Despite universal consensus that computed tomography (CT) overwhelmingly benefits patients when used for appropriate indications, concerns have been raised regarding the potential risk of cancer induction from CT due to the exponentially increased use of CT in medicine. Keeping radiation dose as low as reasonably achievable, consistent with the diagnostic task, remains the most important strategy for decreasing this potential risk. This article summarizes the general technical strategies that are commonly used for radiation dose management in CT. Dose-management strategies for pediatric CT, cardiac CT, dual-energy CT, CT perfusion and interventional CT are specifically discussed, and future perspectives on CT dose reduction are presented.

Purpose To determine the ex vivo ability of dual-energy, dual-source computed tomography (DE-DSCT) with additional tin filtration to differentiate between five groups of human renal stone types. Methods Forty-three renal stones of ten types were categorized into five primary groups based on effective atomic numbers, which were calculated as the weighted average of the atomic numbers of constituent atoms. Stones were embedded in porcine kidneys and placed in a 35cm water phantom. DE-DSCT scans were performed with and without tin filtration at 80/140kV. The CT number ratio [CTR=CT(low)/CT(high)] was calculated on a volumetric voxel-by-voxel basis for each stone. Statistical analysis was performed and receiver operating characteristic (ROC) curves were plotted to compare the difference in CTR with and without tin filtration, and to measure the discrimination between stone groups. Results CTR of non-uric acid stones increased on average by 0.17 (range 0.03–0.36) with tin filtration. The CTR values for non-uric acid stone groups were not significantly different (p>0.05) between any of the two adjacent groups without tin filtration. Use of the additional tin filtration on the high-energy x-ray tube significantly improved the separation of non-uric acid stone types by CTR (p<0.05). The area under the ROC curve increased from 0.78–0.84 without fin filtration to 0.89–0.95 with tin filtration. Conclusion Our results demonstrated better separation between different stone types when additional tin filtration was used on DE-DSCT. The increased spectral separation allowed a 5-group stone classification scheme. Some overlapping between particular stone types still exists, including brushite and calcium oxalate.

The proposed dynamic 4D CT imaging technique generated high spatial and high temporal resolution images without requiring periodic joint motion. Preliminary results from this cadaveric study demonstrate the feasibility of detecting joint instability using this technique.

DECT and VNCa images can identify bone bruising for at least 10 weeks after injury.

Computed tomography colonography images acquired using the IC detector had significantly lower noise than images acquired using the conventional detector. This noise reduction can permit further radiation dose reduction in CTC.

Objective To evaluate the ability of 100/Sn140 kV (Sn, tin filter) dual-energy CT to differentiate urinary stone types in a patient cohort with a wide range of body sizes. Methods 80 human urinary stones were categorised into four groups (uric acid; cystine; struvite, oxalate and brushite together; and apatite) and imaged in 30–50-cm wide water tanks using clinical 100/Sn140 kV protocols. The CT number ratio (CTR) between the low- and high-energy images was calculated. Thresholds for differentiating between stone groups were determined using ROC analysis. Additionally, 86 stones from 66 patients were characterised using the size-adaptive CTR thresholds determined in the phantom study. Results In phantoms, the area under the ROC curve for differentiating between stone groups ranged from 0.71 to 1.00, depending on phantom size. In patients, body width ranged from 28.5 to 50.0 cm, and 79.1% of stones were correctly characterised. Sensitivity and specificity for correctly identifying the stone category were 100% and 100% (group 1), 100% and 95.3% (group 2), 85.7% and 60.9% (group 3), and 52.6% and 92.5% (group 4). Conclusion Dual-energy CT can provide in vivo urinary stone characterisation for patients over a wide range of body sizes.

Enantioselective Pd(II)-catalyzed construction of [3.3.1]-bicyclic ketals from 2-hydroxyphenylboronic acid and enone is reported, yielding enantioenriched [3.3.1]-bicyclic ketals in up to 97% yields and 98% ee.

Objective To demonstrate the feasibility of differentiating uric acid (UA) and non-uric-acid (NUA) renal stones using two consecutive, spatially-registered low- and high-energy scans acquired on a conventional CT system. Materials and Methods A total of 34 patients undergoing clinically indicated dual-source, dual-energy CT exams to differentiate UA and NUA kidney stones were enrolled in this IRB-approved study. Immediately after clinically-indicated dual-source, dual-energy CT and written informed consent, two consecutive scans (one at 80 kV and one at 140 kV) were performed on a conventional CT scanner over the region limited to stones identified on the dual-source scan. After 3D deformable registration of the 80 and 140 kV images, UA and non-UA stones were identified using commercial software. Sensitivity, specificity, and accuracy of stone classification were calculated using the dual-source results as the reference standard. Results A total of 469 stones were identified in dual-source exams (26 UA and 443 NUA). Average in-plane stone diameter was 4.4 ± 2.5 mm (range 2.0 to 18.9 mm). Overall sensitivity, specificity, and accuracy for identifying UA stones were 73%, 90%, and 89%, respectively. The sensitivity, specificity, and accuracy were 95%, 97%, and 97% for stones ≥3 mm (n = 341, 19 UA and 322 NUA). Conclusions Accurate differentiation of UA and NUA renal stones is feasible using two consecutively-acquired and spatially-registered conventional CT scans.