Irrigation of biomass plantations may globally increase water stress more than climate change.

Bioenergy with carbon capture and storage (BECCS) is considered an important negative emissions (NEs) technology, but might involve substantial irrigation on biomass plantations. Potential water stress resulting from the additional withdrawals warrants evaluation against the avoided climate change impact. Here we quantitatively assess potential side effects of BECCS with respect to water stress by disentangling the associated drivers (irrigated biomass plantations, climate, land use patterns) using comprehensive global model simulations. By considering a widespread use of irrigated biomass plantations, global warming by the end of the 21st century could be limited to 1.5 °C compared to a climate change scenario with 3 °C. However, our results suggest that both the global area and population living under severe water stress in the BECCS scenario would double compared to today and even exceed the impact of climate change. Such side effects of achieving substantial NEs would come as an extra pressure in an already water-stressed world and could only be avoided if sustainable water management were implemented globally.

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.

Computed tomography angiography and myocardial computed tomography perfusion in patients with coronary stents: prospective intraindividual comparison with conventional coronary angiography.

OBJECTIVES: This study sought to determine whether adding myocardial computed tomography perfusion (CTP) to computed tomography angiography (CTA) improves diagnostic performance for coronary stents. BACKGROUND: CTA of coronary stents has been limited by nondiagnostic studies caused by metallic stent material and coronary motion. METHODS: CTA and CTP were performed in 91 consecutive patients with stents before quantitative coronary angiography, the reference standard for obstructive stenosis (≥50%). If a coronary stent or vessel was nondiagnostic on CTA, adenosine stress CTP in the corresponding myocardial territory was read for combined CTA/CTP. RESULTS: Patients had an average of 2.5 ± 1.8 coronary stents (1 to 10), with a diameter of 3.0 ± 0.5 mm. Significantly more patients were nondiagnostic for stent assessment by CTA (22%; mainly due to metal artifacts [75%] or motion [25%]) versus CTP (1%; p < 0.001; severe angina precluded CTP in 1 case). The per-patient diagnostic accuracy of CTA/CTP for stents (87%, 95% confidence interval [CI]: 78% to 93%) was significantly higher than that of CTA alone (71%, 95% CI: 61% to 80%; p < 0.001), mainly because nondiagnostic examinations were significantly reduced (p < 0.001). In the analysis of any coronary artery disease, diagnostic accuracy and nondiagnostic rate were also significantly improved by the addition of CTP (p < 0.001). CTA/CTP (7.9 ± 2.8 mSv) had a significantly lower effective radiation dose than angiography (9.5 ± 5.1 mSv; p = 0.005). The area under the receiver-operating characteristic curve for CTA/CTP (0.82, 95% CI: 0.69 to 0.95) was superior to that for CTA (0.69, 95% CI: 0.57 to 0.82; p < 0.001) in identifying patients requiring stent revascularization. CONCLUSIONS: Combined coronary CTA and myocardial CTP improves diagnosis of CAD and in-stent restenosis in patients with stents compared with CTA alone. (Coronary Artery Stent Evaluation With 320-Slice Computed Tomography-The CArS 320 Study [CARS-320]; NCT00967876).

Time efficiency and diagnostic accuracy of new automated myocardial perfusion analysis software in 320-row CT cardiac imaging.

OBJECTIVE: We aimed to evaluate the time efficiency and diagnostic accuracy of automated myocardial computed tomography perfusion (CTP) image analysis software. MATERIALS AND METHODS: 320-row CTP was performed in 30 patients, and analyses were conducted independently by three different blinded readers by the use of two recent software releases (version 4.6 and novel version 4.71GR001, Toshiba, Tokyo, Japan). Analysis times were compared, and automated epi- and endocardial contour detection was subjectively rated in five categories (excellent, good, fair, poor and very poor). As semi-quantitative perfusion parameters, myocardial attenuation and transmural perfusion ratio (TPR) were calculated for each myocardial segment and agreement was tested by using the intraclass correlation coefficient (ICC). Conventional coronary angiography served as reference standard. RESULTS: The analysis time was significantly reduced with the novel automated software version as compared with the former release (Reader 1: 43:08 ± 11:39 min vs. 09:47 ± 04:51 min, Reader 2: 42:07 ± 06:44 min vs. 09:42 ± 02:50 min and Reader 3: 21:38 ± 3:44 min vs. 07:34 ± 02:12 min; p < 0.001 for all). Epi- and endocardial contour detection for the novel software was rated to be significantly better (p < 0.001) than with the former software. ICCs demonstrated strong agreement (≥ 0.75) for myocardial attenuation in 93% and for TPR in 82%. Diagnostic accuracy for the two software versions was not significantly different (p = 0.169) as compared with conventional coronary angiography. CONCLUSION: The novel automated CTP analysis software offers enhanced time efficiency with an improvement by a factor of about four, while maintaining diagnostic accuracy.