Weightbearing CBCT, MDCT, and 2D imaging dosimetry of the foot and ankle

Abstract

Aims: This study compares effective doses associated with 2D lateral, oblique, and AP radiographs with 3D MDCT and Cone Beam CT images of the foot and ankle.Methods: An anthropomorphic phantom of the foot and ankle was constructed from an adult human skeleton and soft tissue equivalent material. Optical stimulated dosimeters were placed at 21 locations within and on tissues and anatomy of interest. Effective dose was calculated following 2007 ICRP recommendations. Three projections were exposed to simulate conventional 2D imaging. Standard and optimized dose MDCT scans were exposed to simulate typical CT options. Ten, 20, and 30cm fields of view, 100 and 120kVp and 4.5 and 6.8mAs exposures were tested using a PedCAT® CBCT device designed for weightbearing imaging. Dose was calculated for an adult as well as for a 5 and 10-year-old child to assess the impact of age on risk estimation.Results: Standard adult effective doses for single foot imaging were 0.6µSv for 2D, 3.8µSv for CBCT, and 25µSv for MDCT (p = 0.0013). Dose differed significantly with age (p = 0.0185). For a 5-year-old, doses rise to 0.8µSv for 2D, 18µSv for CBCT, and 200µSv for MDCT. Small and medium CBCT fields produced adult doses of 2.3 mSv and 0.9 mSv respectively. Conclusions:The effective dose for small FOV CBCT or conventional 2D series examinations is comparable to a few hours of equivalent background dose. Such doses are negligible; therefore, the dose of radiation should not be a concern when considering the use of CBCT imaging for foot/ankle examination.

PedCAT for Radiographic 3D-Imaging in standing position

“…The dose for adults for three radiographs from one foot (Anteroposterior/dorsoplantar + lateral + oblique) was 0.7 Sv, the dose for a bilateral pedCAT scan 4.3 Sv, and the dose for conventional CT of one foot/ankle 25 Sv [10]. The means that a bilateral pedCAT scan has a comparable dose as 18 unilateral radiographs of the foot, and 17% of an unilateral CT of the foot and ankle [10]. This study did also measure the dose of an unilateral pedCAT scan which was 1.4 Sv comparable to 6 unilateral radiographs of the foot, and 5.6% of an unilateral CT of the foot and ankle [10].…”

“…However, the dose as such depends on the structure of the scanned object and is not measured during the imaging. Recently, the dose of foot/ankle radiographs, CT and pedCAT was measured and analysed using a foot and ankle phantom [10]. The dose for adults for three radiographs from one foot (Anteroposterior/dorsoplantar + lateral + oblique) was 0.7 Sv, the dose for a bilateral pedCAT scan 4.3 Sv, and the dose for conventional CT of one foot/ankle 25 Sv [10].…”

“…Recently, the dose of foot/ankle radiographs, CT and pedCAT was measured and analysed using a foot and ankle phantom [10]. The dose for adults for three radiographs from one foot (Anteroposterior/dorsoplantar + lateral + oblique) was 0.7 Sv, the dose for a bilateral pedCAT scan 4.3 Sv, and the dose for conventional CT of one foot/ankle 25 Sv [10]. The means that a bilateral pedCAT scan has a comparable dose as 18 unilateral radiographs of the foot, and 17% of an unilateral CT of the foot and ankle [10].…”

“…The means that a bilateral pedCAT scan has a comparable dose as 18 unilateral radiographs of the foot, and 17% of an unilateral CT of the foot and ankle [10]. This study did also measure the dose of an unilateral pedCAT scan which was 1.4 Sv comparable to 6 unilateral radiographs of the foot, and 5.6% of an unilateral CT of the foot and ankle [10]. For the later clinical use this radiation dose is relativized because virtual radiography could be created from the ped-CAT data as shown in Figure 8.…”

Characterization of 3D joint space morphology using an electrostatic model (with application to osteoarthritis)

“…1. Such a system can provide sub-millimeter isotropic spatial resolution, soft-tissue imaging capability sufficient for a broad range of musculoskeletal imaging tasks, reduced radiation dose in comparison to conventional multidetector CT (MDCT), and suitability to imaging the upper and lower extremities, including weight-bearing exams of the lower extremities (Prakash et al 2011, Muhit et al 2013, Carrino et al 2014, Ludlow and Ivanovic 2014, Tuominen et al 2013). …”