The Effect of Quantitative Computed Tomography Acquisition Protocols on Bone Mineral Density Estimation

Osteoporosis is characterized by bony material loss and decreased bone strength leading to a significant increase in fracture risk. Patient-specific quantitative computed tomography (QCT) finite element (FE) models may be used to predict fracture under physiological loading. Material properties for the FE models used to predict fracture are obtained by converting grayscale values from the CT into volumetric bone mineral density (vBMD) using calibration phantoms. If there are any variations arising from the CT acquisition protocol, vBMD estimation and material property assignment could be affected, thus, affecting fracture risk prediction. We hypothesized that material property assignments may be dependent on scanning and postprocessing settings including voltage, current, and reconstruction kernel, thus potentially having an effect in fracture risk prediction. A rabbit femur and a standard calibration phantom were imaged by QCT using different protocols. Cortical and cancellous regions were segmented, their average Hounsfield unit (HU) values obtained and converted to vBMD. Estimated vBMD for the cortical and cancellous regions were affected by voltage and kernel but not by current. Our study demonstrated that there exists a significant variation in the estimated vBMD values obtained with different scanning acquisitions. In addition, the large noise differences observed utilizing different scanning parameters could have an important negative effect on small subregions containing fewer voxels.

Download Full-text

Bone Mineral Density of the Tarsals and Metatarsals With Reloading

Physical Therapy ◽

10.2522/ptj.20070226 ◽

2008 ◽

Vol 88 (6) ◽

pp. 766-779 ◽

Cited By ~ 5

Author(s):

Mary Kent Hastings ◽

Judy Gelber ◽

Paul K Commean ◽

Fred Prior ◽

David R Sinacore

Keyword(s):

Computed Tomography ◽

Bone Mineral Density ◽

Case Report ◽

Fracture Risk ◽

Bone Mineral ◽

Weight Bearing ◽

Quantitative Computed Tomography ◽

Case Description ◽

Mineral Density ◽

Lateral Column

Background and PurposeBone mineral density (BMD) decreases rapidly with prolonged non–weight bearing. Maximizing the BMD response to reloading activities after NWB is critical to minimizing fracture risk. Methods for measuring individual tarsal and metatarsal BMD have not been available. This case report describes tarsal and metatarsal BMD with a reloading program, as revealed by quantitative computed tomography (QCT).Case DescriptionA 24-year-old woman was non–weight bearing for 6 weeks after right talocrural arthroscopy. Tarsal and metatarsal BMD were measured with QCT 9 weeks (before reloading) and 32 weeks (after reloading) after surgery. A 26-week progressive reloading program was completed. Change scores were calculated for BMD before reloading and BMD after reloading for the total foot (average of all tarsals and metatarsals), tarsals, metatarsals, bones of the medial column (calcaneus, navicular, cuneiforms 1 and 2, and metatarsal 1), and bones of the lateral column (calcaneus, cuboid, cuneiform 3, and metatarsals 2–5). The percent differences in BMD between the involved side and the uninvolved side were calculated.OutcomesBefore reloading, BMD of the involved total foot was 9% lower than that on the uninvolved side. After reloading, BMD increased 22% and 21% for the total foot, 16% and 14% for the tarsals, 29% and 30% for the metatarsals, 14% and 15% for the medial column bones, and 28% and 26% for the lateral column bones on the involved and uninvolved sides, respectively. After reloading, BMD of the involved total foot remained 8% lower than that on the uninvolved side.DiscussionThe increase in BMD with reloading was not uniform across all pedal bones; the metatarsals showed a greater increase than the tarsals, and the lateral column bones showed a greater increase than the medial column bones.

Download Full-text