, ERT 23-Radioth~rapie Conformationnelle et Imagerie Multimodalit~, CHU, Lille, France Previously we have published results of a new accurate and robust method of volume reconstruction based on fuzzy logic, for small and well-delimited targets delineated on MRI (as radiosurgery cases). The convenience of this method for larger and more complex volumes, usually treated by conformal radiotherapy, was questioned. The accuracy and the robustness have been evaluated on phantom targets imaged with different MRI and CT-scanner slice thickness. Four large (volumes: 50-71 cc) and complex (e.g. mimicking prostateseminal vesicles) phantom targets have been created and imaged with a 3D MPRAGE sequence: sagittal, slices thickness 1 mm, 1xlx1 mm voxel size reconstruction, as well as 3, 5, 7, 9 mm slice thickness axial, coronal and sagittal views. Targets were also imaged with CT-scanner and 2, 3, 5, 8 mm slice thickness in spiral and sequential modes. More than 1500 contours have been delineated to generate 100 volumes. The median of the relative errors on calculated volumes with the fuzzy logic method is 3.1% (min: 1.3%-max: 12%). 79% of the errors are less than 5%. There is no correlation between calculated volumes and the slice thickness. With a iclassicalT method and from axial slices, calculated volumes increase gradually with larger slice thickness. The median relative error is 24.3% (min: 12.4%-max: 34.6%) with axial MRI images and is 22.9% (min: 7.6%-max: 46.3%) with CT-scanner images. With the fuzzy logic method, the target volumes displayed are always well-shaped and well-reconstructed, whatever the slice thickness. With a classical TPS and from axial images, the target volumes displayed show deformation of shapes increasing with larger slice thickness. Our method based on fuzzy logic is able to determine larger and more complex target volumes with a better accuracy. Therefore, this method is more robust and less sensitive to slice thickness than classical methods using axial images.
September 9-12 $59
lung window and level settings. Adding a 10 mm uniform margin defines the P-IV. Breathing movement is assessed using '4DCT' technology available with the CT scanner. A 3 mm margin should bound the extent of any GTV movement to allow for setup uncertainties. Noncoplanar beams (7 to 12) are arranged and weighted to meet dose-volume constraints in adjacent organs. These constraints restrict protocol eligibility and guide the total dose prescribed. Total dose includes tissue density corrections, and ranges from 45 to 60 Gy. Treatment is administered in three fractions over 2 weeks using a linear accelerator equipped with a megavoitage (MV) portal imaging device, and kilovoltage (kV) x-ray imaging system. The technical characteristics and validation of this system have been described previously. 1, 2 For each fraction, orthogonal MV images are acquired, along with a volumetric cone-beam dataset. The cone-beam dataset is loaded into a treatment planning system, and fused with the planning CT to assess and correct target position relative to the machine isocentre. Our experience indicates cone-beam CT permits definitive softtissue targeting for extracranial radiosurgery of lung cancer. Future work will incorporate respiration correlated cone-beam reconstruction to verify breathing movement with each fraction. 194 Intensity Modulated Radiation Therapy Patients: Initial Experience in 6 Patients.
for
Pediatric
T. Lam 1, R. Ramaniz, N. Laperriere3, D. Hodgson3. ~Radiation Therapy, Princess Margaret Hospital, Toronto, Ontario; 2Clinical Physics, Princess Margaret Hospital, Toronto, Ontario; 3Radiation Oncology, Princess Margaret Hospital, Toronto, Ontario Objective: There are very few reports of the use of Intensity Modulated Radiation Therapy (IMRT) in pediatric patients. Children in particular may benefit from reduced radiation dose to developing normal tissues. In this report, we explore the potential benefit of IMRT in 6 pediatric patients with rhabdomyosarcoma of the abdomen, pelvis, and lower limb. Methods: An IMRT program has been established at Princess Margaret Hospital based on a CadPlan/Helios calculation engine and a Varian dynamic MLC (dMLC) treatment delivery system. Our IMRT delivery system is based on a sliding window technique. All patients were immobilized on a BodyFix and were under anaesthesia during CT scan as well as during irradiation. Targets and critical structures were drawn on ACQSIM and transferred to a CADPLAN workstation for planning. All critical structure volumes incorporated a margin of 3-5 ram. The patient set-up was verified using portal imaging for the first three days to evaluate any systematic errors and subsequently twice a week for the rest of the treatment. In this report, we are presenting our initial clinical experience in treating these patients with IMRT. Results: We have treated 6 pediatric patients under the age of 10 years. The first 3 patients received systemic chemotherapy as part of their management plan. The first patient was a 28 month old female diagnosed with a group III retroperitoneal embryonal rhabdomyosarcoma involving the celiac axis, pancreas and liver. The second patient was originally diagnosed at age 2 with a group III alveolar rhabdomyosarcoma involving the thigh, left pelvic lymph nodes and para-aortic lymph nodes. She was initially treated with intensive chemotherapy including stem cell transplant, but relapsed in all originally involved sites and received salvage chemotherapy, excision of the thigh mass and radiotherapy to the thigh, ipsilateral pelvic nodes and para-aortic nodes. The third case was a 17-month-old male who underwent a gross total excision of a pelvic embryonal rhabdomyosarcoma that was adjacent to the superior aspect of the bladder and had positive microscopic margins. In all first 3 cases IMRT was able to achieve a
superior dose distritbution to the P-IV and reduce the dose to adjacent normal tissues. IMRT achieved excellent PTV coverage by the 95% isodose while delivering an average 11 Gy less to the vertebral bodies, and reducing dose to the femoral heads by a range of 2-14 Gy. The bowel dose received approximately 4 Gy less with IMRT. In general critical structures doses were less and a superior target coverage was achieved with IMRT compared to conventional conformal plans. Remaining 3 patients are being studied currently and the preliminary results were similar as the first 3 patients. Detailed analysis will be presented. Conclusions: IMRT in these selected pediatric patients resulted in a superior PTV coverage and significant reduction in dose to normal tissues. Pediatric patients particularly stand to benefit from the use of IMRT in view of growth related issues. 195 A New Accurate and Robust Method for Three-Dimensional Definition of Target Volumes Based on a Fuzzy Logic Method.
J.M. Caudre/ier1, M. Vermandef, /. Cameron~, B. Nyin~, M. Coulanges5, J. Rousseau~. ~Ottawa Regional Cancer Centre, University of Ottawa, Ottawa, Ontario; ZUPRES EA 1049, ERT 23-Radioth~rapie Conformationnelle et Imagerie Multimodalite, CHU, Lille, France; 3Department of Radiology, MRI Unit, Ottawa Hospital, University of Ottawa, Ottawa, Ontario; 4Ottawa Regional Cancer Centre, University of Ottawa, Ottawa, Ontario; 5UPRES EA 1049, ERT 23-Radioth~rapie Confonnationnelle et Imagerie Multimodalit~, CHU, Lille, France; 6UPRES EA 1049, ERT 23-Radioth~rapie Conformationnelle et Imagerie Multimodalit~, CHU, Lille, France Previously we have published results of a new accurate and robust method of volume reconstruction based on fuzzy logic, for small and well-delimited targets delineated on MRI (as radiosurgery cases). The convenience of this method for larger and more complex volumes, usually treated by conformal radiotherapy, was questioned. The accuracy and the robustness have been evaluated on phantom targets imaged with different MRI and CT-scanner slice thickness. Four large (volumes: 50-71 cc) and complex (e.g. mimicking prostateseminal vesicles) phantom targets have been created and imaged with a 3D MPRAGE sequence: sagittal, slices thickness 1 mm, 1xlx1 mm voxel size reconstruction, as well as 3, 5, 7, 9 mm slice thickness axial, coronal and sagittal views. Targets were also imaged with CT-scanner and 2, 3, 5, 8 mm slice thickness in spiral and sequential modes. More than 1500 contours have been delineated to generate 100 volumes. The median of the relative errors on calculated volumes with the fuzzy logic method is 3.1% (min: 1.3%-max: 12%). 79% of the errors are less than 5%. There is no correlation between calculated volumes and the slice thickness. With a iclassicalT method and from axial slices, calculated volumes increase gradually with larger slice thickness. The median relative error is 24.3% (min: 12.4%-max: 34.6%) with axial MRI images and is 22.9% (min: 7.6%-max: 46.3%) with CT-scanner images. With the fuzzy logic method, the target volumes displayed are always well-shaped and well-reconstructed, whatever the slice thickness. With a classical TPS and from axial images, the target volumes displayed show deformation of shapes increasing with larger slice thickness. Our method based on fuzzy logic is able to determine larger and more complex target volumes with a better accuracy. Therefore, this method is more robust and less sensitive to slice thickness than classical methods using axial images.