Detection of coronary artery stenosis with sub-milliSievert radiation dose by prospectively ECG-triggered high-pitch spiral CT angiography and iterative reconstruction

Objectives

To evaluate the diagnostic accuracy of sub-milliSievert (mSv) coronary CT angiography (cCTA) using prospectively ECG-triggered high-pitch spiral CT acquisition combined with iterative image reconstruction.

Methods

Forty consecutive patients (52.9?±?8.7 years; 30 men) underwent dual-source cCTA using prospectively ECG-triggered high-pitch spiral acquisition. The tube current-time product was set to 50 % of standard-of-care CT examinations. Images were reconstructed with sinogram-affirmed iterative reconstruction. Image quality was scored and diagnostic performance for detection of ≥50 % stenosis was determined with catheter coronary angiography (CCA) as the reference standard.

Results

CT was successfully performed in all 40 patients. Of the 601 assessable coronary segments, 543 (90.3 %) had diagnostic image quality. Per-patient sensitivity for detection of ≥50 % stenosis was 95.7 % [95 % confidence interval (CI), 76.0-99.8 %] and specificity was 94.1 % (95 % CI, 69.2-99.7 %). Per-vessel sensitivity was 89.5 % (95 % CI, 77.8-95.6 %) with 93.2 % specificity (95 % CI, 86.0-97.0 %). The area under the receiver-operating characteristic curve on per-patient and per-vessel levels was 0.949 and 0.913. Mean effective dose was 0.58?±?0.17 mSv. Mean size-specific dose estimate was 3.14?±?1.15 mGy.

Conclusions

High-pitch prospectively ECG-triggered cCTA combined with iterative image reconstruction provides high diagnostic accuracy with a radiation dose below 1 mSv for detection of coronary artery stenosis.

Key Points

? Cardiac CT with sub-milliSievert radiation dose is feasible in many patients ? High-pitch spiral CT acquisition with iterative reconstruction detects coronary stenosis accurately. ? Iterative reconstruction increases who can benefit from low-radiation cardiac CT.     

Diagnostic accuracy of combined coronary angiography and adenosine stress myocardial perfusion imaging using 320-detector computed tomography: pilot study

Objectives

To determine the diagnostic accuracy of combined 320-detector row computed tomography coronary angiography (CTA) and adenosine stress CT myocardial perfusion imaging (CTP) in detecting perfusion abnormalities caused by obstructive coronary artery disease (CAD).

Methods

Twenty patients with suspected CAD who underwent initial investigation with single-photon-emission computed tomography myocardial perfusion imaging (SPECT-MPI) were recruited and underwent prospectively-gated 320-detector CTA/CTP and invasive angiography. Two blinded cardiologists evaluated invasive angiography images quantitatively (QCA). A blinded nuclear physician analysed SPECT-MPI images for fixed and reversible perfusion defects. Two blinded cardiologists assessed CTA/CTP studies qualitatively. Vessels/territories with both >50 % stenosis on QCA and corresponding perfusion defect on SPECT-MPI were defined as ischaemic and formed the reference standard.

Results

All patients completed the CTA/CTP protocol with diagnostic image quality. Of 60 vessels/territories, 17 (28 %) were ischaemic according to QCA/SPECT-MPI criteria. Sensitivity, specificity, PPV, NPV and area under the ROC curve for CTA/CTP was 94 %, 98 %, 94 %, 98 % and 0.96 (P?<?0.001) on a per-vessel/territory basis. Mean CTA/CTP radiation dose was 9.2?±?7.4 mSv compared with 13.2?±?2.2 mSv for SPECT-MPI (P?<?0.001).

Conclusions

Combined 320-detector CTA/CTP is accurate in identifying obstructive CAD causing perfusion abnormalities compared with combined QCA/SPECT-MPI, achieved with lower radiation dose than SPECT-MPI.

Key Points

? Advances in CT technology provides comprehensive anatomical and functional cardiac information. ? Combined 320-detector CTA/adenosine-stress CTP is feasible with excellent image quality. ? Combined CTA/CTP is accurate in identifying myocardial ischaemia compared with QCA/SPECT-MPI. ? Combined CTA/CTP results in lower patient radiation exposure than SPECT-MPI. ? CTA/CTP may become an established imaging technique for suspected CAD.     

Automated Quantification of Epicardial Adipose Tissue Using CT Angiography: Evaluation of a Prototype Software

Objectives

This study evaluated the performance of a novel automated software tool for epicardial fat volume (EFV) quantification compared to a standard manual technique at coronary CT angiography (cCTA).

Methods

cCTA data sets of 70 patients (58.6?±?12.9 years, 33 men) were retrospectively analysed using two different post-processing software applications. Observer 1 performed a manual single-plane pericardial border definition and EFV_M segmentation (manual approach). Two observers used a software program with fully automated 3D pericardial border definition and EFV_A calculation (automated approach). EFV and time required for measuring EFV (including software processing time and manual optimization time) for each method were recorded. Intraobserver and interobserver reliability was assessed on the prototype software measurements. T test, Spearman’s rho, and Bland–Altman plots were used for statistical analysis.

Results

The final EFV_A (with manual border optimization) was strongly correlated with the manual axial segmentation measurement (60.9?±?33.2 mL vs. 65.8?±?37.0 mL, rho?=?0.970, P?<?0.001). A mean of 3.9?±?1.9 manual border edits were performed to optimize the automated process. The software prototype required significantly less time to perform the measurements (135.6?±?24.6 s vs. 314.3?±?76.3 s, P?<?0.001) and showed high reliability (ICC?>?0.9).

Conclusions

Automated EFV_A quantification is an accurate and time-saving method for quantification of EFV compared to established manual axial segmentation methods.

Key Points

? Manual epicardial fat volume quantification correlates with risk factors but is time-consuming. ? The novel software prototype automates measurement of epicardial fat volume with good accuracy. ? This novel approach is less time-consuming and could be incorporated into clinical workflow.     

Interscan reproducibility of quantitative coronary plaque volume and composition from CT coronary angiography using an automated method

Objectives

Quantitative measurements of coronary plaque volume may play a role in serial studies to determine disease progression or regression. Our aim was to evaluate the interscan reproducibility of quantitative measurements of coronary plaque volumes using a standardized automated method.

Methods

Coronary dual source computed tomography angiography (CTA) was performed twice in 20 consecutive patients with known coronary artery disease within a maximum time difference of 100 days. The total plaque volume (TP), the volume of non-calcified plaque (NCP) and calcified plaque (CP) as well as the maximal remodelling index (RI) were determined using automated software.

Results

Mean TP volume was 382.3?±?236.9 mm³ for the first and 399.0?±?247.3 mm³ for the second examination (p?=?0.47). There were also no significant differences for NCP volumes, CP volumes or RI. Interscan correlation of the plaque volumes was very good (Pearson’s correlation coefficients: r?=?0.92, r?=?0.90 and r?=?0.96 for TP, NCP and CP volumes, respectively).

Conclusions

Automated software is a time-saving method that allows accurate assessment of coronary atherosclerotic plaque volumes in coronary CTA with high reproducibility. With this approach, serial studies appear to be possible.

Key Points

? Reproducibility of coronary atherosclerotic plaque volume in coronary CTA is high. ? Using automated software facilitates quantitative measurements. ? Serial studies to determine progression or regression of coronary plaque are possible.     

Quantification and characterisation of coronary artery plaque volume and adverse plaque features by coronary computed tomographic angiography: a direct comparison to intravascular ultrasound

Objective

We evaluated the performance of manual measures of coronary plaque volumes and atherosclerotic plaque features from coronary CT angiography (CTA), using intravascular ultrasound (IVUS) as the reference.

Methods

Thirty individual coronary plaques with suitable fiduciary markers were identified. Plaque volumes on coronary CTA were manually quantified by two observers and compared to IVUS plaque volumes as interpreted by an independent laboratory. The presence of adverse plaque characteristics—low attenuation plaque (LAP), positive remodelling (PR) and spotty calcification (SC)—on coronary CTA was evaluated and compared to IVUS.

Results

High correlation in plaque volumes was detected between observers (r?=?0.94, P?<?0.0001; 95 % limits of agreement <48.7 mm³, bias 6.6 mm³). Excellent correlation (r?=?0.95, P?<?0.0001) was noted in plaque volume between independent observers and IVUS (95 % limits of agreement <40.6 mm³, bias ?4.4 mm³) and did not differ from IVUS (105.0?±?56.7 vs. 109.4?±?60.7 mm³, P?=?0.2). The frequency of LAP (10 % vs. 17 %), PR (7 % vs. 10 %) and SC (27 % vs. 33 %) was similar between coronary CTA and IVUS (all P?=?NS).

Conclusions

Plaque volume on coronary CTA determined by manual methods demonstrates high correlation and modest agreement to IVUS. Further, coronary CTA demonstrates high accuracy for the identification of adverse plaque characteristics, including LAP, PR and SC.

Key Points

? Coronary CT angiography is a non-invasive test that enables coronary plaque assessment ? Plaque quantification by coronary CT angiography correlates well with intravascular ultrasound findings ? Coronary CT angiography can identify adverse plaque characteristics     

Myocardial perfusion imaging with a cadmium zinc telluride-based gamma camera versus invasive fractional flow reserve

Purpose

Recently introduced ultrafast cardiac SPECT cameras with cadmium zinc telluride-based (CZT) detectors may provide superior image quality allowing faster acquisition with reduced radiation doses. Although the level of concordance between conventional SPECT and invasive fractional flow reserve (FFR) measurement has been studied, that between FFR and CZT-based SPECT is not yet known. Therefore, we aimed to assess the level of concordance between CZT SPECT and FFR in a large patient group with stable coronary artery disease.

Methods

Both invasive FFR and myocardial perfusion imaging with a CZT-based SPECT camera, using Tc-tetrofosmin as tracer, were performed in 100 patients with stable angina and intermediate grade stenosis on invasive coronary angiography. A cut-off value of <0.75 was used to define abnormal FFR.

Results

The mean age of the patients was 64?±?11 years, and 64 % were men. SPECT demonstrated ischaemia in 31 % of the patients, and 20 % had FFR <0.75. The concordance between CZT SPECT and FFR was 73 % on a per-patient basis and 79 % on a per-vessel basis. Discordant findings were more often seen in older patients and were mainly (19 %) the result of ischaemic SPECT findings in patients with FFR ≥0.75, whereas only 8 % had an abnormal FFR without ischaemia as demonstrated by CZT SPECT.

Conclusion

Only 20 – 30 % of patients with intermediate coronary stenoses had significant ischaemia as assessed by CZT SPECT or invasive FFR. CZT SPECT showed a modest degree of concordance with FFR, which is comparable with previous results with conventional SPECT. Further investigations are particularly necessary in patients with normal SPECT and abnormal FFR, especially to determine whether these patients should undergo revascularization.     

High-efficiency SPECT MPI: Comparison of automated quantification, visual interpretation, and coronary angiography

Background

Recently introduced high-efficiency (HE) SPECT cameras with solid-state CZT detectors have been shown to decrease imaging time and reduce radiation exposure to patients. An automated, computer-derived quantification of HE MPI has been shown to correlate well with coronary angiography on one HE SPECT camera system (D-SPECT), but has not been compared to visual interpretation on any of the HE SPECT platforms.

Methods

Patients undergoing a clinically indicated Tc-99m sestamibi HE SPECT (GE Discovery 530c with supine and prone imaging) study over a 1-year period followed by a coronary angiogram within 2 months were included. Only patients with a history of CABG surgery were excluded. Both MPI studies and coronary angiograms were reinterpreted by blinded readers. One hundred and twenty two very low (risk of CAD < 5%) or low (risk of CAD < 10%) likelihood subjects with normal myocardial perfusion were used to create normal reference limits. Computer-derived quantification of the total perfusion deficit at stress and rest was obtained with QPS software. The visual and automated MPI quantification were compared to coronary angiography (≥70% luminal stenosis) by receiver operating curve (ROC) analysis.

Results

Of the 3,111 patients who underwent HE SPECT over a 1-year period, 160 patients qualified for the correlation study (66% male, 52% with a history of CAD). The ROC area under the curve (AUC) was similar for both the automated and the visual interpretations using both supine only and combined supine and prone images (0.69-0.74). Using thresholds determined from sensitivity and specificity curves, the automated reads showed higher specificity (59%-67% vs 27%-60%) and lower sensitivity (71%-72% vs 79%-93%) than the visual reads. By including prone images sensitivity decreased slightly but specificity increased for both. By excluding patients with known CAD and cardiomyopathies, AUC and specificity increased for both techniques (0.72-0.82). The use of a difference score to evaluate ischemic burden resulted in lower sensitivities but higher specificities for both automated and visual quantification. There was good agreement between the visual interpretation and automated quantification in the entire cohort of 160 unselected consecutive patients (r = 0.70-0.81, P < .0001).

Conclusions

Automated and visual quantification of high-efficiency SPECT MPI with the GE Discovery camera provides similar overall diagnostic accuracy when compared to coronary angiography. There was good correlation between the two methods of assessment. Combined supine and prone stress imaging provided the best diagnostic accuracy.     

Hybrid CT angiography and quantitative 15O-water PET for assessment of coronary artery disease: comparison with quantitative coronary angiography

Purpose

CT angiography (CTA) can rule out significant stenoses with a very high reliability, whereas its ability to confirm significant stenoses is suboptimal. In contrast, measurements of myocardial blood flow (MBF) provide information on the haemodynamic consequences of stenoses. Therefore, a combination of the two might improve diagnostic accuracy. We conducted a head-to-head comparison of CTA, measurement of MBF by ¹⁵O-water PET, and hybrid PET/CTA for the detection of significant coronary artery stenoses.

Methods

The study group comprised 44 outpatients scheduled for invasive coronary angiography (ICA) with an intermediate pretest likelihood of coronary artery disease. The patients underwent 64-slice CTA and baseline and hyperaemic PET before ICA with quantitative coronary angiography analysis.

Results

On a per-patient basis, the negative predictive values (NPV; 95 % confidence intervals in parentheses) were 88 % (64 – 97 %) for CTA, 90 % (71 – 97%) for PET and 92 % (74 – 98%) for PET/CTA, and the positive predictive values (PPV) were 71 % (53 – 85%) for CTA, 87 % (68 – 95%) for PET and 100 % (84 – 100%) for PET/CTA. Similarly, on a per-vessel basis the NPVs (which were generally high) were 97 % (94 – 100%) for CTA, 95 % (90 – 99%) for PET and 97 % (95 – 100%) for PET/CTA, and the PPVs (which were lower, but higher with PET/CTA) were 53 % (39 – 66%) for CTA, 53 % (40 – 66%) for PET and 85 % (73 – 97%) for PET/CTA. In six patients, CTA analysis was hampered by the presence of severe calcifications. However, with the addition of the PET data, all six patients were correctly categorized.

Conclusion

Cardiac quantitative hybrid PET/CTA imaging has better diagnostic accuracy than CTA alone and PET alone. CTA has a suboptimal PPV, suggesting that hybrid PET/CTA imaging should be used to assess the significance of coronary stenoses diagnosed by CTA.     

Image quality and radiation dose of low tube voltage 3rd generation dual-source coronary CT angiography in obese patients: a phantom study

Objectives

To assess the influence of tube potential on radiation dose and image quality of third-generation dual-source coronary CT angiography (CTA) in a phantom simulating an obese patient.

Methods

A thoracic phantom was equipped with tubular inserts containing iodine solution and water. A soft-tissue-equivalent ring around the phantom simulated an obese patient. Images were acquired at tube potentials of 80, 100, 120 and 140 kV with second-generation dual-source CT (DSCT) and 70–150 kV (in 10-kV increments) with third-generation DSCT. Contrast-to-noise ratio (CNR) was calculated and CT dose index was recorded.

Results

With second-generation DSCT, CNR was highest for 120 kV (19.0) and decreased with lower tube potential (12.0 at 80 kV) owing to disproportionately increased image noise. With third-generation DSCT, 70- and 80-kV acquisitions showed a smaller increase in noise. CNRs for third-generation DSCT were highest for 70 and 80 kV (21.1 and 21.2, respectively). Compared to 120 kV, radiation dose was 68 % and 49 % lower at 70 kV and 80 kV, respectively.

Conclusion

Third-generation DSCT enables one to perform coronary CTA at 70–80 kV in obese patients without compromising CNR and thus reduces radiation dose by 49–68 %.

Key points

? Low tube potential CT angiography is currently not suitable for obese patients. ? Third-generation DSCT offers substantially increased tube power at low tube potential. ? This enables one to perform coronary CT angiography at 70–80 kV in obese patients. ? Signal-to-noise ratio is maintained owing to increased tube current. ? This approach can be expected to reduce radiation dose by 49–68 %.     

Diagnostic accuracy of 128-slice dual-source CT coronary angiography: a randomized comparison of different acquisition protocols

Objectives

To compare the diagnostic performance and radiation exposure of 128-slice dual-source CT coronary angiography (CTCA) protocols to detect coronary stenosis with more than 50 % lumen obstruction.

Methods

We prospectively included 459 symptomatic patients referred for CTCA. Patients were randomized between high-pitch spiral vs. narrow-window sequential CTCA protocols (heart rate below 65 bpm, group A), or between wide-window sequential vs. retrospective spiral protocols (heart rate above 65 bpm, group B). Diagnostic performance of CTCA was compared with quantitative coronary angiography in 267 patients.

Results

In group A (231 patients, 146 men, mean heart rate 58?±?7 bpm), high-pitch spiral CTCA yielded a lower per-segment sensitivity compared to sequential CTCA (89 % vs. 97 %, P?=?0.01). Specificity, PPV and NPV were comparable (95 %, 62 %, 99 % vs. 96 %, 73 %, 100 %, P?>?0.05) but radiation dose was lower (1.16?±?0.60 vs. 3.82?±?1.65 mSv, P?<?0.001). In group B (228 patients, 132 men, mean heart rate 75?±?11 bpm), per-segment sensitivity, specificity, PPV and NPV were comparable (94 %, 95 %, 67 %, 99 % vs. 92 %, 95 %, 66 %, 99 %, P?>?0.05). Radiation dose of sequential CTCA was lower compared to retrospective CTCA (6.12?±?2.58 vs. 8.13?±?4.52 mSv, P?<?0.001). Diagnostic performance was comparable in both groups.

Conclusion

Sequential CTCA should be used in patients with regular heart rates using 128-slice dual-source CT, providing optimal diagnostic accuracy with as low as reasonably achievable (ALARA) radiation dose.

Key Points

? 128-slice dual-source CT coronary angiography offers several different acquisition protocols. ? Randomized comparison of protocols reveals an optimal protocol selection strategy. ? Appropriate CTCA protocol selection lowers radiation dose, while maintaining high quality. ? CTCA protocol selection should be based on individual patient characteristics. ? A prospective sequential protocol is preferred for CTCA.     

Diagnostic performance of computed tomography coronary angiography to detect and exclude left main and/or three-vessel coronary artery disease

Objectives

To determine the diagnostic performance of CT coronary angiography (CTCA) in detecting and excluding left main (LM) and/or three-vessel CAD (“high-risk” CAD) in symptomatic patients and to compare its discriminatory value with the Duke risk score and calcium score.

Materials and methods

Between 2004 and 2011, a total of 1,159 symptomatic patients (61?±?11 years, 31 % women) with stable angina, without prior revascularisation underwent both invasive coronary angiography (ICA) and CTCA. All patients gave written informed consent for the additional CTCA. High-risk CAD was defined as LM and/or three-vessel obstructive CAD (≥50 % diameter stenosis).

Results

A total of 197 (17 %) patients had high-risk CAD as determined by ICA. The sensitivity, specificity, positive predictive value, negative predictive value, positive and negative likelihood ratios of CTCA were 95 % (95 % CI 91–97 %), 83 % (80–85 %), 53 % (48–58 %), 99 % (98–99 %), 5.47 and 0.06, respectively. CTCA provided incremental value (AUC 0.90, P?<?0.001) in the discrimination of high-risk CAD compared with the Duke risk score and calcium score.

Conclusions

CTCA accurately excludes high-risk CAD in symptomatic patients. The detection of high-risk CAD is suboptimal owing to the high percentage (47 %) of overestimation of high-risk CAD. CTCA provides incremental value in the discrimination of high-risk CAD compared with the Duke risk score and calcium score.

Key Points

? Computed tomography coronary angiography (CTCA) accurately excludes high-risk coronary artery disease. ? CTCA overestimates high-risk coronary artery disease in 47?%. ? CTCA discriminates high-risk CAD better than clinical evaluation and coronary calcification.     

Automatic alignment of myocardial perfusion PET and 64-slice coronary CT angiography on hybrid PET/CT

Background

Hybrid PET/CT allows for acquisition of cardiac PET and coronary CT angiography (CCTA) in one session. However, PET and CCTA are acquired with differing breathing protocols and require software registration. We aimed to validate automatic correction for breathing misalignment between PET and CCTA acquired on hybrid scanner.

Methods

Single-session hybrid PET/CT studies of rest/stress ¹³N-ammonia PET and CCTA in 32 consecutive patients were considered. Automated registration of PET left ventricular (LV) surfaces with CCTA volumes was evaluated by comparing with expert manual alignment by two observers.

Results

The average initial misalignments between the position of LV on PET and CCTA were 27.2?±?11.8, 13.3?±?11.5, and 14.3?±?9.1?mm in x, y, and z axes on rest, and 26.3?±?10.2, 11.1?±?9.5, and 11.7?±?7.1?mm in x, y, and z axes on stress, respectively. The automated PET-CCTA co-registration had 95% agreement as judged visually. Compared with expert manual alignment, the translation errors of the algorithm were 5.3?±?2.8?mm (rest) and 6.0?±?3.5?mm (stress). 3D visualization of combined coronary vessel anatomy and hypoperfusion from PET could be made without further manual adjustments.

Conclusion

Software co-registration of CCTA and PET myocardial perfusion imaging on hybrid PET/CT scanners is necessary, but can be performed automatically, facilitating integrated 3D display on PET/CT.     

320-row CT coronary angiography predicts freedom from revascularisation and acts as a gatekeeper to defer invasive angiography in stable coronary artery disease: a fractional flow reserve-correlated study

Objectives

To determine the accuracy of 320-row multidetector coronary computed tomography angiography (M320-CCTA) to detect functional stenoses using fractional flow reserve (FFR) as the reference standard and to predict revascularisation in stable coronary artery disease.

Methods

One hundred and fifteen patients (230 vessels) underwent M320-CCTA and FFR assessment and were followed for 18 months. Diameter stenosis on invasive angiography (ICA) and M320-CCTA were assessed by consensus by two observers and significant stenosis was defined as ≥50 %. FFR ≤0.8 indicated functionally significant stenoses.

Results

M320-CCTA had 94 % sensitivity and 94 % negative predictive value (NPV) for FFR ≤0.8. Overall accuracy was 70 %, specificity 54 % and positive predictive value 65 %. On receiver operating characteristic (ROC) curve analysis, the area under the curve (AUC) for CCTA to predict FFR ≤0.8 was 0.74 which was comparable with ICA. The absence of a significant stenosis on M320-CCTA was associated with a 6 % revascularisation rate. M320-CCTA predicted revascularisation with an AUC of 0.71 which was comparable with ICA.

Conclusions

M320-CCTA has excellent sensitivity and NPV for functional stenoses and therefore may act as an effective gatekeeper to defer ICA and revascularisation. Like ICA, M320-CCTA lacks specificity for functional stenoses and only has moderate accuracy to predict the need for revascularisation.

Key Points

? Important information about the heart is provided by 320-row multidetector CT coronary angiography (M320-CCTA). ? M320-CCTA accurately detects and excludes functional stenoses determined by fractional flow reserve (FFR). ? Non-significant stenoses on M320-CCTA associated with fewer cardiac events and less revascularisation. ? M320-CCTA may act as a gatekeeper for invasive angiography and inappropriate revascularisation. ? Like ICA, M320-CCTA only has moderate accuracy to predict vessels requiring revascularisation.     

Comparison of diagnostic accuracy and interpretation times for a standard and an advanced 3D visualisation technique in CT colonography

Objective

To compare the diagnostic accuracy of a standard bi-directional, three-dimensional (3D) CT colonography (CTC) fly-through (standard view, SV) with a unidirectional, 3D unfolding technique (panoramic view, PV).

Methods

150 consecutive endoscopically-validated CTC patient datasets were retrospectively reviewed twice by two expert radiologists: first, with bidirectional SV, second, after 6–15 months, with unidirectional PV. Per-polyp sensitivities, percentage of visualised colonic mucosa, and reading times were calculated for both 3D visualisations. Results were tested for statistical significance by equivalence analysis for paired proportions and Student’s paired t-test.

Results

In 81 patients, 236 polyps (101 adenomas, 135 non-adenomas) were detected. Sensitivities for polyps ≤5 mm, 6–9 mm and ≥10 mm were 60.1% (113/188), 92.9% (26/28) and 95.0% (19/20) with bidirectional SV, and 60.6% (114/188), 96.4% (27/28) and 95.0% (19/20) with unidirectional PV. Overall sensitivity for adenomas was 86.1% and 84.2% for SV and PV. Both methods provided equivalent polyp detection, with an equivalence limit set at 5%. PV and SV visualised 98.9?±?1.1% (97.0–99.9%) and 96.2?±?2.3% (91.4–98.8%) of the colonic mucosa (p?>?0.05). Mean interpretation time decreased from 14.6?±?2.5 (9.2–22.8) minutes with SV to 7.5?±?3.2 (5.0–14.4) using PV (p?Conclusion 3D CTC interpretation using unidirectional PV is equally as accurate, but significantly faster than an interpretation based on bidirectional SV.     

Diagnostic performance of low-dose rest/stress Tc-99m tetrofosmin myocardial perfusion SPECT using the 530c CZT camera: Quantitative vs visual analysis

Background

We set out to develop normal databases and prospectively validate abnormality criteria for a low-dose Tc-99m tetrofosmin myocardial perfusion SPECT protocol using the 530c CZT camera.

Methods

All patients received 6 mCi rest/20 mCi stress doses of Tc-99m tetrofosmin. Rest and stress images were obtained over 7-9 and 5-7 minutes according to the chest size. Low-dose CT of the chest was obtained on a standalone CT scanner. Forty patients with very low likelihood (LLK) of coronary artery disease (CAD) were used to define the normal count distributions. The abnormality criteria were prospectively validated in 55 patients who had coronary angiography and in 40 patients with LLK of CAD.

Results

The results for quantitative non-attenuation-corrected (AC) and AC analysis and visual analysis were as follows: sensitivity of 79%, 85%, and 92% (P = NS) and specificity of 44%, 75%, and 56% (P = NS), respectively. The normalcy rates for quantitative non-AC and AC analyses and visual analysis were 95%, 98%, and 98% (P = NS).

Conclusions

We have developed non-AC and AC normal databases for low-dose rest/stress Tc-99m tetrofosmin myocardial perfusion SPECT protocol using the 530c CZT camera. The per-patient diagnostic performance of quantitative analyses is not significantly different from visual analysis by an experienced reader.     

Restriction of the referral of patients with stable angina for CT coronary angiography by clinical evaluation and calcium score: impact on clinical decision making

Objective

To investigate the value of the calcium score (CaSc) plus clinical evaluation to restrict referral for CT coronary angiography (CTCA) by reducing the number of patients with an intermediate probability of coronary artery disease (CAD).

Methods

We retrospectively included 1,975 symptomatic stable patients who underwent clinical evaluation and CaSc calculation and CTCA or invasive coronary coronary angiography (ICA). The outcome was obstructive CAD (≥50 % diameter narrowing) assessed by ICA or CTCA in the absence of ICA. We investigated two models: (1) clinical evaluation consisting of chest pain typicality, gender, age, risk factors and ECG and (2) clinical evaluation with CaSc. Discrimination of the two models was compared. The stepwise reclassification of patients with an intermediate probability of CAD (10–90 %) after clinical evaluation followed by clinical evaluation with CaSc was assessed by clinical net reclassification improvement (NRI).

Results

Discrimination of CAD was significantly improved by adding CaSc to the clinical evaluation (AUC: 0.80 vs. 0.89, P?<?0.001). CaSc and CTCA could be avoided in 9 % using model 1 and an additional 29 % of CTCAs could be avoided using model 2. Clinical NRI was 57 %.

Conclusion

CaSc plus clinical evaluation may be useful in restricting further referral for CTCA by 38 % in symptomatic stable patients with suspected CAD.

Key Points

? CT calcium scores (CaSc) could proiritise referrals for CT coronary angiography (CTCA) ? CaSc provides an incremental discriminatory value of CAD compared with clinical evaluation ? Risk stratification is better when clinical evaluation is combined with CaSc ? Appropriate use of clinical evaluation and CaSc helps avoid unnecessary CTCA referrals     

Contrast agent bolus tracking with a fixed threshold or a manual fast start for coronary CT angiography

Objectives

Comparison of bolus tracking with a fixed threshold versus a manual fast start for coronary CT angiography.

Methods

We retrospectively analysed 320-row coronary CT angiography of 50 patients with suspected or known coronary artery disease. Twenty-five examinations were initiated by a bolus tracking method (group 1), 25 examinations with a manual fast surestart (group 2).

Results

Mean attenuation values in the ascending aorta were 519?±?111 Hounsfield units (HU) in group 1 and 476?±?65 HU in group 2 (p?=?0.10). Assessable vessel lengths were 171?±?44 mm vs 172?±?29 mm for the right coronary artery (p?=?0.91), 11?±?4 mm vs 12?±?4 mm for the left main (p?=?0.9), 163?±?28 mm vs 151?±?26 mm for the left anterior descending coronary artery (p?=?0.11) and 125?±?41 mm vs 110?±?37 mm for the left circumflex coronary artery (p?=?0.18). Image quality for all coronary arteries was not significantly different between the groups (p?>?0.41). The attenuation ratio between the left and right ventricle was 2.8?±?0.7 vs 3.6?±?1.0 (p?=?0.003). Significantly less contrast agent was used in group 2 (64?±?6 ml vs 80?±?0 ml; p?<?0.001).

Conclusions

Bolus tracking with a fixed threshold and with a manual fast start are both suitable methods; the fast start allowed a reduction of contrast agent volumes.

Key Points

? Fixed threshold bolus tracking is suitable for coronary 320-row CT angiography ? Manual fast start bolus tracking can reduce contrast agent volumes ? Manual fast start and fixed threshold initiation achieve good image quality ? Fixed threshold bolus tracking achieves a more reliable contrast bolus position     

Feasibility of prospectively ECG-triggered high-pitch coronary CT angiography with 30 mL iodinated contrast agent at 70 kVp: initial experience

Objectives

To evaluate the feasibility, image quality and radiation dose of prospectively ECG-triggered high-pitch coronary CT angiography (CCTA) with 30 mL contrast agent at 70 kVp.

Methods

Fifty-eight patients with suspected coronary artery disease, a body mass index (BMI) of less than 25 kg/m², sinus rhythm and a heart rate (HR) of less than 70 beats per minute (bpm) were prospectively enrolled in this study. Thirty mL of 370 mg I/mL iodinated contrast agent was administrated at a flow rate of 5 mL/s. All patients underwent prospectively ECG-triggered high-pitch CCTA on a second-generation dual-source CT system at 70 kVp using automated tube current modulation.

Results

Fifty-six patients (96.6 %) had diagnostic CCTA images and two patients (3.4 %) had one vessel with poor image quality each rated as non-diagnostic. No significant effects of HR, HR variability and BMI on CCTA image quality were observed (all P?>?0.05). Effective dose was 0.17?±?0.02 mSv and the size-specific dose estimate was 1.03?±?0.13 mGy.

Conclusion

Prospectively ECG-triggered high-pitch CCTA at 70 kVp with 30 mL of contrast agent can provide diagnostic image quality at a radiation dose of less than 0.2 mSv in patients with a BMI of less than 25 kg/m² and an HR of less than 70 bpm.

Key points

? Prospectively ECG-triggered high-pitch CCTA at 70 kVp/30 mL contrast agent is feasible. ? Diagnostic image quality can be obtained at a radiation dose of less than 0.2 mSv. ? This protocol is suitable for normal-weight patients with slow heart rate.     

Helical CT-enteroclysis in the detection of small-bowel tumours: a meta-analysis

Objective

To perform a meta-analysis to determine sensitivity and specificity estimates of helical CT-enteroclysis in the detection of small-bowel tumours.

Methods

A search for relevant articles published from January 1992 to November 2010 was performed. Study design, patient characteristics and 2?×?2 contingency tables were recorded for eligible studies. Heterogeneity was assessed with the I ² statistic. A bivariate generalised linear random-effects model was used to summarise sensitivity and specificity estimates for small-bowel tumour detection on a per-patient basis. Sensitivity and specificity estimates were compared in different subgroups.

Results

Twelve studies (696 patients) were eligible. The mean small-bowel tumour prevalence was 22.6 % (range 7.7–45.8 %). Inter-study heterogeneity was substantial for sensitivity (I ²?=?66.9 %; 95 % CI 28.7–88.5 %) and low for specificity (I ²?=?10.6 %; 95 % CI 0.0–55.0 %). On a per-patient basis, pooled sensitivity was 92.8 % (95 % CI 71.3–98.5 %) and pooled specificity 99.2 % (95 % CI 94.2–99.9 %) for the diagnosis of small-bowel tumour. Subgroup analysis revealed that small-bowel preparation, more than one imaging pass and large volumes (≥2 L) of enteral contrast agent did not improve tumour detection.

Conclusion

Our meta-analysis confirms that helical CT-enteroclysis has high degrees of sensitivity and specificity for small-bowel tumour detection. However, our findings reinforce the need for more standardised individual studies.

Key Points

? Helical CT-enteroclysis is highly sensitive for the diagnosis of small-bowel tumours. ? Helical CT-enteroclysis is highly specific for the diagnosis of small-bowel tumours, ? Helical CT-enteroclysis can be used as a first-line investigation. ? A single enteric phase examination provides optimal tumour detection.     

Next generation coronary CT angiography: in vitro evaluation of 27 coronary stents

Objectives

To evaluate in-stent lumen visibility of 27 modern and commonly used coronary stents (16 individual stent types, two stents at six different sizes each) utilising a third-generation dual-source CT system.

Methods

Stents were implanted in a plastic tube filled with contrast. Examinations were performed parallel to the system's z-axis for all stents (i.e. 0°) and in an orientation of 90° for stents with a diameter of 3.0 mm. Two stents were evaluated in different diameters (2.25 to 4.0 mm). Examinations were acquired with a collimation of 96?×?0.6 mm, tube voltage of 120 kVp with 340 mAs tube current. Evaluation was performed using a medium-soft (Bv40), a medium-sharp (Bv49) and a sharp (Bv59) convolution kernel optimised for vascular imaging.

Results

Mean visible stent lumen of stents with 3.0 mm diameter ranged from 53.3 % (IQR 48.9???56.7 %) to 73.9 % (66.7???76.7 %), depending on the kernel used at 0°, and was highest at an orientation of 90° with 80.0 % (75.6???82.8 %) using the Bv59 kernel, strength 4. Visible stent lumen declined with decreasing stent size.

Conclusions

Use of third-generation dual-source CT enables stent lumen visibility of up to 80 % in metal stents and 100 % in bioresorbable stents.

Key Points

? Blooming artefacts impair in–stent lumen visibility of coronary stents in CT angiography. ? CT enables stent lumen visibility of up to 80 % in metal stents. ? Stent lumen visibility varies with stent orientation and size. ? CT angiography may be a valid alternative for detecting in-stent restenosis.