The feasibility of low iodine dynamic CT angiography with test bolus for evaluation of lower extremity peripheral artery disease.

OBJECTIVE: This study aims to determine if low iodine dynamic computed tomography angiography performed after a fixed delay or test bolus acquisition demonstrates high concordance with clinical computed tomography angiography (using a routine amount of iodinated contrast) to display lower extremity peripheral arterial disease. METHODS: After informed consent, low iodine dynamic computed tomography angiography examination (using either a fixed delay or test bolus) using 50 ml of iodine contrast media was performed. A subsequent clinical computed tomography angiography using standard iodine dose (115 or 145 ml) served as the reference standard. A vascular radiologist reviewed dynamic and clinical computed tomography angiography images to categorize the lumen into "not opacified", "<50% stenosis", " 50 ̶70% stenosis", ">70% stenosis", and "occluded" for seven arterial segments in each lower extremity. Concordance between low iodine dynamic computed tomography angiography and the routine iodine reference standard was calculated. The clinical utility of 4D volume-rendered images was also evaluated. RESULTS: Sixty-eight patients (average age 66.1 ± 12.3 years, male; female = 49: 19) were enrolled, with 34 patients each undergoing low iodine dynamic computed tomography angiography using fixed delay and test bolus techniques, respectively. One patient assigned to the test bolus group did not undergo low iodine computed tomography angiography due to unavailable delayed time. The fixed delay was 13 s, with test bolus acquisition resulting in a mean variable delay prior to image acquisition of 19.5 s (range; 8-32 s). Run-off to the ankle was observed using low iodine dynamic computed tomography angiography following fixed delay and test bolus acquisition in 76.4% (26/34) and 100% (33/33) of patients, respectively (p = 0.005). Considering extremities with run-off to the ankle and without severe artifact, the concordance rate between low iodine dynamic computed tomography angiography and the routine iodine reference standard was 86.8% (310/357) using fixed delay and 97.9% (425/434) using test bolus (p < 0.001). 4D volume-rendered images using fixed delay and test bolus demonstrated asymmetric flow in 57.7% (15/26) and 58.1% (18/31) (p = 0.978) of patients, and collateral blood flow in 11.5% (3/26) and 22.6% (7/31) of patients (p = 0.319), respectively. CONCLUSION: Low iodine dynamic computed tomography angiography with test bolus acquisition has a high concordance with routine peripheral computed tomography angiography performed with standard iodine dose, resulting in improved run-off to the ankle compared to dynamic computed tomography angiography performed after a fixed delay. This method is useful for minimizing iodine dose in patients at risk for contrast-induced nephropathy. 4D volume-rendered computed tomography angiography images provide useful dynamic information.

Symptomatic and Radiographic Manifestations of Kidney Stone Recurrence and Their Prediction by Risk Factors: A Prospective Cohort Study.

BACKGROUND: Meaningful interpretation of changes in radiographic kidney stone burden requires understanding how radiographic recurrence relates to symptomatic recurrence and how established risk factors predict these different manifestations of recurrence. METHODS: We recruited first-time symptomatic stone formers from the general community in Minnesota and Florida. Baseline and 5-year follow-up study visits included computed tomography scans, surveys, and medical record review. We noted symptomatic recurrence detected by clinical care (through chart review) or self-report, and radiographic recurrence of any new stone, stone growth, or stone passage (comparing baseline and follow-up scans). To assess the prediction of different manifestations of recurrence, we used the Recurrence of Kidney Stone (ROKS) score, which sums multiple baseline risk factors. RESULTS: Among 175 stone formers, 19% had symptomatic recurrence detected by clinical care and 25% detected by self-report; radiographic recurrence manifested as a new stone in 35%, stone growth in 24%, and stone passage in 27%. Among those with a baseline asymptomatic stone (54%), at 5 years, 51% had radiographic evidence of stone passage (accompanied by symptoms in only 52%). Imaging evidence of a new stone or stone passage more strongly associated with symptomatic recurrence detected by clinical care than by self-report. The ROKS score weakly predicted one manifestation-symptomatic recurrence resulting in clinical care (c-statistic, 0.63; 95% confidence interval, 0.52 to 0.73)-but strongly predicted any manifestation of symptomatic or radiographic recurrence (5-year rate, 67%; c-statistic, 0.79; 95% confidence interval, 0.72 to 0.86). CONCLUSIONS: Recurrence after the first stone episode is both more common and more predictable when all manifestations of recurrence (symptomatic and radiographic) are considered.

Individualized Delay for Abdominal Computed Tomography Angiography Bolus-Tracking Based on Sequential Monitoring: Increased Aortic Contrast Permits Decreased Injection Rate and Lower Iodine Dose.

OBJECTIVE: The aim of this study was to determine if computed tomography (CT) angiography using an individualized transition delay (CTA-ID) would facilitate reductions in injection rate and iodine dose. METHODS: The CTA-ID was performed in 20 patients with routine injection rate and iodine dose; 20 patients with injection rate lowered by 1 mL/s; and 40 patients with injection rate lowered by 1 mL/s with 29% less iodine. Routine CTAs in the same or size-matched patients served as controls. Diagnostic image quality and intra-arterial CT numbers were assessed. RESULTS: The median transition delay between aortic threshold and CTA-ID image acquisition was significantly longer than with conventional bolus tracking (mean increase, 13.3 seconds; P < 0.0001), with image quality being the same or better. Intra-arterial CT numbers were 200 Hounsfield units or greater for 80 of 80 CTA-ID, but not for 6 of 49 (12%) internal control or for 11 of 80 (14%) size-matched control patients. CONCLUSION: The CTA-ID bolus-tracking software alters transition delays to permit diagnostic CTA examinations despite slower injection rate and less iodine.

Detection and Characterization of Renal Stones by Using Photon-Counting-based CT.

Purpose To compare a research photon-counting-detector (PCD) CT scanner to a dual-source, dual-energy CT scanner for the detection and characterization of renal stones in human participants with known stones. Materials and Methods Thirty study participants (median age, 61 years; 10 women) underwent a clinical renal stone characterization scan by using dual-energy CT and a subsequent research PCD CT scan by using the same radiation dose (as represented by volumetric CT dose index). Two radiologists were tasked with detection of stones, which were later characterized as uric acid or non-uric acid by using a commercial dual-energy CT analysis package. Stone size and contrast-to-noise ratio were additionally calculated. McNemar odds ratios and Cohen k were calculated separately for all stones and small stones (≤3 mm). Results One-hundred sixty renal stones (91 stones that were ≤ 3 mm in axial length) were visually detected. Compared with 1-mm-thick routine images from dual-energy CT, the odds of detecting a stone at PCD CT were 1.29 (95% confidence interval: 0.48, 3.45) for all stones. Stone segmentation and characterization were successful at PCD CT in 70.0% (112 of 160) of stones versus 54.4% (87 of 160) at dual-energy CT, and was superior for stones 3 mm or smaller at PCD CT (45 vs 25 stones, respectively; P = .002). Stone characterization agreement between scanners for stones of all sizes was substantial (k = 0.65). Conclusion Photon-counting-detector CT is similar to dual-energy CT for helping to detect renal stones and is better able to help characterize small renal stones. © RSNA, 2018.

Assessment of aortic wall thrombus predicts outcomes of endovascular repair of complex aortic aneurysms using fenestrated and branched endografts.

OBJECTIVE: The goal of this study was to investigate the correlation between atherothrombotic aortic wall thrombus (AWT) and clinical outcomes in patients treated by fenestrated-branched endovascular aortic repair (F-BEVAR) and present a new classification system for assessment of AWT burden. METHODS: The clinical data of 301 patients treated for pararenal and thoracoabdominal aortic aneurysms (TAAAs) by F-BEVAR was reviewed. The study excluded 89 patients with extent I to III TAAA because of extensive laminated thrombus within the aneurysm sac. Computed tomography angiograms were analyzed in all patients to determine the location, extent, and severity of atherothrombotic AWT. The aorta was divided into three segments: ascending and arch (A), thoracic (B) and renal-mesenteric (C). Volumetric measurements (cm3) of AWT were performed using TeraRecon software (TeraRecon Inc, Foster City, Calif). These volumes were used to create an AWT index by dividing the AWT volume from the total aortic volume. A classification system was proposed using objective assessment of the number of affected segments, thrombus type, thickness, area, and circumference. Clinical outcomes included 30-day mortality, neurologic and gastrointestinal complications, renal events (Risk, Injury, Failure, Loss of kidney function, End-stage renal disease [RIFLE]), and solid organ infarction. RESULTS: The study included 212 patients, 169 men (80%) and 43 women (20%), with a mean age of 76 ± 7 years. A total of 700 renal-mesenteric arteries were incorporated (3.1 ± 1 vessels/patient). AWT was classified as mild in 98 patients (46%) and was considered moderate or severe in 114 (54%). There was one death (0.5%) at 30 days. Solid organ infarction was present in 50 patients (24%), and acute kidney injury occurred in 45 patients (21%) by RIFLE criteria. An association with higher AWT indices was found for time to resume enteral diet (P = .0004) and decline in renal function (P = .0003). Patients with acute kidney injury 2 by RIFLE criterion had significantly higher (P = .002) AWT index scores in segment B. Spinal cord injury occurred in three patients (1.4%) and stroke in four (1.9%), but were not associated with the AWT index. Severity of AWT using the new proposed classification system correlated with the AWT index in all three segments (P < .001). Any of the end points occurred in 35% of the patients with mild and in 53% of those with moderate or severe AWT (P = .016). CONCLUSIONS: AWT predicts solid organ infarction, renal function deterioration, and longer time to resume enteral diet after F-BEVAR of pararenal and type IV TAAAs. Evaluation of AWT should be part of preoperative planning and decision making for selection of the ideal method of treatment in these patients.

Reducing Iodine Contrast Volume in CT Angiography of the Abdominal Aorta Using Integrated Tube Potential Selection and Weight-Based Method Without Compromising Image Quality.

OBJECTIVE: The purpose of this study is to determine whether image quality was maintained when a weight-based protocol incorporating tube potential selection was used to select lower iodine contrast volumes for aortic CT angiography (CTA). MATERIALS AND METHODS: Patients with potentially decreased renal function underwent CTA performed with the iodinated contrast volume determined using a table incorporating different tube potentials and patient weights. The image quality of CTA examinations performed with a reduced iodine volume (hereafter known as "low-iodine CTA examinations"), internal control CTA examinations (i.e., prior examinations), and size-matched control CTA examinations was evaluated in separate reading sessions conducted by three vascular radiologists who were blinded as to the contrast volume and tube potential used. Side-by-side unblinded comparison of the examinations was also performed. Aortic attenuation and the contrast-to-noise ratio were measured. Comparisons were performed using the Wilcoxon signed rank test. RESULTS: Fifty low-iodine CTA examinations, 36 internal control CTA examinations, and 50 size-matched control CTA examinations were performed. Contrast volumes were 63% lower when the protocol based on tube potential and patient weight was used (mean contrast volume, 49 mL for low-iodine CTA vs 133 mL for internal control CTA and 138 mL for size-matched control CTA). The mean volume CT dose index was 15.1 mGy for low-iodine CTA versus 18.8 mGy for internal control CTA (p < 0.001), and 15.3 mGy for low-iodine CTA versus 17.1 mGy for size-matched control CTA (p = 0.11). Of the image quality and diagnostic confidence evaluations for low-iodine CTA examinations, over 97% had acceptable image quality and diagnostic confidence for blinded (50/50) and unblinded (35/36) comparisons. Aortic attenuation was similar between groups (p = 0.13-0.71). CONCLUSION: A weight-based protocol that incorporates tube potential selection allows the use of substantially lower volumes of iodinated contrast material in aortic CTA while maintaining acceptable image quality.

White Paper of the Society of Computed Body Tomography and Magnetic Resonance on Dual-Energy CT, Part 3: Vascular, Cardiac, Pulmonary, and Musculoskeletal Applications.

This is the third of a series of 4 white papers that represent Expert Consensus Documents developed by the Society of Computed Body Tomography and Magnetic Resonance through its Task Force on dual-energy computed tomography. This paper, part 3, describes computed tomography angiography and thoracic, cardiac, vascular, and musculoskeletal clinical applications. At the end of the discussion of each application category (vascular, cardiac, pulmonary, and musculoskeletal), we present our consensus opinions on the current clinical utility of the application and opportunities for further research.

White Paper of the Society of Computed Body Tomography and Magnetic Resonance on Dual-Energy CT, Part 4: Abdominal and Pelvic Applications.

This is the fourth of a series of 4 white papers that represent expert consensus documents developed by the Society of Computed Body Tomography and Magnetic Resonance through its task force on dual-energy computed tomography. This article, part 4, discusses DECT for abdominal and pelvic applications and, at the end of each, will offer our consensus opinions on the current clinical utility of the application and opportunities for further research.

A multi-reader in vitro study using porcine kidneys to determine the impact of integrated circuit detectors and iterative reconstruction on the detection accuracy, size measurement, and radiation dose for small (<4 mm) renal stones.

Background Detection of small renal calculi has benefitted from recent advances in computed tomography (CT) scanner design. Information regarding observer performance when using state-of-the-art CT scanners for this application is needed. Purpose To assess observer performance and the impact of radiation dose for detection and size measurement of <4 mm renal stones using CT with integrated circuit detectors and iterative reconstruction. Material and Methods Twenty-nine <4 mm calcium oxalate stones were randomly placed in 20 porcine kidneys in an anthropomorphic phantom. Four radiologists used a workstation to record each calculus detection and size. JAFROC Figure of Merit (FOM), sensitivity, false positive detections, and calculus size were calculated. Results Mean calculus size was 2.2 ± 0.7 mm. The CTDIvol values corresponding to the automatic exposure control settings of 160, 80, 40, 25, and 10 Quality Reference mAs (QRM) were 15.2, 7.9, 4.2, 2.7, and 1.3 mGy, respectively. JAFROC FOM was ≥ 0.97 at ≥ 80 QRM, ≥ 0.89 at ≥ 25 QRM, and was inferior to routine dose (160 QRM) at 10 QRM (0.72, P < 0.05). Per-calculus sensitivity remained ≥ 85% for every reader at ≥ 25 QRM. Mean total false positive detections per reader were ≤ 3 at ≥ 80 QRM, but increased substantially for two readers ( ≥ 12) at ≤ 40 QRM. Measured calculus size significantly decreased at ≤ 25 QRM ( P ≤ 0.01). Conclusion Using low dose renal CT with iterative reconstruction and ≥ 25 QRM results in high sensitivity, but false positive detections increase for some readers at very low dose levels (≤ 40 QRM). At very low doses with iterative reconstruction, measured calculus size will artifactually decrease.

Detection and Clinical Patterns of Nephron Hypertrophy and Nephrosclerosis Among Apparently Healthy Adults.

BACKGROUND: Even among ostensibly healthy adults, there is often mild pathology in the kidney. The detection of kidney microstructural variation and pathology by imaging and the clinical pattern associated with these structural findings is unclear. STUDY DESIGN: Cross-sectional (clinical-pathologic correlation). SETTING & PARTICIPANTS: Living kidney donors at Mayo Clinic (Minnesota and Arizona sites) and Cleveland Clinic 2000 to 2011. PREDICTORS: Predonation kidney function, risk factors, and contrast computed tomographic scan of the kidneys. These scans were segmented for cortical volume and medullary volume, reviewed for parenchymal cysts, and scored for kidney surface roughness. OUTCOMES: Nephrosclerosis (glomerulosclerosis, interstitial fibrosis/tubular atrophy, and arteriosclerosis) and nephron size (glomerular volume, mean profile tubular area, and cortical volume per glomerulus) determined from an implantation biopsy of the kidney cortex at donation. RESULTS: Among 1,520 living kidney donors, nephrosclerosis associated with increased kidney surface roughness, cysts, and smaller cortical to medullary volume ratio. Larger nephron size (nephron hypertrophy) associated with larger cortical volume. Nephron hypertrophy and larger cortical volume associated with higher systolic blood pressure, glomerular filtration rate, and urine albumin excretion; larger body mass index; higher serum uric acid level; and family history of end-stage renal disease. Both nephron hypertrophy and nephrosclerosis associated with older age and mild hypertension. The net effect of both nephron hypertrophy and nephrosclerosis associating with cortical volume was that nephron hypertrophy diminished volume loss with age-related nephrosclerosis and fully negated volume loss with mild hypertension-related nephrosclerosis. LIMITATIONS: Kidney donors are selected on health, restricting the spectrum of pathologic findings. Kidney biopsies in living donors are a small tissue sample leading to imprecise estimates of structural findings. CONCLUSIONS: Among apparently healthy adults, the microstructural findings of nephron hypertrophy and nephrosclerosis differ in their associations with kidney function, macrostructure, and risk factors.

White Paper of the Society of Computed Body Tomography and Magnetic Resonance on Dual-Energy CT, Part 2: Radiation Dose and Iodine Sensitivity.

This is the second of a series of 4 white papers that represent Expert Consensus Documents developed by the Society of Computed Body Tomography and Magnetic Resonance through its task force on dual-energy computed tomography. This paper, part 2, addresses radiation dose and iodine sensitivity in dual-energy computed tomography.

White Paper of the Society of Computed Body Tomography and Magnetic Resonance on Dual-Energy CT, Part 1: Technology and Terminology.

This is the first of a series of 4 white papers that represent Expert Consensus Documents developed by the Society of Computed Body Tomography and Magnetic Resonance through its task force on dual-energy computed tomography (DECT). This article, part 1, describes the fundamentals of the physical basis for DECT and the technology of DECT and proposes uniform nomenclature to account for differences in proprietary terms among manufacturers.

Nephrocalcinosis is a risk factor for kidney failure in primary hyperoxaluria.

Stone formation and nephrocalcinosis are both very common features of primary hyperoxaluria, yet the extent of each disease varies markedly between patients. Here we studied whether kidney damage from nephrocalcinosis and/or stone related events contributed to end-stage kidney disease (ESKD). Clinical information was analyzed from 348 patients enrolled in the Rare Kidney Stone Consortium Primary Hyperoxaluria registry and included demographic, laboratory and imaging features. Among all patients there were 277 with type 1, 37 with type 2, and 34 with type 3 primary hyperoxaluria. Overall, 58% passed a stone (mean 0.3/year) and one or more urologic procedures were required by 70% of patients (mean 0.15/year). Nephrocalcinosis was found in 34% of patients, including 41% with type 1 primary hyperoxaluria. High urine oxalate was associated with increased risk for both nephrocalcinosis and stone number, while low urine citrate was a risk factor for stone events and stone number. After adjustment for the type of primary hyperoxaluria, diagnosis by family screening and age at first image, the overall adjusted hazard ratio for ESKD among those with a history of nephrocalcinosis was 1.7 [95% CI 1.0-3.0], while the risk was 4.0 [1.9-8.5] for new onset nephrocalcinosis during follow-up. In contrast, the number of stones and stone events were not significantly associated with ESKD risk. Thus, nephrolithiasis and nephrocalcinosis appear to be pathophysiologically distinct entities. The presence of nephrocalcinosis implies increased risk for ESKD.

Feasibility of discriminating uric acid from non-uric acid renal stones using consecutive spatially registered low- and high-energy scans obtained on a conventional CT scanner.

OBJECTIVE: The objective of our study was to show the feasibility of distinguishing between uric acid (UA) and non-UA renal stones using two consecutive spatially registered low- and high-energy scans acquired on a conventional CT system. SUBJECTS AND METHODS: A total of 33 patients undergoing clinically indicated dual-source dual-energy CT examinations to differentiate UA from non-UA renal stones were enrolled in this study. Immediately after patients underwent clinically indicated dual-source dual-energy CT, two consecutive scans (one at 80 kV and one at 140 kV) were obtained on a conventional CT scanner over the region limited to the stones identified on the dual-source scans. After 3D deformable registration of the 80- and 140-kV images, UA and non-UA stones were identified using commercial software. The 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 the dual-source examinations (26 UA and 443 non-UA stones). The average in-plane stone diameter was 4.4 ± 2.5 (SD) mm (range, 2.0-18.9 mm). The overall sensitivity, specificity, and accuracy for identifying UA stones were 73.1%, 90.1%, and 89.1%, respectively. The sensitivity, specificity, and accuracy were 94.7%, 96.9%, and 96.8% for stones 3 mm or larger (n = 341 [19 UA and 322 non-UA]). CONCLUSION: Accurate differentiation of UA from non-UA renal stones is feasible using two consecutively acquired and spatially registered conventional CT scans.

Three-dimensional Physical Modeling: Applications and Experience at Mayo Clinic.

Radiologists will be at the center of the rapid technologic expansion of three-dimensional (3D) printing of medical models, as accurate models depend on well-planned, high-quality imaging studies. This article outlines the available technology and the processes necessary to create 3D models from the radiologist's perspective. We review the published medical literature regarding the use of 3D models in various surgical practices and share our experience in creating a hospital-based three-dimensional printing laboratory to aid in the planning of complex surgeries.

Age, kidney function, and risk factors associate differently with cortical and medullary volumes of the kidney.

The kidney atrophies in patients with advanced chronic kidney disease (CKD) but factors influencing kidney size in normal adults are less clear. To help define this, we measured kidney volumes on contrast-enhanced computed tomographic images from 1344 potential kidney donors (aged 18-75 years). Cortical volume per body surface area progressively declined in both genders with increased age. Statistically, this was primarily dependent on the age-related decline in glomerular filtration rate (GFR). Independent predictors of increased cortical volume per body surface area were male gender, increased GFR, increased 24-h urine albumin, current smoker, and decreased high-density lipid cholesterol. Medullary volume per body surface area increased with age in men, while it increased with age in women until the age of 50 years followed by a subsequent decline. Independent predictors of increased medullary volume per body surface area were older age, male gender, increased GFR, increased 24-h urine albumin, increased serum glucose, and decreased serum uric acid. Thus, while cortical volume declines with age along the same biological pathway as the age-related decline in GFR, albuminuria and some risk factors are actually associated with increased cortical or medullary volume among relatively healthy adults. Underlying hypertrophy or atrophy of different nephron regions may explain these findings.

Phenotypic characterization of kidney stone formers by endoscopic and histological quantification of intrarenal calcification.

Interstitial Randall's plaques and collecting duct plugs are distinct forms of renal calcification thought to provide sites for stone retention within the kidney. Here we assessed kidney stone precursor lesions in a random cohort of stone formers undergoing percutaneous nephrolithotomy. Each accessible papilla was endoscopically mapped following stone removal. The percent papillary surface area covered by plaque and plug were digitally measured using image analysis software. Stone composition was determined by micro-computed tomography and infrared analysis. A representative papillary tip was biopsied. The 24-h urine collections were used to measure supersaturation and crystal growth inhibition. The vast majority (99%) of stone formers had Randall's plaque on at least 1 papilla, while significant tubular plugging (over 1% of surface area) was present in about one-fifth of patients. Among calcium oxalate stone formers the amount of Randall's plaque correlated with higher urinary citrate levels. Tubular plugging correlated positively with pH and brushite supersaturation but negatively with citrate excretion. Lower urinary crystal growth inhibition predicted the presence of tubular plugging but not plaque. Thus, tubular plugging may be more common than previously recognized among patients with all types of stones, including some with idiopathic calcium oxalate stones.

A case-control study of intentional occlusion of accessory renal arteries during endovascular aortic aneurysm repair.

OBJECTIVE: The purpose of this study was to evaluate outcomes of patients treated by intentional coverage of accessory renal artery (ARA) during endovascular abdominal aneurysm repair (EVAR). METHODS: The clinical data of 119 patients (110 male and nine female; mean age, 75 years) from a cohort of 811 patients treated by EVAR from 1998 to 2009 was reviewed. Patients who had intentional coverage of at least one ARA (group A) were compared with two control groups, which included patients with no ARA (group B) and those who had ARA preserved during EVAR (group C). All three groups of patients were matched for age, gender, hypertension, and preoperative estimated glomerular filtration rate (eGFR). Paired pre- and postoperative computed tomography angiography was analyzed for the presence and volume of kidney infarction. End points were changes in eGFR, chronic kidney disease (CKD) stage, blood pressure measurements, presence and volume of kidney infarction, freedom from reintervention, and endoleak. RESULTS: There were 42 patients in group A, 42 in group B, and 35 in group C. Demographics, cardiovascular risk factors, and CKD classification were similar in all three groups. Among patients in group A, 44 ARAs were intentionally covered with ARAs originating from the proximal neck in 22 patients, the aneurysm sac in 20, and the iliac arteries in two. There was one (1%) early death in the entire study. Early morbidity was similar in all three groups, including four patients (9%) in group A, four (9%) in group B, and four (11%) in group C (P = .9). Six (5%) patients had >25% decrease in eGFR, including two who had ARA coverage. None of the patients required dialysis. After a mean follow-up of 37 months, there were no differences in late renal function deterioration, changes in eGFR, CKD stage, or blood pressure measurements among the three groups. Three of the 18 patients (17%) with ARA >3 mm arising from the aneurysm sac developed a type II endoleak requiring coil embolization. Kidney infarction was noted in 28 patients (67%) in group A. Freedom from reintervention at 2 years was similar in groups A (64%), B (80%), and C (96%; P = .09). CONCLUSIONS: Intentional ARA occlusion during EVAR was not associated with changes in renal function or blood pressure measurements, even when performed in patients with more advanced renal dysfunction. Type II endoleak may result from persistent outflow into large (>3 mm) ARAs that arise from the aneurysm sac.

Urinary stone differentiation in patients with large body size using dual-energy dual-source computed tomography.

OBJECTIVE: To evaluate the ability of 100/Sn140 kV (Sn, tin filter) dual-energy computed tomography (CT) to differentiate urinary stone types in a patient cohort with a wide range of body sizes. METHODS: Eighty 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 receiver operating characteristics (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. KEY POINTS: • Dual-energy CT helps assessment of urinary stone composition in vivo. • 100/Sn140 kV DECT differentiates among four stone types with 79.1 % accuracy. • In vivo diagnostic test achievable in patients with many body sizes.

Automatic selection of tube potential for radiation dose reduction in vascular and contrast-enhanced abdominopelvic CT.

OBJECTIVE: The purpose of this study is to assess the ability of a novel automatic tube potential selection tool to reduce radiation dose while maintaining diagnostic quality in CT angiography (CTA) and contrast-enhanced abdominopelvic CT. MATERIALS AND METHODS: One hundred one CTA examinations and 90 contrastenhanced abdominopelvic examinations were performed using an automatic tube potential selection tool on a 128-MDCT scanner. Two vascular radiologists and two abdominal radiologists evaluated the image quality for sharpness, noise, artifact, and diagnostic confidence. In a subset of patients who had undergone prior studies (CTA, 28 patients; abdominopelvic CT, 25 patients), a side-by-side comparison was performed by a separate radiologist. Dose reduction and iodine contrast-to-noise ratio resulting from use of the tool were calculated. RESULTS: For CTA, 80 or 100 kV was selected for 73% of the scans, with a mean dose reduction of 36% relative to the reference 120-kV protocol. For abdominopelvic CT examinations, 80 or 100 kV was used for 55% of the scans, with a mean dose reduction of 25%. Overall dose reduction relative to the reference 120-kV protocol was 25% and 13% for CTA and abdominopelvic CT scans, respectively. Over 98% of scans had acceptable sharpness, noise texture, artifact, and diagnostic confidence for both readers and diagnostic tasks; 94-100% of scans had acceptable noise. Iodine contrast-to-noise ratio was significantly higher than (p < 0.001) or similar to (p = 0.11) that of prior scans, and equivalent quality was achieved despite the dose reduction. CONCLUSION: Automatic tube potential selection provides an efficient and quantitativeway to guide the selection of the optimal tube potential for CTA and abdominopelvic CT examinations.