Quantitative analysis of 90Y Bremsstrahlung SPECT-CT images for application to 3D patient-specific dosimetry.
OBJECTIVE
The aim of this study was to evaluate the accuracy of the activity quantification of single-photon emission computed tomography/computed tomography (SPECT-CT) (90)Y-Bremsstrahlung images and to validate the S-voxel method.


METHODS
An anthropomorphic torso phantom with radioactive inserts ((90)Y) was acquired by SPECT-CT. Constant calibration factors (cps/MBq) for the quantification were evaluated, considering different volume, shape, position inside the phantom, activity concentration and background, and distance from detectors. S-voxel values (EGSnrc) were implemented in MATLAB R0086 USA software. Dose comparisons between S-voxel and the conventional Medical Internal Radiation Dose method were repeated in a group of 11 patients administered with (90)Y-DOTATATE.


RESULTS
Using the appropriate calibration factors to recover the volume variability, the error about the measurement repeatability and the activity variation was within 4%. The variability of activity quantification, depending on the position in the phantom, detector distance, and background, was <10%, <5%, and <10%, respectively. The absorbed-dose values calculated by OLINDA were in agreement with the mean dose values obtained by the S-voxel method (difference, <10%).


CONCLUSIONS
The results confirm that, with the hybrid SPECT-CT system, quantitative analysis of SPECT (90)Y-Bremsstrahlung images and the generation of three-dimensional dose distributions are feasible. The improved analysis of Bremsstrahlung images could have a notable clinical impact, allowing to address the dosimetric verification to patients during the course of therapy.
Fabbri
Cinzia
C
Division of Medical Physics, Bufalini Hospital, Ghirotti 286, Cesena, Italy.
Sarti
Graziella
G
Cremonesi
Marta
M
Ferrari
Mahila
M
Di Dia
Amalia
A
Agostini
Monica
M
Botta
Francesca
F
Paganelli
Giovanni
G
D000465:Algorithms; D002138:Calibration; D004307:Dose-Response Relationship, Radiation; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods; D007668:Kidney / Q000528:radiation effects; D019047:Phantoms, Imaging; D011874:Radiometry / Q000379:methods*; D019275:Radiopharmaceuticals; D011879:Radiotherapy Dosage; D015203:Reproducibility of Results; D015899:Tomography, Emission-Computed, Single-Photon / Q000379:methods*; D014057:Tomography, X-Ray Computed / Q000379:methods*; D015021:Yttrium Radioisotopes
D019275:Radiopharmaceuticals; D015021:Yttrium Radioisotopes