Imaging algorithms and CT protocols in trauma patients: survey of Swiss emergency centers.

OBJECTIVES: To identify imaging algorithms and indications, CT protocols, and radiation doses in polytrauma patients in Swiss trauma centres. METHODS: An online survey with multiple choice questions and free-text responses was sent to authorized level-I trauma centres in Switzerland. RESULTS: All centres responded and indicated that they have internal standardized imaging algorithms for polytrauma patients. Nine of 12 centres (75 %) perform whole-body CT (WBCT) after focused assessment with sonography for trauma (FAST) and conventional radiography; 3/12 (25 %) use WBCT for initial imaging. Indications for WBCT were similar across centres being based on trauma mechanisms, vital signs, and presence of multiple injuries. Seven of 12 centres (58 %) perform an arterial and venous phase of the abdomen in split-bolus technique. Six of 12 centres (50 %) use multiphase protocols of the head (n = 3) and abdomen (n = 4), whereas 6/12 (50 %) use single-phase protocols for WBCT. Arm position was on the patient`s body during scanning (3/12, 25 %), alongside the body (2/12, 17 %), above the head (2/12, 17 %), or was changed during scanning (5/12, 42 %). Radiation doses showed large variations across centres ranging from 1268-3988 mGy*cm (DLP) per WBCT. CONCLUSIONS: Imaging algorithms in polytrauma patients are standardized within, but vary across Swiss trauma centres, similar to the individual WBCT protocols, resulting in large variations in associated radiation doses. KEY POINTS: • Swiss trauma centres have internal standardized imaging algorithms for trauma patients • Whole-body CT is most commonly used for imaging of trauma patients • CT protocols and radiation doses vary greatly across Swiss trauma centres.

Advanced virtual monoenergetic images: improving the contrast of dual-energy CT pulmonary angiography.

AIM: To investigate the value of advanced virtual monoenergetic image reconstruction (mono-plus) from dual-energy computed tomography (CT) for improving the contrast of CT pulmonary angiography (CTPA). MATERIALS AND METHODS: Forty consecutive patients (25 women, mean 62.5 years, range 28-87 years) underwent 192-section dual-source CTPA with dual-energy CT (90/150 SnkVp) after the administration of 60 ml contrast media (300 mg iodine/ml). Conventional virtual monochromatic images at 60 keV and 17 mono-plus image datasets from 40-190 keV (in 10 keV steps) were reconstructed. Subjective image quality (artefacts, subjective noise) was rated. Attenuation was measured in the pulmonary trunk and in the right lower lobe pulmonary artery; noise was measured in the periscapular musculature. The signal-to-noise (SNR) and contrast-to-noise ratios (CNR) were calculated for each patient and dataset. Comparisons between monochromatic images and mono-plus images were performed by repeated measures analysis of variance (ANOVA) with post-hoc Bonferroni correction. RESULTS: Interreader agreement was good to excellent for subjective image quality (ICC: 0.616-0.889). As compared to conventional 60 keV images, artefacts occurred less (p=0.001) and subjective noise was rated lower (p<0.001) in mono-plus 40 keV images. Noise was lower (p<0.001), and the SNR and CNR in the pulmonary trunk and right lower lobe pulmonary artery were higher (both, p<0.001) in mono-plus 40 keV images compared to conventional monoenergetic 60 keV images. Transient interruption of contrast (TIC) was found in 14/40 (35%) of patients, with subjective contrast being similar 8/40 (20%) or higher 32/40 (80%) in mono-plus 40 keV as compared to conventional monoenergetic 60 keV images. CONCLUSIONS: Compared to conventional virtual monoenergetic imaging, mono-plus images at 40 keV improve the contrast of dual-energy CTPA.

Advanced modelled iterative reconstruction for abdominal CT: qualitative and quantitative evaluation.

AIM: To determine qualitative and quantitative image-quality parameters in abdominal imaging using advanced modelled iterative reconstruction (ADMIRE) with third-generation dual-source 192 section CT. MATERIALS AND METHODS: Forty patients undergoing abdominal portal-venous CT at different tube voltage levels (90, 100, 110, and 120 kVp, n = 10 each) and 10 consecutive patients undergoing abdominal non-enhanced low-dose CT (100 kVp, 60 mAs) using a third-generation dual-source 192 section CT machine in the single-source mode were included. Images were reconstructed with filtered back projection (FBP) and ADMIRE (strength levels 1-5). Two blinded, independent readers subjectively determined image noise, artefacts, visibility of small structures, and image contrast, and measured attenuation in the liver, spleen, kidney, muscle, fat, and urinary bladder, and objective image noise. RESULTS: Subjective noise was significantly lower and image contrast significantly higher for each increasing ADMIRE strength level and also for ADMIRE 1 compared to FBP (all, p < 0.001). No significant differences were found for artefact and visibility ratings among image sets (all, p > 0.05). Attenuation was similar across tube voltage-image datasets in all anatomical regions (all, p > 0.05). Objective noise was significantly lower for each increasing ADMIRE strength level, and for ADMIRE 1 compared to FBP (all, p < 0.001, maximal reduction 53%). Independent predictors of noise were tube voltage (p < 0.05) and current (p < 0.001), diameter (p < 0.05), and reconstruction algorithm (p<0.001); the amount of noise reduction was related only to the reconstruction algorithm (p < 0.001). CONCLUSION: Abdominal CT using ADMIRE results in an improved image quality with lower image noise as compared with FBP, while the attenuation of various anatomical regions remains constant among reconstruction algorithms.

[Computed tomography for imaging of pediatric congenital heart disease]. / Die Computertomographie bei der Bildgebung von Kindern mit kongenitalen Herzvitien.

Congenital heart diseases are the most common congenital abnormalities of development. In general, echocardiography and cardiac catheter angiography are considered the gold standard for the evaluation of congenital heart disease. Cardiac magnetic resonance imaging has become an important supplementary imaging modality because of its ability to provide an accurate morphological and functional evaluation. The role of cardiac computed tomography in the imaging of patients with congenital heart disease is becoming increasingly more important due to the development of low radiation dose protocols and improvements in the spatial and temporal resolution. In the preoperative depiction and follow-up after surgical repair of congenital heart diseases, cardiac computed tomography provides detailed information of the heart, the venous and arterial pulmonary circulation as well as systemic arteries. This article reviews the technical aspects of cardiac CT and the modification of examination protocols according to the expected pathology and patient age. The potentials and limitations of the various radiation dose reduction strategies are outlined.

Mitral annular disjunction in patients with severe aortic stenosis: Extent and reproducibility of measurements with computed tomography.

OBJECTIVES: To determine with CT the prevalence and extent of mitral annular disjunction (MAD) in patients undergoing transcatheter aortic valve replacement (TAVR) and its association with mitral valve disease and arrhythmia. METHODS: We retrospectively evaluated 408 patients (median age, 82 years; 186 females) with severe aortic stenosis undergoing ECG-gated cardiac CT with end-systolic data acquisition. Baseline and follow-up data were collected in the context of a national registry. Two blinded, independent observers evaluated the presence of MAD on multi-planar reformations. Maximum MAD distance (left atrial wall-mitral leaflet junction to left ventricular myocardium) and circumferential extent of MAD were assessed on CT using dedicated post-processing software. Associated mitral valve disease was determined with echocardiography. RESULTS: 7.8 % (32/408) of patients with severe aortic stenosis had MAD. The maximum MAD was 3.5 mm (interquartile range: 3.0-4.0 mm). The circumferential extent of MAD comprised 34 ±â€¯15 % of the posterior and 26 ±â€¯12 % of the entire mitral annulus. Intra- and interobserver agreement for the detection of MAD on CT were excellent (kappa: 0.90 ±â€¯0.02 and 0.92 ±â€¯0.02). Mitral regurgitation (p = 1.00) and severe mitral annular calcification (p = 0.29) were similarly prevalent in MAD and non-MAD patients. Significantly more patients with MAD (6/32; 19 %) had mitral valve prolapse compared to those without (6/376; 2 %; p < 0.001). MAD was not associated with arrhythmia before and after TAVR (p > 0.05). CONCLUSIONS: Using CT, MAD was found in 7.8 % of patients with severe aortic stenosis, with a higher prevalence in patients with mitral valve prolapse. We found no association of MAD with arrhythmia before or after TAVR.

Evaluation of an acetated Ringer-based contrast material mixture for postmortem computed tomography angiography.

PURPOSE: The purpose of this study was to compare an established postmortem contrast medium mixture based on polyethylene glycol (PEG) to an isotonic crystalloid with acetated Ringer solution (AR) as the base, both mixed with water-soluble iodinated contrast medium for postmortem computed tomography angiography (PMCTA) with the aim to avoid alterations of the corpse during autopsy. MATERIALS AND METHODS: The study included 20 cadavers; 10 had PMCTA with AR and 10 with PEG. PMCTA images were analyzed with respect to image quality, vascular contrast patterns and artifacts. Autopsy was evaluated for visual, organ, vessel and haptic alterations. The Wilcoxon rank sum test was used to search for differences in image quality between the two groups. Statistical significance was set at P<0.05. RESULTS: AR provided excellent contrast within the right coronary artery (P<0.001) but a lack of contrast within the left coronary artery (P=0.008) whereas PEG showed the opposite. A better image quality was observed in the PEG group by comparison with the AR group for right common carotid artery (P=0.03), left common carotid artery (P=0.01) and left coronary artery (P=0.008). No differences were found for ascending aorta (P=0.65), aortic arch (P=0.09), right circle of Willis (P=0.17), left circle of Willis (P=0.08), inferior vena cava (P=0.07) and abdominal aorta (P=0.08). Severe extravasation occurred in all (10/10; 100%) cadavers in the AR group but in none (0/10; 0%) in the PEG group (P<0.001). At autopsy, visual alteration with lilac discoloration of the face was observed in 4/10 cadavers (40%) in the AR group and in 9/10 cadavers (90%) in the PEG group (P=0.057). Haptic alterations were observed in 3/10 cadavers (30%) in the AR group and 10/10 cadavers (100%) in the PEG group (P=0.003). CONCLUSION: AR results in contrast medium mixture extravasation in all cadavers, but PEG altered the autopsy more severely. Both carrier substances result in specific substance-related artifacts and dependent opacification of the coronary arteries, but PEG is recommended for PMCTA exclusively with regard to diagnostic imaging.

[Influence of body mass index on coronary artery opacification in 64-slice CT angiography]. / Einfluss des Bodymass-Index auf den Kontrast in den Koronararterien mit der 64-Schicht-CT.

PURPOSE: To evaluate the influence of the body mass index (BMI) on coronary artery opacification in 64-slice CT. MATERIAL AND METHODS: Sixty-two patients retrospectively underwent ECG-gated 64-slice CT coronary angiography (tube potential 120 kV, tube current time product 650 mAs) after intravenous injection of 80 ml of iodinated contrast agent (320 mg/ml, 5 ml/s). Attenuation values (HU) were measured and contrast-to-noise ratios (CNR) were calculated in the right coronary artery (RCA) and left main artery (LMA). The CNR was defined as the difference between the mean attenuation in the vessel and the mean attenuation in the perivascular fat tissue divided by the image noise in the ascending aorta. The height and weight of the patients at the time of the CT scan were recorded and the BMI was calculated. RESULTS: The mean BMI was 26.2 +/- 3.2 kg/m (2) (range 19.7 - 32.2 kg/m (2)), the mean attenuation in the LMA was 330 +/- 64 HU, and the mean attenuation in the RCA was 309 +/- 68 HU. The CNR in the LMA was 16.7 +/- 3.8, and the CNR in the RCA was 15.9 +/- 3.6. The image noise in the ascending aorta significantly correlated with the BMI (r = 0.36, p < 0.01). A weak negative correlation was found between the BMI and LMA attenuation (r = - 0.28, p < 0.05), whereas no significant correlation was found for the RCA (r = - 0.21, p = 0.12). A significant negative correlation was found between the BMI and the CNR in the RCA (r = - 0.41, p < 0.05) and the LMA (r = - 0.47, p < 0.001). CONCLUSION: With constant scan parameters and a constant contrast medium amount, the CNR in both coronary arteries decreases while the BMI increases. This implies a modification of previously standardized and fixed examinations with respect to individually adapted protocols with variable parameters for CT coronary angiography.

Coronal ultra-thick multiplanar CT reconstructions (MPR) of the pelvis in the multiple trauma patient: an alternative for the initial conventional radiograph.

PURPOSE: Multiple trauma patients with clinically suspected pelvic fractures often directly undergo a CT scan. However, the initial portable pelvis film (PPF) for further follow-up is then not available. This study examines whether coronal ultra-thick multiplanar reconstructions from CT data are similar when compared with the initial PPF, thus having the potential to serve as an alternative baseline image. MATERIALS AND METHODS: Initial PPF and coronal ultra-thick multiplanar CT reconstructions of 33 multiple trauma patients with pelvic fractures were retrospectively analyzed by two independent radiologists with regard to image quality, visualization of anatomical landmarks, and diagnostic accuracy. The primary diagnosis of pelvic fractures was made by using thin axial CT images and thin slice coronal and sagittal reconstructions and served as the standard of reference. RESULTS: Coronal ultra-thick multiplanar CT reconstructions were superior to PPF regarding image adjustment (p < 0.02), absence of overlaying structures (p < 0.05), and overall image quality (p < 0.01). Visualization of most anatomical landmarks was similar with both modalities, except of the iliosacral joint and acetabular lines which were more accurately depicted on ultra-thick multiplanar CT reconstructions (p < 0.05). Diagnostic accuracy of coronal ultra-thick CT reconstructions was similar to PPF regarding most fracture types, except of a higher accuracy of coronal ultra-thick CT reconstructions for iliosacral joint and acetabular column fractures (p < 0.05). CONCLUSION: Coronal ultra-thick multiplanar CT reconstructions of the pelvis provide similar image quality and diagnostic accuracy compared to PPF and are therefore suited as alternative baseline image in multiple trauma patients who directly undergo CT.

[Severe, reversible cerebral ischaemia following a diving accident]. / Schwere, reversible zerebrale Ischämie nach Tauchunfall.

CASE HISTORY AND CLINICAL FINDINGS: A 33-year-old experienced female diver complained of headache and chest pain when emerging after a dive. When she was rescued, tetraplegia, clouding of consciousness and aphasia were stated. The first measures consisted in the securing of the vital functions and the immediate administration of pure oxygen. Then she was transferred to the next hospital. During the 7-hour-transfer the sensory disturbances and the palsy of the left body side improved. EXAMINATIONS: Computed tomography with contrast agent revealed a subcortical parieto-occipital brain edema in the left hemisphere without midline shift. Additionally a magnetic resonance imaging (MRI) after the second pressure chamber treatment showed a smaller brain edema on the right side. DIAGNOSIS, THERAPY AND COURSE: The findings supported the diagnosis of decompression sickness type II. On the evening after the diving accident a generalised seizure occurred. Due to repeated cerebral seizures 20 mg of diazepam were administered. This was followed by a transport to the next health facility with a pressure chamber.  After two pressure chamber treatments within 24 hours the clinical symptoms disappeared, the neurological examination was unremarkable and MRI had returned to normal. CONCLUSION: An acute decompression sickness is diagnosed purely clinically. In case of even the slightest suspicion the patient should be transported to a health facility with a pressure chamber as quickly as possible because this significantly improves prognosis. Up to that point, the administration of pure oxygen is indicated. Imaging methods realised within the first hours/days are valuable for securing the diagnosis. Follow-up MRI-scans serve to reflect the course of the disease.

Surgical treatment of unruptured intracranial aneurysms in a low-volume hospital--outcome and review of literature.

BACKGROUND: The aim of this study was to evaluate surgical outcome of unruptured intracranial aneurysms (UIAs) in a low-volume hospital and compare the results with the recent literature. METHODS: A retrospective review of all consecutive craniotomies for UIA from July 1999 through June 2009 was performed. Morbidity was defined as modified Rankin Scale (mRS) ≥ 3 and evaluated six weeks after surgery. Cognitive function was evaluated at rehabilitation-to-home discharge. A PubMed database search (2001-2011) seeking retrospective, single-center studies reporting on surgical outcome of UIAs was performed. RESULTS: There were 47 procedures performed in 42 patients to treat 50 UIAs (mean of 5 annual craniotomies). The mean age was 54.7 ± 12.1 years and mean aneurysm size was 7.6 ± 4.0mm. Favorable outcome (mRS 0-2) at six weeks after surgery was achieved in 45 of 47 procedures (95.7%). Aneurysm size ≥ 12 mm was statistically significant related to adverse outcome defined as mRS change ≥ 1 (71% vs. 29%; p = 0.018). Five patients (10.6%) with favorable neurological outcome (mRS 2) presented with cognitive impairment at rehabilitation-to-home discharge. There was no significant difference in overall morbidity and mortality comparing low- and high-volume hospitals (4.0% vs. 4.8%; p = 0.85). CONCLUSIONS: Low-volume hospitals may achieve good results for surgical treatment of UIAs. The results indicate that defining numeric operative volume thresholds is not feasible to guide centralization of aneurysm treatment.

[Use of multislice CT in the evaluation of patients with acute chest pain]. / Die Abklärung des akuten Thoraxschmerzes mit der Computertomographie.

Acute chest pain is a common symptom but triage decisions in these patients remain a challenge. Patient's history, cardiac enzyme levels, or electrocardiograms often are unspecific. Nowadays, multidetector-row computed tomography (CT) currently represents the imaging modality of choice for diagnosing or excluding pulmonary embolism (PE) or acute aortic syndrome (AAS). Furthermore, recent studies have demonstrated advantages for non-invasive imaging of the coronary arteries by CT. The so called triple rule-out CT allows the depiction of the pulmonary arteries, the thoracic aorta, and the coronary arteries within a single examination with a simultaneous attenuation of these three vessel territories. This enables the detection of life-threatening such as PE, AAS and ACS, as well as of non-life-threatening diseases causing acute chest pain.

[Cardiac low-dose computed tomography]. / Kardiale Niedrigdosis-Computertomographie.

Cardiac CT has evolved to a robust and accurate imaging modality in the cardiac diagnostic armamentarium. However, technical developments had been accompanied with an overall increase in radiation exposure. In the last years, several technical developments and algorithms aimed at the reduction of radiation exposure in cardiac CT. The most relevant dose reduction strategies will be highlighted in this article including appropriate indications for cardiac CT, different ECG synchronization techniques, reduction of tube voltage, and high-pitch CT studies.

Impact of vessel attenuation on quantitative coronary angiography with 64-slice CT.

The aim of the study was to determine the impact of vessel attenuation on quantitative 64-slice computed tomography coronary angiography (CTCA). CTCA and invasive quantitative coronary angiography (QCA) were performed in 100 consecutive patients (42 women, 58 men; mean age 64.4+/-9.4 years; age range 39-87 years). In QCA, stenoses were quantified with dedicated software, whereas in CTCA, stenosis severity was assessed with an electronic caliper tool: stenoses were graded in 10% steps and assigned as either a calcified or non-calcified lesion. Vessel attenuation in the left main (LMA) and the proximal right coronary artery (RCA) were measured and correlated with differences in quantifications of stenosis grade between QCA and CTCA. A total of 113 coronary stenoses were detected by both methods (94 significant and 19 non-significant); 52 stenoses were rated as non-calcified and 61 as calcified lesions. The mean difference between QCA and quantitative CTCA grading was 5.1+/-16.9% (range -27 to 46%) overall; 1.9+/-14.2% (range -27 to 38%) for non-calcified lesions and 7.8+/-18.6% (range -23 to 46%) for calcified lesions. Mean vessel attenuation was 362+/-76 HU (range 191-584 HU) in the LMA and 333+/-81 HU (range 162-564 HU) in the RCA. Attenuation did not significantly correlate with differences in QCA and CTCA gradings, neither overall nor for calcified or non-calcified lesions. When 64-slice CTCA is used, coronary vessel attenuation had no impact on the quantitative grading of stenoses.

Multislice computed tomography coronary angiography for risk stratification in patients with an intermediate pretest likelihood.

OBJECTIVES: To assess whether multislice computed tomography coronary angiography (MSCTA) may be useful for risk stratification of patients with suspected coronary artery disease (CAD) at intermediate pretest likelihood according to Diamond and Forrester. DESIGN AND PATIENTS: MSCTA images were evaluated for the presence of significant CAD in 316 patients with suspected CAD (60% male, average (SD) age 57 (11) years) and an intermediate pretest likelihood according to Diamond and Forrester. Patients were followed up to determine the occurrence of an event. MAIN OUTCOME MEASURES: A combined end point of all-cause mortality, non-fatal infarction and unstable angina requiring revascularisation. RESULTS: Significant CAD was seen in 89 patients (28%), whereas normal MSCTA or non-significant CAD was seen in the remaining 227 (72%) patients. During follow-up (median 621 days (25-75th centile 408-835) an event occurred in 13 patients (4.8%). The annualised event rate was 0.8% in patients with normal MSCT, 2.2% in patients with non-significant CAD and 6.5% in patients with significant CAD. Moreover, MSCTA remained a significant predictor (p<0.05) of events after multivariate correction (hazard ratio = 3.460 (95% CI 1.142 to 10.480). CONCLUSIONS: The results suggest that in patients with an intermediate pretest likelihood, MSCTA is highly effective in re-stratifying patients into either a low or high post-test risk group. These results further emphasise the usefulness of non-invasive imaging with MSCTA in this patient population.

Combining dual-source computed tomography coronary angiography and calcium scoring: added value for the assessment of coronary artery disease.

OBJECTIVE: To prospectively investigate the diagnostic accuracy of dual-source 64-slice computed tomography coronary angiography (CTCA), calcium scoring (CS) and both methods combined for assessing significant coronary artery stenoses relative to conventional coronary angiography (CCA). DESIGN, SETTING AND PATIENTS: Prospective, single-centre study conducted in a referral centre enrolling 74 consecutive patients (24 women; mean age 62 (SD 12) years) from August-October 2006. All study participants underwent CS, CTCA and CCA. Diagnostic accuracy was calculated for CS, CTCA and both methods combined relative to CCA. Not-evaluative segments at computed tomography were considered false positive. RESULTS: CCA identified 139 stenoses in 36 patients. Average heart rate during CTCA was 68 (13) bpm (range 35-102 bpm), and 2% of segments (21/1001) in 11% of patients (8/74) were not evaluative. Considering these as false positives, per-patient sensitivity and specificity was 98% and 87%. When using CS cut-off values of 0 to exclude and >or=400 to predict stenosis, sensitivity and specificity of CS was 100% and 70%, respectively. Combining CS and CTCA in all patients correctly reclassified five patients, while six were falsely classified as stenotic, all of them correctly classified with CTCA alone. Using CS only in patients with not-evaluative segments correctly reclassified five patients while avoiding misclassifications (sensitivity 98%, specificity 100%). CONCLUSION: Dual-source CTCA allows the diagnosis of significant stenoses with a high diagnostic accuracy. Selectively combining CS with CTCA in patients with not-evaluative coronary segments improves specificity from 87% to 100% without decreasing the high sensitivity of 98%.

Low-dose CT coronary angiography in the step-and-shoot mode: diagnostic performance.

OBJECTIVE: To investigate the performance of low-dose, dual-source computed tomography (DSCT) coronary angiography in the step-and-shoot (SAS) mode for the diagnosis of significant coronary artery stenoses in comparison with conventional coronary angiography (CCA). DESIGN, SETTING AND PATIENTS: Prospective, single-centre study conducted in a referral centre enrolling 120 patients (71 men, mean (SD) age 68 (9) years, mean (SD) body mass index 26.2 (3.2) kg/m2). All study participants underwent DSCT in the SAS mode and CCA within 14 days. Twenty-seven patients were given intravenous beta blockers for heart rate reduction before CT. Patients were excluded if a target heart rate 50%) stenoses. Sensitivity, specificity, negative (NPV) and positive predictive values (PPV) were determined, with CCA being the standard of reference. Radiation dose values were calculated. RESULTS: DSCT coronary angiography in the SAS mode was successfully performed in all 120 patients. Mean (SD) heart rate during scanning was 59 (6) bpm (range 44-69). 1773/1803 coronary segments (98%) were depicted with a diagnostic image quality in 109/120 patients (91%). The overall patient-based sensitivity, specificity, PPV and NPV for the diagnosis of significant stenoses were 100%, 93%, 94% and 100%, respectively. The mean (SD) effective dose of the CT protocol was 2.5 (0.8) mSv (range 1.2-4.4). CONCLUSIONS: DSCT coronary angiography in the SAS mode allows, in selected patients with a regular heart rate, the accurate diagnosis of significant coronary stenoses at a low radiation dose.