CT volumetry of the skeletal tissues

Brindle, James; Trindade, A. Alexandre; Pichardo, Jose C.; Myers, Scott L.; Shah, Amish P.; Bolch, Wesley E.

doi:10.1118/1.2337272

Cited by 4 publications

(3 citation statements)

References 12 publications

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“…As discussed previously in Brindle et al (2006), gray-scale CT image segmentation of the skeletal tissues into regions of cortical bone and spongiosa is problematic and not readily amenable to automation. Consequently, these regions of each skeletal site were segmented manually using an in-house IDL program CT-Contours originally developed and described by Nipper et al (2002).…”

Section: Methodsmentioning

confidence: 99%

An image-based skeletal dosimetry model for the ICRP reference adult male—internal electron sources

et al. 2011

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Target tissues include the active bone marrow, associated with radiogenic leukemia, and total shallow marrow, associated with radiogenic bone cancer. Monoenergetic electron emissions are considered over the energy range 1 keV to 10 MeV for the following sources: bone marrow (active and inactive), trabecular bone (surfaces and volumes), and cortical bone (surfaces and volumes). Specific absorbed fractions are computed according to the MIRD schema, and are given as skeletal-averaged values in the paper with site-specific values reported in both tabular and graphical format in an electronic annex. The distribution of cortical bone and spongiosa at the macroscopic dimensions of the phantom, as well as the distribution of trabecular bone and marrow tissues at the microscopic dimensions of the phantom, are imposed through detailed analyses of whole-body ex-vivo CT images (1 mm resolution) and spongiosa-specific ex-vivo microCT images (30 μm resolution), respectively, taken from a 40-year male cadaver. The method utilized in this work includes: (1) explicit accounting for changes in marrow self-dose with variations in marrow cellularity, (2) explicit accounting for electron escape from spongiosa, (3) explicit consideration of spongiosa cross-fire from cortical bone, and (4) explicit consideration of the ICRP’s change in the surrogate tissue region defining the location of the osteoprogenitor cells (from a 10-μm endosteal layer covering the trabecular and cortical surfaces, to a 50-μm shallow marrow layer covering trabecular and medullary cavity surfaces). Skeletal-averaged values of absorbed fraction in the present model are noted to be very compatible with those weighted by the skeletal tissue distributions found in the ICRP Publication 110 adult male and female voxel phantoms, but are in many cases incompatible with values used in current and widely implemented internal dosimetry software.

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Section: Methodsmentioning

confidence: 99%

An image-based skeletal dosimetry model for the ICRP reference adult male—internal electron sources

et al. 2011

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“…All segmentation files were visually inspected by the first author for quality assurance purposes. The accuracy of the manual segmentation and the magnitude of intersegmenter variability have both been investigated by Brindle et al (15).…”

Section: Sv Estimationmentioning

confidence: 99%

Method for Estimating Skeletal Spongiosa Volume and Active Marrow Mass in the Adult Male and Adult Female

Pichardo¹,

Trindade²,

Brindle³

et al. 2007

Journal of Nuclear Medicine

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Active bone marrow is one of the more radiosensitive tissues in the human body and, hence, it is important to predict and possibly avoid myelotoxicity in radionuclide therapies. The MIRD schema currently used to calculate marrow dose generally requires knowledge of the patient's total skeletal active marrow mass-a value that, at present, cannot be directly measured. Conceptually, the active marrow mass in a given skeletal region may be obtained given knowledge of the trabecular spongiosa volume (SV) of the bone site. A recent study has established a multiple regression model to easily calculate total skeletal SV (or TSSV) based on simple skeletal measurements obtained from a pelvic CT scan or radiograph. This model, based on data from only 20 cadavers, did not account for sex differences in TSSV. This study thus extends this work toward sex-specific models. Methods: Twenty male and 20 female cadavers were subjected to whole-body CT. Bone sites containing active bone marrow were manually segmented to obtain SV at each site. In addition to age and height, 14 CT-based skeletal measurements were recorded for each cadaver. Multiple linear regression techniques were used to determine the best subset of measurements that allowed an accurate prediction of TSSV. Results: A pooled model (R 2 5 0.76) and a sex-specific model (R 2 5 0.79) are provided. A leave-one-out analysis reveals that these models predict total SV with less than 10% error for 50%-70% of subjects, and with less than 20% error for 70%-90% of subjects. Tables were constructed that provide the percent distribution of SV in active-marrow containing bone sites for both males and females. Conclusion: This study provides models that can be used to simply, yet accurately, predict total SV in individuals within the clinical setting. The models require only 2 or 3 skeletal measurements that can be easily measured on a pelvic CT scan. Even though this study does not conclusively determine which model is best at predicting TSSV, the sex-specific model is most consistent at providing reasonable estimates of TSSV. This study also explains how the predictive TSSV model can be used to estimate patient-specific active bone marrow mass under the assumption of reference values of marrow volume fraction and bone marrow cellularity by skeletal site.

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“…Contours were drawn on randomly determined regions from all slices delineating the kidney into cortex versus medulla/pelvis sub-sections as well as glomerulus versus proximal tubule versus distal tubule versus other sub-sections. Note that although the fractions of occupancy, f c were measured in mice, they were also applied to the human model; corresponding measurements could be performed in humans, from cadavers (Brindle et al 2006) or surgical samples (De Jong et al 2004).…”

Section: Compartmental S-valuesmentioning

confidence: 99%

A nephron-based model of the kidneys for macro-to-micro α-particle dosimetry

et al. 2012

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Targeted α-particle therapy is a promising treatment modality for cancer. Due to the short path-length of α-particles, the potential efficacy and toxicity of these agents is best evaluated by microscale dosimetry calculations instead of whole-organ, absorbed fraction-based dosimetry. Yet time-integrated activity (TIA), the necessary input for dosimetry, can still only be quantified reliably at the organ or macroscopic level. We describe a nephron-and cellular-based kidney dosimetry model for α-particle radiopharmaceutical therapy, more suited to the short range and high linear energy transfer of α-particle emitters, which takes as input kidney or cortex TIA and through a macro to micro model-based methodology assigns TIA to micro-level kidney substructures. We apply a geometrical model to provide nephron-level S-values for a range of isotopes allowing for pre-clinical and clinical applications according to the medical internal radiation dosimetry (MIRD) schema. We assume that the relationship between whole-organ TIA and TIA apportioned to microscale substructures as measured in an appropriate pre-clinical mammalian model also applies to the human. In both, the pre-clinical and the human model, microscale substructures are described as a collection of simple geometrical shapes akin to those used in the Cristy-Eckerman phantoms for normal organs. Anatomical parameters are taken from the literature for a human model, while murine parameters are measured ex vivo. The murine histological slides also provide the data for volume of occupancy of the different compartments of the nephron in the kidney: glomerulus versus proximal tubule versus distal tubule. Monte Carlo simulations are run with activity placed in the different nephron compartments for several α-particle emitters currently under investigation in radiopharmaceutical therapy. The S-values were calculated for the α-emitters and their descendants between the different nephron compartments for both the human and murine models. The renal cortex and medulla S-values were 3 Author to whom any correspondence should be addressed.

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CT volumetry of the skeletal tissues

Cited by 4 publications

References 12 publications

An image-based skeletal dosimetry model for the ICRP reference adult male—internal electron sources

An image-based skeletal dosimetry model for the ICRP reference adult male—internal electron sources

Method for Estimating Skeletal Spongiosa Volume and Active Marrow Mass in the Adult Male and Adult Female

A nephron-based model of the kidneys for macro-to-micro α-particle dosimetry

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