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.

Psoas muscle area and attenuation are highly predictive of complications and mortality after complex endovascular aortic repair.

OBJECTIVE: The present study evaluated the psoas muscle area and attenuation (radiodensity), quantified by computed tomography, together with clinical risk assessment, as predictors of outcomes after fenestrated and branched endovascular aortic repair (FBEVAR). METHODS: The present single-center study included 504 patients who had undergone elective FBEVAR for pararenal or thoracoabdominal aortic aneurysms. The clinical risk assessment included age, sex, comorbidities, body mass index, glomerular filtration rate, aneurysm size and extent, cardiac stress test results, ejection fraction, and American Society of Anesthesiologists (ASA) score. Preoperative computed tomography was used to measure the psoas muscle area and attenuation at the L3 level. The lean psoas muscle area (LPMA; area in cm2 multiplied by attenuation in Hounsfield units [HU]) was calculated by multiplying the area by the attenuation. The risk factors for 90-day mortality, major adverse events (MAEs), and long-term mortality were determined using multivariable analysis. MAEs included 30-day or in-hospital death, acute kidney injury, myocardial infarction, respiratory failure, paraplegia, stroke, and bowel ischemia. A novel risk stratification method was proposed according to the strongest predictors of mortality and MAEs on multivariable analysis. RESULTS: The 30-day mortality, 90-day mortality, and MAE rates were 2.0%, 5.6%, and 20%, respectively. The independent predictors of 90-day mortality were chronic obstructive pulmonary disease, chronic kidney disease, ASA score, and LPMA. The independent predictors of MAEs were aneurysm diameter, glomerular filtration rate, and LPMA. For long-term mortality, the independent predictors were chronic kidney disease, congestive heart failure, extent I-III thoracoabdominal aortic aneurysms, ASA score, and LPMA. The patients were stratified into three groups according to the ASA score and LPMA: low risk, ASA score II or LPMA >350 cm2HU (n = 290); medium risk, ASA score III and LPMA ≤350 cm2HU (n = 181); and high risk, ASA score IV and LPMA ≤350 cm2HU (n = 33). The 90-day mortality and MAE rates were 1.7% and 16% in the low-, 7.2% and 24% in the medium-, and 30% and 33% in the high-risk patients, respectively (P < .001 and P = .02, respectively). Patients with ASA score IV and LPMA <200 cm2HU, indicating sarcopenia (n = 14) had a 43% risk of death within 90 days. The 3-year survival estimates were 80% ± 3% for the low-, 70% ± 4% for the medium-, and 35% ± 9% for the high-risk patients (P < .001). The mean follow-up time was 3.1 ± 2.3 years. CONCLUSIONS: LPMA was a strong predictor of outcomes and the only independent predictor of both mortality and MAEs after FBEVAR. A high muscle mass was protective against complications, regardless of the ASA score. Risk stratification based on the ASA score and LPMA can be used to identify patients at excessively high operative risk.

Prospective nonrandomized study to evaluate cone beam computed tomography for technical assessment of standard and complex endovascular aortic repair.

OBJECTIVE: The objective of this study was to analyze the utility of cone beam computed tomography (CBCT) for technical assessment of standard and complex endovascular aneurysm repair (EVAR). METHODS: Data of consecutive patients who underwent standard or complex EVAR in 2016 and 2017 at our institution were entered into a prospective database and analyzed retrospectively. There were 154 patients (126 male; mean age, 74 ± 8 years) enrolled in a prospective study between 2016 and 2017. A total of 170 aortic procedures were investigated, including 85 fenestrated-branched EVARs (F-BEVARs), 42 abdominal and thoracic EVARs, 32 EVARs with iliac branch devices, and 11 aorta-related interventions. Technical assessment was done using CBCT with and without contrast enhancement, digital subtraction angiography (DSA), and computed tomography angiography (CTA). Patients with stage 3B or stage 4 chronic kidney disease had CBCT without contrast enhancement. Radiation exposure (mean dose-area product), effective dose (ED), and amount of iodine contrast agent were analyzed. End points were presence of any endoleak, positive findings warranting possible intervention (stent kink or compression, type I or type III endoleak, dissection, thrombus), and need for secondary intervention. RESULTS: Radiation exposure and amount of iodine contrast agent were significantly higher (P < .05) for F-BEVAR compared with other aortic procedures (174±101 Gy∙cm2 vs 1135±113 Gy∙cm2 and 144±60 mL vs 122±49 mL). ED averaged 74±36 mSv for the aortic procedure, 18 ± 18 mSv for fluoroscopy, 7 ± 7 mSv for DSA acquisition, 15±7 mSv for CBCT, and 34±17 mSv for CTA imaging (P < .001). Endoleak detection was significantly higher (P < .001) with CBCT (53%) compared with DSA (14%) and CTA (46%). CBCT identified 52 positive findings in 43 patients (28%), higher for F-BEVAR compared with other aortic procedures (35% vs 16%; P = .01). Positive findings included stent compression or kink in 29 patients (17%), type I or type III endoleak in 16 patients (10%), and arterial dissection or thrombus in 7 patients (5%). Of these, 28 patients (18%) had positive findings that prompted an intraoperative (17%) or delayed intervention (1%). Another 15 patients (10%) with minor positive findings were observed with no clinical consequence. DSA alone would not have detected positive findings in 34 of 43 patients (79%), including 21 patients (49%) who needed secondary interventions. CTA diagnosed two (1%) additional endoleaks requiring intervention (one type IC, one type IIIC) that were not diagnosed by CBCT. Replacing DSA and CTA by CBCT would have resulted in 53% ± 13% reduction in amount of iodine contrast agent and 55% ± 12% reduction in ED (P < .05). CONCLUSIONS: CBCT reliably detected positive findings prompting immediate revisions in nearly one of five patients, with the highest rates among F-BEVAR patients. Detection of any endoleak was higher with CBCT compared with DSA or CTA, but most endoleaks were observed. DSA alone failed to detect positive findings warranting revisions.

Natural history of isolated type II endoleaks in patients treated by fenestrated-branched endovascular repair for pararenal and thoracoabdominal aortic aneurysms.

OBJECTIVE: Type II endoleaks (T2ELs) are common after endovascular aneurysm repair (EVAR), but little is known about their natural history in patients treated by fenestrated-branched EVAR (F/BEVAR). We sought to evaluate the natural history of isolated T2EL after F/BEVAR for pararenal aortic aneurysms (PRAs) and thoracoabdominal aortic aneurysms (TAAAs). METHODS: Consecutive patients enrolled in a prospective nonrandomized study to investigate F/BEVAR for PRAs and TAAAs at a single institution (2014-2017) were identified. Computed tomography angiography images at discharge and during follow-up were reviewed. Patients with ≥12 months of follow-up were included and divided in two groups for comparison based on the presence or absence of T2ELs. Patients with any non-T2ELs were excluded. Multivariable logistic regression was used to assess factors associated with T2EL occurrence. Primary outcomes were absolute and relative sac diameter change and sac diameter increase >5 mm. Secondary outcomes included overall survival, aorta-related death, reinterventions, and conversion or rupture. RESULTS: There were 184 patients (136 male [74%]) with PRAs (n = 70 [38%]) and TAAAs (n = 114 [62%]) with an average age of 74 ± 7 years included. Isolated T2ELs were seen in 76 patients (41%); of these, 71 T2ELs (93%) were primary. Patients with T2ELs were more likely to have larger aneurysms (mean baseline diameter, 66 ± 8 mm vs 63 ± 8 mm; P = .01), patent inferior mesenteric artery (66% vs 32%; P < .001), and more lumbar arteries (mean, 6 ± 1 vs 4 ± 1; P < .001). In the multivariable analysis, these were all independently associated with T2EL occurrence. Of all T2ELs, only 18 (24%) resolved spontaneously during a mean follow-up of 31 ± 15 months. Mean absolute sac diameter reduction for patients without T2ELs and with T2ELs, at 12 and 36 months, was 10.2 ± 5.9 mm vs 2.6 ± 6.4 mm and 16.3 ± 7.3 mm vs 5.7 ± 11.3 mm, respectively (P < .001). For the same groups, the mean percentage sac diameter reduction at 12 and 36 months was 16.4% ± 9.4% vs 3.8% ± 9.8% and 26.4% ± 11.6% vs 8.8% ± 17.7%, respectively (P < .001). Overall, 13 patients showed sac increase >5 mm, and all these instances were recorded in the T2EL group; 8 required reintervention. T2ELs were not associated with decreased overall survival, freedom from aorta-related death, or freedom from any reintervention. CONCLUSIONS: Isolated T2ELs are common after F/BEVAR for PRAs and TAAAs, usually seen early; they are most often associated with inferior mesenteric or lumbar artery flow and tend to persist in follow-up. Their presence is associated with impaired sac shrinkage and risk of sac growth with subsequent need for secondary interventions. Although not associated with decreased overall survival or loss of freedom from aorta-related death, T2ELs require serial imaging surveillance.

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.

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.

Understanding, justifying, and optimizing radiation exposure for CT imaging in nephrourology.

An estimated 4-5 million CT scans are performed in the USA every year to investigate nephrourological diseases such as urinary stones and renal masses. Despite the clinical benefits of CT imaging, concerns remain regarding the potential risks associated with exposure to ionizing radiation. To assess the potential risk of harmful biological effects from exposure to ionizing radiation, understanding the mechanisms by which radiation damage and repair occur is essential. Although radiation level and cancer risk follow a linear association at high doses, no strong relationship is apparent below 100 mSv, the doses used in diagnostic imaging. Furthermore, the small theoretical increase in risk of cancer incidence must be considered in the context of the clinical benefit derived from a medically indicated CT and the likelihood of cancer occurrence in the general population. Elimination of unnecessary imaging is the most important method to reduce imaging-related radiation; however, technical aspects of medically justified imaging should also be optimized, such that the required diagnostic information is retained while minimizing the dose of radiation. Despite intensive study, evidence to prove an increased cancer risk associated with radiation doses below ~100 mSv is lacking; however, concerns about ionizing radiation in medical imaging remain and can affect patient care. Overall, the principles of justification and optimization must remain the basis of clinical decision-making regarding the use of ionizing radiation in medicine.

Predictors of Symptomatic Kidney Stone Recurrence After the First and Subsequent Episodes.

OBJECTIVE: To predict symptomatic recurrence among community stone formers with one or more previous stone episodes. PATIENTS AND METHODS: A random sample of incident symptomatic kidney stone formers in Olmsted County, Minnesota, was followed for all symptomatic stone episodes resulting in clinical care from January 1, 1984, through January 31, 2017. Clinical and radiographic characteristics at each stone episode predictive of subsequent episodes were identified. RESULTS: There were 3364 incident kidney stone formers with 4951 episodes. The stone recurrence rates per 100 person-years were 3.4 (95% CI, 3.2-3.7) after the first episode, 7.1 (95% CI, 6.4-7.9) after the second episode, 12.1 (95% CI, 10.3-13.9) after the third episode, and 17.6 (95% CI, 15.1-20.0) after the fourth or higher episode (P<.001 for trend). A parsimonious model identified the following independent risk factors for recurrence: younger age; male sex; higher body mass index; family history of stones; pregnancy; incident asymptomatic stone on imaging before the first episode; suspected stone episode before the first episode; history of a brushite, struvite, or uric acid stone; no history of calcium oxalate monohydrate stone; kidney pelvic or lower pole stone on imaging; no ureterovesical junction stone on imaging; number of kidney stones on imaging; and diameter of the largest kidney stone on imaging. The model had a C-index corrected for optimism of 0.681 and was used to develop a prediction tool. The risk of recurrence in 5 years ranged from 0.9% to 94%, depending on risk factors, number of past episodes, and years since the last episode. CONCLUSION: The revised Recurrence Of Kidney Stone tool predicts the risk of symptomatic recurrence by using readily available clinical characteristics of stone formers.

Impact of onlay fusion and cone beam computed tomography on radiation exposure and technical assessment of fenestrated-branched endovascular aortic repair.

OBJECTIVE: The objective of this study was to analyze the impact of advanced imaging applications and cone beam computed tomography (CBCT) on radiation exposure of the patient and operator and detection of technical problems during fenestrated-branched endovascular aortic repair (F-BEVAR) for treatment of pararenal aneurysms and thoracoabdominal aortic aneurysms (TAAAs). METHODS: We reviewed the clinical data of 386 consecutives patients (289 male; mean age, 75 ± 8 years) treated by F-BEVAR for 196 pararenal aneurysms and 190 TAAAs (mean, 3.4 ± 0.9 targeted vessels/patient) between 2007 and 2017. Radiation exposure (cumulative air kerma) was analyzed in three fixed imaging systems used between 2007 and 2011 (system 1), 2012 and 2016 (system 2), and 2016 and 2017 (system 3). Onlay fusion and CBCT were available with systems 2 and 3, whereas digital zoom with fusion overlay was used with system 3. Operator effective dose was measured per month using a radiation dosimeter badge. Computed tomography angiography and CBCT were analyzed for findings requiring immediate revision or secondary interventions. End points were patient radiation exposure; operator effective dose; procedure technical success; and 30-day rates of mortality, major adverse events, and secondary interventions. RESULTS: F-BEVAR was performed using system 1 in 98 patients, system 2 in 198 patients, and system 3 in 90 patients. Use of onlay fusion/CBCT was 0% with system 1, 42% with system 2, and 98% with system 3. Procedures performed with onlay fusion/CBCT had significantly (P < .05) higher technical success (99.4% vs 98.8%) and lower contrast material volume (155 ± 58 mL vs 172 ± 80 mL), fluoroscopy time (83 ± 34 minutes vs 94 ± 49 minutes), and cumulative air kerma (2561 ± 1920 mGy vs 3767 ± 2307 mGy). Despite higher case volume and increasing complexity during the experience, operator effective dose decreased to 9 ± 4 × 10-2 mSv/case with system 3 compared with 26 ± 3 × 10-2 mSv/case with system 1 and 20 ± 2 × 10-2 mSv/case with system 2 (P = .001). Among 219 patients who had no CBCT, 18 (8%) had computed tomography angiography findings that prompted secondary interventions before dismissal. Conversely, among 167 patients who had CBCT, 14 patients (8%) had intraoperative CBCT findings requiring immediate revision, with no additional secondary interventions. Patients treated with onlay fusion/CBCT had significantly (P < .05) lower mortality (4% vs 1%), major adverse events (43% vs 19%), and secondary interventions (10% vs 4%) at 30 days. CONCLUSIONS: Radiation exposure and operator effective dose significantly decreased with evolution of F-BEVAR experience and use of advanced imaging applications such as onlay fusion and CBCT. CBCT allowed immediate assessment and identified intraoperative technical problems, leading to immediate revision and avoiding early secondary interventions.

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.

The Changing Incidence and Presentation of Urinary Stones Over 3 Decades.

OBJECTIVE: To evaluate trends in the incidence of kidney stones and characteristics associated with changes in the incidence rate over 3 decades. PATIENTS AND METHODS: Adult stone formers in Olmsted County, Minnesota, from January 1, 1984, to December 31, 2012, were validated and characterized by age, sex, stone composition, and imaging modality. The incidence of kidney stones per 100,000 person-years was estimated. Characteristics associated with changes in the incidence rate over time were assessed using Poisson regression models. RESULTS: There were 3224 confirmed symptomatic (stone seen), 606 suspected symptomatic (no stone seen), and 617 incidental asymptomatic kidney stone formers. The incidence of confirmed symptomatic kidney stones increased from the year 1984 to 2012 in both men (145 to 299/100,000 person-years; incidence rate ratio per 5 years, 1.14, P<.001) and women (51 to 217/100,000 person-years; incidence rate ratio per 5 years, 1.29, P<.001). Overall, the incidence of suspected symptomatic kidney stones did not change, but that of asymptomatic kidney stones increased. Utilization of computed tomography for confirmed symptomatic stones increased from 1.8% in 1984 to 77% in 2012; there was a corresponding higher increased incidence of symptomatic small stones (≤3 mm) than of larger stones (>3 mm). Confirmed symptomatic kidney stones with documented spontaneous passage also increased. The incidence of kidney stones with unknown composition increased more than that of stones with known composition. CONCLUSION: The incidence of both symptomatic and asymptomatic kidney stones has increased dramatically. The increased utilization of computed tomography during this period may have improved stone detection and contributed to the increased kidney stone incidence.

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.

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.

Planning endovascular aortic repair with standard and fenestrated-branched endografts.

Endovascular aortic repair (EVAR) has been accepted as the first treatment option in most patients with infrarenal and thoracic aortic aneurysms. Advantages include its minimal invasive approach and lower risk of mortality and morbidity compared to open surgical repair. In patients with complex aneurysms involving side branches, novel techniques of parallel, fenestrated and branched endografts have expanded the indications of EVAR. Preoperative planning is of paramount importance to achieve technical success and to minimize risks of these procedures. In most centers, anatomical measurements are based on helical computed tomography angiography and/or magnetic resonance angiography. This article summarizes the most important aspects on planning standard and complex EVAR to treat aortic aneurysms and dissections.

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.

Kidney Function After the First Kidney Stone Event.

OBJECTIVE: To determine whether there is a persistent decline in kidney function after the first kidney stone event. PATIENT AND METHODS: Incident symptomatic stone formers and age- and sex-matched controls underwent 2 study visits 90 days apart to assess kidney function, complete a survey, and have their medical records reviewed. Kidney function was compared between stone formers and controls adjusting for clinical, blood, and urine risk factors. RESULTS: There were 384 stone formers and 457 controls. At visit 1, a median of 104 days after the stone event, stone formers compared with controls had similar serum creatinine (0.86 vs 0.84 mg/dL; P=.23), higher serum cystatin C (0.83 vs 0.72 mg/L; P<.001), higher urine protein (34.2 vs 19.7 mg/24 h; P<.001) levels, and were more likely to have albuminuria (24 h urine albumin >30 mg: 5.4% vs 2.2%; P=.02). Findings were similar after adjustment for risk factors and at visit 2, a median of 92 days after visit 1. In the 173 stone formers with serum creatinine levels from care before study participation, the mean serum creatinine level was 0.84 mg/dL before the stone event, increased to 0.97 mg/dL (P<.001) at the stone event, but returned to 0.85 mg/dL (P=.38) after the stone event (visit 1). CONCLUSIONS: Incident symptomatic stone formers have a rise in serum creatinine levels that resolves. However, stone formers have sustained higher cystatin C levels and proteinuria that may affect long-term risk of chronic kidney disease.

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.

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.