A systematic review of the utility of 1.5 versus 3 Tesla magnetic resonance brain imaging in clinical practice and research

Objective

MRI at 3?T is said to be more accurate than 1.5?T MR, but costs and other practical differences mean that it is unclear which to use.

Methods

We systematically reviewed studies comparing diagnostic accuracy at 3?T with 1.5?T. We searched MEDLINE, EMBASE and other sources from 1 January 2000 to 22 October 2010 for studies comparing diagnostic accuracy at 1.5 and 3?T in human neuroimaging. We extracted data on methodology, quality criteria, technical factors, subjects, signal-to-noise, diagnostic accuracy and errors according to QUADAS and STARD criteria.

Results

Amongst 150 studies (4,500 subjects), most were tiny, compared old 1.5?T with new 3?T technology, and only 22 (15?%) described diagnostic accuracy. The 3?T images were often described as “crisper”, but we found little evidence of improved diagnosis. Improvements were limited to research applications [functional MRI (fMRI), spectroscopy, automated lesion detection]. Theoretical doubling of the signal-to-noise ratio was not confirmed, mostly being 25?%. Artefacts were worse and acquisitions took slightly longer at 3?T.

Conclusion

Objective evidence to guide MRI purchasing decisions and routine diagnostic use is lacking. Rigorous evaluation accuracy and practicalities of diagnostic imaging technologies should be the routine, as for pharmacological interventions, to improve effectiveness of healthcare.

Key Points

? Higher field strength MRI may improve image quality and diagnostic accuracy. ? There are few direct comparisons of 1.5 and 3?T MRI. ? Theoretical doubling of the signal-to-noise ratio in practice was only 25?%. ? Objective evidence of improved routine clinical diagnosis is lacking. ? Other aspects of technology improved images more than field strength.     

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 dual-source CT coronary angiography with prospective ECG-triggering on different heart rate patients

Objective

To evaluate the diagnostic accuracy of dual-source CT (DSCT) prospective ECG-triggering coronary angiography in patients with different heart rate (HR).

Methods

103 patients with suspected coronary artery disease underwent DSCT prospective ECG-triggered coronary angiography and invasive coronary angiography (ICA). The patients were grouped by HR during CT scans: low HR (??60?bpm, n?=?34); medium HR (60?n?=?36) and high HR (>70?bpm, n?=?33). The sensitivity and specificity of DSCT in detecting ??50% stenosis were compared among subgroups where ICA was the gold standard. Image quality was scored using a 4-point scale.

Results

A total of 1,580 (95.9%) coronary artery segments were evaluable. Sensitivity and specificity were 82.8% and 98.4%, 88.3% and 98.7%, and 80.3% and 98.6% for different subgroups (all p?>?0.05). The overall area under the curve of the receiver-operating characteristic analysis was 0.94. The image quality scores were 3.1?±?0.3, 3.1?±?0.3 and 3.0?±?0.4 for subgroups (p?>?0.05). The overall average effective radiation dose was 3.60?±?1.60?mSv.

Conclusion

DSCT coronary angiography with prospective ECG-triggering could be just as accurate in patients with medium to high HR compared to those with low HR.     

Accuracy, image quality and radiation dose comparison of high-pitch spiral and sequential acquisition on 128-slice dual-source CT angiography in children with congenital heart disease

Objectives

To compare accuracy, image quality and radiation dose between high-pitch spiral and sequential modes on 128-slice dual-source computed tomographic (DSCT) angiography in children with congenital heart disease (CHD).

Methods

Forty patients suspected with CHD underwent 128-slice DSCT angiography with high-pitch mode and sequential mode respectively. All the anomalies were confirmed by the surgical and/or the conventional cardiac angiography (CCA) findings. The diagnostic accuracy, the subjective and objective image quality and effective radiation doses were compared.

Results

There was no significant difference in diagnostic accuracy (χ ² ?=?0.963, P?>?0.05), the objective parameters for image quality (P?>?0.05) and the image quality of great vessels (u?=?167.500, P?>?0.05) between the two groups. The image quality of intracardiac structures and coronary arteries was significantly better in the sequential mode group than that in the high-pitch group (u?=?112.500 and 100.000, P?t?=?5.287, P?Conclusions Both the high-pitch and the sequential modes for 128-slice DSCT angiography provide high accuracy for the assessment of CHD in children, while the high-pitch mode, even with some image quality decrease, further significantly lowers the radiation dose.

Key Points

? Modern CT provides excellent anatomical detail of congenital heart disease. ? Dual source CT systems offer high-pitch spiral and sequential modes. ? The high-pitch mode provides high accuracy for the assessment of CHD. ? A few images using the high-pitch mode were occasionally slightly degraded. ? But the high-pitch mode significantly lowers the radiation dose.     

Coronary CT angiography: image quality, diagnostic accuracy, and potential for radiation dose reduction using a novel iterative image reconstruction technique��comparison with traditional filtered back projection

Objectives

To compare image noise, image quality and diagnostic accuracy of coronary CT angiography (cCTA) using a novel iterative reconstruction algorithm versus traditional filtered back projection (FBP) and to estimate the potential for radiation dose savings.

Methods

Sixty five consecutive patients (48 men; 59.3?±?7.7?years) prospectively underwent cCTA and coronary catheter angiography (CCA). Full radiation dose data, using all projections, were reconstructed with FBP. To simulate image acquisition at half the radiation dose, 50% of the projections were discarded from the raw data. The resulting half-dose data were reconstructed with sinogram-affirmed iterative reconstruction (SAFIRE). Full-dose FBP and half-dose iterative reconstructions were compared with regard to image noise and image quality, and their respective accuracy for stenosis detection was compared against CCA.

Results

Compared with full-dose FBP, half-dose iterative reconstructions showed significantly (p?=?0.001 ?C p?=?0.025) lower image noise and slightly higher image quality. Iterative reconstruction improved the accuracy of stenosis detection compared with FBP (per-patient: accuracy 96.9% vs. 93.8%, sensitivity 100% vs. 100%, specificity 94.6% vs. 89.2%, NPV 100% vs. 100%, PPV 93.3% vs. 87.5%).

Conclusions

Iterative reconstruction significantly reduces image noise without loss of diagnostic information and holds the potential for substantial radiation dose reduction from cCTA.     

Diagnostic accuracy of segmental enhancement inversion for diagnosis of renal oncocytoma at biphasic contrast enhanced CT: systematic review

Objectives

To use systematic review to evaluate the diagnostic accuracy of segmental enhancement inversion (SEI) at contrast-enhanced biphasic multi-detector computed tomography (MDCT) for the diagnosis of renal oncocytoma.

Methods

Several electronic databases were searched through October 2013. Two reviewers independently selected studies that met the inclusion criteria and extracted data. Study quality was assessed with the QUADAS-2 tool. The primary 2?×?2 data were investigated with forest plot and ROC plot of sensitivity and specificity.

Results

Four studies met the inclusion criteria (307 patients). Considerable heterogeneity between studies precluded meta-analysis. Two studies from the same group of investigators demonstrated reasonable diagnostic accuracy (sensitivity 59-80 % and specificity 87-99 %), while two others did not (sensitivity 0-6 %, specificity 93-100 %). Possible reasons for this include timing of biphasic MDCT and methods of interpretation but not size of lesion.

Conclusions

SEI is a specific imaging finding of renal oncocytoma with highly variable sensitivity. This substantial heterogeneity across studies and between institutions suggests that further validation of this imaging finding is necessary prior to application in clinical practice.

Key Points

? SEI on CT in small renal masses is specific for oncocytoma. ? Sensitivity of SEI varies substantially between studies and across institutions. ? Variability could relate to CT timing or methods of interpretation. ? High accuracy of SEI has only been reported by one group. ? Validation of SEI is needed prior to clinical implementation.     

High diagnostic accuracy of prospective ECG-gating 64-slice computed tomography coronary angiography for the detection of in-stent restenosis: in-stent restenosis assessment by low-dose MDCT

Objectives

The accuracy of computed tomography (CT) for assessment of coronary stents is as yet unproven and radiation exposure has been a concern. The aim of our study is to compare radiation dose and diagnostic performance of CT with prospective ECG-triggering versus retrospective ECG-triggering for the detection of in-stent restenosis (ISR).

Methods

We enrolled 168 consecutive patients with suspected ISR, 83 studied using CT with prospective ECG-triggering (group 1) and 85 using retrospective ECG-triggering (group 2).

Results

Prevalence of ISR according to catheter angiography was 24% in both groups. The overall evaluability was similar (93% in group 1 vs 95% in group 2). Artefact sub-analysis showed a significantly lower number of blooming and higher number of slice misalignment in group 1 vs group 2. In the stent-based analysis using only evaluable stents, specificity, positive predictive value and accuracy were significantly higher in group 1 (100%, 100% and 99%, respectively) than in group 2 (97%, 91% and 95%, respectively, p?<?0.05). Group 1 was exposed to a lower radiation dose compared with group 2 (4.3?±?1.4?mSv vs 18.5?±?5.5?mSv, p?<?00.1).

Conclusions

CT with prospective ECG-triggering can improve diagnostic accuracy of non-invasive imaging of coronary stents with a significant reduction in radiation exposure     

Dynamic CT myocardial perfusion imaging: performance of 3D semi-automated evaluation software

Objectives

To evaluate the performance of three-dimensional semi-automated evaluation software for the assessment of myocardial blood flow (MBF) and blood volume (MBV) at dynamic myocardial perfusion computed tomography (CT).

Methods

Volume-based software relying on marginal space learning and probabilistic boosting tree-based contour fitting was applied to CT myocardial perfusion imaging data of 37 subjects. In addition, all image data were analysed manually and both approaches were compared with SPECT findings. Study endpoints included time of analysis and conventional measures of diagnostic accuracy.

Results

Of 592 analysable segments, 42 showed perfusion defects on SPECT. Average analysis times for the manual and software-based approaches were 49.1?±?11.2 and 16.5?±?3.7 min respectively (P?<?0.01). There was strong agreement between the two measures of interest (MBF, ICC?=?0.91, and MBV, ICC?=?0.88, both P?<?0.01) and no significant difference in MBF/MBV with respect to diagnostic accuracy between the two approaches for both MBF and MBV for manual versus software-based approach; respectively; all comparisons P?>?0.05.

Conclusions

Three-dimensional semi-automated evaluation of dynamic myocardial perfusion CT data provides similar measures and diagnostic accuracy to manual evaluation, albeit with substantially reduced analysis times. This capability may aid the integration of this test into clinical workflows.

Key Points

? Myocardial perfusion CT is attractive for comprehensive coronary heart disease assessment. ? Traditional image analysis methods are cumbersome and time-consuming. ? Automated 3D perfusion software shortens analysis times. ? Automated 3D perfusion software increases standardisation of myocardial perfusion CT. ? Automated, standardised analysis fosters myocardial perfusion CT integration into clinical practice.     

Use of positive oral contrast agents in abdominopelvic computed tomography for blunt abdominal injury: meta-analysis and systematic review

Objectives

To determine whether positive oral contrast agents improve accuracy of abdominopelvic CT compared with no, neutral or negative oral contrast agent.

Methods

Literature was searched for studies evaluating the diagnostic performance of abdominopelvic CT with positive oral contrast agents against imaging with no, neutral or negative oral contrast agent. Meta-analysis reviewed studies correlating CT findings of blunt abdominal injury with positive and without oral contrast agents against surgical, autopsy or clinical outcome allowing derivation of pooled sensitivity and specificity. Systematic review was performed on studies with common design and reference standard.

Results

Thirty-two studies were divided into two groups. Group 1 comprised 15 studies comparing CT with positive and without oral contrast agents. Meta-analysis of five studies from group 1 provided no difference in sensitivity or specificity between CT with positive or without oral contrast agents. Group 2 comprised 17 studies comparing CT with positive and neutral or negative oral contrast agents. Systematic review of 12 studies from group 2 indicated that neutral or negative oral contrasts were as effective as positive oral contrast agents for bowel visualisation.

Conclusions

There is no difference in accuracy between CT performed with positive oral contrast agents or with no, neutral or negative oral contrast agent.

Key Points

? There is no difference in the accuracy of CT with or without oral contrast agent. ? There is no difference in the accuracy of CT with Gastrografin or water. ?Omission of oral contrast, utilising neutral or negative oral contrast agent saves time, costs and decreases risk of aspiration.     

Clinical examination versus magnetic resonance imaging in the pretreatment staging of cervical carcinoma: systematic review and meta-analysis

Objectives

To review the literature on the diagnostic performance of clinical examination and magnetic resonance imaging (MRI) in detecting parametrial invasion and advanced stage disease (FIGO stage ≥ IIB) in patients with cervical carcinoma.

Methods

Reports of studies were searched using the MEDLINE, EMBASE and Cochrane databases. Two observers reported on data relevant for analysis and methodological quality using the QUADAS scoring system. Publication bias was analysed using Deeks funnel plots. Covariates were added to the model to study the influence on the summary results of the technical and methodological aspects of the clinical examination and MRI.

Results

In total, 3,254 patients were included. Partial verification bias was often encountered. Pooled sensitivity was 40 % (95 % CI 25–58) for the evaluation of parametrial invasion with clinical examination and 84 % (95 % CI 76–90) with MRI, 53 % (95 % CI 41–66) for the evaluation of advanced disease with clinical examination, and 79 % (95 % CI 64–89) with MRI. Pooled specificities were comparable between clinical examination and MRI. Different technical aspects of MRI influenced the summary results.

Conclusions

MRI is significantly better than clinical examination in ruling out parametrial invasion and advanced disease in patients with cervical carcinoma.

Key Points

? MRI has a higher sensitivity than clinical examination for staging cervical carcinoma. ? Clinical examination and MRI have comparably high specificity for staging cervical carcinoma. ? Quality of clinical examination studies was lower than that of MRI studies. ? The use of newer MRI techniques positively influences the summary results. ? Anaesthesia during clinical examination positively influences the summary results.     

Computed tomography angiography of carotid and coronary artery via a single-bolus injection protocol: a feasibility study using 320-row multidetector CT

Objectives

To investigate the feasibility of using a single-dose injection protocol in CT angiography (CTA) of the carotid and coronary artery with 320-row multidetector CT.

Methods

A total of 82 consecutive patients with suspected carotid artery disease underwent an original CTA protocol aiming at capturing the extra-cranial carotid arteries and coronary arteries simultaneously using 320-row MDCT. The image quality, attenuation, and CNRs of the carotid and coronary arteries were assessed. The lag time (between two separated volumetric acquisitions) was compared between patients with and without cardiac venous opacification (CVO). The contrast medium volume and radiation dose were recorded.

Results

The image quality was 99.4 % diagnostic in carotid and 86.9 % in coronary artery segments. The mean attenuation of carotid and coronary arteries ranged from 462.2 Hu to 533.7 Hu, 415.9 Hu to 454.7 Hu respectively. The mean CNR of the carotid and coronary artery ranged from 15.8 to 18.9 and 17.7 to 20.4 respectively. The lag time in patients with and without CVO was 5.75?±?1.64 s vs. 4.21?±?1.14 s (p?<?0.05). The mean radiation dose was 6.6?±?4.1 mSv.The mean contrast media volume was 71.9?±?9.1 ml.

Conclusions

The carotid and coronary artery can be imaged simultaneously via our original single-dose injection CTA protocol using 320-row CT with adequate image quality.

Key Points

? Carotid and coronary 320-row CTA can be achieved in a single-dose injection. ? Longer coverage was achieved with two or more volumes using 320-row CT. ? The single-dose protocol allows a reduced contrast agent dose of about 72 ml.     

Assessment of myocardial fibrosis and coronary arteries in hypertrophic cardiomyopathy using combined arterial and delayed enhanced CT: comparison with MR and coronary angiography

Objectives

We sought to determine the feasibility and accuracy of dual-source computed tomography (DSCT) in assessing coronary artery disease and myocardial fibrosis of hypertrophic cardiomyopathy (HCM) compared with cardiac magnetic resonance (CMR) imaging and coronary angiography (CA).

Methods

Forty-seven consecutive patients with HCM were prospectively enrolled. DSCT images were acquired in the arterial and late phases following intravenous contrast medium. The CMR and CA were performed within 7 days. Independent blinded readers read each study. Patients were classified according to myocardial delayed enhanced (MDE) CMR, coronary artery stenosis by CA, and arterial and MDE-DSCT. The diagnostic accuracy of DSCT in detecting coronary stenosis and MDE was analysed.

Results

Wall thickness determined by DSCT was strongly correlated with MR results (r?=?0.91). DSCT and CMR MDE showed substantial agreement for the detection of myocardial fibrosis on per-patient and per-segment levels. The CT classification of patients by arterial stenosis and delayed enhancement had excellent agreement with MR and CA methods.

Conclusions

The comprehensive cardiac CT examination provides reliable coronary artery and myocardial assessments. MDE-DSCT is a robust alternative method to MDE-CMR in assessing myocardial fibrosis in HCM particularly in patients with pacemakers or other contraindications to CMR.

Key Points

? Enhanced cardiac CT provides comprehensive assessment of patients with hypertrophic cardiomyopathy (HCM). ? Myocardial delayed enhanced-CT has comparable accuracy to MDE-MR in detecting HCM fibrosis. ? MDE-CT provides a robust alternative for HCM patients with MR contraindications.     

Accuracy of CT angiography in the diagnosis of acute gastrointestinal bleeding: systematic review and meta-analysis

Objective

To assess the diagnostic accuracy of computed tomography (CT) angiography in the evaluation of patients with an episode of acute gastrointestinal haemorrhage.

Methods

Systematic review and meta-analysis to estimate pooled accuracy indices. A bivariate random effects model was adjusted to obtain a summary receiver-operating characteristic (sROC) curve and the corresponding area under the curve (AUC).

Results

Twenty-two studies were included and provided data on 672 patients (range of age 5–74) with a mean age of 65 years. The overall sensitivity of CT angiography for detecting active acute GI haemorrhage was 85.2 % (95 % CI 75.5 % to 91.5 %). The overall specificity of CT angiography was 92.1 % (95 % CI 76.7 % to 97.7 %). The likelihood ratios for positive and negative test results were 10.8 (95 % CI 3.4 to 34.4) and 0.16 (95 % CI 0.1 to 0.27) respectively, with an AUC of 0.935 (95 % CI 0.693 to 0.989). The sources of heterogeneity explored had no significant impact on diagnostic performance.

Conclusions

CT shows high diagnostic accuracy and is an excellent diagnostic tool for detection and localising of intestinal bleeding sites. It is highly available, provides fast detection and localisation of the bleeding site, and is minimally invasive.

Key Points

? CT angiography is increasingly used for investigating severe gastrointestinal bleeding. ? This systematic review and meta-analysis updates previous ones. ? In patients with massive gastrointestinal bleeding, CT angiography/MDCT detects bleeding accurately. ? CT angiography is useful in locating the bleeding site and determining appropriate treatment.     

Diagnostic performance of coronary CT angiography for stenosis detection according to calcium score: systematic review and meta-analysis

Objectives

A systematic review and meta-analysis to assess sensitivity and specificity of coronary CT angiography (CCTA) for significant stenosis at different degrees of coronary calcification.

Methods

A literature search was performed including studies describing test characteristics of CCTA for significant stenosis, performed with at least 16-MDCT and according to calcium score (CS). Invasive coronary angiography was the reference standard. Pooled sensitivity and specificity of CCTA by CS categories and CT equipment were calculated.

Results

Of 14,121 articles, 51 studies reported on the impact of calcium scoring on diagnostic performance of CCTA and could be included in the systematic review. Twenty-seven of these studies (5,203 participants) were suitable for meta-analysis. On a patient-basis, sensitivity of CCTA for significant stenosis was 95.8, 95.6, 97.6 and 99.0% for CS 0–100, 101–400, 401–1,000 and >1,000 respectively. Specificity was 91.2, 88.2, 50.6 and 84.0% respectively. Specificity of CCTA was significantly lower for CS 401–1,000 due to lack of patients without significant stenosis. Sensitivity and specificity of 16-MDCT were significantly lower compared to more modern CT systems.

Conclusions

Even in cases of severe coronary calcification, sensitivity and specificity of CCTA for significant stenosis are high. With 64-MDCT and newer CT systems, a CS cut-off for performing CCTA no longer seems indicated.

Key Points

? Decisions about performing coronary CT angiography (CCTA) sometimes depend on calcium scoring. ? CCTA is highly sensitive for coronary stenosis. ? With 16-MDCT, however, heavy calcification reduces specificity for significant stenosis. ? For 64-MDCT (and above), CCTA has high specificity, even with severe coronary calcification.     

Effect of hybrid iterative reconstruction technique on quantitative and qualitative image analysis at 256-slice prospective gating cardiac CT

Objectives

To evaluate the effect of hybrid iterative reconstruction on qualitative and quantitative parameters at 256-slice cardiac CT.

Methods

Prospective cardiac CT images from 20 patients were analysed. Paired image sets were created using 3 reconstructions, i.e. filtered back projection (FBP) and moderate- and high-level iterative reconstructions. Quantitative parameters including CT-attenuation, noise, and contrast-to-noise ratio (CNR) were determined in both proximal- and distal coronary segments. Image quality was graded on a 4-point scale.

Results

Coronary CT attenuation values were similar for FBP, moderate- and high-level iterative reconstruction at 293?±?74-, 290?±?75-, and 283?±?78 Hounsfield units (HU), respectively. CNR was significantly higher with moderate- and high-level iterative reconstructions (10.9?±?3.5 and 18.4?±?6.2, respectively) than FBP (8.2?±?2.5) as was the visual grading of proximal vessels. Visualisation of distal vessels was better with high-level iterative reconstruction than FBP. The mean number of assessable segments among 289 segments was 245, 260, and 267 for FBP, moderate- and high-level iterative reconstruction, respectively; the difference between FBP and high-level iterative reconstruction was significant. Interobserver agreement was significantly higher for moderate- and high-level iterative reconstruction than FBP.

Conclusions

Cardiac CT using hybrid iterative reconstruction yields higher CNR and better image quality than FBP.

Key Points

? Cardiac CT helps clinicians to assess patients with coronary artery disease ? Hybrid iterative reconstruction provides improved cardiac CT image quality ? Hybrid iterative reconstruction improves the number of assessable coronary segments ? Hybrid iterative reconstruction improves interobserver agreement on cardiac CT     

Comparison of image quality and radiation dose of different pulmonary CTA protocols on a 128-slice CT: high-pitch dual source CT, dual energy CT and conventional spiral CT

Objectives

To compare image quality and radiation dose of high-pitch dual-source computed tomography (DSCT), dual energy CT (DECT) and conventional single-source spiral CT (SCT) for pulmonary CT angiography (CTA) on a 128-slice CT system.

Methods

Pulmonary CTA was performed with five protocols: high-pitch DSCT (100?kV), high-pitch DSCT (120?kV), DECT (100/140?kV), SCT (100?kV), and SCT (120?kV). For each protocol, 30 sex, age, and body-mass-index (mean 25.3?kg/m²) matched patients were identified. Retrospectively, two observers subjectively assessed image quality, measured CT attenuation (HU±SD) at seven central and peripheral levels, and calculated signal-to-noise-ratio (SNR) and contrast-to-noise-ratio (CNR). Radiation exposure parameters (CTDIvol and DLP) were compared.

Results

Subjective image quality was rated good to excellent in >92% (>138/150) with an interobserver agreement of 91.4%. The five protocols did not significantly differ in image quality, neither by subjective, nor by objective measures (SNR, CNR). By contrast, radiation exposure differed between protocols: significant lower radiation was achieved by using high-pitch DSCT at 100?kV (p?Conclusions SCT, high-pitch DSCT, and DECT protocols techniques result in similar subjective and objective image quality, but radiation exposure was significantly lower with high-pitch DSCT at 100?kV.

Key Points

• New CT protocols show promising results in pulmonary embolism assessment.
• High-pitch dual-source CT (DSCT) at 100?kV provides radiation dose savings for pulmonary CTA.
• High-pitch DSCT at 100?kV maintains diagnostic image quality for pulmonary CTA.
• Dual energy CT uses more radiation but also provides lung perfusion evaluation.
• Whether the additional perfusion data is worth the extra radiation remains undetermined.

     

Computed tomography coronary angiography accuracy in women and men at low to intermediate risk of coronary artery disease

Objectives

To investigate the diagnostic accuracy of CT coronary angiography (CTCA) in women at low to intermediate pre-test probability of coronary artery disease (CAD) compared with men.

Methods

In this retrospective study we included symptomatic patients with low to intermediate risk who underwent both invasive coronary angiography and CTCA. Exclusion criteria were previous revascularisation or myocardial infarction. The pre-test probability of CAD was estimated using the Duke risk score. Thresholds of less than 30?% and 30–90?% were used for determining low and intermediate risk, respectively. The diagnostic accuracy of CTCA in detecting obstructive CAD (≥50?% lumen diameter narrowing) was calculated on patient level. P?<?0.05 was considered significant.

Results

A total of 570 patients (46?% women [262/570]) were included and stratified as low (women 73?% [80/109]) and intermediate risk (women 39?% [182/461]). Sensitivity, specificity, PPV and NPV were not significantly different in and between women and men at low and intermediate risk. For women vs. men at low risk they were 97?% vs. 100?%, 79?% vs. 90?%, 80?% vs. 80?% and 97?% vs. 100?%, respectively. For intermediate risk they were 99?% vs. 99?%, 72?% vs. 83?%, 88?% vs. 93?% and 98?% vs. 99?%, respectively.

Conclusion

CTCA has similar diagnostic accuracy in women and men at low and intermediate risk.

Key Points

? Coronary artery disease (CAD) is increasingly investigated by computed tomography angiography (CTCA). ? CAD detection or exclusion by CTCA is not different between sexes. ? CTCA diagnostic accuracy was similar between low and intermediate risk sex-specific-groups. ? CTCA rarely misses obstructive CAD in low–intermediate risk women and men. ? CAD yield by invasive coronary angiography after positive CTCA is similar between sex-risk-specific groups.     

How far can the radiation dose be lowered in head CT with iterative reconstruction? Analysis of imaging quality and diagnostic accuracy

Objective

To evaluate the imaging quality of head CT at lowered radiation dose by combining filtered back projection (FBP) and iterative reconstruction (IR) algorithms.

Methods

Experimental group A (n?=?66) underwent CT with 43 % tube current reduction, and group B (n?=?58) received an equivalent reduced dose by lowering the tube voltage. An age- and sex-matched control group (n?=?72) receiving the conventional radiation dose was retrospectively collected. Imaging for the control group was reconstructed by FBP only, while images for groups A and B were reconstructed by FBP and IR. The signal-to-noise ratios (SNRs), contrast-to-noise ratios (CNRs), sharpness, number of infarcts and severity of subcortical arteriosclerotic encephalopathy (SAE) were compared to assess imaging quality and diagnostic accuracy.

Results

There were no significant differences in SNRs and CNRs between group A and the control group. There were significantly decreased SNRs and increased CNRs in group B. Image sharpness decreased in both groups. Correlations between detected infarcts and severity of SAE across FBP and IR were high (r?=?0.73-0.93). Head diameter was the only significant factor inversely correlated with infratentorial imaging quality.

Conclusion

Head CT with 43 % reduced tube current reconstructed by IR provides diagnostic imaging quality for outpatient management.

Key Points

? Cranial CT using iterative reconstruction provides diagnostic images with 43 % mAs reduction. ? Blurring of infratentorial images becomes evident using low-radiation head CT. ? Head diameter was inversely correlated with imaging quality in the infratentorium. ? Lowering tube kilovoltage requires a higher radiation dose to maintain image quality.     

Low tube voltage and low contrast material volume cerebral CT angiography

Objectives

To evaluate the image quality, radiation dose and diagnostic accuracy of low kVp and low contrast material volume cerebral CT angiography (CTA) in intracranial aneurysm detection.

Methods

One hundred twenty patients were randomly divided into three groups (n?=?40 for each): Group A, 70 ml iodinated contrast agent/120 kVp; group B, 30 ml/100 kVp; group C, 30 ml/80 kVp. The CT numbers, noise, signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were measured in the internal carotid artery (ICA) and middle cerebral artery (MCA). Subjective image quality was evaluated. For patients undergoing DSA, diagnostic accuracy of CTA was calculated with DSA as reference standard and compared.

Results

CT numbers of ICA and MCA were higher in groups B and C than in group A (P?<?0.01). SNR and CNR in groups A and B were higher than in group C (both P?<?0.05). There was no difference in subjective image quality among the three groups (P?=?0.939). Diagnostic accuracy for aneurysm detection among these groups had no statistical difference (P?=?1.00). Compared with group A, the radiation dose of groups B and C was decreased by 45 % and 74 %.

Conclusion

Cerebral CTA at 100 or 80 kVp using 30 ml contrast agent can obtain diagnostic image quality with a low radiation dose while maintaining the same diagnostic accuracy for aneurysm detection.

Key Points

? Cerebral CTA is feasible using 100/80 kVp and 30 ml contrast agent. ? This approach obtains diagnostic image quality with 45–74 % radiation dose reduction. ? Diagnostic accuracy for intracranial aneurysm detection seems not to be compromised.     

Tube potential can be lowered to 80 kVp in test bolus phase of CT coronary angiography (CTCA) and CT pulmonary angiography (CTPA) to save dose without compromising diagnostic quality

Objectives

The purpose of this study was to determine whether performing the test bolus (TB) of computed tomography coronary angiography (CTCA) and computed tomography pulmonary angiography (CTPA) at 80 kVp reduces dose without compromising diagnostic quality.

Methods

An 80 kVp TB protocol for CTCA and CTPA was retrospectively compared to standard TB protocol (non-obese: 100 kVp, obese: 120 kVp). CT angiogram parameters were unchanged between cohorts. Thirty-seven consecutive 80 kVp TB CTCA images were compared to 53 standard CTCA images. Fifty consecutive CTPAs from each protocol were analysed. Diagnostic quality of the CT angiogram was assessed by: mean attenuation, signal-to-noise ratio (SNR) in the ascending aorta (AA) in CTCA and in the main pulmonary artery (MPA) in CTPA, diagnostic rate, and number of repeated monitoring scans. Mean effective dose was estimated using the dose-length product.

Results

Mean TB effective doses were significantly lower (P?Conclusions Routinely performing TB at 80 kVp, regardless of body habitus, in CTCA and CTPA results in a small but significant dose reduction, without compromising CT angiogram diagnostic quality.

Key Points

? CT coronary angiography is performed to exclude the presence of significant coronary atherosclerosis. ? CT pulmonary angiography is performed to diagnose pulmonary thromboembolism. ? This retrospective study showed dose reduction by performing test bolus at 80 kVp. ? Diagnosis can be made with reduced exposure to ionising radiation.