A Method for the Assessment of Heterogeneity in Total Bone Marrow
N Weisse*, S Yip, P Scully, M Juckett, R Mattison, R Jeraj, University of Wisconsin, Madison, WITH-A-WAB-7 Thursday 8:00AM - 9:55AM Room: Wabash Ballroom
Purpose: Spatial heterogeneity of hematological disease is suspected to affect treatment response. In this study, we developed a method to quantitatively assess heterogeneity in bone marrow response to treatment via a voxel-to-voxel analysis for intra- and inter-regional marrow assessment.
Methods: The method begins with articulated registration - registration of whole body CTs by auto-segmenting individual bones then rigidly aligning them - of pre- and post-treatment CTs. Resulting segmentations and transformations are applied to the respective PET data allowing for voxel-to-voxel comparisons. Intra- and inter-regional heterogeneity of PET uptake and response is assessed through four distinct analyses: (1) Intra-regional uptake heterogeneity, (2) Intra-regional response heterogeneity, (3) Inter-regional uptake heterogeneity, and (4) Inter-regional response heterogeneity. Mean SUV (SUVmean) and SUV coefficient of variation (SUVCoV)) are calculated within each region at each time point. Response (R) is calculated as a change in SUVmean). The method was applied to two patients with acute myeloid leukemia having received standard '7+3' induction chemotherapy, but experiencing different clinical responses.
Results: In the two patients, our method revealed wide variation in uptake and response within skeletal regions. Intra-regionally we observed high uptake heterogeneity in all regions (SUVCoV> 0.8) as well as high response heterogeneity; this was evidenced by standard deviations of Rmean) spanning 0.7xRmean) to 1.3xRmean). Despite clear heterogeneity within each region, inter-regional uptake heterogeneity was low (CoV<0.05 for both patients pre-treatment). Interestingly, the method revealed significantly different inter-regional response heterogeneity between the patients, with the clinically responding patient having a more homogeneous response (variation of Rmean) <0.06), than the non-responding patient (variation of Rmean) <0.14).
Conclusion: The newly developed heterogeneity assessment method allows for a quantitative assessment of bone marrow response. The localization of treatment failure could assist in clinical decision making by discriminating between responding and non-responding patients.
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