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Comparison of Yttrium-90 Dosimetry of Single Energy Window and Dual Energy Window SPECT/CT Imaging Protocols

L Chen1*, (1) Banner MD Anderson Cancer Center, Gilbert, AZ

Presentations

(Sunday, 7/12/2020)   [Eastern Time (GMT-4)]

Room: AAPM ePoster Library

Purpose:
This aim of this study is to compare the dosimetry results from two different Y-90 bremsstrahlung SPECT/CT imaging acquisition and reconstruction protocols.

Methods:
Post-treatment Y-90 SPECT/CT imaging was used to assess the Y-90 microspheres delivery. The patients were imaged on Siemens Symbia T16 system with medium energy collimator, 28s/view for 128 views over 360°. Low dose CT images were used for attenuation correction. The SPECT projection images were reconstructed with a matrix size 128 X 128, 4.8 mm pixel size. The manufacturer recommended SPECT acquisition protocol used a wide single energy window 50 - 150 keV with filtered backprojection reconstruction. A dual-energy window based scatter correction SPECT protocol, developed by Siman et al, used primary energy window 90-124 keV with 310-400 keV energy for background compensation (BC). The SPECT images were reconstructed using the Flash3D algorithm with 4 iterations and 8 subsets, and a 4.8 mm FWHM post-reconstruction Gaussian filter.

A dose of 125 Gy was prescribed to the right posterior segment (500 cc volume) of a HCC patient. The patient received 2.64 GBq Y-90 activity and performed a SPECT/CT scan with these two protocols within 24 hours post-treatment. The voxel-based Y-90 dose distributions were computed using local deposition method with the MIM SurePlan Y-90 dosimetry software.

Results:
The SPECT images of dual-energy window BC protocol looks sharper than that of single energy window protocol. The maximum and mean doses of tumor are 133 and 64 Gy for single energy window protocol, while those of dual-energy window are 274 and 110 Gy, respectively.

Conclusion:
Both image quality and accuracy of the liver dosimetry of optimized dual-energy window BC SPECT/CT protocol is superior over traditional single energy window protocol. The single energy window protocol results the Y-90 dosimetry underestimated.

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