Fuminari Tatsugami

Accuracy of low-dose computed tomography coronary angiography using prospective electrocardiogram-triggering: first clinical experience

AIMSnTo evaluate the accuracy of low-dose computed tomography coronary angiography (CTCA) using prospective ECG-triggering for the assessment of coronary artery disease (CAD).nnnMETHODS AND RESULTSnA total of 30 patients (19 males, 11 females, mean age 58.8 +/- 9.9 years) underwent low-dose CTCA and invasive coronary angiography (CA) [median 2 days (0, 41)]. Before CT scanning, intravenous beta-blocker was administered in 18 of 30 patients as heart rate (HR) was >65 b.p.m., achieving a mean HR of 55.7 +/- 7.9 b.p.m. CAD was defined as coronary artery narrowing > or =50%, using CA as standard of reference. The estimated mean effective radiation dose was 2.1 +/- 0.7 mSv (range: 1.0-3.3), yielding 96.0% (383/399) of evaluable segments. On an intention-to-diagnose-base, all non-evaluative segments were included in the analysis. Vessels with a non-evaluative segment and no further finding were censored as false positive. Patient-based analysis revealed sensitivity, specificity, positive predictive value, and negative predictive value of 100, 83.3, 90.0, and 100%, respectively. The respective values per vessel were 100, 88.9, 85.7, and 100%, respectively.nnnCONCLUSIONnProspective ECG-triggering allows low-dose CTCA and provides high diagnostic accuracy in the assessment of CAD in patients with stable sinus rhythm and a low heart rate.

Evaluation of a body mass index-adapted protocol for low-dose 64-MDCT coronary angiography with prospective ECG triggering

OBJECTIVEnBecause an increase in body mass index (weight in kilograms divided by height squared in meters) confers higher image noise at coronary CT angiography, we evaluated a body mass index-adapted scanning protocol for low-dose 64-MDCT coronary angiography with prospective ECG triggering.nnnSUBJECTS AND METHODSnOne hundred one consecutively registered patients underwent coronary CTA with prospective ECG triggering with a fixed contrast protocol (80 mL of iodixanol, 50-mL saline chaser, flow rate of 5 mL/s). Tube voltage (range, 100-120 kV) and current (range, 450-700 mA) were adapted to body mass index. Attenuation was measured, and contrast-to-noise ratio was calculated for the proximal right coronary artery and left main coronary artery. Image noise was determined for each patient as the SD of attenuation in the ascending aorta.nnnRESULTSnBody mass index ranged from 18.2 to 38.8, and mean effective radiation dose from 1.0 to 3.2 mSv. There was no correlation between body mass index and image noise (r = 0.11, p = 0.284), supporting the validity of the body mass index-adapted scanning protocol. However, body mass index was inversely correlated with vessel attenuation (right coronary artery, r = -0.45, p < 0.001; left main coronary artery, r = -0.47, p < 0.001) and contrast-to-noise ratio (right coronary artery, r = -0.39, p < 0.001; left main coronary artery, r = -0.37, p < 0.001).nnnCONCLUSIONnUse of the proposed body mass index-adapted scanning parameters results in similar image noise regardless of body mass index. Increased bolus dilution due to larger blood volume may account for the decrease in contrast-to-noise ratio and vessel attenuation in patients with higher body mass index, but the contrast bolus was not adapted to body mass index in this study.

Diagnostic accuracy of computed tomography coronary angiography and evaluation of stress-only single-photon emission computed tomography/computed tomography hybrid imaging : comparison of prospective electrocardiogram-triggering vs. retrospective gating

AIMSnTo determine diagnostic accuracy, effective radiation dose, and potential value of computed tomography coronary angiography (CTCA) for hybrid imaging with single-photon emission computed tomography (SPECT) comparing prospective electrocardiogram (ECG)-triggering vs. retrospective ECG-gating.nnnMETHODS AND RESULTSnTwo hundred patients underwent standard myocardial stress/rest- SPECT perfusion imaging, which served as standard of reference. One hundred consecutive patients underwent 64-slice CTCA using prospective ECG-gating, and were compared with 100 patients who had previously undergone CTCA using retrospective ECG-gating. For predicting ischaemia, CTCA with prospective ECG-triggering and a stenosis cut-off >50% had a per-vessel sensitivity, specificity, negative, and positive predictive value of 100, 84, 100, and 30%; respective values for CTCA with retrospective ECG-gating were similar (P = n.s.): 86, 83, 98, and 33%. Combining CTCA with stress-only SPECT revealed 100% clinical agreement with regard to perfusion defects, and provided additional information in half the patients on preclinical coronary findings. Effective radiation dose was 2.2 +/- 0.7 mSv for CTCA with prospective ECG-triggering, and 19.7 +/- 4.2 mSv with retrospective ECG-gating (P < 0.001) (5.4 +/- 0.8 vs. 24.1 +/- 4.3 mSv for hybrid imaging).nnnCONCLUSIONnProspective ECG-triggering for CTCA reduces radiation dose by almost 90% without affecting diagnostic performance. Combined imaging with stress-only SPECT is an attractive alternative to standard stress/rest-SPECT for evaluation of coronary artery disease, offering additional information on preclinical atherosclerosis.

Low-dose CT coronary angiography using prospective ECG-triggering: impact of mean heart rate and heart rate variability on image quality.

RATIONALE AND OBJECTIVESnThe aim of this study was to evaluate the effect of mean heart rate (HR) and HR variability on image quality in low-dose computed tomographic coronary angiography (CTCA) using prospective electrocardiographic (ECG) triggering.nnnMATERIALS AND METHODSnOne hundred thirty-six consecutive patients were scheduled for low-dose CTCA using prospective ECG triggering. The image quality of all coronary segments was rated on a 5-point scale by two independent readers (scores of 1-3 were considered diagnostic, and scores of 4 and 5 were considered nondiagnostic). Intravenous beta blockers were administered targeting HR < 65 beats/min before scanning, but not if HR increased during scanning.nnnRESULTSnAfter the exclusion of seven patients because of arrhythmia (n = 4) or mean HRs > 65 beats/min despite using beta blockers (n = 3), 129 patients underwent computed tomographic scanning. The estimated mean effective radiation dose was 2.2 +/- 0.7 mSv (range, 1.1-3.5). The mean HR during scanning was 58.4 +/- 6.6 beats/min (range, 44.2-80.1), with a variability of 1.6 +/- 1.0 beats/min (range, 0.2-5.3). Mean HR (r = 0.49, P < .001) but not mean HR variability (r = 0.14) was related to image quality. Nondiagnostic image quality on CTCA was found in 5% of the coronary segments in 21 of 129 patients. However, on receiver-operating characteristic analysis, a cutoff HR of 62 beats/min was determined, below which nondiagnostic segments were significantly less frequent (2% vs 14%, P < .001).nnnCONCLUSIONnProspective triggering allows low-dose CTCA but requires a low HR. Because a low HR offers a prolonged diastole, widening the optimal phase for scanning, HR variability seems to have a negligible impact on image quality.

Body physique and heart rate variability determine the occurrence of stair-step artefacts in 64-slice CT coronary angiography with prospective ECG-triggering.

The purpose of this study was to describe and characterize the frequency and extent of stair-step artefacts in computed tomography coronary angiography (CTCA) with prospective electrocardiogram (ECG)-triggering and to identify their determinants. One hundred and forty three consecutive patients (55 women, mean age 57u2009±u200913xa0years) underwent 64-slice CTCA using prospective ECG-triggering. Occurrence of stair-step artefacts in CTCA of the thoracic wall and the coronary arteries was determined and maximum offset was measured. If stair-step artefacts occurred in both cases, a difference between thoracic wall and coronary artery offset of 0.6xa0mm or greater was attributed to additional motion of the heart. Mean effective radiation dose was 2.1u2009±u20090.7xa0mSv (range 1.0–3.5xa0mSv). Eighty-nine patients (62%) had stair-step artefacts in CTCA of the coronary arteries (mean offset of 1.7u2009±u20091.1xa0mm), while only 77 patients had thoracic wall stair-step artefacts (mean offset of 1.0u2009±u20090.3xa0mm; significantly different, Pu2009<u20090.001). Stair-step artefacts in CTCA of the thoracic wall were determined by BMI and weight (Pu2009<u20090.01), while artefacts in CTCA of the coronary arteries were associated with heart rate variability (Pu2009<u20090.05). Stair-step artefacts in CTCA with prospective ECG-triggering are determined by (a) motion of the entire patient during table travel, particularly in large patients and (b) by motion of the heart, particularly when heart rates are variable.

Body size-adapted dose of contrast material and scanning protocol in 320-detector row CT coronary angiography.

Objective: Because an increase in patient body size produces lower vessel attenuation and higher image noise in computed tomography coronary angiography (CTCA), a protocol in which the dose of contrast material was adapted to the body weight, and tube voltage and current were adapted to the body mass index (BMI) was evaluated. Methods: A total of 136 patients who underwent CTCA were assigned to 1 of 2 protocols; the patients received 40 mL of contrast material (A; n = 52), or 0.7 mL/kg of contrast material (B; n = 84). Tube voltage and current were adapted to the BMI. Results: In group A, there was no significant correlation between BMI and image noise (r = −0.21, P = 0.15). However, BMI correlated inversely with contrast-to-noise ratio (CNR; right coronary artery, r = −0.29, P < 0.05; left main coronary artery, r = −0.33, P < 0.05) and image quality score (r = −0.55, P < 0.001). In group B, there was no significant correlation between BMI and image noise (r = −0.14, P = 0.21), CNR (right coronary artery: r = −0.09, P = 0.45; left main coronary artery: r = −0.07, P = 0.55), and image quality score (r = 0.03, P = 0.79). Conclusions: Use of a body size-adapted dose of contrast material and scanning protocol results in similar CNR and image quality independent of individual BMI.

Incidental detection of a pulmonary adenocarcinoma on low-dose computed tomography used for attenuation correction in myocardial perfusion imaging with SPECT

A 68-year-old patient with known 3-vessel coronary artery disease, a history of aortocoronary bypass surgery, and presently without chest pain, was referred to myocardial perfusion imaging for preoperative risk assessment as infrarenal aortic aneurysm repair was planned. Single photon emission computed tomography (CT) revealed normal myocardial perfusion at adenosine-stress and at rest. However, the CT scan used for attenuation correction (AC) demonstrated a large tumor in the right upper lung as an incidental finding, and the patient was referred for staging with F-18 fluorodeoxyglucose positron emission tomography/CT and subsequently to thoracic surgery. The lesion was resected and diagnosed to be an adenocarcinoma (stage pT2, cN0, cM0). When last seen, the patient was recovering well from surgery.