Anders Svensson

Heart rate variability and heat sensation during CT coronary angiography: Low-osmolar versus iso-osmolar contrast media

Background: During computed tomography coronary angiography (CTCA) unexpected changes in heart rate while scanning may affect image quality. Purpose: To evaluate whether an iso-osmolar contrast medium (IOCM, iodixanol) and a low-osmolar contrast medium (LOCM, iomeprol) affect heart rate and experienced heat sensation differently. Material and Methods: One hundred patients scheduled for CTCA were randomized to receive either iodixanol 320 mgI/ml or iomeprol 400 mgI/ml. Depending on their heart rate, the patients were assigned to one of five scanning protocols, each optimized for different heart rate ranges. During scanning the time between each heart beat (hb) was recorded, and the corresponding heart rate was calculated. For each contrast medium (CM) the average heart rate, the variation in heart rate from individual mean heart rate, and the mean deviation from the predefined scanning protocol were calculated. Experience of heat was obtained immediately after scanning by using a visual analog scale (VAS). Examination quality was rated by two radiologists on a three-point scale. Results: The mean variation in heart rate after IOCM was 1.4 hb/min and after LOCM it was 4.4 hb/min (NS). The mean deviations in heart rate from that in the predefined scanning protocol were 2.0 hb/min and 4.7 hb/min, respectively (NS). A greater number of arrhythmic hb were observed after LOCM compared with IOCM (P<0.001). There was no statistically significant difference in image quality. The LOCM group reported a stronger heat sensation after CM injection than the IOCM group (VAS =36 mm and 18 mm, P<0.05). Conclusion: At clinically used concentrations the IOCM, iodixanol 320 mgI/ml, does not increase the heart rate during CTCA and causes less heart arrhythmia and less heat sensation than the LOCM, iomeprol 400 mgI/ml.

Time-resolved computed tomography of the liver: retrospective, multi-phase image reconstruction derived from volumetric perfusion imaging

AbstractObjectiveTo assess feasibility and image quality (IQ) of a new post-processing algorithm for retrospective extraction of an optimised multi-phase CT (time-resolved CT) of the liver from volumetric perfusion imaging.MethodsSixteen patients underwent clinically indicated perfusion CT using 4D spiral mode of dual-source 128-slice CT. Three image sets were reconstructed: motion-corrected and noise-reduced (MCNR) images derived from 4D raw data; maximum and average intensity projections (time MIP/AVG) of the arterial/portal/portal-venous phases and all phases (total MIP/ AVG) derived from retrospective fusion of dedicated MCNR split series. Two readers assessed the IQ, detection rate and evaluation time; one reader assessed image noise and lesion-to-liver contrast.ResultsTime-resolved CT was feasible in all patients. Each post-processing step yielded a significant reduction of image noise and evaluation time, maintaining lesion-to-liver contrast. Time MIPs/AVGs showed the highest overall IQ without relevant motion artefacts and best depiction of arterial and portal/portal-venous phases respectively. Time MIPs demonstrated a significantly higher detection rate for arterialised liver lesions than total MIPs/AVGs and the raw data series.ConclusionTime-resolved CT allows data from volumetric perfusion imaging to be condensed into an optimised multi-phase liver CT, yielding a superior IQ and higher detection rate for arterialised liver lesions than the raw data series.Key Points• Four-dimensional computed tomography is limited by motion artefacts and poor image quality. • Time-resolved-CT facilitates 4D-CT data visualisation, segmentation and analysis by condensing raw data. • Time-resolved CT demonstrates better image quality than raw data images. • Time-resolved CT improves detection of arterialised liver lesions in cirrhotic patients.

Hepatic contrast medium enhancement at computed tomography and its correlation with various body size measures

Background When the same dose of iodine is given to all patients when performing abdominal computed tomography (CT) there may be a wide inter-individual variation in contrast medium (CM) enhancement of the liver. Purpose To evaluate if any of the measures body height (BH), body mass index (BMI), lean body mass (LBM), ideal body weight (IBW), and body surface area (BSA) correlated better than body weight (BW) with hepatic enhancement, and to compare the enhancement when using iodixanol and iomeprol. Material and Methods One hundred patients referred for standard three-phase CT examination of abdomen were enrolled. Body weight and height were measured at the time of the CT examination. Forty grams of iodine (iodixanol 320 mg I/mL or iomeprol 400 mg I/mL) was injected at a rate of 1.6 g-I/s, followed by a 50 mL saline flush. The late arterial phase was determined by using a semi-automatic smart prep technique with a scan delay of 20 s. The hepatic parenchymal phase started automatically 25 s after the late arterial phase. CM concentration was estimated by placement of regions of interest in aorta (native and late arterial phase) and in liver (native and parenchymal phase). Results BW (r = −0.51 and −0.64), LBM (r = −0.54 and −0.59), and BSA (r = −0.54 and −0.65) showed the best correlation coefficients with aortic and hepatic parenchymal enhancement, respectively, without any significant differences between the measures. Comparing iodixanol and iomeprol there was no significant difference in aortic enhancement. The liver enhancement was significantly higher (P < 0.05) using iodixanol than iomeprol. Conclusion To achieve a consistent hepatic enhancement, CM dose may simply be adjusted to body weight instead of using more complicated calculated parameters based on both weight and height.

Is training essential for interpreting cardiac computed tomography

Background: Cardiac computed tomography (CT) has gained increasing acceptance for diagnosing obstructive coronary artery disease (CAD). Several guidelines have been published on required education for proficiency in the interpretation of these examinations. Purpose: To describe the learning-curve effect of the interpretation of 100 consecutive cardiac CT examinations aimed at diagnosing CAD. The diagnostic accuracy of radiologists and radiographers was also compared. Material and Methods: Two radiologists and two radiographers, all with no prior experience in evaluation of cardiac CT, independently underwent a dedicated training program of 100 examinations randomized into 10 blocks (sessions), with 10 cases in each. They independently evaluated the coronary arteries regarding significant obstructive CAD. After every session, individual feedback on diagnostic accuracy and comparison with the corresponding invasive coronary angiography (currently regarded as the gold standard to detect coronary lesions) was given. The time required for interpretation was recorded. Results: The mean review time decreased (P<0.0001) successively during the 10 sessions for all the observers together. The first session had a mean review time of 32 min, and the last session 16 min. No significant improvement in sensitivity, specificity, or negative predictive value (NPV) was observed. For positive predictive value (PPV), there was an improvement for the radiologists (P<0.05), but not for the radiographers. The radiographers had a higher total specificity compared to the radiologists (P<0.01). Conclusion: The review time for novices in cardiac CT was approximately halved during the first 100 cases, with maintained accuracy. There was a learning-curve effect in PPV for the radiologists. The diagnostic accuracy of dedicated radiographers indicates that they might be considered to be included as part of the evaluation team.

Hypo‐Attenuated Leaflet Thickening and Reduced Leaflet Motion in Sutureless Bioprosthetic Aortic Valves

Background The prevalence of hypo‐attenuated leaflet thickening (HALT) and reduced leaflet motion (RLM) is unknown in surgically implanted bioprostheses because systematic investigation of HALT and/or RLM is limited to a few catheter‐based valves. The aim of this study was to investigate the prevalence of HALT and RLM by cardiac computed tomography in patients who underwent surgical aortic valve replacement and received a Perceval sutureless aortic valve bioprosthesis. Methods and Results This was a single‐center prospective observational study that included 47 patients (83.5% of the total number of implantations) who underwent surgical aortic valve replacement with implantation of the Perceval sutureless bioprosthesis (LivaNova PLC, London, UK) at Karolinska University Hospital in Stockholm, Sweden from 2012 to 2016 and were studied by cardiac computed tomography. Cardiac computed tomography was performed at a median of 491 days (range 36–1247 days) postoperatively. HALT was found in 18 (38%) patients and RLM in 13 (28%) patients. All patients with RLM had HALT. Among patients with HALT, 5 out of 18 patients (28%) were treated with anticoagulation (warfarin or any novel oral anticoagulant) at the time of cardiac computed tomography. Among patients with RLM, 3 out of 13 patients (23%) were treated with anticoagulation. Conclusions HALT and RLM were prevalent in the surgically implanted Perceval sutureless aortic valve bioprosthesis. Both HALT and RLM were found in patients with ongoing anticoagulation treatment. Whether these findings are associated with adverse events needs further study. Clinical Trial Registration URL: http://www.clinicaltrials.gov. Unique identifier: NCT02671474.

Plasma nitrate/nitrite removal by peritoneal dialysis might predispose infants with low blood pressure to cerebral ischaemia

The underlying pathogenic mechanisms of neurological complications in infants undergoing peritoneal dialysis (PD) are poorly understood. We report on four male infants treated with PD who developed symptomatic cerebral ischaemia. Blood pressure (BP) levels were low both before the event and at presentation. In two patients, we observed that the removal of nitrate and nitrite by PD could have impaired the nitrate/nitrite–-nitrite oxide (NO) pathway, a system that generates NO independently of NO synthase. Our observation suggests that low BP and reduced NO bioavailability puts infants treated with PD at risk for impaired cerebral blood flow and consequently for brain ischaemia.

Anomalous origin of right coronary artery from the pulmonary artery

A 37-year-old woman with no previous cardiovascular risk factors had sudden onset of transient symptoms of speech impediment. The case was judged as a transient ischaemic attack and brain computed tomography (CT) showed no abnormal findings. Echocardiography revealed no patent foramen ovalis but there was an abnormal arterial flow in the interventricular septum, which raised the suspicious of a coronary fistula. A cardiac computed tomography angiography (CTA) revealed an abnormal origin of the right coronary artery from the pulmonary artery (ARCAPA) with collaterals between the left and right coronary system. In a multidisciplinary conference, it was decided to postpone surgical correction since the patient was at the time asymptomatic and had normal right and left ventricular systolic function and no signs of myocardial ischaemia on exercise test.

The effect of arm positioning on timing and enhancement of intravenous contrast media at coronary computed tomography angiography

Background Adequate intravenous contrast media (CM) enhancement is crucial for evaluation of the coronary arteries. Purpose To compare the timing and enhancement of intravenous CM at coronary computed tomography angiography (CCTA) when positioning the arms in the traditional superior direction with that of positioning them in the ventral direction during the CM injection. Material and Methods One hundred patients were randomized into two groups. Group A (n = 50) had their arms positioned in the superior direction, resting on a head and arm support. Group B (n = 50) held their arms resting on the front panel of the computer tomography (CT) scanner. Scanning delay time was defined by test bolus technique. A total of 60 mL iodixanol, 320 mg/mL, was followed by a 50 mL saline flush at 6 mL/s. Cardiac output (CO) and heart rate (HR) were obtained before scanning. The attenuation was calculated by placing regions of interest (ROI) in ascending aorta, left atrium, and inferior vena cava. Results More patients in group A compared with group B (26 versus 14) showed a higher attenuation of the left atrium in comparison to the ascending aorta (P < 0.05). Body weight (BW) and CO were significantly related to the attenuation of ascending aorta (P < 0.01). Conclusion By placing the arms in a ventral, instead of superior position the frequency of too early imaging at CCTA can be reduced.

Triple Arterial Phase CT of the Liver with Radiation Dose Equivalent to That of Single Arterial Phase CT: Initial Experience

Purpose To develop and evaluate a triple arterial phase CT liver protocol with a similar radiation dose to that of standard single arterial phase CT in study subjects suspected of having hepatocellular carcinoma (HCC). Materials and Methods The study consisted of a retrospective part A for protocol development (n = 15) and a prospective part B to evaluate diagnostic accuracy (n = 38). All 53 participants underwent perfusion CT with 50 mL contrast material between August 2013 and September 2014. Group B underwent an additional standard multiphasic liver CT examination with 120 mL of contrast material (range, 70-143 mL). Image sets from triple arterial phase imaging were reconstructed from perfusion CT by fusing images from three dedicated arterial time points. Triple arterial phase CT and standard single arterial phase CT were compared by two readers, who assessed subjective image quality and HCC detection rate. A third reader served as reference reader and assessed objective image quality. The paired Student t test, Wilcoxon signed rank test, jackknife alternative free-response receiver operating characteristic (JAFROC), and JAFROC curve were applied. Results The mean volume CT dose index was 11.6 mGy for triple arterial phase CT and 11.9 mGy for standard single arterial phase CT (P = .73). Triple arterial phase CT showed lower image noise and better contrast-to-noise ratio compared with standard single arterial phase CT (P < .001 and P = .032, respectively); however, there was no significant difference in lesion-to-liver-contrast ratio (P = .31). Subjective image quality was good for both protocols. The detection rate of the 65 HCC lesions was 82% for reader 1 and 83% for reader 2 at triple arterial phase CT and 80% for reader 1 and 77% for reader 2 at standard single arterial phase CT (P = .4). Conclusion Triple arterial phase imaging is feasible at the same radiation dose as that used for standard single arterial phase CT. Triple arterial phase imaging provides equivalent to superior image quality and equal HCC detection rate despite the use of less than half the contrast material dose used at standard single arterial phase CT.

Influence of tube potential on CT body composition analysis

OBJECTIVES Our purpose was to investigate whether tube potential in contrast-enhanced computed tomography (CT) affects body composition analysis. METHODS Images from dual-source, dual-energy CT from the abdomen with intravenous contrast media administration were used. A total of 17 patients (11 women, mean age 52) with a mean body mass index of 20.8 kg/cm2 were included. Simultaneously acquired images with a tube voltage of 80 kV and 140 kV were compared. Body composition was analyzed on a single slice at the L3 level. Parameters evaluated included muscle and fat attenuation (Hounsfield units [HU]), skeletal muscle index (cm2/m2), muscle area (cm2), and steatotic muscle area (cm2). Significant differences between 80 kV and 140 kV series were compared using the paired Students t test. RESULTS Tube potential affected muscle attenuation with an average difference of 17% between 80 kV and 140 kV series (48 HU versus 41 HU, P < 0.01), fat attenuation (-84 HU versus -69 HU, P < 0.01), skeletal muscle index of 5.2% (40.1 cm2/m2 versus 42.2 cm2/m2, P < 0.01), muscle area of 5.1% (117 cm2 versus 123 cm2, P < 0.01), and steatotic muscle area of 12.9% (31 cm2 versus 35 cm2, P < 0.01). CONCLUSION Tube potential significantly affects body segmentation in contrast-enhanced CT.