RT Journal Article
SR Electronic
T1 Comparison of three radiation dosimetry models for Yttrium-90 microsphere radioembolotherapy
JF Journal of Nuclear Medicine
JO J Nucl Med
FD Society of Nuclear Medicine
SP 209
OP 209
VO 50
IS supplement 2
A1 Kappadath, S. Cheenu
A1 Erwin, William
A1 Mutha, Pritesh
A1 Prasad, Shashank
A1 Murthy, Ravi
YR 2009
UL http://jnm.snmjournals.org/content/50/supplement_2/209.abstract
AB 209 Objectives Quantify differences of 3 dosimetry models for treatment of hepatic tumors with 90Y-microsphere radioembolotherapy (RE). Methods The 90Y microsphere (SIR-Spheres, Sirtex Medical, Australia) package insert recommends a cumulative liver dose <80Gy via a simple dosimetry model that assumes uniform 90Y distribution in tumor and liver & organ masses based on MIRD Standard Man (SM): total body 73.7kg, liver 1.91kg, lung 1kg. Two 3-compartment (liver, tumor, lung) partition models were investigated: CT-based (CTB) & weight-based (WTB). The main difference between them is in estimation of liver mass: in CTB it was estimated from CT image segmentation; while in WTB the SM liver mass was scaled by patient weight/sex. SM lung mass was scaled by patient weight/sex for CTB & WTB. Tumor fraction was estimated from CT & tumor uptake was estimated from pre-therapy 99mTc-MAA SPECT/CT. Model differences in estimated lung, liver, tumor doses were analyzed for 11 patients. Results The mean absolute liver mass difference was 0.64kg between CTB & SM and 0.42kg between CTB & WTB. Lung doses (3–12Gy) were similar between all 3 models with mean difference 0.1±1.5Gy. WTB & CTB non-tumor liver doses (4–31Gy) were similar with mean difference 0.7±5.5Gy but lower than SM by ~28Gy. WTB & CTB tumor doses (63–227Gy) were similar with mean difference 10±35Gy but higher than SM by ~65Gy. Conclusions The more realistic WTB or CTB models, that incorporate patient anatomical and functional data, yielded lower normal liver but similar lung doses than SM, and therefore should be the preferred methodology for 90Y RE treatments.