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/m(2)) 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 < 0.01 in all). Radiation exposure of DECT was in between SCT at 100 kV and 120 kV. 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.

Radiation dose reduction by using 100-kV tube voltage in cardiac 64-slice computed tomography: a comparative study.

OBJECTIVE: To evaluate a 100-kilovoltage (kV) tube voltage protocol regarding radiation dose and image quality, in comparison with the standard 120 kV setting in cardiac computed tomography angiography (CCTA). METHODS: 103 patients undergoing retrospective ECG-gated helical 64-slice CCTA were enrolled (100 kV group: 51 patients; 120 kV group: 52 patients). Inclusion criteria were: (1) BMI <28 kg/m(2); (2) weight <85 kg; (3) coronary calcium score <300 Agatston Units (AU). Quantitative image quality parameters were calculated [image noise, contrast-to-noise ratio (CNR), intracoronary CT-attenuation (HU)]. Each coronary artery segment (AHA/ACC-16-segments-classification) was evaluated for image quality on a 4-point scale. RESULTS: There was no statistical difference in age, gender, BMI and eff. tube current (mAs), and the use of ECG-tube current modulation (50.9% vs. 50% of patients) between both groups. 84.2% of patients in the 100 kV group had zero calcium score or less than 100 AU, the remaining had between 100 and 300 AU. The effective radiation dose was significantly lower in the 100 kV group with mean 7.1 mSv+/-2.4 (range, 3.4-11.1) compared to the 120 kV group with 13.4 mSv+/-5.2 (range, 6.3-22.7) (p<0.001) (dose reduction, 47%). In the 100 kV group, the use of ECG-dependent tube current modulation reduced the radiation exposure (by 44.8%) to 5.3 mSv+/-1.1 (range, 3.4-8.5 mSv) (p<0.001), the dose without was 9.6 mSv+/-1.1 (range, 6.3-11.1). Image noise in the coronary arteries was not different between both groups with 29.8 and 30.5 SD [HU], respectively. CNR in the 100 kV group was with 20.9+/-6.8 for the coronary arteries and with 19.9+/-5.9 for the aorta similar to the 120 kV group. Intraluminal CT-attenuation (HU) of the coronary arteries were higher in the 100 kV group (p<0.001). Image quality on 100 kV scans was excellent in 86.3%, good in 9.2%, acceptable in 3.1% of coronary segments; 1.4% were non-interpretable (in 1/4 due to increased image noise because of BMI >25 kg/m(2)). CONCLUSIONS: The 100 kV protocol significantly reduces the radiation dose in CCTA in patients with a low BMI <25 kg/m(2) and a low calcium load while maintaining high image quality and the advantages of helical scan algorithm.

Clinical relevance and scope of accidental extracoronary findings in coronary computed tomography angiography: a cardiac versus thoracic FOV study.

OBJECTIVE: To assess the spectrum and clinical relevance of extracoronary findings in coronary CT angiography (CCTA), and to compare a small (cardiac) field of view (FOV) to a large (thoracic) FOV setting. MATERIAL AND METHODS: 1084 consecutive patients (mean 57 years) with low-to-intermediate risk of coronary artery disease were enrolled. 542 CCTA scans were interpreted with small FOV (160-190mm(2)) encompassing the cardiac region. In another 542 CCTA (patients matched for age and gender), read-out of an additional full FOV (>320mm(2)) covering the thorax was performed. Clinical relevance of extracoronary findings was considered as either "significant" or "non-significant". "Significant" findings were subclassified as either score 1: findings necessitating immediate therapeutic actions, or score 2: findings with undoubted clinical or prognostic relevance, requiring clinical awareness, follow-up or further investigations (non-urgent). "Non-significant" findings were assigned to either score 3: findings not requiring follow-up or further tests, or as score 4: irrelevant incidental findings. RESULTS: Significantly more patients with extracoronary findings were identified by using a full FOV with 43.2% (234/542) compared to a small FOV with 33.6% (182/542) (p=0.001). Similarly, a higher total number of extracoronary findings (n=394) was found on full FOV compared to small FOV (n=250) (p<0.001). The detection rate of clinically significant findings was higher by using full FOV compared to small FOV (25.6% versus 15.4%) (p<0.001), out of those 2.2% versus 1.8% of findings required immediate actions (score 1), and 23.4% versus 13.6% (p=0.0001), respectively were of clinical relevance (non-urgent, score 2). The rate of malign findings was 0.2%, and of acute pulmonary embolism 0.1%. More lung pathologies were observed by using full FOV compared to small FOV (22% versus 7%) (p<0.0001), and the detection rate of intrapulmonary nodules increased by 2.1%. Prevalence of aortic valve calcification (n=72) was 13.3%, out of those 7% had less than 2cm(2) aortic valve orifice area. CONCLUSIONS: The interpretation of extracoronary findings on CCTA scans is mandatory given high prevalence of clinically significant findings by using a full "thoracic" FOV.

Diagnostic performance of 64-slice computed tomography in evaluation of coronary artery bypass grafts.

OBJECTIVE: The purpose of this study was to compare the diagnostic accuracy of 64-slice CT with that of invasive angiography in the detection of greater than 50% graft stenosis within 2 weeks of coronary artery bypass grafting and to investigate the clinical value of 64-slice CT. SUBJECTS AND METHODS: Forty-one patients (70 grafts, 46 arterial and 24 venous) underwent 64-slice CT a mean of 2.6 years after minimally invasive or conventional coronary artery bypass surgery. RESULTS: All 70 grafts were assessable, and none of the grafts was excluded from analysis. For the detection of 50-90% graft stenosis, the sensitivity of CT was 75%, the specificity was 95%, the positive predictive value was 67%, and the negative predictive value was 97% (true disease prevalence, 8/70 grafts; 11%). Greater than 50% graft stenosis and occlusion pooled together (prevalence, 14/70; 20%) were detected with a sensitivity of 85%, specificity of 95%, positive predictive value of 80%, and negative predictive value of 96%. Vein graft disease was found in eight (42%) of 19 patent vein grafts (graft age, 15.6 +/- 2.3 years). The disease was nonobstructive in three (16%) of the 19 grafts. The course of the left internal mammary artery was median retrosternal (< 1 cm deep) in 33.3% of conventionally sutured grafts. CONCLUSION: Sixty-four-slice CT angiography can be used for accurate exclusion of greater than 50% graft stenosis, but detection of distal anastomotic stenosis is limited, and the degree of stenosis can be overestimated. The advantages of CT, however, are that it is noninvasive, vein graft disease can be diagnosed at an early stage, and complementary evaluation of extracardiac anatomic features provides useful information before coronary artery bypass grafting is redone.

Publication output in telemedicine during the period January 1964 to July 2003.

The MEDLINE database was used to survey the period January 1964 to July 2003 for the number of publications relating to telemedicine (n = 5911), as well as their distribution by country (n = 42). Publications per million inhabitants were then correlated with each country's population density, gross national product, human development index (HDI) and number of PCs per 1000 inhabitants. Telemedicine publications made up 0.05% of all medical publications cited in MEDLINE. American and European countries along with others classified as industrialized produced 97% of all telemedicine publications. In terms of publications per million inhabitants, Norway and Finland took the lead. There were significant correlations between telemedicine publications per capita and HDI (r = -0.60), number of PCs per 1000 inhabitants (r = 0.73) and gross national product per capita (r = 0.69), but not population density (r = -0.12).