Repeat coronary computed tomographic angiography in patients with a prior scan excluding significant stenosis

BACKGROUND

ACCF/SCCT/ACR/AHA/ASE/ASNC/NASCI/SCAI/SCMR 2010 Appropriate Use Criteria for Cardiac Computed Tomography (AUC2010) does not incorporate prior coronary computed tomographic angiography (CCTA) results in the appropriateness of a CCTA examination. The purpose of this study was to explore the criteria for forgoing repeat CCTA among patients with clinical scenarios suggesting CCTA as appropriate after prior CCTA excluding coronary artery disease.

METHODS AND RESULTS

Among patients from a single center (February 2006 to April 2013) who underwent appropriate CCTA based on AUC2010, consecutive 555 CCTAs, which had a prior CCTA excluding significant stenosis (>50% stenosis in diameter), were selected. The median time difference between the studies was 34.2 (Q1-Q3, 22.9-50.1) months. Significant stenosis was detected at the time of repeat scan (by CCTA or subsequent catheter angiography) in 13.3% (74 of 555). A multivariable logistic model (C-statistic, 0.74; bootstrapped overfitting bias, 0.8%) identified 3 predictors of significant stenosis: time difference between the studies >3 years (adjusted odds ratio, 2.1; 95% confidence interval, 1.2-3.5), diabetes mellitus (odds ratio, 2.4; 95% confidence interval,1.4-4.3), and 26% to 50% stenosis on the initial CCTA (odds ratio, 5.6; 95% confidence interval, 3.2-9.6). When these 3 factors were all absent (corresponding to 31.9% of the population), the probability of significant stenosis was 4.5% (95% confidence interval, 2.7-7.4%), whereas 17.1% of patients had significant stenosis among those with at least 1 positive variable. When coronary arteries were completely normal at the initial scan, the prevalence of significant stenosis was only 1.8% irrespective of other factors, and no patient underwent revascularization.

CONCLUSIONS

Nondiabetic patients with a prior CCTA <3 years showing no or ≤25% stenosis had a <5% prevalence of significant stenosis. The value of repeat CCTA in this group is likely small, especially when the prior CCTA demonstrated normal coronaries, even if the clinical scenario considered a CCTA appropriate.

Accuracy and reproducibility of automated, standardized coronary transluminal attenuation gradient measurements

Coronary computed tomography angiography (CCTA) contrast opacification gradients, or transluminal attenuation gradients (TAG) offer incremental value to predict functionally significant lesions. This study introduces and evaluates an automated gradients software package that can potentially supplant current, labor-intensive manual TAG calculation methods. All 60 major coronary arteries in 20 patients who underwent a clinically indicated single heart beat 320 × 0.5 mm detector row CCTA were retrospectively evaluated by two readers using a previously validated manual measurement approach and two additional readers who used the new automated gradient software. Accuracy of the automated method against the manual measurements, considered the reference standard, was assessed via linear regression and Bland-Altman analyses. Inter- and intra-observer reproducibility and factors that can affect accuracy or reproducibility of both manual and automated TAG measurements, including CAD severity and iterative reconstruction, were also assessed. Analysis time was reduced by 68% when compared to manual TAG measurement. There was excellent correlation between automated TAG and the reference standard manual TAG. Bland-Altman analyses indicated low mean differences (1 HU/cm) and narrower inter- and intra-observer limits of agreement for automated compared to manual measurements (25 and 36% reduction with automated software, respectively). Among patient and technical factors assessed, none affected agreement of manual and automated TAG measurement. Automated 320 × 0.5 mm detector row gradient software reduces computation time by 68% with high accuracy and reproducibility.

Overestimation of pretest probability of coronary artery disease by Duke clinical score in patients undergoing coronary CT angiography in a Japanese population

BACKGROUND

The Duke clinical score (DCS) is commonly used to estimate the pretest probability of coronary artery disease (CAD). However, the criterion was developed in a population undergoing catheter angiography.

OBJECTIVE

To test the hypothesis that DCS overestimates the CAD probability when applied to patients evaluated with coronary CT angiography (CCTA). A second objective is to compute an adjustment of the calculated DCS to apply to this population.

METHODS

The DCS was calculated for the 3996 consecutive CCTA studies (February 2009 to April 2013) performed for symptomatic patients with no known CAD. Performance of the DCS for the detection of CAD was evaluated by the area under the receiver operating characteristic curve. Using the training cohort (n = 2789), a linear regression line between the calculated probability and the observed prevalence of CAD identified a modified DCS cutoff for a better risk categorization; this was internally validated by a separate cohort (n = 1207).

RESULTS

The DCS showed a good discrimination (area under the receiver operating characteristic curve = 0.71) for the detection of CAD (prevalence = 23.3%). The calibration analysis showed an overall 2.4-fold overestimation by DCS with a DCS < 23% corresponding to the low-risk category (ie, observed prevalence of CAD < 10%). There was no appropriate DCS cutoff to define high-risk category (ie, prevalence > 90%). The validation cohort showed a prevalence of 9.4% when DCS < 23% was used to define low risk.

CONCLUSION

Among patients who underwent CCTA, DCS overestimated the pretest probability by at least 2-fold; the DCS < 23% should define the lower risk probability. The DCS poorly identifies high-risk population and thus development of new CCTA-based criteria is warranted.

4D CT and lung cancer surgical resectability: a technical innovation

A 74-year-old man presents with a left upper lobe lung adenocarcinoma, which demonstrated a wide base intimately with the aortic arch. We utilised 4D CT technique with a wide field of view CT unit to preoperatively determine likely surgical resectability. We propose that 4D CT may be of use in further investigating lung cancer with likely invasion of adjacent structures.

Prognostic Value of Nonobstructive and Obstructive Coronary Artery Disease Detected by Coronary Computed Tomography Angiography to Identify Cardiovascular Events

Background—

The contribution of plaque extent to predict cardiovascular events among patients with nonobstructive and obstructive coronary artery disease (CAD) is not well defined. Our objective was to evaluate the prognostic value of plaque extent detected by coronary computed tomography angiography.

Methods and Results—

All consecutive patients without prior CAD referred for coronary computed tomography angiography to evaluate for CAD were included. Examination findings were classified as normal, nonobstructive (<50% stenosis), or obstructive (≥50%). Based on the number of segments with disease, extent of CAD was classified as nonextensive (≤4 segments) or extensive (>4 segments). The cohort included 3242 patients followed for the primary outcome of cardiovascular death or myocardial infarction for a median of 3.6 (2.1–5.0) years. In a multivariable analysis, the presence of extensive nonobstructive CAD (hazard ratio, 3.1; 95% confidence interval, 1.5–6.4), nonextensive obstructive (hazard ratio, 3.0; 95% confidence interval, 1.3–6.9), and extensive obstructive CAD (hazard ratio, 3.9; 95% confidence interval, 2.2–7.2) were associated with an increased rate of events, whereas nonextensive, nonobstructive CAD was not. The addition of plaque extent to a model that included clinical probability as well as the presence and severity of CAD improved risk prediction.

Conclusions—

Among patients with nonobstructive CAD, those with extensive plaque experienced a higher rate of cardiovascular death or myocardial infarction, comparable with those who have nonextensive disease. Even among patients with obstructive CAD, greater extent of nonobstructive plaque was associated with higher event rate. Our findings suggest that regardless of whether obstructive or nonobstructive disease is present, the extent of plaque detected by coronary computed tomography angiography enhances risk assessment.

Vascular communications between donor and recipient tissues after successful full face transplantation

The vascular reorganization after facial transplantation has important implications on future surgical planning. The purpose of this study was to evaluate blood flow (BF) after full face transplantation using wide area-detector computed tomography (CT) techniques. Three subjects with severe craniofacial injury who underwent full face transplantation were included. All subjects underwent a single anastomosis bilaterally of the artery and vein, and the recipient tongue was preserved. Before and after surgery, dynamic volume CT studies were analyzed for vascular anatomy and blood perfusion. Postsurgical CT showed extensive vascular reorganization for external carotid artery (ECA) angiosome; collateral flows from vertebral, ascending pharyngeal or maxillary arteries supplied the branches from the recipient ECAs distal to the ligation. While allograft tissue was slightly less perfused when the facial artery was the only donor artery when compared to an ECA-ECA anastomosis (4.4 ± 0.4% vs. 5.7 ± 0.7%), allograft perfusion was higher than the recipient normal neck tissue. BF for the recipient tongue was maintained from contralateral/donor arteries when the lingual artery was sacrificed. Venous drainage was adequate for all subjects, even when the recipient internal jugular vein was anastomosed in end-to-end fashion on one side. In conclusion, dynamic CT identified adequate BF for facial allografts via extensive vascular reorganization.

Correlation between early direct communication of positive CT pulmonary angiography findings and improved clinical outcomes

BACKGROUND

Despite a general consensus that rapid communication of critical radiology findings from radiologists to referring physicians is imperative, a possible association with superior patient outcomes has not been confirmed. The objective of this study was to evaluate the correlation between early direct communication of CT image findings by radiologists to referring physicians and better clinical outcomes in patients with acute pulmonary embolism (PE).

METHODS

This was a retrospective, single-institution, cohort study that included 796 consecutive patients (February 2006 to March 2010) who had acute PE confirmed by CT pulmonary angiography (CTPA) and whose treatment had not been initiated at the time of CTPA acquisition. The time from CTPA to direct communication of the diagnosis was evaluated for its association with time from CTPA to treatment initiation and with 30-day mortality. Cox regression analysis was performed with inverse probability weighting by propensity scores calculated using 20 potential confounding factors.

RESULTS

In 93.4% of patients whose first treatment was anticoagulation, the referring physicians started treatment after receiving direct notification of the diagnosis from the radiologist. Late communication (&gt; 1.5 h after CTPA; n = 291) was associated with longer time to treatment initiation (adjusted hazard ratio [HR], 0.714; 95% CI, 0.610-0.836; P &lt; .001) and higher all-cause and PE-related 30-day mortality (HR, 1.813; 95% CI, 1.163-2.828; P = .009; and HR, 2.625; 95% CI, 1.362-5.059; P = .004, respectively).

CONCLUSIONS

Delay (&gt; 1.5 h of CTPA acquisition) in direct communication of acute PE diagnosis from radiologists to referring physicians was significantly correlated with a higher risk of delayed treatment initiation and death within 30 days.

Computed tomography angiography and perfusion to assess coronary artery stenosis causing perfusion defects by single photon emission computed tomography: the CORE320 study

AIMS

To evaluate the diagnostic power of integrating the results of computed tomography angiography (CTA) and CT myocardial perfusion (CTP) to identify coronary artery disease (CAD) defined as a flow limiting coronary artery stenosis causing a perfusion defect by single photon emission computed tomography (SPECT).

METHODS AND RESULTS

We conducted a multicentre study to evaluate the accuracy of integrated CTA-CTP for the identification of patients with flow-limiting CAD defined by ≥50% stenosis by invasive coronary angiography (ICA) with a corresponding perfusion deficit on stress single photon emission computed tomography (SPECT/MPI). Sixteen centres enroled 381 patients who underwent combined CTA-CTP and SPECT/MPI prior to conventional coronary angiography. All four image modalities were analysed in blinded independent core laboratories. The prevalence of obstructive CAD defined by combined ICA-SPECT/MPI and ICA alone was 38 and 59%, respectively. The patient-based diagnostic accuracy defined by the area under the receiver operating characteristic curve (AUC) of integrated CTA-CTP for detecting or excluding flow-limiting CAD was 0.87 [95% confidence interval (CI): 0.84-0.91]. In patients without prior myocardial infarction, the AUC was 0.90 (95% CI: 0.87-0.94) and in patients without prior CAD the AUC for combined CTA-CTP was 0.93 (95% CI: 0.89-0.97). For the combination of a CTA stenosis ≥50% stenosis and a CTP perfusion deficit, the sensitivity, specificity, positive predictive, and negative predicative values (95% CI) were 80% (72-86), 74% (68-80), 65% (58-72), and 86% (80-90), respectively. For flow-limiting disease defined by ICA-SPECT/MPI, the accuracy of CTA was significantly increased by the addition of CTP at both the patient and vessel levels.

CONCLUSIONS

The combination of CTA and perfusion correctly identifies patients with flow limiting CAD defined as ≥50 stenosis by ICA causing a perfusion defect by SPECT/MPI.

Volumetric quantification of type II endoleaks: an indicator for aneurysm sac growth following endovascular abdominal aortic aneurysm repair

PURPOSE

To test the hypothesis that type II endoleak cavity volume (ECV) and endoleak cavity diameter (ECD) measurements are accurate indicators of aneurysm sac volume (ASV) enlargement in patients who undergo endovascular aneurysm repair (EVAR) in the abdominal aorta.

MATERIALS AND METHODS

The institutional review board approved and waived the need to obtain patient consent for this HIPAA-compliant retrospective study. In 72 patients who underwent EVAR, 160 computed tomographic (CT) angiography studies revealed type II endoleaks. Corresponding to these 160 CT angiography studies, 113 CT follow-up studies (in 52 patients) were available and were included in the analysis. ECV measurements were obtained by two observers in consensus by using arterial enhanced phase (ECVAEP) and 70-second delayed enhanced phase (ECVDEP) CT images. The ECVDEP was also normalized as the ECV/ASV ratio. Maximum (ECDM) and transverse (ECDT) ECDs were determined from delayed enhanced phase images. The outcome was determined as interval increase (>2%) in ASV versus stable or decreasing (≤2%) ASV. Receiver operating characteristic (ROC) analysis was used to compare the accuracy of type II ECV and ECD measurements in indicating interval increase in ASV.

RESULTS

In 56 (49.5%) of 113 CT studies in type II endoleaks, there was an interval increase in ASV. The accuracies of ECVDEP (area under the ROC curve [AUC], 0.85) and normalized ECVDEP (AUC, 0.86) were superior to the accuracies of ECDM (AUC, 0.73), ECDT (AUC, 0.73), and ECVAEP (AUC, 0.66). At ROC curve analysis, the sensitivity, specificity, and positive and negative predictive values for type II endoleak cavities with an ECVDEP of less than 0.5 mL for showing no future sac volume enlargement were 33% (19 of 57), 100% (56 of 56), 100% (19 of 19), and 60% (56 of 94), respectively.

CONCLUSION

With use of the delayed enhanced phase of CT angiography, ECV measurement is an accurate indicator of aneurysm sac enlargement.

ACR appropriateness criteria imaging for transcatheter aortic valve replacement

Although aortic valve replacement is the definitive therapy for severe aortic stenosis, almost half of patients with severe aortic stenosis are unable to undergo conventional aortic valve replacement because of advanced age, comorbidities, or prohibitive surgical risk. Treatment options have been recently expanded with the introduction of catheter-based implantation of a bioprosthetic aortic valve, referred to as transcatheter aortic valve replacement. Because this procedure is characterized by lack of exposure of the operative field, image guidance plays a critical role in preprocedural planning. This guideline document evaluates several preintervention imaging examinations that focus on both imaging at the aortic valve plane and planning in the supravalvular aorta and iliofemoral system. The ACR Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed every 2 years by a multidisciplinary expert panel. The guideline development and review include an extensive analysis of current medical literature from peer-reviewed journals and the application of a well-established consensus methodology (modified Delphi) to rate the appropriateness of imaging and treatment procedures by the panel. In those instances in which evidence is lacking or not definitive, expert opinion may be used to recommend imaging or treatment.

ACR Appropriateness Criteria ® imaging of mesenteric ischemia

Mesenteric ischemia is a rare disease associated with high morbidity and mortality. Acute mesenteric ischemia is most commonly secondary to embolism followed by arterial thrombosis, nonocclusive ischemia, and less commonly venous thrombosis. Chronic mesenteric ischemia is almost always caused by atherosclerotic disease, with rare causes including fibromuscular dysplasia and vasculitis. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed every 2 years by a multidisciplinary expert panel. The guideline development and review include an extensive analysis of current medical literature from peer reviewed journals and the application of a well-established consensus methodology (modified Delphi) to rate the appropriateness of imaging and treatment procedures by the panel. In those instances where evidence is lacking or not definitive, expert opinion may be used to recommend imaging or treatment. Patients with mesenteric ischemia usually present with nonspecific abdominal symptoms and laboratory findings. This document evaluates and rates the appropriateness of imaging to evaluate patients with clinically suspected mesenteric ischemia. While catheter-based angiography has been considered the reference standard and enables diagnosis and treatment, advances in computed tomography have made it a first-line test in many patients because it is a fast, widely available, and noninvasive study. Abdominal radiographs and ultrasound have a limited role in diagnosing mesenteric ischemia but are commonly the first ordered tests in patients with abdominal pain and may diagnose more common pathologies.

Upper extremity composite tissue allotransplantation imaging

OBJECTIVE

Upper extremity (UE) transplantation is the most commonly performed composite tissue allotransplantation worldwide. However, there is a lack of imaging standards for pre- and posttransplant evaluation. This study highlights the protocols and findings of UE allotransplantation toward standardization and implementation for clinical trials.

METHODS

Multimodality imaging protocols for a unilateral hand transplant candidate and a bilateral mid-forearm level UE transplant recipient include radiography, computed tomography (CT), magnetic resonance (MR) imaging, catheter angiography, and vascular ultrasonography. Pre- and posttransplant findings, including dynamic CT and MR performed for assessment of motor activity of transplanted hands, are assessed, and image quality of vessels and bones on CT and MR evaluated.

RESULTS

Preoperative imaging demonstrates extensive skeletal deformity and variation in vascular anatomy and vessel patency. Posttransplant images confirm bony union in anatomical alignment and patency of vascular anastomoses. Mild differences in rate of vascular enhancement and extent of vascular networks are noted between the 2 transplanted limbs. Dynamic CT and MR demonstrate a 15° to 30° range of motion at metacarpophalangeal joints and 90° to 110° at proximal interphalangeal joints of both transplanted hands at 8 months posttransplant. Image quality was slightly better for CT than for MR in the first subject, while MR was slightly better in the second subject.

CONCLUSION

Advanced vascular and musculoskeletal imaging play an important role in surgical planning and can provide novel posttransplantation data to monitor the success of the procedure. Implementation of more standardized protocols should enable a more comprehensive assessment to evaluate the efficacy in clinical trials.

Reduced radiation exposure for face transplant surgical planning computed tomography angiography

Objective

To test the hypothesis that wide area detector face transplant surgical planning CT angiograms with simulated lower radiation dose and iterative reconstruction (AIDR3D) are comparable in image quality to those with standard tube current and filtered back projection (FBP) reconstruction.

Materials and Methods

The sinograms from 320-detector row CT angiography of four clinical candidates for face transplantation were processed utilizing standard FBP, FBP with simulated 75, 62, and 50% tube current, and AIDR3D with corresponding dose reduction. Signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were measured at muscle, fat, artery, and vein. Image quality for each reconstruction strategy was assessed by two independent readers using a 4-point scale.

Results

Compared to FBP, the median SNR and CNR for AIDR3D images were higher at all sites for all 4 different tube currents. The AIDR3D with simulated 50% tube current achieved comparable SNR and CNR to FBP with standard dose (median muscle SNR: 5.77 vs. 6.23; fat SNR: 6.40 vs. 5.75; artery SNR: 43.8 vs. 45.0; vein SNR: 54.9 vs. 55.7; artery CNR: 38.1 vs. 38.6; vein CNR: 49.0 vs. 48.7; all p-values >0.19). The interobserver agreement in the image quality score was good (weighted κ = 0.7). The overall score and the scores for smaller arteries were significantly lower when FBP with 50% dose reduction was used. The AIDR3D reconstruction images with 4 different simulated doses achieved a mean score ranging from 3.68 to 3.82 that were comparable to the scores from images reconstructed using FBP with original dose (3.68–3.77).

Conclusions

Simulated radiation dose reduction applied to clinical CT angiography for face transplant planning suggests that AIDR3D allows for a 50% reduction in radiation dose, as compared to FBP, while preserving image quality.

Computed tomography angiography for transcatheter aortic valve replacement

BACKGROUND

Transcatheter aortic valve replacement (TAVR) is an established alternative to surgery for patients with severe, symptomatic aortic stenosis who are not suitable candidates for surgical replacement of the aortic valve. The computed tomography (CT) technologist has a critical role in the care of patients undergoing TAVR. Because image acquisition and postprocessing for TAVR planning are highly complex, it is important for CT technologists involved in the planning to understand clinical detail, protocols, potential pitfalls, and factors that may influence workflow.

PURPOSE

To describe, from the CT technologist's point of view, the details of CT angiography acquisition and postprocessing at 1 institution for patients being screened for TAVR.

DISCUSSION

For TAVR patients, CT image acquisition and postprocessing is essential for a successful intervention. It is clinically essential to maintain and execute a detailed, standardized imaging approach.

CONCLUSION

TAVR planning is among the most complex procedures in radiology. For these patients, meticulous image acquisition and image postprocessing protocols are paramount, and successful patient outcomes depend on attention to clinical detail, protocols, potential pitfalls, and factors that may influence workflow.

Simulated 50 % radiation dose reduction in coronary CT angiography using adaptive iterative dose reduction in three-dimensions (AIDR3D)

To compare the image quality of coronary CT angiography (CTA) studies between standard filtered back projection (FBP) and adaptive iterative dose reduction in three-dimensions (AIDR3D) reconstruction using CT noise additional software to simulate reduced radiation exposure. Images from 93 consecutive clinical coronary CTA studies were processed utilizing standard FBP, FBP with 50 % simulated dose reduction (FBP50 %), and AIDR3D with simulated 50 % dose reduction (AIDR50 %). Signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were measured within 5 regions-of-interest, and image quality for each reconstruction strategy was assessed by two independent readers using a 4-point scale. Compared to FBP, the SNR measured from the AIDR50 % images was similar or higher (airway: 38.3 ± 12.7 vs. 38.5 ± 14.5, p = 0.81, fat: 5.5 ± 1.9 vs. 5.4 ± 2.0, p = 0.20, muscle: 3.2 ± 1.2 vs. 3.1 ± 1.3, p = 0.38, aorta: 22.6 ± 9.4 vs. 20.2 ± 9.7, p < 0.0001, liver: 2.7 ± 1.0 vs. 2.3 ± 1.1, p < 0.0001), while the SNR of the FBP50 % images were all lower (p values < 0.0001). The CNR measured from AIDR50 % images was also higher than that from the FBP images for the aorta relative to muscle (20.5 ± 9.0 vs. 18.3 ± 9.2, p < 0.0001). The interobserver agreement in the image quality score was excellent (κ = 0.82). The quality score was significantly higher for the AIDR50 % images compared to the FBP images (3.6 ± 0.6 vs. 3.3 ± 0.7, p = 0.004). Simulated radiation dose reduction applied to clinical coronary CTA images suggests that a 50 % reduction in radiation dose can be achieved with adaptive iterative dose reduction software with image quality that is at least comparable to images acquired at standard radiation exposure and reconstructed with filtered back projection.

Cine computed tomography angiography evaluation of blood flow for full face transplant surgical planning

OBJECTIVE

Screening for full face transplantation candidates includes computed tomographic vascular mapping of the external carotid distribution for potential arterial and venous anastomoses. The purpose of this study is to illustrate the benefits and drawbacks of cine computed tomographic imaging for preoperative vascular mapping compared with best arterial and venous phase static images.

METHODS

Two image data sets were retrospectively created and compared for diagnostic findings. The first set of images was the clinical cine computed tomographic acquisition including all phases. The second set of images was composed of the best arterial and best venous phases extracted from the cine loop and determined by the quality of contrast enhancement. For each patient, the benefits and drawbacks of the cine loop were documented in consensus by a plastic surgeon and a radiologist.

RESULTS

Cine loop analysis identified retrograde arterial filling not illustrated on the static images alone. Cine assessment identified most of the major vessels necessary for surgery, whereas the static images depicted small vessels more clearly, particularly in the crowded vessel takeoffs.

CONCLUSIONS

Cine computed tomographic images provide data on direction of blood flow, which is important for preoperative planning. Combination of cine computed tomographic and the best static images will allow comprehensive vascular assessment necessary for future successful full face transplantation.