Image quality and radiation exposure at pulmonary CT angiography with 100- or 120-kVp protocol: prospective randomized study

PURPOSE: To prospectively compare 16-section multidetector computed tomography (CT) at 100 and 120 kVp for image quality and radiation dose. MATERIALS AND METHODS: The study had institutional review board approval; written informed consent was obtained. Sixty patients were referred for evaluation of suspected pulmonary embolism with CT angiography. Patients were randomly assigned to a 100-kVp (n = 30; 17 men, 13 women; mean age, 66 years +/- 17 [standard deviation]; range, 19-89 years) or 120-kVp (n = 30; 15 men, 15 women; mean age, 62 years +/- 15; range, 28-86 years) protocol. Other scanning parameters were kept constant. Contrast medium was injected automatically with bolus tracking. Pulmonary vessel enhancement and image noise were quantified; signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were calculated. Subjective vessel contrast was assessed by two radiologists in consensus. Effective dose was calculated on the basis of dose length product and volume CT dose index. Results of both protocols were compared by using the chi(2) test and Student t test. RESULTS: The 100-kVp protocol had a nonsignificantly higher mean vessel attenuation than the 120-kVp protocol (386.8 HU +/- 130.1 vs 317.9 HU +/- 112.5; P = .56) and a nonsignificantly higher image noise (16.9 HU +/- 5.8 vs 13.7 HU +/- 6.2; P = .84), which resulted in almost identical SNR (25.3 +/- 11.7 vs 27.0 +/- 14.5; P = .37) and CNR (22.0 +/- 11.2 vs 22.9 +/- 13.1; P = .51). There was no significant difference in subjective image quality between protocols. Mean effective dose for the 100-kVp protocol was significantly lower than that for the 120-kVp protocol (1.37 mSv +/- 0.39 vs 2.44 mSv +/- 0.97; -44%; P < .001). CONCLUSION: Reduction of kilovoltage from 120 to 100 kVp resulted in significant reduction of effective dose at pulmonary CT angiography, without significant loss of objective or subjective image quality.     

Multiphase CT angiography versus single-phase CT angiography: comparison of image quality and radiation dose

BACKGROUND AND PURPOSE: Conventional CT angiography (CTA) is acquired during only a short interval in the arterial phase, which limits its ability to evaluate the cerebral circulation. Our aim was to compare the image quality and radiation dose of conventional single-phase CTA (SP-CTA) with a multiphase CTA (MP-CTA) algorithm reconstructed from a perfusion CT (PCT) dataset.MATERIALS AND METHODS: Fifty consecutive patients undergoing head CTA and PCT in 1 examination were enrolled. The PCT dataset was obtained with 40.0-mm-detector coverage, 5.0-mm axial thickness, 80 kilovolt peak (kVp), 180 mA, and 30 mL of contrast medium. MP-CTA was reconstructed from the same PCT dataset with an axial thickness of 0.625 mm by using a new axial reconstruction algorithm. A conventional SP-CTA dataset was obtained with 0.625-mm axial thickness, 120 kVp, 350 mA, and 60 mL of contrast medium. We compared image quality, vascular enhancement, and radiation dose.RESULTS: SP-CTA and MP-CTA of 50 patients (male/female ratio, 31/19; mean age, 59.25 years) were analyzed. MP-CTA was significantly better than SP-CTA in vascular enhancement (P = .002), in the absence of venous contamination (P = .006), and was significantly higher in image noise (P < .001). MP-CTA used less contrast medium than SP-CTA and could demonstrate hemodynamic information. The effective dose of MP-CTA was 5.73 mSv, which was equal to that in conventional PCT, and it was 3.57 mSv in SP-CTA.CONCLUSION: It is feasible that MP-CTA may provide both CTA and PCT results. Compared with SP-CTA, MP-CTA provides comparable image quality, better vascular enhancement, hemodynamic information, and more noise with less detail visibility with a lower tube voltage. The radiation dose of MP-CTA is higher than that of SP-CTA, but the dose can be reduced by altering the sampling interval.

Cerebral CT angiography (CTA) is a well-established minimally invasive diagnostic procedure used to detect cerebral aneurysms, acute vascular occlusions, or vasospasms and even predicts hematoma expansion in acute intracerebral hemorrhage.^1–6 Cerebral perfusion CT (PCT) is an important tool to evaluate cerebral ischemia, infarction, cerebral vascular reserve, and microvascular permeability of intracranial neoplasms.⁷ With PCT, the linear relationship between contrast concentration and pixel intensity lends itself more readily to quantification of blood flow values, compared with bolus contrast MR perfusion imaging.^8,9 PCT generates parametric maps of blood flow, including cerebral blood flow (CBF), cerebral blood volume (CBV), and mean transit time (MTT), by using complex deconvolution algorithms.⁷ In a systematic review, the authors concluded that the most accurate assessment of the site of occlusion, infarct core, salvageable brain tissue, and collateral circulation in patients suspected of acute stroke is by a combination of PCT and CTA.¹⁰ Compared with the dose used for single-detector-row CT, thin-section, multidetector CT (MDCT) requires an increased radiation dose for both CTA and PCT examinations.^11–13 To attain an “as low as reasonably achievable radiation dose,” many techniques have been tried to optimize radiation-dose levels in MDCT CTA.Currently, most commercialized CT scanners provide axial scanning in maximum z-axis coverage of 40-mm (2.5 mm × 16) sections; thin-thickness reconstruction modes can be scanned in 20-mm (0.625 mm × 32) sections. During acquisition of conventional CTA, only a short interval in the arterial phase is taken for reconstruction. We call this “single-phase CTA” (SP-CTA). During PCT examinations, to evaluate the area of attenuation change, we acquired axial scans of sequential images at the same level in a fixed or variable time interval (ie, multiphase mode). With the increasing scanning speed of CT, the time interval can be reduced to 0.5 second in state-of-the-art MDCT. Scanning coverage is still a problem because of the cone beam geometry in current MDCT. The fully sampled region, the region covered by every view in the scanning, is less than the cylinder, with a height equal to the detector isocenter coverage.^14,15 To overcome this problem, we used extrapolation during the back projection process. The cone beam effect increases farther away from the isocenter and becomes more prominent with a larger FOV. Under such conditions, a novel vendor reconstruction algorithm has been developed to solve the cone beam effect, conducting a 40-mm beam of 64i × 0.625 mm in an axial scanning. We can then obtain raw data of thin-section PCT and perform postprocessing to reconstruct CTA from this thin-section PCT. Because such CTA images contain data from different time points, we call the technique “multiphase CTA” (MP-CTA), in contrast to conventional single-phase (SP-CTA). This study was designed to compare the image quality and radiation dose of MP-CTA by using the novel thin-reconstruction algorithm from the PCT dataset with the SP-CTA data from the same patient.     

Reduced iodine load with CT coronary angiography using dual-energy imaging: A prospective randomized trial compared with standard coronary CT angiography

BackgroundThere is concern regarding the administration of iodinated contrast to patients with impaired renal function because of the increased risk of contrast-induced nephropathy.ObjectiveEvaluate image quality and feasibility of a protocol with a reduced volume of iodinated contrast and utilization of dual-energy coronary CT angiography (DECT) vs a standard iodinated contrast volume coronary CT angiography protocol (SCCTA).MethodsA total of 102 consecutive patients were randomized to SCCTA (n = 53) or DECT with rapid kVp switching (n = 49). Eighty milliliters and 35 mL of iodinated contrast were administered in the SCCTA and DECT cohorts, respectively. Two readers measured signal and noise in the coronary arteries; signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were calculated. A 5-point signal/noise Likert scale was used to evaluate image quality; scores of <3 were nondiagnostic. Agreement was assessed through kappa analyses.ResultsDemographics and radiation dose were not significantly different; there was no difference in CNR between both cohorts (P = .95). A significant difference in SNR between the groups (P = .02) lost significance (P = .13) when adjusted for body mass index. The median Likert score was inferior for DECT for reader 1 (3.6 ± 0.6 vs 4.3 ± 0.6; P < .001) but not reader 2 (4.1 ± 0.6 vs 4.3 ± 0.5; P = .06). Agreement in diagnostic interpretability in the DECT and SCCTA groups was 91% (95% confidence interval, 86%–100%) and 96% (95% confidence interval, 90%–100%), respectively.ConclusionDECT resulted in inferior image quality scores but demonstrated comparable SNR, CNR, and rate of diagnostic interpretability without a radiation dose penalty while allowing for >50% reduction in contrast volume compared with SCCTA.     

Effect of caffeine on SPECT myocardial perfusion imaging during regadenoson pharmacologic stress: Rationale and design of a prospective, randomized, multicenter study

Background

Caffeine attenuates the coronary hyperemic response to adenosine by competitive A_2A receptor blockade. This study aims to determine whether oral caffeine administration compromises diagnostic accuracy in patients undergoing vasodilator stress myocardial perfusion imaging (MPI) with regadenoson, a selective adenosine A_2A agonist.

Methods

This multicenter, randomized, double-blind, placebo-controlled, parallel-group study includes patients with suspected coronary artery disease who regularly consume caffeine. Each participant undergoes three SPECT MPI studies: a rest study on day 1 (MPI-1); a regadenoson stress study on day 3 (MPI-2), and a regadenoson stress study on day 5 with double-blind administration of oral caffeine 200 or 400 mg or placebo capsules (MPI-3; n = 90 per arm). Only participants with ≥1 reversible defect on the second MPI study undergo the subsequent stress MPI test. The primary endpoint is the difference in the number of reversible defects on the two stress tests using a 17-segment model. Pharmacokinetic/pharmacodynamic analyses will evaluate the effect of caffeine on the regadenoson exposure-response relationship. Safety will also be assessed.

Conclusion

The results of this study will show whether the consumption of caffeine equivalent to 2-4 cups of coffee prior to an MPI study with regadenoson affects the diagnostic validity of stress testing (ClinicalTrials.gov number, NCT00826280).     

Comparison of radiation dose,contrast enhancement and image quality of prospective ECG-Gated CT coronary angiography: Single versus dual source CT

IntroductionThe updated National Institute of Clinical Excellence (NICE) guidelines of 2017 state that new generation cardiac CT scanners (Aquilion ONE, Brilliance iCT, Discovery CT750 HD and Somatom Definition Flash) are recommended as an option for first-line imaging of the coronary arteries in people with suspected stable coronary artery disease (with an estimated likelihood of coronary artery disease of 10–29%) in whom imaging with earlier generation CT scanners is difficult. New generation cardiac CT scanners are also recommended as an option for first-line evaluation of disease progression, to establish need for revascularisation in people with known coronary artery disease in whom imaging with earlier generation CT scanners is difficult. CT scanning might not be necessary in situations in which immediate revascularisation is being considered. The European Society of Cardiology 2019 clinical practice guidelines recommend non-invasive functional imaging for myocardial ischaemia or coronary CT angiography (CTA) as the initial test to diagnose CAD in symptomatic patients in whom obstructive CAD cannot be excluded by clinical assessment alone. Given increased computed tomography coronary angiogram (CTCA) utilisation, radiation dose, contrast enhancement and image quality of prospective ECG-gated CTCA between 256-slice single-source and 192x2-slice dual-source CT scanners were retrospectively evaluated.MethodsProspectively gated CTCA data from 63 patients on a 256-slice CT (group A) and 71 patients on a 192x2-slice dual source CT (group B) from January to December 2016 were retrospectively evaluated respectively. Scanner-reported dose length product values were used with a conversion factor (k = 0.014 mSv/mGy x cm) to estimate effective dose. Contrast enhancement was assessed with mean CT attenuation at selected regions of interest on axial coronary images. Image quality of the coronary arteries was assessed by a 4-point grading score (1 = non-diagnostic, 4 = excellent image quality).ResultsThe radiation doses in group B were significantly lower than group A (3.68 + 2.13 mSv versus 4.81 + 1.56 mSv, p < 0.001). There were no significant differences in contrast enhancement in the left coronary artery, proximal right coronary artery and left ventricular wall for both groups. Vessel image quality scores for group B were higher than group A (right coronary artery (RCA): 3.2 + 0.7 versus 2.4 + 0.7, p < 0.001; left anterior descending (LAD) artery: 3.0 + 0.8 vs 2.5 + 0.6, p < 0.001; left circumflex (LCx) artery: 3.3 + 0.7 vs 2.6 + 0.6, p < 0.001). Coronary artery contour scores for group B were significantly higher than group A (RCA: 3.2 + 0.8 versus 2.3 + 0.7, p < 0.001; LAD: 3.0 + 0.7 versus 2.4 + 0.6, p < 0.001; LCx: 3.3 + 0.6 versus 2.5 + 0.6, p < 0.001).ConclusionProspective ECG-gated CTCA performed on 192x2-slice CT results in better image quality and lower radiation dose than 256-slice CT. There were no significant differences in contrast enhancement in left main coronary artery (LMCA), proximal RCA and left ventricular wall in both groups.Implications for practiceIn institutions with both 256-slice and 192x2-slice CT scanners, we recommend that CTCAs be preferentially performed using the 192x2-slice CT scanner.     

Regadenoson-stress myocardial CT perfusion and single-photon emission CT: Rationale,design, and acquisition methods of a prospective,multicenter, multivendor comparison

Pharmacologic stress myocardial CT perfusion (CTP) has been reported to be a viable imaging modality for detection of myocardial ischemia compared with single-photon emission CT (SPECT) in several single-center studies. However, regadenoson-stress CTP has not previously been compared with SPECT in a multicenter, multivendor study. The rationale and design of a phase 2, randomized, cross-over study of regadenoson-stress myocardial perfusion imaging by CTP compared with SPECT are described herein. The study will be conducted at approximately 25 sites by using 6 different CT scanner models, including 64-, 128-, 256-, and 320-slice systems. Subjects with known/suspected coronary artery disease will be randomly assigned to 1 of 2 imaging procedure sequences; rest and regadenoson-stress SPECT on day 1, then regadenoson-stress CTP and rest CTP/coronary CT angiography (same acquisition) on day 2; or regadenoson-stress CTP and rest CTP/CT angiography on day 1, then rest and regadenoson-stress SPECT on day 2. The prespecified primary analysis examines the agreement rate between CTP and SPECT for detecting or excluding ischemia (≥2 or 0–1 reversible defects, respectively), as assessed by 3 independent blinded readers for each modality. Non-inferiority will be indicated if the lower boundary of the 95% CI for the agreement rate is within 0.15 of 0.78 (the observed agreement rate in the regadenoson pivotal trials). The protocol described herein will support the first evaluation of regadenoson-stress CTP by using multiple scanner types compared with SPECT.     

Adenosine versus regadenoson comparative evaluation in myocardial perfusion imaging: Results of the ADVANCE phase 3 multicenter international trial

Background  Earlier phase 1 and 2 studies have shown that regadenoson has desirable features as a stress agent for myocardial perfusion imaging. Methods and Results  This multicenter, double-blinded phase 3 trial involved 784 patients at 54 sites. Each patient underwent 2 sets of gated single photon emission computed tomography myocardial perfusion imaging studies: an initial qualifying study with adenosine and a subsequent randomized study with either regadenoson (2/3 of patients) or adenosine. Regadenoson was administered as a rapid bolus (<10 seconds) of 400 μg. The primary endpoint was to demonstrate noninferiority by showing that the difference in the strength of agreement in detecting reversible defects, based on blinded reading, between sequential adenosine-regadenoson images and adenosine-adenosine images, lay above a prespecified noninferiority margin. Other prospectively defined safety and tolerability comparisons and supporting analyses were also performed. The average agreement rate based on the median of 3 independent blinded readers was 0.63±0.03 for regadenoson-adenosine and 0.64±0.04 for adenosine-adenosine—a 1% absolute difference with the lower limit of the 95% confidence interval lying above the prespecified noninferiority margin. Side-by-side interpretation of regadenoson and adenosine images provided comparable results for detecting reversible defects. The peak increase in heart rate was greater with regadenoson than adenosine, but the blood pressure nadir was similar. A summed symptom score of flushing, chest pain, and dyspnea was less with regadenoson than adenosine (P=.013). Conclusions  This phase 3 trial shows that regadenoson provides diagnostic information comparable to a standard adenosine infusion. There were no serious drug-related side effects, and regadenoson was better tolerated than adenosine.     

在双源CT冠状动脉成像中应用不同低剂量扫描方案对影像质量和辐射剂量的影响:随机研究

目的比较在128层双源CT冠状动脉成像中应用不同低剂量扫描方案的图像质量、辐射剂量和它们与心率的关系。材料与方法此研究通过当地伦理委员会审查,所有病人都知情同意。272例病人(男175例,女97例,平均年龄分     

Nuclear myocardial perfusion imaging with a novel cadmium-zinc-telluride detector SPECT/CT device: first validation versus invasive coronary angiography

Purpose  

We evaluated the diagnostic accuracy of attenuation corrected nuclear myocardial perfusion imaging (MPI) with a novel hybrid single photon emission computed tomography (SPECT)/CT device consisting of an ultrafast dedicated cardiac gamma camera with cadmium-zinc-telluride (CZT) solid-state semiconductor detectors integrated onto a multislice CT scanner to detect coronary artery disease (CAD). Invasive coronary angiography served as the standard of reference.     

Diagnostic performance of combined noninvasive coronary angiography and myocardial perfusion imaging using 320-MDCT: the CT angiography and perfusion methods of the CORE320 multicenter multinational diagnostic study

OBJECTIVE: Coronary MDCT angiography has been shown to be an accurate noninvasive tool for the diagnosis of obstructive coronary artery disease (CAD). Its sensitivity and negative predictive value for diagnosing percentage of stenosis are unsurpassed compared with those of other noninvasive testing methods. However, in its current form, it provides no information regarding the physiologic impact of CAD and is a poor predictor of myocardial ischemia. CORE320 is a multicenter multinational diagnostic study with the primary objective to evaluate the diagnostic accuracy of 320-MDCT for detecting coronary artery luminal stenosis and corresponding myocardial perfusion deficits in patients with suspected CAD compared with the reference standard of conventional coronary angiography and SPECT myocardial perfusion imaging. CONCLUSION: We aim to describe the CT acquisition, reconstruction, and analysis methods of the CORE320 study.     

64层CT盆腔动脉成像质量及辐射剂量的研究

目的初步探讨64层CT盆腔动脉成像中低mAs技术应用价值,评价其图像质量和辐射剂量。方法选取50例日常盆腔增强检查患者随机分为A、B2组,A组24例使用250mAs进行CT盆腔动脉成像,B组26例使用100mAs。通过cT机自动得到CT剂量指数（CT dose index,CTDI）和剂量长度乘积（dose length product,DLP）。对2组扫描数据分别进行多种图像后处理,2名有经验的影像科医师采用双盲法评价图像质量,测量噪声及CT值。两组图像ROI的CT值、噪声、SNR、辐射剂量及图像质量评分用两独立样本t检验进行统计分析。2名医师评分一致性采用Kappa检验。结果A组盆腔动脉分支图像质量评分为2．9±O．1,B组为2．8±0．1,2组之间比较差异无统计学意义（P〉0．05）。A组CTDI、DLP和ED分别为14．7、458．5±13．3和8．7±0．3,而B组分别为6．4、179．9±8．9和3。4±0．2,2组CTDI、DLP和ED之间比较差异有统计学意义（P〈O．05）。2组问髂内动脉平均SNR差异有统计学意义。A组评价144分支,B组评价156分支,A、B组优良者分别达到100％和98．1％。结论低mAs盆腔动脉扫描可在保证图像质量的同时显著降低辐射剂量。     

Coronary CT angiography in step-and-shoot technique with 256-slice CT: impact of the field of view on image quality, craniocaudal coverage, and radiation exposure

Purpose

To evaluate the effect of a small field of view (FOV) for step-and-shoot coronary computed tomography angiography (CCTA) on craniocaudal z-coverage per scan step, image quality, and radiation exposure.

Methods

53 patients underwent prospectively ECG-gated CCTA on a 256-slice MDCT scanner using either a FOV > 250 mm (group 1, n = 29) or a FOV ≤ 250 mm (group 2, n = 24). Craniocaudal z-coverage was determined on coronal multiplanar reformations. Image noise, signal-to-noise ratio, contrast-to-noise ratio, and qualitative image parameters were assessed. Radiation dose was estimated from the dose length product and was standardized for a scan range from the main pulmonary artery to the diaphragm in order to make both groups comparable.

Results

Diagnostic image quality was achieved in 91.3% of the coronary artery segments of group 1 and 89.9% in group 2 (p = 0.201). There were no major differences in image noise, SNR, and CNR between both groups. A smaller FOV leads to an increase of craniocaudal coverage of a single CT scan step (r = − 0.879; p ≤ 0.001). There was an increase of 23.8% of the mean z-coverage per scanned subvolume in group 2 (59.9 mm vs. 48.8 mm). Radiation dose was significantly lower in group 2 (229 vs. 285 mGy cm, respectively).

Conclusion

The use of a small transverse FOV for step-and-shoot CCTA at a wide detector CT scanner leads to an increased z-coverage. 2 scan volumes are enough to image the cardiac anatomy. Radiation dose is decreased without negative impact on image quality.