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EP-1397 USEFULNESS OF CONE BEAM CT FOR CRANIAL STEREOTACTIC RADIOSURGERY PLANNING
S530
ESTRO 31
Results: For the whole-brain PTV mean D2% was 3722 cGy (range 3693-3757cGy) and mean D98% was 2568 cGy (range 2540-2589 cGy). The hippocampus mean D100% was 838 cGy (range 768-892 cGy) and the mean max dose was 1569 cGy (range 1428-1606 cGy). The max dose to optic nerves and optic chiasm for all patients did not exceed 3750 cGy. HI mean value was 0.35 (range 0.33-0.36). Mean number of segments was 105 (range 90-125) and mean number of monitor units was 1155 (range 1081-1279). Conclusions: We show the feasibility of planning HS WBRT using ELEKTA equipment (CMS Monaco TPS and ELEKTA Infinity linac) according to the very demanding compliance criteria defined by the RTOG 0933 protocol. EP-1397 USEFULNESS OF CONE BEAM CT FOR CRANIAL STEREOTACTIC RADIOSURGERY PLANNING S. San José Maderuelo1, J.F. Calvo Ortega1, M. Pozo Massó1, S. Moragues Femenia1, E. Puertas Calvo1, J. Casals Farran1 1 Hospital Quiron Barcelona, Radiotherapy, Barcelona, Spain Figure 1 left: 94% pixels passing 0.7mm corrected 1%/1mm Gamma for a nasopharynx case Figure 1 right: 98.2% pixles passing non corrected 2%/2mm Gamma for a moving liver case Conclusions: The use of gafchromic film provided high spatial and absolute dose information for radiosurgery DQA. We found excellent agreement between the film and the planned dose with maximum film doses below 10Gy. The slightly better agreement for the extracranial moving cases can likely be explained with the use of smaller collimators and steeper dose gradients for intracranial targets and the resolution limitations of the film analysis. As conclusion we found excellent agreement below 1mm for the spatial dose distribution for all cases as expected by the delivery of robotic radiosurgery. We recommend film based DQA for commissioning, complicated shaped targets and at least every other week. The authors would like to thank Gary Gluckman of 3Cognition, Bill Main of Accuray and Xiang Yu of Ashland for their support.
ELECTRONIC POSTER: PHYSICS TRACK: IMAGING: FOCUS ON CLINICAL APPLICATIONS EP-1396 FEASIBILITY OF HIPPOCAMPAL-SPARING WHOLE-BRAIN RADIOTHERAPY USING ELEKTA EQUIPMENT A. Nevelsky1, N. Ieumwananonthachai2, O. Kaidar - Person1, R. BarDeroma1, H. Nasrallah1, R. Ben-Yosef1, A. Kuten1 1 Rambam Medical Center, Oncology, Haifa, Israel 2 Chulabhorn and Siriraj Hospital, Oncology, Bangkok, Thailand Purpose/Objective: Sparing the hippocampus during cranial radiotherapy represents a significant challenge with respect to contouring and treatment planning. Several publications reported about hippocampal-sparing whole-brain radiotherapy (HS WBRT) using Tomotherapy and Varian equipment.The purpose of this work is to evaluate the feasibility of HS WBRT using the ELEKTA Infinity linear accelerator and CMS Monaco treatment planning system (TPS). Materials and Methods: Ten patients previously treated with wholebrain radiotherapy (WBRT) underwent repeated planning in attempt to spare the hippocampus region. MRI-CT fusion sets created for every patient were used for delineation of hippocampus, optic nerves and chiasm. Hippocamus avoidance region was generated by expanding the hippocampus volumetrically by 5 mm. RTOG 0933 recommendations were applied for treatment planning. The wholebrain dose was prescribed to 30 Gy in 15 fractions. IMRT plans for the ELEKTA Infinity linear accelerator (MLC leaf width 1.0 cm) were created using CMS Monaco 2.04 TPS based on a 9 field arrangement and step-and-shoot delivery method. The quality of the plans was evaluated using D2% and D98% for whole-brain PTV (defined as whole brain excluding hippocampus avoidance region), D100% and Maximum Dose to the Hippocampus and Maximum Dose to Optic nerves and Chiasm. Homogeneity Index (HI) defined as (D2%-D98%)/Dmean was used to quantify dose homogeneity in the PTV. The RTOG per protocol compliance criteria applied: Whole-brain PTV D2% < 3750 cGy (D2% < 4000cGy is an acceptable variation), D98% > 2500 cGy; hippocampus D100% < 900 cGy and Dmax < 1600 cGy (Dmax<1700 cGy is an acceptable variation); optic chiasm and optic nerves max dose < 3750 cGy.
Purpose/Objective: To assess the feasibility of cone beam computed tomography (CBCT) images for cranial stereotactic radiosurgery (SRS) treatment planning. Materials and Methods: Cranial radiosurgery treatments are delivered in our department using a Varian 2100 CD linac equipped with the On Board Imaging (OBI) system. The called half-fan technique is the one selected in our facility for cranial CBCT acquisitions. HU values were measured for several CBCTs and conventional CT scans (Siemens Somaton Sensation), using a dedicated phantom with different materials (Catphan). A two tailed Student t-test was used for HU comparison aim. Three patients were planned based-on the conventional CT scan (pCT) in Eclipse treatment planning system (version 10.0). For each patient, a CBCT scan was obtained in treatment position according to the setup of the Eclipse plan. The CBCT set was imported into Eclipse system and fused with the pCT. Isocenter plan, organs at risk (brainstem, chiasma, and optic nerves) and target volume were transferred from pCT to CBCT data set in order to re-calculate the treatment plan on the CBCT scan, by keeping the original monitor units. AAA model with heterogeneity correction enabled were used for dose calculations. Dose distributions were compared on the CBCT images to conventional pCT images. Results: Measured CBCT HU values were significant lower than conventional CT images for each material of the Catphan phantom (p< 0.05). Dose differences within 3% in target and normal structures were found when dose distributions of the same plan were computed on the CBCT and conventional CT images. Conclusions: Although a significant difference on the calibration curve was detected between CBCT and pCT images, important dose differences were not found on treatments computed with Eclipse system. We consider that OBI-CBCT tomography is reliable enough for dose calculation in cranial SRS treatments. CBCT allows the acquisition of a planning CT in the same treatment setup and so it would be possible to reduce uncertainties related to imaging process during a frameless stereotactic planning. EP-1398 MAMMOGRAPHY IMAGE SEGMENTATION, TUMOR RECOGNITION AND AUTOMATIC MODEL BUILDING V. Mateev1, I. Marinova1, A. Chakarova2 1 Technical University of Sofia, Department of Electrical Apparatus, Sofia, Bulgaria 2 National Hospital of Oncology, Department of Radiotherapy, Sofia, Bulgaria Purpose/Objective: Computer-aided diagnosis systems are usually used for marking conspicuous structures and sections by sophisticated image segmentation techniques. Anatomy objects are particularly complex structures, and their segmentation is an important step for studies in temporal change detection of morphology, as well as for 2D/3D/4D visualization, diagnosis, screening and surgical planning modeling. The objects to be segmented are anatomical structures which are often non rigid and complex in shape, and exhibit considerable variability from person to person. This combined with an absence of explicit shape models that capture the deformations in anatomy, makes the segmentation task challenging. Aim of this work is a sophisticated method for automatic mammography images segmentation applied for 2D/3D vector model building, tumor detection and its size classification.
ESTRO 31
Results: For the whole-brain PTV mean D2% was 3722 cGy (range 3693-3757cGy) and mean D98% was 2568 cGy (range 2540-2589 cGy). The hippocampus mean D100% was 838 cGy (range 768-892 cGy) and the mean max dose was 1569 cGy (range 1428-1606 cGy). The max dose to optic nerves and optic chiasm for all patients did not exceed 3750 cGy. HI mean value was 0.35 (range 0.33-0.36). Mean number of segments was 105 (range 90-125) and mean number of monitor units was 1155 (range 1081-1279). Conclusions: We show the feasibility of planning HS WBRT using ELEKTA equipment (CMS Monaco TPS and ELEKTA Infinity linac) according to the very demanding compliance criteria defined by the RTOG 0933 protocol. EP-1397 USEFULNESS OF CONE BEAM CT FOR CRANIAL STEREOTACTIC RADIOSURGERY PLANNING S. San José Maderuelo1, J.F. Calvo Ortega1, M. Pozo Massó1, S. Moragues Femenia1, E. Puertas Calvo1, J. Casals Farran1 1 Hospital Quiron Barcelona, Radiotherapy, Barcelona, Spain Figure 1 left: 94% pixels passing 0.7mm corrected 1%/1mm Gamma for a nasopharynx case Figure 1 right: 98.2% pixles passing non corrected 2%/2mm Gamma for a moving liver case Conclusions: The use of gafchromic film provided high spatial and absolute dose information for radiosurgery DQA. We found excellent agreement between the film and the planned dose with maximum film doses below 10Gy. The slightly better agreement for the extracranial moving cases can likely be explained with the use of smaller collimators and steeper dose gradients for intracranial targets and the resolution limitations of the film analysis. As conclusion we found excellent agreement below 1mm for the spatial dose distribution for all cases as expected by the delivery of robotic radiosurgery. We recommend film based DQA for commissioning, complicated shaped targets and at least every other week. The authors would like to thank Gary Gluckman of 3Cognition, Bill Main of Accuray and Xiang Yu of Ashland for their support.
ELECTRONIC POSTER: PHYSICS TRACK: IMAGING: FOCUS ON CLINICAL APPLICATIONS EP-1396 FEASIBILITY OF HIPPOCAMPAL-SPARING WHOLE-BRAIN RADIOTHERAPY USING ELEKTA EQUIPMENT A. Nevelsky1, N. Ieumwananonthachai2, O. Kaidar - Person1, R. BarDeroma1, H. Nasrallah1, R. Ben-Yosef1, A. Kuten1 1 Rambam Medical Center, Oncology, Haifa, Israel 2 Chulabhorn and Siriraj Hospital, Oncology, Bangkok, Thailand Purpose/Objective: Sparing the hippocampus during cranial radiotherapy represents a significant challenge with respect to contouring and treatment planning. Several publications reported about hippocampal-sparing whole-brain radiotherapy (HS WBRT) using Tomotherapy and Varian equipment.The purpose of this work is to evaluate the feasibility of HS WBRT using the ELEKTA Infinity linear accelerator and CMS Monaco treatment planning system (TPS). Materials and Methods: Ten patients previously treated with wholebrain radiotherapy (WBRT) underwent repeated planning in attempt to spare the hippocampus region. MRI-CT fusion sets created for every patient were used for delineation of hippocampus, optic nerves and chiasm. Hippocamus avoidance region was generated by expanding the hippocampus volumetrically by 5 mm. RTOG 0933 recommendations were applied for treatment planning. The wholebrain dose was prescribed to 30 Gy in 15 fractions. IMRT plans for the ELEKTA Infinity linear accelerator (MLC leaf width 1.0 cm) were created using CMS Monaco 2.04 TPS based on a 9 field arrangement and step-and-shoot delivery method. The quality of the plans was evaluated using D2% and D98% for whole-brain PTV (defined as whole brain excluding hippocampus avoidance region), D100% and Maximum Dose to the Hippocampus and Maximum Dose to Optic nerves and Chiasm. Homogeneity Index (HI) defined as (D2%-D98%)/Dmean was used to quantify dose homogeneity in the PTV. The RTOG per protocol compliance criteria applied: Whole-brain PTV D2% < 3750 cGy (D2% < 4000cGy is an acceptable variation), D98% > 2500 cGy; hippocampus D100% < 900 cGy and Dmax < 1600 cGy (Dmax<1700 cGy is an acceptable variation); optic chiasm and optic nerves max dose < 3750 cGy.
Purpose/Objective: To assess the feasibility of cone beam computed tomography (CBCT) images for cranial stereotactic radiosurgery (SRS) treatment planning. Materials and Methods: Cranial radiosurgery treatments are delivered in our department using a Varian 2100 CD linac equipped with the On Board Imaging (OBI) system. The called half-fan technique is the one selected in our facility for cranial CBCT acquisitions. HU values were measured for several CBCTs and conventional CT scans (Siemens Somaton Sensation), using a dedicated phantom with different materials (Catphan). A two tailed Student t-test was used for HU comparison aim. Three patients were planned based-on the conventional CT scan (pCT) in Eclipse treatment planning system (version 10.0). For each patient, a CBCT scan was obtained in treatment position according to the setup of the Eclipse plan. The CBCT set was imported into Eclipse system and fused with the pCT. Isocenter plan, organs at risk (brainstem, chiasma, and optic nerves) and target volume were transferred from pCT to CBCT data set in order to re-calculate the treatment plan on the CBCT scan, by keeping the original monitor units. AAA model with heterogeneity correction enabled were used for dose calculations. Dose distributions were compared on the CBCT images to conventional pCT images. Results: Measured CBCT HU values were significant lower than conventional CT images for each material of the Catphan phantom (p< 0.05). Dose differences within 3% in target and normal structures were found when dose distributions of the same plan were computed on the CBCT and conventional CT images. Conclusions: Although a significant difference on the calibration curve was detected between CBCT and pCT images, important dose differences were not found on treatments computed with Eclipse system. We consider that OBI-CBCT tomography is reliable enough for dose calculation in cranial SRS treatments. CBCT allows the acquisition of a planning CT in the same treatment setup and so it would be possible to reduce uncertainties related to imaging process during a frameless stereotactic planning. EP-1398 MAMMOGRAPHY IMAGE SEGMENTATION, TUMOR RECOGNITION AND AUTOMATIC MODEL BUILDING V. Mateev1, I. Marinova1, A. Chakarova2 1 Technical University of Sofia, Department of Electrical Apparatus, Sofia, Bulgaria 2 National Hospital of Oncology, Department of Radiotherapy, Sofia, Bulgaria Purpose/Objective: Computer-aided diagnosis systems are usually used for marking conspicuous structures and sections by sophisticated image segmentation techniques. Anatomy objects are particularly complex structures, and their segmentation is an important step for studies in temporal change detection of morphology, as well as for 2D/3D/4D visualization, diagnosis, screening and surgical planning modeling. The objects to be segmented are anatomical structures which are often non rigid and complex in shape, and exhibit considerable variability from person to person. This combined with an absence of explicit shape models that capture the deformations in anatomy, makes the segmentation task challenging. Aim of this work is a sophisticated method for automatic mammography images segmentation applied for 2D/3D vector model building, tumor detection and its size classification.