Patient-specific dosimetry within the field of molecular radiotherapy continues to pose a challenge owing to the difficulty in predicting marrow toxicity. This study examined the correlation between total pelvic spongiosa volume (TPSV) and independent variables, which include both readily measured or calculated anthropometric parameters (AP), and image-based skeletal measurements requiring computed tomography (CT) images or skeletal radiographs. Fourteen (14) patients (5 male and 9 female) undergoing total hip arthroplasty (THA) were subjected to modified pelvic CT scans. These scans were utilized to estimate TPSV, which was comprised of the volumes of spongiosa within the L5 vertebra, os coxae, sacrum, and both proximal femurs. The APs investigated included total body height (TBH), total body mass (TBM), body mass index (BMI), body surface area (BSA), maximum effective mass (MEM), lean body mass (LBM), and fat-free mass (FFM). Skeletal measurements were also obtained from the CT images of the pelvic region. Correlation coefficients (r) were obtained for TPSV and each set of APs as well as each set of skeletal measurements. Total body height (r = 0. 80) and os coxae height (r = 0.83) had the highest correlation coefficients of all the APS and skeletal measurements, respectively. FFM (r = 0.50), LBM (r = 0.42), TBM (r = 0.11), and BSA (r = 0.11) did not correlate well with TPSV, which accounts for approximately 45% of total spongiosa seen throughout the skeleton at sites associated with active bone marrow. Skeletal height measurements appear to have a much higher correlation with TPSV than either their corresponding skeletal width measurements or parameters that are a function of an individual's TBM.

Computed tomography (CT) is an important and widely used modality in the diagnosis and treatment of various cancers. In the field of molecular radiotherapy, the use of spongiosa volume (combined tissues of the bone marrow and bone trabeculae) has been suggested as a means to improve the patient-specificity of bone marrow dose estimates. The noninvasive estimation of an organ volume comes with some degree of error or variation from the true organ volume. The present study explores the ability to obtain estimates of spongiosa volume or its surrogate via manual image segmentation. The variation among different segmentation raters was explored and found not to be statistically significant (p value >0.05). Accuracy was assessed by having several raters manually segment a polyvinyl chloride (PVC) pipe with known volumes. Segmentation of the outer region of the PVC pipe resulted in mean percent errors as great as 15% while segmentation of the pipe's inner region resulted in mean percent errors within approximately 5%. Differences between volumes estimated with the high-resolution CT data set (typical of ex vivo skeletal scans) and the low-resolution CT data set (typical of in vivo skeletal scans) were also explored using both patient CT images and a PVC pipe phantom. While a statistically significant difference (p value <0.002) between the high-resolution and low-resolution data sets was observed with excised femoral heads obtained following total hip arthroplasty, the mean difference between high-resolution and low-resolution data sets was found to be only 1.24 and 2.18 cm3 for spongiosa and cortical bone, respectively. With respect to differences observed with the PVC pipe, the variation between the high-resolution and low-resolution mean percent errors was a high as approximately 20% for the outer region volume estimates and only as high as approximately 6% for the inner region volume estimates. The findings from this study suggest that manual segmentation is a reasonably accurate and reliable means for the in vivo estimation of spongiosa volume. This work also provides a foundation for future studies where spongiosa volumes are estimated by various raters in more comprehensive CT data

Autosomal dominant or benign osteopetrosis is a rare genetic disorder of osteoclasts that results in dense but brittle bone structures. Patients with osteopetrosis may be scheduled for total knee arthroplasty to treat painful and functionally limiting osteoarthrosis. A search of the published literature produced no citation concerning anesthesia for patients with autosomal dominant osteopetrosis undergoing total knee arthroplasty. We present a case report detailing our experience and discuss considerations for the care of future patients with autosomal dominant osteopetrosis.