An estimate of 90Y dosimetry for bremsstrahlung SPECT/CT imaging in liver therapy with 90Y microspheres. 2021

Karin Knešaurek
Division of Nuclear Medicine, Department of Radiology, Icahn School of Medicine at Mount Sinai, Box 1141, One Gustave L. Levy Place, New York, NY, 10029, USA. Electronic address: karin.knesaurek@mssm.edu.

OBJECTIVE Bremsstrahlung SPECT/CT (bSPECT/CT) is one of the most common methods for post-therapy imaging in 90Y microspheres selective internal radiation therapy (SIRT) of liver cancers. Here, we are proposing a simple approach using bSPECT/CT to estimate mean absorbed dose to the liver in patients undergoing treatment with 90Y microspheres. METHODS In our previous study comparing 90Y dosimetry obtained using bSPECT/CT vs PET/CT, we found that there was a large difference between the mean absorbed dose values to the whole-liver. However, there was a high linear correlation between the doses, which presented an opportunity for quantitative assessment using bSPECT/CT 90Y imaging. In this study, after treatment with 90Y microspheres, 43 patients were immediately imaged on a dual-head Infinia SPECT/CT gamma camera and on a mCT PET/CT system. Images from 25 of the patients, randomly selected, were used to calculate the correlation of mean liver doses obtained from bSPECT/CT vs. PET/CT. For the remaining 18 patients, the calculated correlation was used to estimate doses obtained from bSPECT/CT, and these estimations were then compared to the doses obtained from PET/CT, considered the gold standard for quantitative analysis. RESULTS From the 25 selected patients, the calculated linear correlation between bSPECT/CT and PET/CT 90Y mean absorbed doses in whole liver was high (r^2 = 0.97), with a slope of 2.80 and an intercept of -0.63. This linear fit was used to calculate the bSPECT/CT doses for the remaining 18 patients. For these patients, the mean whole-liver dose obtained from bSPECT/CT fitted data vs that obtained from PET/CT were 50.59 Gy and 50.81 Gy, respectively. The average dose difference was 0.2 ± 5.4 Gy (range -18.2%-13.0%). The repeatability coefficient was 10.5 (20.8 % of the mean). CONCLUSIONS Although quantitative bremsstrahlung imaging is difficult, it is possible to calculate adequate estimates of whole-liver dosimetry from bSPECT/CT imaging that is calibrated using its correlation with post-therapy PET/CT 90Y images.

UI MeSH Term Description Entries
D008099 Liver A large lobed glandular organ in the abdomen of vertebrates that is responsible for detoxification, metabolism, synthesis and storage of various substances. Livers
D008113 Liver Neoplasms Tumors or cancer of the LIVER. Cancer of Liver,Hepatic Cancer,Liver Cancer,Cancer of the Liver,Cancer, Hepatocellular,Hepatic Neoplasms,Hepatocellular Cancer,Neoplasms, Hepatic,Neoplasms, Liver,Cancer, Hepatic,Cancer, Liver,Cancers, Hepatic,Cancers, Hepatocellular,Cancers, Liver,Hepatic Cancers,Hepatic Neoplasm,Hepatocellular Cancers,Liver Cancers,Liver Neoplasm,Neoplasm, Hepatic,Neoplasm, Liver
D008863 Microspheres Small uniformly-sized spherical particles, of micrometer dimensions, frequently labeled with radioisotopes or various reagents acting as tags or markers. Latex Beads,Latex Particles,Latex Spheres,Microbeads,Bead, Latex,Beads, Latex,Latex Bead,Latex Particle,Latex Sphere,Microbead,Microsphere,Particle, Latex,Particles, Latex,Sphere, Latex,Spheres, Latex
D006801 Humans Members of the species Homo sapiens. Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D000072078 Positron Emission Tomography Computed Tomography An imaging technique that combines a POSITRON-EMISSION TOMOGRAPHY (PET) scanner and a CT X RAY scanner. This establishes a precise anatomic localization in the same session. CT PET,CT PET Scan,PET CT Scan,PET-CT,PET-CT Scan,Positron Emission Tomography-Computed Tomography,CT PET Scans,CT Scan, PET,CT Scans, PET,PET CT Scans,PET Scan, CT,PET Scans, CT,PET-CT Scans,Scan, CT PET,Scan, PET CT,Scan, PET-CT,Scans, CT PET,Scans, PET CT,Scans, PET-CT
D014057 Tomography, X-Ray Computed Tomography using x-ray transmission and a computer algorithm to reconstruct the image. CAT Scan, X-Ray,CT Scan, X-Ray,Cine-CT,Computerized Tomography, X-Ray,Electron Beam Computed Tomography,Tomodensitometry,Tomography, Transmission Computed,X-Ray Tomography, Computed,CAT Scan, X Ray,CT X Ray,Computed Tomography, X-Ray,Computed X Ray Tomography,Computerized Tomography, X Ray,Electron Beam Tomography,Tomography, X Ray Computed,Tomography, X-Ray Computer Assisted,Tomography, X-Ray Computerized,Tomography, X-Ray Computerized Axial,Tomography, Xray Computed,X Ray Computerized Tomography,X Ray Tomography, Computed,X-Ray Computer Assisted Tomography,X-Ray Computerized Axial Tomography,Beam Tomography, Electron,CAT Scans, X-Ray,CT Scan, X Ray,CT Scans, X-Ray,CT X Rays,Cine CT,Computed Tomography, Transmission,Computed Tomography, X Ray,Computed Tomography, Xray,Computed X-Ray Tomography,Scan, X-Ray CAT,Scan, X-Ray CT,Scans, X-Ray CAT,Scans, X-Ray CT,Tomographies, Computed X-Ray,Tomography, Computed X-Ray,Tomography, Electron Beam,Tomography, X Ray Computer Assisted,Tomography, X Ray Computerized,Tomography, X Ray Computerized Axial,Transmission Computed Tomography,X Ray Computer Assisted Tomography,X Ray Computerized Axial Tomography,X Ray, CT,X Rays, CT,X-Ray CAT Scan,X-Ray CAT Scans,X-Ray CT Scan,X-Ray CT Scans,X-Ray Computed Tomography,X-Ray Computerized Tomography,Xray Computed Tomography
D015021 Yttrium Radioisotopes Unstable isotopes of yttrium that decay or disintegrate emitting radiation. Y atoms with atomic weights 82-88 and 90-96 are radioactive yttrium isotopes. Radioisotopes, Yttrium
D015899 Tomography, Emission-Computed, Single-Photon A method of computed tomography that uses radionuclides which emit a single photon of a given energy. The camera is rotated 180 or 360 degrees around the patient to capture images at multiple positions along the arc. The computer is then used to reconstruct the transaxial, sagittal, and coronal images from the 3-dimensional distribution of radionuclides in the organ. The advantages of SPECT are that it can be used to observe biochemical and physiological processes as well as size and volume of the organ. The disadvantage is that, unlike positron-emission tomography where the positron-electron annihilation results in the emission of 2 photons at 180 degrees from each other, SPECT requires physical collimation to line up the photons, which results in the loss of many available photons and hence degrades the image. CAT Scan, Single-Photon Emission,CT Scan, Single-Photon Emission,Radionuclide Tomography, Single-Photon Emission-Computed,SPECT,Single-Photon Emission-Computed Tomography,Tomography, Single-Photon, Emission-Computed,Single-Photon Emission CT Scan,Single-Photon Emission Computer-Assisted Tomography,Single-Photon Emission Computerized Tomography,CAT Scan, Single Photon Emission,CT Scan, Single Photon Emission,Emission-Computed Tomography, Single-Photon,Radionuclide Tomography, Single Photon Emission Computed,Single Photon Emission CT Scan,Single Photon Emission Computed Tomography,Single Photon Emission Computer Assisted Tomography,Single Photon Emission Computerized Tomography,Tomography, Single-Photon Emission-Computed

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