- Email: [email protected]
MV cone-beam CT technique
S200
I. J. Radiation Oncology
● Biology ● Physics
Volume 60, Number 1, Supplement, 2004
present in the CBCT data, and (2) the AP view of the pelvis contains features which are sensitive to and can be used for the reliable determination of out-of-plane rotations and translations. This technique is theoretically applicable to other rigid bony structures such as the cranial vault or skull base where the accuracy of computer-controlled radiation therapy techniques such as IMRT depends critically upon set-up accuracy. This study was supported by NIH grants 8R011EB002164 and EB002470.
118
A Novel Hardware Design for Image and Dose Guided Radiotherapy
B. Hesse, S. Nill, T. Tuecking, U. Oelfke Medical Physics, DKFZ, Heidelberg, Germany Purpose/Objective: Conventional radiation therapy assumes that possible movements of organs during therapy can either be neglected or taken into account in the planning phase. In this presentation, we describe a novel imaging hardware set-up to overcome this limitation. The imaging hardware was designed and integrated into a standard medical accelerator to provide a tomographic and a beams eye view imaging which provides a radiographic localisation of bone and soft-tissue targets. Furthermore this novel imaging hardware provides also a system for verifying of the delivered dose by means of entrance dosimetry. Materials/Methods: For imaging purposes a kV X-ray tube (POWERPHOS, SIEMENS) was integrated with a SIEMENS Primus linear accelerator. The kV X-ray tube was mounted opposite to the source of the therapy beam. As a detector a flat-panel device RID1640 (Perkin Elmer Optoelectronics, Germany) was mounted on the side of the therapy beam in front of the patient. The amorphous silicon flat-panel imager provides 1024 ⫻ 1024 pixels with 400 mm pitch and an active area of 40.96cm ⫻ 40.96cm. While the flat-panel is irradiated with the kV x-ray from its front side, the detector is irradiated from the back side with the MV therapy beam. This imaging set-up provides on one hand a tomographic cone beam imaging system which allows monitoring the patient’s anatomy in treatment position just before the start of the treatment fraction. On the other hand it allows acquiring an image of a volume of interest of the patient e.g. the treatment volume in fluoroscopic mode during therapy beam application utilising the pulse recess of the Linac beam. Because both the therapy beam and the diagnostic x-ray beam are mounted on the same beam axis the fluoroscopic images can be used to match these fluoroscopic views with images of the shape of the treatment. These images are acquired nearly at the same time just with the same flat-panel detector by an interlaced read out of the detector between MV and kV X-ray beam. For CT image reconstruction we use a standard 3D algorithm (Feldkamp, Kress). The flat-panel imager is used as a 2D beam monitor to record the intensity modulated fluence distribution of incoming photons of the therapy beam. Different sample IMRT plans based on a solid water phantom and an anthropomorphic head and body phantom were generated using the Virtuos/KonRad inverse planning system (DKFZ / SIEMENS, Heidelberg, Germany). The IMRT beams from these pre-calculated treatment plans were delivered and recorded with the flat-panel imager by acquiring sequences of images. The treatment set-up of the phantom was verified by the imaging system. Results: Compared to the dose of a conventional CT first results of the tomographic cone beam images show with a similar dose a contrast resolution of about 1% for objects larger than 3mm and a spatial resolution of about 1mm for high contrast objects. A very good agreement could be seen between planned and measured entrance fluence distributions for each IMRT beam. The error was calculated to be less than ⫾2%. An error of less then ⫾2mm was seen for isodose lines down to the 50% line. For the lower isodose lines or regions with steep dose gradients the error somewhat increases. Different dose measurements in a water tank indicate that the therapy beam quality is not significant affected by the flat-panel. Only the absolute dose is reduced by 10% because of the additional attenuation. Conclusions: We have integrated an imaging system with a medical linear accelerator for kV tomographic and beam’s eye view imaging which provides a radiographic target localisation and for delivered therapy beam verification. Preliminary results show that image acquisition in tomographic and radiographic mode gives high quality images, sufficient for patient set-up and for target localisation before and during therapy beam application. A method of in vivo dose reconstruction based on measurements of entrance beams was developed and tested by means of comparisons with sample IMRT plans. Generally good agreement was seen between planning, reconstruction and direct measurement of the three-dimensional dose distribution.
119
Full 3-D Treatment Verification Using An Aggregated kV/MV Cone-Beam CT Technique
F. Yin, H. Guan, R. Hammoud, M. Ajlouni, D. Pradhan, J. H. Kim Radiation Oncology, Henry Ford Health System, Detroit, MI Purpose/Objective: Full 3-D treatment verification is desirable and yet to be achieved for conformal radiation therapy, especially for IMRT. Conventionally, treatment portals are verified with 2-D portal images which lack of 3-D anatomical information around the treatment volume. The use of MV portal CT for 3-D treatment verification is limited due to excessive radiation. While the gantry-mounted kV CT delivers much less dose for 3-D verification, it lacks the treatment portal information. This dilemma could be resolved by using both kV and MV imaging devices, orthogonally mounted on the linac gantry. The purpose of this study is to develop an aggregated adaptive cone-beam CT technique for full 3-D treatment verification. Materials/Methods: In this study, we took an aggregated approach to effectively reconstruct CT images with the combination of full kV projections and truncated MV projections. Cone-beam reconstruction was based on adaptive multilevel algebraic technique (MLS-ART). The projections were acquired using a Varian CL21EX accelerator with both a kV imaging device and an aSi500 portal imager mounted orthogonally on the gantry. At present, each MV projection image was acquired using one monitor unit which could be potentially reduced. The low-exposure kV projections were acquired to reconstruct anatomical CT images and the MV projections were added to enhance the anatomical information around the treatment volume in the reconstructed CT images. To minimize the radiation dose, only limited numbers of kV and MV projections were acquired and only the truncated MV projections were acquired to cover the treatment volume. Phantoms for different anatomical sites were used in this study. The effects of total number of projections, the combination of numbers of kV and MV projections, different
Proceedings of the 46th Annual ASTRO Meeting
anatomical sites, and the attenuation coefficient conversion between the MV and kV projections on the quality of reconstructed adaptive 3-D cone-beam CT were also investigated. Results: Preliminary results from phantom studies indicated that adaptive kV/MV cone-beam CT images generated using as low as 9 truncated MV projections (⬍10 MUs) and 18 full kV projections provide reasonable estimation of 3-D treatment anatomy for treatment verification. The details of the treatment anatomy improve as the projection number increases. Cross-calibration using a CT phantom with multiple density inserts provides proper conversion between kV and MV projections for kV/MV cone-beam reconstruction. Orthogonal dual-image acquisition could also reduce the acquisition time by about 30 –50%. Conclusions: The dual-energy adaptive cone-beam reconstruction introduced a new 3-D verification technique with clinically acceptable dosage. It provides not only 3-D anatomy but also the treatment volume information. Based on the 3-D anatomical structures effectively reconstructed using limited number of projections, dose verification and gated cone-beam CT may become possible for real-time 3-D IMRT dose and anatomy verification.
120
What is the Role of F-18 FDG PET Within Randomized Multicenter Clinical Trials for Multi-Modality Treatment of Non-Small Cell Lung Cancer Stage III
M. Schmuecking,1 R. Bonnet,2 R. Baum,1 M. Scheithauer,3 N. Presselt,4 C. Schneider,2 T. Kohl,4 A. Niesen,1 J. Leonhardi,5 K. Mueller,8 K. Kloetzer,6 T. Wendt3 1 Dept. of Nuclear Medicine/PET Center, Zentralklinik Bad Berka, Bad Berka, Germany, 2Dept. of Pneumology, Zentralklinik Bad Berka, Bad Berka, Germany, 3Dept. of Radiation Oncology, University of Jena, Jena, Germany, 4Dept. of Thoracic Surgery, Zentralklinik Bad Berka, Bad Berka, Germany, 5Dept of Diagnostic Radiology, Zentralklinik Bad Berka, Bad Berka, Germany, 6Dept. of Radiation Oncology, University Teaching Hospital Gera, Gera, Germany, 7Dept. of Pathology, Zentralklinik Bad Berka, Bad Berka, Germany, 8Dept. of Pathology, University Hospital Bergmannsheil Bochum, Bochum, Germany Purpose/Objective: To evaluate the role of F-18 FDG PET for staging, therapy management, molecular radiation treatment planning and early therapy response after neoadjuvant chemoradiation and its effect on survival as compared to histopathologic tumor response (regression grade), findings in 76/141 patients (center Bad Berka) with non-small cell lung cancer stage III are analyzed prospectively in an ongoing multicenter trial (LUCAS-MD, principal study center Bad Berka/Jena). Materials/Methods: Inclusion criteria: histologically confirmed NSCLC stage IIIA/IIIB. Neoadjuvant treatment: 2–3 cycles of chemotherapy with paclitaxel/carboplatin and a block of chemoradiation (45Gy, 1.5Gy b.i.d., concomitant with paclitaxel/ carboplatin) followed by surgery. Pretherapeutic staging of all patients: PET scan in addition to a spiral CT and/or MRI. Second PET scan after completion of neoadjuvant therapy prior to surgery. Documentation of lymph node involvement evaluated by PET according to Naruke/ATS-LCSG classification. Assessment of the tumor standardized uptake values (SUV), the tumor to background SUV ratio (T/B ratio), the metabolic tumor diameter (MTD) and the metabolic tumor index (MTI ⫽ SUV ⫻ MTD) in all primary tumors and metastatic lymph nodes. Image fusion of PET with CT data followed by molecular radiation treatment planning. Sampling of lymph nodes during surgery according to Naruke classification. Evaluation of histological regression grade and correlation with PET for primary tumor and each lymph node location. Statistical analyses: Wilcoxon-, chi-square-, Mantel-Haenszel-test, Kaplan-Meier-method, multivariate Cox-regression. Results: Upstaging in 6/76 patients due to distant metastases. Downstaging in 2/76 (metabolic PET staging T2N0M0 bzw. T3N0M0). Tumor specific survival for all patients after 12 and 36 months: 70% and 35%. Paraoperative lethality below 4%. Complete vs. incomplete metabolic remission after 24 months: 73% vs. 22% (p ⫽ 0,032). Regression grade (RG) III/IIb (no/less than 10% of vital tumor cells) vs. RG IIa/I (more than 10% vital tumor cells) after 24 months: 66% vs. 35% (p ⫽ 0,016). Multivariate Cox-analysis for SUV: p ⬎ 0,05. Statistical power of the tests: 70% so far. If PET was used additionally for the 3D-planning procedure of radiation therapy, the planning target volume (PTV) could be changed in 83% of the patients, in 22% the PTV was reduced substantially (mean 12%, maximum 25%, p ⬍ 0.05) leading to a reduction of dose to the organs at risk, e.g., Vlung (20Gy) could be reduced up to 17% (p ⫽ 0.02). Conclusions: Integration of PET in clinical trials enables a more accurate therapy management. F-18 FDG PET precedes CT in measuring the tumor response after neoadjuvant treatment and may predict (long term) therapeutic outcome in stage III NSCLC. Histological regression grade correlates well with metabolic remission as detected by PET. The initial SUV of F-18 FDG correlating with cellular differentiation and proliferation capacity of tumor cells is not an independent prognostic factor for NSCLC in contrast to recent publications with heterogeneous patient populations (i.e. study population with different stages (e.g. I-IIIB) receiving different therapies). PET is a complementary tool to anatomic imaging modalities for an exact localization of nodal involvement and the extent of the primary tumor. Using metabolic tumor localization by PET in addition to anatomic delineation by CT scan, a better tumor control may be achieved.
121
Early FDG-PET Imaging After Radical Radiotherapy for Non-Small Cell Lung Cancer: Inflammatory Changes in Normal Tissues Correlate with Tumor Response and do not Confound Therapeutic Response Evaluation
R. Hicks, M. MacManus, J. Matthews, A. Hogg, D. Binns, D. Rischin, D. Ball, L. Peters Peter MacCallum Cancer Centre, East Melbourne, VIC, Australia Purpose/Objective: To investigate the relationship between PET-detected inflammatory changes in irradiated normal tissues and metabolic response at tumor sites in patients receiving radical radiotherapy (RRT) or chemo/RT for non-small cell lung cancer (NSCLC). The prognostic significance of these changes was also studied. We have previously reported that metabolic response powerfully predicts survival.
S201
I. J. Radiation Oncology
● Biology ● Physics
Volume 60, Number 1, Supplement, 2004
present in the CBCT data, and (2) the AP view of the pelvis contains features which are sensitive to and can be used for the reliable determination of out-of-plane rotations and translations. This technique is theoretically applicable to other rigid bony structures such as the cranial vault or skull base where the accuracy of computer-controlled radiation therapy techniques such as IMRT depends critically upon set-up accuracy. This study was supported by NIH grants 8R011EB002164 and EB002470.
118
A Novel Hardware Design for Image and Dose Guided Radiotherapy
B. Hesse, S. Nill, T. Tuecking, U. Oelfke Medical Physics, DKFZ, Heidelberg, Germany Purpose/Objective: Conventional radiation therapy assumes that possible movements of organs during therapy can either be neglected or taken into account in the planning phase. In this presentation, we describe a novel imaging hardware set-up to overcome this limitation. The imaging hardware was designed and integrated into a standard medical accelerator to provide a tomographic and a beams eye view imaging which provides a radiographic localisation of bone and soft-tissue targets. Furthermore this novel imaging hardware provides also a system for verifying of the delivered dose by means of entrance dosimetry. Materials/Methods: For imaging purposes a kV X-ray tube (POWERPHOS, SIEMENS) was integrated with a SIEMENS Primus linear accelerator. The kV X-ray tube was mounted opposite to the source of the therapy beam. As a detector a flat-panel device RID1640 (Perkin Elmer Optoelectronics, Germany) was mounted on the side of the therapy beam in front of the patient. The amorphous silicon flat-panel imager provides 1024 ⫻ 1024 pixels with 400 mm pitch and an active area of 40.96cm ⫻ 40.96cm. While the flat-panel is irradiated with the kV x-ray from its front side, the detector is irradiated from the back side with the MV therapy beam. This imaging set-up provides on one hand a tomographic cone beam imaging system which allows monitoring the patient’s anatomy in treatment position just before the start of the treatment fraction. On the other hand it allows acquiring an image of a volume of interest of the patient e.g. the treatment volume in fluoroscopic mode during therapy beam application utilising the pulse recess of the Linac beam. Because both the therapy beam and the diagnostic x-ray beam are mounted on the same beam axis the fluoroscopic images can be used to match these fluoroscopic views with images of the shape of the treatment. These images are acquired nearly at the same time just with the same flat-panel detector by an interlaced read out of the detector between MV and kV X-ray beam. For CT image reconstruction we use a standard 3D algorithm (Feldkamp, Kress). The flat-panel imager is used as a 2D beam monitor to record the intensity modulated fluence distribution of incoming photons of the therapy beam. Different sample IMRT plans based on a solid water phantom and an anthropomorphic head and body phantom were generated using the Virtuos/KonRad inverse planning system (DKFZ / SIEMENS, Heidelberg, Germany). The IMRT beams from these pre-calculated treatment plans were delivered and recorded with the flat-panel imager by acquiring sequences of images. The treatment set-up of the phantom was verified by the imaging system. Results: Compared to the dose of a conventional CT first results of the tomographic cone beam images show with a similar dose a contrast resolution of about 1% for objects larger than 3mm and a spatial resolution of about 1mm for high contrast objects. A very good agreement could be seen between planned and measured entrance fluence distributions for each IMRT beam. The error was calculated to be less than ⫾2%. An error of less then ⫾2mm was seen for isodose lines down to the 50% line. For the lower isodose lines or regions with steep dose gradients the error somewhat increases. Different dose measurements in a water tank indicate that the therapy beam quality is not significant affected by the flat-panel. Only the absolute dose is reduced by 10% because of the additional attenuation. Conclusions: We have integrated an imaging system with a medical linear accelerator for kV tomographic and beam’s eye view imaging which provides a radiographic target localisation and for delivered therapy beam verification. Preliminary results show that image acquisition in tomographic and radiographic mode gives high quality images, sufficient for patient set-up and for target localisation before and during therapy beam application. A method of in vivo dose reconstruction based on measurements of entrance beams was developed and tested by means of comparisons with sample IMRT plans. Generally good agreement was seen between planning, reconstruction and direct measurement of the three-dimensional dose distribution.
119
Full 3-D Treatment Verification Using An Aggregated kV/MV Cone-Beam CT Technique
F. Yin, H. Guan, R. Hammoud, M. Ajlouni, D. Pradhan, J. H. Kim Radiation Oncology, Henry Ford Health System, Detroit, MI Purpose/Objective: Full 3-D treatment verification is desirable and yet to be achieved for conformal radiation therapy, especially for IMRT. Conventionally, treatment portals are verified with 2-D portal images which lack of 3-D anatomical information around the treatment volume. The use of MV portal CT for 3-D treatment verification is limited due to excessive radiation. While the gantry-mounted kV CT delivers much less dose for 3-D verification, it lacks the treatment portal information. This dilemma could be resolved by using both kV and MV imaging devices, orthogonally mounted on the linac gantry. The purpose of this study is to develop an aggregated adaptive cone-beam CT technique for full 3-D treatment verification. Materials/Methods: In this study, we took an aggregated approach to effectively reconstruct CT images with the combination of full kV projections and truncated MV projections. Cone-beam reconstruction was based on adaptive multilevel algebraic technique (MLS-ART). The projections were acquired using a Varian CL21EX accelerator with both a kV imaging device and an aSi500 portal imager mounted orthogonally on the gantry. At present, each MV projection image was acquired using one monitor unit which could be potentially reduced. The low-exposure kV projections were acquired to reconstruct anatomical CT images and the MV projections were added to enhance the anatomical information around the treatment volume in the reconstructed CT images. To minimize the radiation dose, only limited numbers of kV and MV projections were acquired and only the truncated MV projections were acquired to cover the treatment volume. Phantoms for different anatomical sites were used in this study. The effects of total number of projections, the combination of numbers of kV and MV projections, different
Proceedings of the 46th Annual ASTRO Meeting
anatomical sites, and the attenuation coefficient conversion between the MV and kV projections on the quality of reconstructed adaptive 3-D cone-beam CT were also investigated. Results: Preliminary results from phantom studies indicated that adaptive kV/MV cone-beam CT images generated using as low as 9 truncated MV projections (⬍10 MUs) and 18 full kV projections provide reasonable estimation of 3-D treatment anatomy for treatment verification. The details of the treatment anatomy improve as the projection number increases. Cross-calibration using a CT phantom with multiple density inserts provides proper conversion between kV and MV projections for kV/MV cone-beam reconstruction. Orthogonal dual-image acquisition could also reduce the acquisition time by about 30 –50%. Conclusions: The dual-energy adaptive cone-beam reconstruction introduced a new 3-D verification technique with clinically acceptable dosage. It provides not only 3-D anatomy but also the treatment volume information. Based on the 3-D anatomical structures effectively reconstructed using limited number of projections, dose verification and gated cone-beam CT may become possible for real-time 3-D IMRT dose and anatomy verification.
120
What is the Role of F-18 FDG PET Within Randomized Multicenter Clinical Trials for Multi-Modality Treatment of Non-Small Cell Lung Cancer Stage III
M. Schmuecking,1 R. Bonnet,2 R. Baum,1 M. Scheithauer,3 N. Presselt,4 C. Schneider,2 T. Kohl,4 A. Niesen,1 J. Leonhardi,5 K. Mueller,8 K. Kloetzer,6 T. Wendt3 1 Dept. of Nuclear Medicine/PET Center, Zentralklinik Bad Berka, Bad Berka, Germany, 2Dept. of Pneumology, Zentralklinik Bad Berka, Bad Berka, Germany, 3Dept. of Radiation Oncology, University of Jena, Jena, Germany, 4Dept. of Thoracic Surgery, Zentralklinik Bad Berka, Bad Berka, Germany, 5Dept of Diagnostic Radiology, Zentralklinik Bad Berka, Bad Berka, Germany, 6Dept. of Radiation Oncology, University Teaching Hospital Gera, Gera, Germany, 7Dept. of Pathology, Zentralklinik Bad Berka, Bad Berka, Germany, 8Dept. of Pathology, University Hospital Bergmannsheil Bochum, Bochum, Germany Purpose/Objective: To evaluate the role of F-18 FDG PET for staging, therapy management, molecular radiation treatment planning and early therapy response after neoadjuvant chemoradiation and its effect on survival as compared to histopathologic tumor response (regression grade), findings in 76/141 patients (center Bad Berka) with non-small cell lung cancer stage III are analyzed prospectively in an ongoing multicenter trial (LUCAS-MD, principal study center Bad Berka/Jena). Materials/Methods: Inclusion criteria: histologically confirmed NSCLC stage IIIA/IIIB. Neoadjuvant treatment: 2–3 cycles of chemotherapy with paclitaxel/carboplatin and a block of chemoradiation (45Gy, 1.5Gy b.i.d., concomitant with paclitaxel/ carboplatin) followed by surgery. Pretherapeutic staging of all patients: PET scan in addition to a spiral CT and/or MRI. Second PET scan after completion of neoadjuvant therapy prior to surgery. Documentation of lymph node involvement evaluated by PET according to Naruke/ATS-LCSG classification. Assessment of the tumor standardized uptake values (SUV), the tumor to background SUV ratio (T/B ratio), the metabolic tumor diameter (MTD) and the metabolic tumor index (MTI ⫽ SUV ⫻ MTD) in all primary tumors and metastatic lymph nodes. Image fusion of PET with CT data followed by molecular radiation treatment planning. Sampling of lymph nodes during surgery according to Naruke classification. Evaluation of histological regression grade and correlation with PET for primary tumor and each lymph node location. Statistical analyses: Wilcoxon-, chi-square-, Mantel-Haenszel-test, Kaplan-Meier-method, multivariate Cox-regression. Results: Upstaging in 6/76 patients due to distant metastases. Downstaging in 2/76 (metabolic PET staging T2N0M0 bzw. T3N0M0). Tumor specific survival for all patients after 12 and 36 months: 70% and 35%. Paraoperative lethality below 4%. Complete vs. incomplete metabolic remission after 24 months: 73% vs. 22% (p ⫽ 0,032). Regression grade (RG) III/IIb (no/less than 10% of vital tumor cells) vs. RG IIa/I (more than 10% vital tumor cells) after 24 months: 66% vs. 35% (p ⫽ 0,016). Multivariate Cox-analysis for SUV: p ⬎ 0,05. Statistical power of the tests: 70% so far. If PET was used additionally for the 3D-planning procedure of radiation therapy, the planning target volume (PTV) could be changed in 83% of the patients, in 22% the PTV was reduced substantially (mean 12%, maximum 25%, p ⬍ 0.05) leading to a reduction of dose to the organs at risk, e.g., Vlung (20Gy) could be reduced up to 17% (p ⫽ 0.02). Conclusions: Integration of PET in clinical trials enables a more accurate therapy management. F-18 FDG PET precedes CT in measuring the tumor response after neoadjuvant treatment and may predict (long term) therapeutic outcome in stage III NSCLC. Histological regression grade correlates well with metabolic remission as detected by PET. The initial SUV of F-18 FDG correlating with cellular differentiation and proliferation capacity of tumor cells is not an independent prognostic factor for NSCLC in contrast to recent publications with heterogeneous patient populations (i.e. study population with different stages (e.g. I-IIIB) receiving different therapies). PET is a complementary tool to anatomic imaging modalities for an exact localization of nodal involvement and the extent of the primary tumor. Using metabolic tumor localization by PET in addition to anatomic delineation by CT scan, a better tumor control may be achieved.
121
Early FDG-PET Imaging After Radical Radiotherapy for Non-Small Cell Lung Cancer: Inflammatory Changes in Normal Tissues Correlate with Tumor Response and do not Confound Therapeutic Response Evaluation
R. Hicks, M. MacManus, J. Matthews, A. Hogg, D. Binns, D. Rischin, D. Ball, L. Peters Peter MacCallum Cancer Centre, East Melbourne, VIC, Australia Purpose/Objective: To investigate the relationship between PET-detected inflammatory changes in irradiated normal tissues and metabolic response at tumor sites in patients receiving radical radiotherapy (RRT) or chemo/RT for non-small cell lung cancer (NSCLC). The prognostic significance of these changes was also studied. We have previously reported that metabolic response powerfully predicts survival.
S201