Effect of a hypertensive response during exercise on growth rates of aortic diameters

BACKGROUND

Aortic diameters are related to age, sex, and body size. There are a scarcity of data on the long-term sequelae of a hypertensive response to exercise (HRE) on aortic diameters. In this retrospective cohort study, we aimed to evaluate the relationship between the growth rates of the aorta in individuals with a HRE.

METHODS

Our analysis included follow-up data of 649 patients recruited between January 2009 and December 2014 with a HRE. Participants with known connective tissue disease or a history of acute aortic syndrome were excluded. Sinus of Valsalva (SoV) and ascending aorta (AscAo) diameters were measured by transthoracic echocardiography using leading edge to leading edge convention at end-diastole.

RESULTS

At baseline, median age, maximum systolic blood pressure (BP), body mass index (BMI), diameter of the SoV, and AscAo were 62 years, 208 mmHg, 26.9 kg/m2, 35 mm, and 35 mm respectively. 32% of patients were female and 67% had hypertension. After a median follow-up of 7.1 years, mean yearly growth rates (±SD) of the SoV and AscAo were 0.09 (0.41) mm and 0.13 (0.56) mm respectively. No significant associations were observed between growth rates of aortic diameters and maximum systolic and diastolic BP or when considering only individuals with a baseline diameter > 40mm.

CONCLUSION

In this large cohort study, maximum systolic and diastolic BP during exercise showed no association with growth rates of aortic diameters. Furthermore, the mean growth rates of aortic diameters in this population were in line with growth rates in a normal population.

Post-hoc motion correction for coronary computed tomography angiography without additional radiation dose - Improved image quality and interpretability for “free”

Objective

To evaluate the impact of a motion-correction (MC) algorithm, applicable post-hoc and not dependent on extended padding, on the image quality and interpretability of coronary computed tomography angiography (CCTA).

Methods

Ninety consecutive patients undergoing CCTA on a latest-generation 256-slice CT device were prospectively included. CCTA was performed with prospective electrocardiogram-triggering and the shortest possible acquisition window (without padding) at 75% of the R-R-interval. All datasets were reconstructed without and with MC of the coronaries. The latter exploits the minimal padding inherent in cardiac CT scans with this device due to data acquisition also during the short time interval needed for the tube to reach target currents and voltage (“free” multiphase). Two blinded readers independently assessed image quality on a 4-point Likert scale for all segments.

Results

A total of 1,030 coronary segments were evaluated. Application of MC both with automatic and manual coronary centerline tracking resulted in a significant improvement in image quality as compared to the standard reconstruction without MC (mean Likert score 3.67 [3.50;3.81] vs 3.58 [3.40;3.73], P = 0.005, and 3.7 [3.55;3.82] vs 3.58 [3.40;3.73], P < 0.001, respectively). Furthermore, MC significantly reduced the proportion of non-evaluable segments and patients with at least one non-evaluable coronary segment from 2% to as low as 0.3%, and from 14% to as low as 3%. Reduction of motion artifacts was predominantly observed in the right coronary artery.

Conclusions

A post-hoc device-specific MC algorithm improves image quality and interpretability of prospectively electrocardiogram-triggered CCTA and reduces the proportion of non-evaluable scans without any additional radiation dose exposure.

Predicting non-response in patient-reported outcome measures: results from the Swiss quality assurance programme in cardiac inpatient rehabilitation

BACKGROUND

Quality assurance programmes measure and compare certain health outcomes to ensure high-quality care in the health-care sector. The outcome of health-related quality of life is typically measured by patient-reported outcome measures (PROMs). However, certain patient groups are less likely to respond to PROMs than others. This non-response bias can potentially distort results in quality assurance programmes.

OBJECTIVE

Our study aims to identify relevant predictors of non-response during assessment using the PROM MacNew Heart Disease questionnaire in cardiac rehabilitation.

METHODS

This is a cross-sectional study based on data from the Swiss external quality assurance programme. All patients aged 18 years or older who underwent inpatient cardiac rehabilitation in 16 Swiss rehabilitation clinics between 2016 and 2019 were included. Patients' socio-demographic and basic medical data were analysed descriptively by comparing two groups: non-responders and responders. We used a random intercept logistic regression model to estimate the associations of patient characteristics and clinic differences with non-response.

RESULTS

Of 24 572 patients, there were 33.3% non-responders and 66.7% responders. The mean age was 70 years, and 31.0% were women. The regression model showed that being female was associated with non-response [odds ratio (OR) 1.22; 95% confidence interval (CI) 1.14-1.30], as well as having no supplementary health insurance (OR 1.49; 95% CI 1.39-1.59). Each additional year of age increased the chance of non-response by an OR of 1.02 (95% CI 1.02-1.02). Not being a first language speaker of German, French or Italian increased the chance of non-response by an OR of 6.94 (95% CI 6.03-7.99). Patients admitted directly from acute care had a higher chance of non-response (OR 1.23; 95% CI 1.10-1.38), as well as patients being discharged back into acute care after rehabilitation (OR 3.89; 95% CI 3.00-5.04). Each point on the cumulative illness rating scale total score increased the chance of non-response by an OR of 1.05 (95% CI 1.04-1.05). Certain diagnoses also influenced the chance of non-response. Even after adjustment for known confounders, response rates differed substantially between the 16 clinics.

CONCLUSION

We have found significant non-response bias among certain patient groups, as well as across different treatment facilities. Measures to improve response rates among patients with known barriers to participation, as well as among different treatment facilities, need to be considered, particularly when PROMs are being used for comparison of providers in quality assurance programmes or outcome evaluation.

[Heart Patients and Exposure to Altitude]

Overall, heart patients should be advised individually with respect to their tolerance of altitudes. However, the historical reflex that altitude 'per se' is bad for heart patients should become a thing of the past. Adequately treated and stable patients can usually go up to an altitude of 2500 m without any restrictions. Higher altitudes are also possible for a large number of patients, but may require an adaptation of the medication and further clarification. This is especially the case when physical work is to be performed at great heights.

Ultra-low-dose coronary artery calcium scoring using novel scoring thresholds for low tube voltage protocols-a pilot study

Aims

To determine if tube-adapted thresholds for coronary artery calcium (CAC) scoring by computed tomography at 80 kilovolt-peak (kVp) tube voltage and 70-kVp yield comparable results to the standard 120-kVp protocol.

Methods and results

We prospectively included 103 patients who underwent standard scanning with 120-kVp tube voltage and additional scans with 80 kVp and 70 kVp. Mean body mass index (BMI) was 27.9 ± 5.1 kg/m2. For the lowered tube voltages, we applied novel kVp-adapted thresholds for calculation of CAC scores and compared them with standard 120-kVp scans using intraclass correlation and Bland-Altman (BA) analysis. Furthermore, risk-class (CAC score 0/1-10/11-100/101-400/>400) changes were assessed. Median CAC score from 120-kVp scans was 212 (interquartile range 25-901). Thirteen (12.6%) patients had zero CAC. Using the novel kVp-adapted thresholds, CAC scores derived from 80-kVp scans showed excellent correlation (r = 0.994, P < 0.001) with standard 120-kVp scans with BA limits of agreement of -235 (-39.5%) to 172 (28.9%). Similarly, for 70-kVp scans, correlation was excellent (r = 0.972, P < 0.001) but with broader limits of agreement of -476 (-85.0%) to 270 (48.2%). Only 2 (2.8%) reclassifications were observed for the 80-kVp scans in patients with a BMI <30 kg/m2 (n = 71), and 2 (6.1%) for the 70-kVp scans in patients with a BMI <25 kg/m2 (n = 33). Mean effective radiation dose was 0.60 ± 0.07 millisieverts (mSv), 0.19 ± 0.02 mSv, and 0.12 ± 0.01 mSv for the 120-kVp, 80-kVp, and 70-kVp scans, respectively.

Conclusion

The present study suggests that CAC scoring with reduced peak tube voltage is accurate if kVp-adapted thresholds for calculation of CAC scores are applied while offering a substantial further radiation dose reduction.

A low-dose and an ultra-low-dose contrast agent protocol for coronary CT angiography in a clinical setting: quantitative and qualitative comparison to a standard dose protocol

OBJECTIVE

To evaluate the impact of a low-dose (LD) and an ultra-LD (ULD) contrast protocol for coronary CT angiography on qualitative and quantitative image parameters in a clinical setting.

METHODS

We scanned 120 consecutive patients with a 256-slice CT scanner applying a LD (60 patients, 35-55 ml) or ULD (60 patients, 25-45 ml) contrast protocol adapted to the body mass index. Visually assessed image quality and attenuation measured in each coronary segment were retrospectively compared in 20 consecutive patients scanned with a normal-dose (ND, 40-105 ml) contrast protocol.

RESULTS

Visually assessed image quality did not differ significantly among protocols. By contrast, attenuation obtained from the ULD protocol (median contrast volume 35 ml) differed significantly from the LD (median 45 ml) and ND (median 70 ml) protocols in the coronary segments (316 ± 52 vs 363 ± 60 and 359 ± 52 HU, p < 0.001). Attenuation did not differ significantly between the LD and ND protocol. The proportion of patients with inadequate coronary vessel attenuation was significantly higher (p < 0.001) in the ULD protocol (37%) than in the ND (5%) and LD (10%) protocols but did not differ significantly between the ND and LD protocols.

CONCLUSION

In a clinical setting, a LD contrast protocol with a median volume of 45 ml is feasible for the latest generation 256-slice coronary CT angiography as it yields attenuation comparable to a ND protocol. By contrast, the implementation of an ULD protocol remains challenging. Advances in knowledge: Although not perceived by the naked eye, an ULD contrast protocol in a clinical setting yields attenuation below a threshold for diagnostic image quality.

Hybrid CCTA/SPECT myocardial perfusion imaging findings in patients with anomalous origin of coronary arteries from the opposite sinus and suspected concomitant coronary artery disease

BACKGROUND

Anomalous coronary arteries originating from the opposite sinus of Valsalva (ACAOS) are associated with adverse cardiac events. Discrimination between ACAOS and coronary artery disease (CAD)-related perfusion defects may be difficult. The aim of the present study was to investigate the value of hybrid coronary computed tomography angiography (CCTA)/SPECT-MPI in patients with ACAOS and possible concomitant CAD.

METHODS

We retrospectively identified 46 patients (mean age 56 ± 12 years) with ACAOS revealed by CCTA who underwent additional SPECT-MPI. ACAOS with an interarterial course were classified as malignant, whereas all other variants were considered benign. CCTA/SPECT-MPI hybrid imaging findings (ischemia or scar) were analyzed according to the territory subtended by an anomalous vessel or a stenotic coronary artery.

RESULTS

Twenty-six (57%) patients presented with malignant ACAOS. Myocardial ischemia or scar was found only in patients who had concomitant obstructive CAD in the vessel matching the perfusion defect as evidenced by hybrid CCTA/SPECT imaging.

CONCLUSION

Hybrid CCTA/SPECT-MPI represents a valuable non-invasive tool to discriminate the impact of ACAOS from concomitant CAD on myocardial ischemia. Our results suggest that in a middle-aged population myocardial ischemia due to ACAOS per se may be exceedingly rare and is more likely attributable to concomitant CAD.

Fused cardiac hybrid imaging with coronary computed tomography angiography and positron emission tomography in patients with complex coronary artery anomalies

OBJECTIVE

To provide data on the value of fused cardiac hybrid imaging with coronary computed tomography angiography (CCTA) and positron emission tomography myocardial perfusion imaging (PET-MPI) in patients with complex coronary artery anomalies (CCAA).

DESIGN/SETTING

This is a retrospective, single-center study.

PATIENTS

Seven consecutive patients with CCAA (mean 57 ± 7 y, 86% were male) who underwent clinically indicated hybrid CCTA/PET-MPI between 2005 and 2015 in our clinic were included. The findings from both modalities and fused cardiac hybrid imaging were evaluated in these patients.

RESULTS

Out of the seven patients with CCAA, two patients had Bland-White-Garland anomaly, two patients showed a coronary artery fistula, two patients showed a "single right," and one patient showed a "single left" coronary artery. Semiquantitative fused hybrid CCTA/PET-MPI depicted inferolateral scar matching the territory of a nonanomalous vessel with significant concomitant coronary artery disease (CAD) in one patient only. In contrast, analysis of quantitative myocardial blood flow (MBF) as assessed by fused hybrid CCTA/PET-MPI revealed abnormally reduced flow capacities in the territories subtended by the anomalous vessels in 4 patients.

CONCLUSIONS

In this case series of middle-aged patients with CCAA, perfusion defects as assessed by semiquantitative PET-MPI were rare and attributable to concomitant CAD rather than to the anomalous vessel itself. By contrast, impaired MBF as assessed by quantitative hybrid CCTA/PET-MPI was revealed in the majority of patients in the vessel territories subtended by the anomalous coronary artery itself. Fused hybrid CCTA/PET-MPI incorporating information on morphology and on semiquantitative and quantitative myocardial perfusions may provide added value for the management of patients with CCAA.

Minimized Radiation and Contrast Agent Exposure for Coronary Computed Tomography Angiography: First Clinical Experience on a Latest Generation 256-slice Scanner

RATIONALE AND OBJECTIVES

The aim of the study was to evaluate the impact of the latest coronary computed tomography angiography (CCTA) techniques allowing a radiation- and contrast-sparing protocol on image quality in unselected patients referred for exclusion of suspected coronary artery disease (CAD).

MATERIALS AND METHODS

This prospective study was approved by the local ethics committee, and all patients provided written informed consent. Between March and June 2015, 89 consecutive patients (61% male; mean age 55 ± 11 years) referred for exclusion of CAD by 256-slice CCTA using prospective electrocardiogram triggering were included. Tube voltage (80-120 kVp), tube current (180-310 mA) as well contrast agent volume (25-45 mL) and flow rate (3.5-5 mL/s) were adapted to body mass index. Signal intensity was measured by placing a region of interest in the aortic root, the left main artery, and the proximal right coronary artery. Image noise was measured in the aortic root. Two independent blinded readers semi-quantitatively assessed the image quality regarding motion, noise, and contrast on a 4-point scale.

RESULTS

Median contrast agent volume and median effective radiation dose were 35 mL (interquartile range, 30-40 mL) and 0.5 mSv (interquartile range, 0.4-0.6 mSv), respectively. Mean attenuation in the aortic root was 412 ± 89 Hounsfield units. Diagnostic image quality was obtained in 1050 of 1067 (98.4%) coronary segments and, on an intention-to-diagnosis basis, in 85 of 89 (95.5%) patients. Below a cut-off heart rate of 67 beats/min, only 1 of 974 (0.1%) coronary segments was nondiagnostic.

CONCLUSION

A radiation- and contrast-sparing protocol for CCTA on a latest generation 256-slice computed tomography scanner yields diagnostic image quality in patients referred for CAD exclusion in daily clinical routine.

Prevalence and characteristics of coronary artery anomalies detected by coronary computed tomography angiography in 5 634 consecutive patients in a single centre in Switzerland

STUDY PRINCIPLES

Coronary computed tomography angiography (CCTA) allows three-dimensional visualisation of the origin, course and ending of the coronary vessels with high spatial resolution, yielding an accurate depiction of coronary artery anomalies (CAAs). This study sought to determine the prevalence, incidence and characteristics of CAAs detected with CCTA in a single centre in Switzerland.

METHODS

CAAs were retrospectively identified in 5 634 consecutive patients referred for CCTA between March 2007 and July 2015. Single coronary arteries, Bland-White-Garland syndrome, anomalous coronary arteries originating from the opposite site of the sinus of Valsalva (ACAOS) with an interarterial course and coronary artery fistulas were classified as potentially malignant CAAs.

RESULTS

We identified 145 patients with CAAs, resulting in an overall prevalence of 2.6% and cumulative incidence of 2.1% in all patients referred for CCTA in the observation period. Forty-nine (33.8%) patients showed malignant CAAs including 1 (0.7%) patient with Bland-White-Garland syndrome, 7 (4.8%) with single coronary arteries, 36 (24.8%) with ACAOS and an interarterial course, and 5 (3.5%) with coronary artery fistulas. The remaining 96 (66.2%) patients were classified as having benign variants.

CONCLUSIONS

The prevalence of CAA detected by CCTA is not negligible. Because of its noninvasive nature, relatively low cost and low radiation exposure, a further increase in the utilisation of CCTA may be expected, which may consequently be paralleled by an increasing absolute number of incidentally detected CAAs. Hence, awareness of the main issues and possible management strategies regarding CAAs is of importance for every treating physician.

Multicentre multi-device hybrid imaging study of coronary artery disease: results from the EValuation of INtegrated Cardiac Imaging for the Detection and Characterization of Ischaemic Heart Disease (EVINCI) hybrid imaging population

AIMS

Hybrid imaging provides a non-invasive assessment of coronary anatomy and myocardial perfusion. We sought to evaluate the added clinical value of hybrid imaging in a multi-centre multi-vendor setting.

METHODS AND RESULTS

Fourteen centres enrolled 252 patients with stable angina and intermediate (20-90%) pre-test likelihood of coronary artery disease (CAD) who underwent myocardial perfusion scintigraphy (MPS), CT coronary angiography (CTCA), and quantitative coronary angiography (QCA) with fractional flow reserve (FFR). Hybrid MPS/CTCA images were obtained by 3D image fusion. Blinded core-lab analyses were performed for CTCA, MPS, QCA and hybrid datasets. Hemodynamically significant CAD was ruled-in non-invasively in the presence of a matched finding (myocardial perfusion defect co-localized with stenosed coronary artery) and ruled-out with normal findings (both CTCA and MPS normal). Overall prevalence of significant CAD on QCA (>70% stenosis or 30-70% with FFR≤0.80) was 37%. Of 1004 pathological myocardial segments on MPS, 246 (25%) were reclassified from their standard coronary distribution to another territory by hybrid imaging. In this respect, in 45/252 (18%) patients, hybrid imaging reassigned an entire perfusion defect to another coronary territory, changing the final diagnosis in 42% of the cases. Hybrid imaging allowed non-invasive CAD rule-out in 41%, and rule-in in 24% of patients, with a negative and positive predictive value of 88% and 87%, respectively.

CONCLUSION

In patients at intermediate risk of CAD, hybrid imaging allows non-invasive co-localization of myocardial perfusion defects and subtending coronary arteries, impacting clinical decision-making in almost one every five subjects.

Early safety outcome following transcatheter aortic valve implantation: is the amount of contrast media used a matter of concern?

QUESTIONS UNDER STUDY

The study objective was to evaluate the impact of the amount of contrast medium used for transcatheter aortic valve implantation (TAVI) on short-term outcome. Patients undergoing TAVI are exposed to repeat contrast medium application both for preprocedural screening and during the TAVI procedure itself. Whether the amount of contrast media is associated with worse outcome is unclear.

METHODS

A total of 257 patients were included (median age 82.7 years) and divided into two groups with preserved and reduced kidney function (glomerular filtration rate <60 ml/min/1.73 m2), respectively. Total volume of contrast media administered during and within 5 days prior to TAVI was analysed. A combined early safety endpoint at 30 days was evaluated.

RESULTS

The early safety endpoint was reached by 31 patients and acute kidney injury occurred in 22 patients. The median total volume of contrast media administered was 144 ml (interquartile range 81-225 ml). The amount of contrast did not independently predict the early safety endpoint in the overall population (odds ratio [OR] 0.93, 95% confidence interval [CI] 0.56 to 1.53, p = 0.774) and in subgroups with preserved and reduced kidney function. Change in creatinine was an independent strong predictor of the early safety endpoint in the overall population (OR 18.13, 95% CI 4.70 to 69.99, p <0.001), as well as in subgroups with preserved and reduced kidney function. The amount of contrast did not predict a change in creatinine within 72 hours following TAVI (r = 0.02, 95% CI -0.02 to 0.07, p = 0.368).

CONCLUSION

Decreased kidney function after TAVI influences outcome. When rather small amounts of contrast media are used for screening and the TAVI procedure itself, the amount of contrast media seems not to be an independent predictor of outcome, further suggesting that decreased kidney function after TAVI is multifactorial.

Quantification of epicardial and intrathoracic fat volume does not provide an added prognostic value as an adjunct to coronary artery calcium score and myocardial perfusion single-photon emission computed tomography

AIMS

To compare the predictive value of epicardial and intrathoracic fat volume (EFV, IFV), coronary artery calcium (CAC) score, and single-photon emission computed tomography (SPECT) myocardial perfusion imaging (MPI) for major adverse cardiac events (MACE).

METHODS AND RESULTS

Follow-up was obtained in 275 patients with known or suspected coronary artery disease (CAD), who underwent SPECT-MPI including non-contrast cardiac computed tomography (CT) for attenuation correction to evaluate ischaemic heart disease and in whom EFV, IFV, and CAC score were calculated from non-contrast CT. Associations between fat volume, traditional cardiovascular risk factors, CAC score, and SPECT-MPI results were assessed and MACE predictors identified by Cox proportional hazard regression and global χ(2) statistics. After a median follow-up of 2.9 years, MACE were recorded in 38 patients. In univariate Cox regression analysis, EFV and IFV were predictors of MACE (P = 0.013 and P = 0.004, respectively). In multivariate analysis, EFV and IFV provided incremental predictive value beyond traditional cardiovascular risk factors (P < 0.05 and P < 0.01). However, after adjustment for CAC score and SPECT-MPI results, EFV and IFV fell short of statistical significance as independent outcome predictors.

CONCLUSION

Quantification of EFV and IFV is associated with MACE and may improve risk stratification beyond traditional cardiovascular risk factors. However, once CAC score and/or SPECT-MPI results are known, EFV and IFV do not provide any added clinically relevant prognostic value. Further studies may identify the subpopulation with the largest relative merit of EFV and IFV as an adjunct to SPECT-MPI and CAC score.

Association of left bundle branch block with obstructive coronary artery disease on coronary CT angiography: a case-control study

AIMS

Left bundle branch block (LBBB) is considered an unfavourable prognostic marker in patients with underlying heart disease. Testing for coronary artery disease (CAD) is often prompted by incidental LBBB finding, but published studies disagree about a significant association between LBBB and CAD. We therefore assessed the association of LBBB with previously unknown CAD in patients undergoing coronary computed tomography angiography (CCTA).

METHODS AND RESULTS

We enrolled 818 patients (mean age 57.2 ± 11.1 years, 106 patients with presumably new LBBB and 712 controls) without known CAD who underwent 64-slice CCTA. Image quality was assessed for each coronary segment. Comparison of obstructive CAD prevalence (defined as ≥50% stenosis) was performed using triple case-matching for pre-test probability (based on age, gender, and symptom typicality) in 101 LBBB patients and 303 matched controls with diagnostic quality in all segments. We found no difference in obstructive CAD prevalence between LBBB patients and matched controls (15 vs. 16%, P = 0.88). Similarly, there were no significant differences in cardiovascular risk factors (CVRF), stenosis severity, CAD extent, non-obstructive CAD, and vessel-based analysis between patient groups. Image quality was very high in LBBB patients and comparable to controls. On multivariate analysis, age, gender, typical angina, and CVRF, but not LBBB (P = 0.94), emerged as significant and independent predictors of obstructive CAD.

CONCLUSION

CAD prevalence is similar in LBBB patients at low-to-moderate pre-test probability compared with controls with similar CVRF matched for age, gender, and symptom typicality. CCTA is a useful imaging modality in LBBB patients, providing comparable image quality to non-LBBB controls.

MR-based attenuation correction for cardiac FDG PET on a hybrid PET/MRI scanner: comparison with standard CT attenuation correction

PURPOSE

The aim of this study was to evaluate the feasibility of attenuation correction (AC) for cardiac (18)F-labelled fluorodeoxyglucose (FDG) positron emission tomography (PET) using MR-based attenuation maps.

METHODS

We included 23 patients with no known cardiac history undergoing whole-body FDG PET/CT imaging for oncological indications on a PET/CT scanner using time-of-flight (TOF) and subsequent whole-body PET/MR imaging on an investigational hybrid PET/MRI scanner. Data sets from PET/MRI (with and without TOF) were reconstructed using MR AC and semi-quantitative segmental (20-segment model) myocardial tracer uptake (per cent of maximum) and compared to PET/CT which was reconstructed using CT AC and served as standard of reference.

RESULTS

Excellent correlations were found for regional uptake values between PET/CT and PET/MRI with TOF (n = 460 segments in 23 patients; r = 0.913; p < 0.0001) with narrow Bland-Altman limits of agreement (-8.5 to +12.6 %). Correlation coefficients were slightly lower between PET/CT and PET/MRI without TOF (n = 460 segments in 23 patients; r = 0.851; p < 0.0001) with broader Bland-Altman limits of agreement (-12.5 to +15.0 %). PET/MRI with and without TOF showed minimal underestimation of tracer uptake (-2.08 and -1.29 %, respectively), compared to PET/CT.

CONCLUSION

Relative myocardial FDG uptake obtained from MR-based attenuation corrected FDG PET is highly comparable to standard CT-based attenuation corrected FDG PET, suggesting interchangeability of both AC techniques.