Dual-Source Dual-Energy CT Portal Venous Phase Abdominal CT Scans in Large Body Habitus Patients: Preliminary Observations on Image Quality and Material Decomposition

Abstract

Purpose Our objective was to evaluate image quality (IQ) and material decomposition in patients with large body habitus undergoing portal venous phase abdominal computed tomography (CT) scans on dual-source dual-energy CT (dsDECT) scanners. Methods This retrospective analysis included 30 scans from consecutive patients (19 males/11 females, mean ± SD age = 55.3 ± 17.5 years, range = 27–87 years) with large body habitus (≥90 kg, mean ± SD weight = 105.4 ± 12.35, range = 91–145 kg) who underwent portal venous phase abdominal DECT examinations on dsDECT scanner between Jan 2015 and Dec 2015. Qualitative and quantitative evaluation of IQ of DECT data sets (blended, iodine, and virtual noncontrast images) was performed. The patients were categorized into 2 groups (group A, ≤104 kg; group B, >104 kg). Results The mean ± SD patient body weight in group A was 97.2 ± 4.5 kg (range = 91–104 kg) and 114.8 ± 11.7 kg (range = 104.3–145.2 kg) for patients in group B. The diagnostic acceptability of the blended images in patients > 104 kg was lower (3.6 vs 4, <3 in 4/14 vs 0/16, P = 0.03). The extension of visceral anatomy beyond DE field of view (DEFOV) was seen in 60% (28 organs in 18 patients), the most common organs being liver and spleen. The incidence of visceral organs outside DEFOV was significantly higher in patients > 104 kg (18 vs 10, P = 0.03). Outside the DEFOV, blended images demonstrated higher image noise (mean: 14.48, range = 10.09–26.83 vs mean: 9.5, range = 7.3–15.8) P < 0.001) and lower signal-to-noise ratio (mean: 4.15, range = 1.5–7.6 vs mean: 7.5, range = 4.2–9.9) P < 0.001), and material-specific information was not available in this region. Within the DEFOV, the IQ of iodine maps and virtual non-contrast images were diagnostically acceptable with diagnostic acceptability of 3 or greater in nearly all patients. A 40-cm transverse diameter cut-off provided a good predictor of extension of visceral anatomy outside the effective DEFOV. Conclusions Dual-source DECT allows diagnostically acceptable IQ and material separation in patients with large body habitus with the major limitation of exclusion of patient anatomy and organs outside the effective dual-energy field of view.

Vascular computed tomography angiography technique and indications

“…Recent versions of DECT platforms and software upgrades have the capability to automate post-processing such that DECT image reconstructions do not hinder workflow (67). Recent studies have shown that single source rapid switching rsDECT suffers from increased beam hardening/streak artifacts on material specific images and patient anatomy can extend outside dual energy field of view (FOV) on dual source scanners (68)(69)(70). However, newer detector-based spectral CT scanners have no limitations on FOV, gantry rotation time or cross-scatter (67).…”

Image Quality Evaluation in Dual-Energy CT of the Chest, Abdomen, and Pelvis in Obese Patients With Deep Learning Image Reconstruction

“…However, the application of DL image reconstruction in dual-energy CT applications has been limited by insufficient tube output for satisfactory image quality, which can be particularly problematic in obese patients. Rapid-switching single-source dual-energy CT has before now experienced image degradation from photon starvation in material decomposition dual-energy CT in patients >250 lb (113 kg), and larger patient body habitus has necessitated larger gantry bore openings further challenging imaging geometry and contributing to increased streaking and beam hardening artifacts 9–12 …”

“…Rapid-switching single-source dual-energy CT has before now experienced image degradation from photon starvation in material decomposition dual-energy CT in patients >250 lb (113 kg), and larger patient body habitus has necessitated larger gantry bore openings further challenging imaging geometry and contributing to increased streaking and beam hardening artifacts. [9][10][11][12] A new x-ray tube has recently been developed (Quantix 160; GE Healthcare, Waukesha, WI), which may provide sufficient tube output for DL image reconstruction applications in obese patients. 13 This next-generation x-ray tube platform incorporates a digital cathode, dual flat emitter, wide-view target, and liquid metal bearing that support up to 1300 mA flux at 160 mm of coverage, thereby allowing higher effective flux utilization per unit of time.…”