Purpose: To generate parametric images of tumor hypoxia in a tumor-bearing rat model using voxel-based compartmental analysis of dynamic fluorine-18 labeled misonidazole (18F-FMISO) microPET? images, and to compare th...Purpose: To generate parametric images of tumor hypoxia in a tumor-bearing rat model using voxel-based compartmental analysis of dynamic fluorine-18 labeled misonidazole (18F-FMISO) microPET? images, and to compare the parametric images thus derived with static “late” 18F-FMISO microPET? images for the detection of tumor hypoxia. Materials and Methods: Nude rats bearing HT-29 colorectal carcinoma xenografts (≈1.5 - 2 cm in diameter) in the right hind limb were positioned in a custom-fabricated, animal-specific foam mold. Animals were injected via the tail vein with ≈55.5 MBq 18F-FMISO and continuously imaged for either 60 or 120 minutes, with additional late static images up to 3 hour post-injection. The raw list-mode data was reconstructed into 37 - 64 frames with earlier frames of shorter time durations (12 - 15 seconds) and later frames of longer durations (up to 300 seconds). Time activity curves (TACs) were generated over regions encompassing the tumor as well as an artery, the latter for use as an input function. A beta version of a compartmental modeling package (BioGuide?, Philips Healthcare) was used to generate parametric images of k3 and Ki, rate constants of entrapment and flux of 18F-FMISO, respectively. Results: Data for 7 HT-29 tumor xenografts were presented, 6 of which yielded clear areas of tumor hypoxia as defined by Ki/k3 maps. Importantly, intratumoral foci with high 18F-FMISO uptakes on the late images did not always exhibit high Ki/k3 values and may there- fore represent false-positives for radiobiologically significant hypoxia. Conclusions: This study attempts to quantify tumor hypoxia using compartmental analysis of dynamic 18F-FMISO PET images in rodent xenograft tumor models. The results demonstrate feasibility of the approach in small-animal imaging studies, and provide evidence for the possible unreliability of late-time static imaging of 18F-FMISO PET in identifying tumor hypoxia.展开更多
With the development of social economy and radiotherapy technique,proton/heavy ion radiotherapy has been applied widely to clinical practices.At present,there are at least 29 hospitals in China at various stages of pl...With the development of social economy and radiotherapy technique,proton/heavy ion radiotherapy has been applied widely to clinical practices.At present,there are at least 29 hospitals in China at various stages of planning,construction,commissioning or clinical operation of medical proton/heavy ion beam radiotherapy equipment.Compared with common radiotherapy accelerators used in conventional external beam radiotherapy,the proton/heavy ion therapy system has more stringent requirements for quality control so as to achieve an optimum therapeutic effect.In order to protect the health rights of patients undergoing radiotherapy,to facilitate the relevant administrative supervision departments to carry out standard-based approval and routine supervision and to promote the development of related medical undertakings,the standard for testing of quality control for medical proton/heavy ion beam radiotherapy equipment is drafted to fill the gap in this regard in China and even worldwide.The standard contains five indicators and corresponding testing methods for radiological protection and safety and 16 indicators for quality control of equipment performance.The standard is a mandatory standard and is based on the relevant Chinese legal requirements for the testing of radiotherapy equipment,so all the indicators listed in the standard shall be tested.During the drafting of the standard,the opinions from hospitals that are currently using proton/heavy ion medical accelerators for radiotherapy purpose and from the related equipment manufacturers were taken into account.The draft standard was revised with reference to these opinions and the feasibility of the related quality control requirements.The official version of the standard was released on March 7,2023,and implementation is scheduled to begin on March 1,2024.展开更多
文摘Purpose: To generate parametric images of tumor hypoxia in a tumor-bearing rat model using voxel-based compartmental analysis of dynamic fluorine-18 labeled misonidazole (18F-FMISO) microPET? images, and to compare the parametric images thus derived with static “late” 18F-FMISO microPET? images for the detection of tumor hypoxia. Materials and Methods: Nude rats bearing HT-29 colorectal carcinoma xenografts (≈1.5 - 2 cm in diameter) in the right hind limb were positioned in a custom-fabricated, animal-specific foam mold. Animals were injected via the tail vein with ≈55.5 MBq 18F-FMISO and continuously imaged for either 60 or 120 minutes, with additional late static images up to 3 hour post-injection. The raw list-mode data was reconstructed into 37 - 64 frames with earlier frames of shorter time durations (12 - 15 seconds) and later frames of longer durations (up to 300 seconds). Time activity curves (TACs) were generated over regions encompassing the tumor as well as an artery, the latter for use as an input function. A beta version of a compartmental modeling package (BioGuide?, Philips Healthcare) was used to generate parametric images of k3 and Ki, rate constants of entrapment and flux of 18F-FMISO, respectively. Results: Data for 7 HT-29 tumor xenografts were presented, 6 of which yielded clear areas of tumor hypoxia as defined by Ki/k3 maps. Importantly, intratumoral foci with high 18F-FMISO uptakes on the late images did not always exhibit high Ki/k3 values and may there- fore represent false-positives for radiobiologically significant hypoxia. Conclusions: This study attempts to quantify tumor hypoxia using compartmental analysis of dynamic 18F-FMISO PET images in rodent xenograft tumor models. The results demonstrate feasibility of the approach in small-animal imaging studies, and provide evidence for the possible unreliability of late-time static imaging of 18F-FMISO PET in identifying tumor hypoxia.
文摘With the development of social economy and radiotherapy technique,proton/heavy ion radiotherapy has been applied widely to clinical practices.At present,there are at least 29 hospitals in China at various stages of planning,construction,commissioning or clinical operation of medical proton/heavy ion beam radiotherapy equipment.Compared with common radiotherapy accelerators used in conventional external beam radiotherapy,the proton/heavy ion therapy system has more stringent requirements for quality control so as to achieve an optimum therapeutic effect.In order to protect the health rights of patients undergoing radiotherapy,to facilitate the relevant administrative supervision departments to carry out standard-based approval and routine supervision and to promote the development of related medical undertakings,the standard for testing of quality control for medical proton/heavy ion beam radiotherapy equipment is drafted to fill the gap in this regard in China and even worldwide.The standard contains five indicators and corresponding testing methods for radiological protection and safety and 16 indicators for quality control of equipment performance.The standard is a mandatory standard and is based on the relevant Chinese legal requirements for the testing of radiotherapy equipment,so all the indicators listed in the standard shall be tested.During the drafting of the standard,the opinions from hospitals that are currently using proton/heavy ion medical accelerators for radiotherapy purpose and from the related equipment manufacturers were taken into account.The draft standard was revised with reference to these opinions and the feasibility of the related quality control requirements.The official version of the standard was released on March 7,2023,and implementation is scheduled to begin on March 1,2024.
