A retrospective evaluation of patient acceptance of computed tomography colonography ("virtual colonoscopy") in comparison with conventional colonoscopy in an average risk screening population

PURPOSE

To evaluate patient acceptance of computed tomography (CT) colonography compared with conventional colonoscopy by means of a self-assessed questionnaire.

MATERIAL AND METHODS

Four-hundred-and-one patients with valid address information from our patient collective were preselected. Patient acceptance was evaluated retrospectively using a self-assessed questionnaire. The patients underwent CT colonography in our institution using 4x or 16x multi-detector row (MDR) CT. Two-hundred-and-forty-six patients returned a completed questionnaire, 157 of these indicating that they had undergone both virtual and conventional colonoscopy.

RESULTS

One-hundred-and-twenty (76.4%) of the 157 patients would undergo another CT colonography if necessary, while only 14 patients would not. One-hundred-and-sixteen (73.9%) patients favored the actual examination procedure of CT colonography (P<0.0001), while only 6.4% preferred the conventional method. Preparation prior to CT colonography was experienced as more convenient than preparation prior to conventional colonoscopy (52.2% versus 14%).

CONCLUSION

CT colonography was preferred in terms of both preparation and the actual procedure itself.

Enhancing gray-to-white matter contrast in 3T T1 spin-echo brain scans by optimizing flip angle

BACKGROUND AND PURPOSE

Compared with MR imaging at 1.5T T1-weighted spin-echo imaging at 3T shows up with reduced gray-to-white matter contrast. The purpose of the present study was to show the effects of alterations of different flip angles as an easily accessible parameter to increase gray-to-white matter contrast.

METHODS

Spin-echo T1 sequences of 6 healthy volunteers were acquired in a 3T head scanner with 5 different flip angles. Observer-independent contrast-to-noise ratios for gray versus white matter from different flip angles, as well as subjective ratings of image quality from 2 blinded neuroradiologists, were compared statistically.

RESULTS

Gray-to-white matter contrast increased significantly with decreasing flip angle. No artifacts were introduced by decreasing flip angles, and T1 contrast characteristics were robust and stable at lowered flip angles. Also, specific absorption ratios significantly decreased with decreasing flip angles.

CONCLUSION

Using a flip angle of 50 degrees significantly increases gray-to-white matter contrast in T1 spin-echo brain scans at 3T B0 field strength.

Automatic determination of minimal cardiac motion phases for computed tomography imaging: initial experience

Low motion phases for cardiac computed tomography reconstructions are currently detected manually in a user-dependent selection process which is often time consuming and suboptimal. The concept of motion maps was recently introduced to achieve automatic phase selection. This pilot study compared the accuracy of motion-map phase selection to that with manual iterative selection. The study included 20 patients, consisting of one group with low and one with high heart rate. The technique automatically derives a motion strength function between multiple low-resolution reconstructions through the cardiac cycle, with periods of lowest difference between neighboring phases indicating minimal cardiac motion. A high level of agreement was found for phase selection achieved with the motion map approach compared with the manual iterative selection process. The motion maps allowed automated quiescent phase detection of the cardiac cycle in 85% of cases, with best results at low heart rates and for the left coronary artery. They can also provide additional information such as the presence of breathing artifacts. Motion maps show promise as a rapid off-line tool to automatically detect quiescent cardiac phases in a variety of patients.

Multislice MR first-pass myocardial perfusion imaging: impact of the receiver coil array

PURPOSE

To compare a new 12-element body phased-array coil with a conventional four-element surface receiver coil array to provide increased signal-to-noise ratios (SNRs) for cardiac steady state free precession (SSFP) perfusion imaging.

MATERIALS AND METHODS

Thirteen consecutive patients were included in the study. Patients were examined both with a four-element surface coil array and a 12-element body coil array. First-pass myocardial perfusion imaging using saturation recovery SSFP was acquired during antecubital injection of Gd-DTPA. Imaging parameters: TR 2.8 msec/TE 1.3 msec, flip angle 50 degrees , bandwidth 960 Hz/pixel and half-Fourier acquisition. SNR was calculated using six regions of interest (ROI) for the myocardial perfusion scans. Calculations of corresponding ROIs using the two different coil setups were compared using analysis of variance (ANOVA). Semiquantitative perfusion parameters were calculated for both groups.

RESULTS

The mean SNR in myocardial perfusion imaging increased by 21% using the 12-element coil setup (P < 0.001) when compared to the four-element coil. ROI comparisons revealed an increased signal inhomogeneity with the 12-element coil when compared to four-element coil experiments. Absolute normal range values of semiquantitative perfusion parameters were consistently higher using the 12-element coil setup (P < 0.001).

CONCLUSION

The 12-element coil array provides higher SNR, but these improvements come with trade-offs in image homogeneity. Increased SNR translates into higher semiquantitative perfusion values and offers the potential for improved detection of perfusion defects.

CT colonography: comparison of a colon dissection display versus 3D endoluminal view for the detection of polyps

The purpose of this study was to compare sensitivity, specificity, and postprocessing time of a colon dissection approach to regular 3D-endoluminal workup of computed tomography (CT) colonography for the detection of polypoid lesions. Twenty-one patients who had received conventional colonoscopy after CT colonography were selected; 18 patients had either colon polyps or colon cancer and three had no findings. CT colonography was performed using a 4-channel multi-detector-row (MDR) CT in ten cases and a 16-channel MDR-CT in 11 cases. A blinded reader retrospectively evaluated all colonographies using both viewing methods in a randomized order. Thirty-seven polyps were identified by optical colonoscopy. An overall per-lesion sensitivity of 47.1% for lesions smaller than 5 mm, 56.3% for lesions between 5 mm and 10 mm, and 75.0% for lesion larger than 10 mm was calculated using the colon dissection approach. This compared to an overall per-lesion sensitivity of 35.3% (<5 mm), 81.5% (5-10 mm), and 100.0% (>10 mm) using the endoluminal view. The average time consumption for CT colonography evaluation with the colon dissection software was 10 min versus 38 min using the endoluminal view. A colon dissection approach may provide a significant time advantage for evaluation of CT colonography while obtaining a high sensitivity. It is especially superior in the detection of lesions smaller than 5 mm.

Noninvasive coronary angiography with multislice computed tomography

CONTEXT

Multislice computed tomography (MSCT) has recently evolved as a modality for noninvasive coronary imaging.

OBJECTIVE

To assess the accuracy and robustness of MSCT vs the criterion standard of invasive coronary angiography for detection of obstructive coronary artery disease.

DESIGN, SETTING, AND PATIENTS

Prospective, single-center study conducted in a referral center setting in Germany and enrolling 103 consecutive patients (mean age, 61.5 [SD, 9.7] years) from November 2003-August 2004 who were undergoing both invasive coronary angiography and MSCT using a scanner with 16 detector rows.

MAIN OUTCOME MEASURES

Blinded results for both modalities compared using the patient as the primary unit of analysis, with supplementary segment- and vessel-based analyses.

RESULTS

One thousand three hundred eighty-four segments (> or =1.5 mm diameter) were identified by invasive coronary angiography; nondiagnostic image quality of MSCT was identified for only 88 (6.4%) of these segments, mainly due to faster heart rates. Compared with invasive coronary angiography for detection of significant lesions (>50% stenosis), segment-based sensitivity, specificity, and positive and negative predictive values of MSCT were 95%, 98%, 87%, and 99%, respectively. Quantitative comparison of MSCT and invasive coronary angiography showed good correlation (r = 0.87, P<.001), with MSCT systematically measuring greater-percentage stenoses (bias, +12%). In the patient-based analysis, the area under the receiver operating characteristic curve was 0.97 (95% confidence interval, 0.90-1.00), indicating high discriminative power to identify patients who might be candidates for revascularization (>50% left main artery stenosis and/or >70% stenosis in any other epicardial vessel). Threshold optimization allowed either detection of these patients with 100% sensitivity at a reasonable false-positive rate (specificity, 76.5%; MSCT stenosis, >66%) or optimization of both the sensitivity and specificity (>90%; MSCT stenosis, >76%).

CONCLUSIONS

Multislice computed tomography provides high accuracy for noninvasive detection of suspected obstructive coronary artery disease. This promising technology has potential to complement diagnostic invasive coronary angiography in routine clinical care.

[GI hemorrhage with fulminant shock induced by jejunal gastrointestinal stromal tumor (GIST) coincident with duodenal neuroendocrine carcinoma (NET) + neurofibromatosis (NF) -- case report and review of the literature]

BACKGROUND

The incidence of neuroendocrine tumors (NET) and of gastrointestinal stromal tumors (GIST) is 0.5 and 1 - 2 in 100,000; the prevalence of neurofibromatosis is 1 in 3000 live births in Western countries.

CASE REPORT

A 43-year-old white woman with a six-month history of meleana, paleness, vertigo and fatigue was not referred to any gastrointestinal doctor for diagnostic work-up. Finally, she collapsed and was admitted to hospital because of an acute gastrointestinal bleeding. Endoscopically the source of bleeding could not be localized while blood in the duodenum and proximal jejunum was demonstrable. The source of bleeding could not be identified by endoscopy, CT scan or angiography. The patient developed a fulminant gastrointestinal hemorrhage with hemoglobin levels below 3.5 g %. An emergency laparotomy and pylorus-preventing Whipple operation was performed. Pathological studies showed a GIST with 3.5 cm diameter of the proximal jejunum which was the source of bleeding. Coincidentally a neuroendocrine carcinoma of the duodenum was found.

CONCLUSION

This case is the first presentation of the coincidence of a neuroendocrine carcinoma of the duodenum with a jejunal bleeding gastrointestinal stromal tumor in neurofibromatosis type1 which led to hemorrhagic shock. In neurofibromatosis -- even if non-symptomatic -- the increased incidence of tumor needs to be considered.

Ungewöhnlicher Fremdkörper im oberen Gastrointestinaltrakt als Ursache eines unklaren Abdomens

The risk of penetration of vena cava filters through the wall of the vena cava is estimated to be as high as 25%, although clinical symptoms are observed far less frequently in patients with this complication. Due to the close relationship between vena cava and duodenum, the latter can be injured by dislocated filters. We describe the presentation, evaluation, and treatment of a patient with a cava filter protruding into the duodenum, and we review the literature.

Multi-detector row CT: is prospective electrocardiographic triggering improving the detection of small pulmonary tumors?

RATIONALE AND OBJECTIVES

To compare prospectively ECG-triggered multi-detector row computed tomography (ECG-MDR-CT) and multi-detector row computed tomography (MDR-CT) without triggering for the detection of pulmonary tumors.

MATERIALS AND METHODS

100 patients with proven or suspected tumors were referred for CT of the lung for staging of lung metastases. First, a non-enhanced scan was performed using prospective ECG-triggering on a four-row multidetector helical CT scanner, followed by a contrast-enhanced scan without triggering. The diagnostic assessibility in detecting intrapulmonary nodules and mediastinal structures was graded using a 5-point scale (rated 1 = bad to 5 = very good image quality).

RESULTS

ECG-MDR-CT images detected a total of 26% more pulmonary nodules than MDR-CT. For tumors <5 mm, the detection rate was 62% higher using ECG-triggered scans (P = .024). Subjective assessment found median demarcation ratings for all pulmonary findings of 4 (ECG-MDR-CT) versus 3 (MDR-CT). Mediastinal structures were delineated better using ECG triggering. The median ranking for demarcation of pulmonary findings <10 mm was 4 on ECG-MDR-CT and 3 on MDR-CT, respectively. For vessels and the left bronchus, the median of demarcation was 4 on triggered images and 2 on MDR-CT, respectively. The median values referring to the demarcation of mediastinal structures were not significantly different between ECG-MDR-CT and MDR-CT.

CONCLUSION

Our data indicate the superiority of prospectively triggered ECG-MDR-CT over MDR-CT for the diagnosis of small pulmonary tumors using a 4-row multidetector CT.

Numerical simulation of air temperature and airflow patterns in the human nose during expiration

Recovery of heat and water during expiration is an important but not yet fully understood function of the nose. The presented study investigated cooling of the expiratory air for heat recovery within the human nose applying numerical simulation. A numerical simulation in a bilateral three-dimensional model of the human nose based on computed tomography was employed. Temperature distribution and airflow patterns during expiration were displayed. Cooling of the expiratory air primarily takes place in the areas of inferior and middle turbinate. Areas of the highest decrease in temperature are characterized by turbulent airflow with vortices of low velocity. Numerical results showed good concordance with experimental in vivo temperature measurements. Heating of inspired air not only depends on inspiration but also on expiration. Cooling the warm expiratory air may be regarded as an important factor for heat recovery. Furthermore, the results demonstrate the close relation between heat exchange and airflow patterns.

Lokale Radiofrequenzablation von Leberherden - Möglichkeiten und Grenzen

Radiofrequency ablation (RFA) is currently the most established technique for the local destruction of tumors within the liver. It is technically straightforward, can be repeated and combines a high efficiency in tissue destruction with a low to moderate incidence of complications. This review explains the principle of RFA and lists currently available systems. In addition, the rationale behind RFA is discussed, and an overview of clinical indications, results and complications is presented. One of the main problems in assessing the clinical value of RFA is the fact that no large and controlled randomized studies are available, while the number of ablations and treated tumor entities are steadily increasing. From a technical point of view, the major problem is the still limited volume of necrosis that is achievable. The indication for RFA has to be discussed as interdisciplinary. A complete tumor necrosis should be the aim of all ablations, with the exception of symptomatic metastases of neuroendocrine tumors. The value of additional chemotherapy to RFA is still unclear, especially in the treatment of liver metastases.

Noninvasive coronary angiography with 16-detector row CT: effect of heart rate

PURPOSE

To evaluate the effect of heart rate on the quality of coronary angiograms obtained with 16-detector row computed tomography (CT) by using temporally enhanced three-dimensional (3D) approaches.

MATERIALS AND METHODS

The local ethics committee approved the study, and informed consent was obtained from all patients. Fifty patients underwent coronary CT angiography (heart rate range, 45-103 beats per minute). Raw data from helical CT and electrocardiography (ECG) were saved in a combined data set. Retrospectively ECG-gated images were reconstructed at preselected phases (50% and 80%) of the cardiac cycle. A 3D voxel-based approach with cardiac phase weighting was used for reconstruction. Testing for correlation between heart rate, cardiac phase reconstruction window, and image quality was performed with Kruskal-Wallis analysis. Image quality (freedom from cardiac motion-related artifacts) was referenced against findings at conventional angiography in a secondary evaluation step. Regression analysis was performed to calculate heart rate thresholds for future beta-blocker application.

RESULTS

A significant negative correlation was observed between heart rate and image quality (r = 0.80, P < .001). Motion artifact-free images were available for 44 (88%) patients and were achieved consistently at a heart rate of 80 or fewer beats per minute (n = 39). Best image quality was achieved at 75 or fewer beats per minute. Segmental analysis revealed that 97% of arterial segments (diameter > or = 1.5 mm according to conventional angiography) were assessable at 80 or fewer beats per minute. Premature ventricular contractions and rate-contained arrhythmia did not impede diagnostic assessment of the coronary arteries in 10 (83%) of the 12 patients affected.

CONCLUSION

Motion-free coronary angiograms can be obtained consistently with 16-detector row CT scanners and adaptive multicyclic reconstruction algorithms in patients with heart rates of less than 80 beats per minute.

Effect of iodine concentration of contrast media on contrast enhancement in multislice CT of the pancreas

The purpose of this study was to determine the influence of two different iodine concentrations of the non-ionic contrast agent, Iomeprol, on contrast enhancement in multislice CT (MSCT) of the pancreas. To achieve this MSCT of the pancreas was performed in 50 patients (mean age 57+/-14 years) with suspected or known pancreatic tumours. The patients were randomly assigned to group A (n=25 patients) or group B (n=25 patients). There were no statistically significant differences in age, height or weight between the patients of the two groups. The contrast agent, Iomeprol, was injected with iodine concentrations of 300 mg ml(-1) in group A (130 ml, injection rate 5 ml s(-1)) and 400 mg ml(-1) in group B (98 ml, injection rate 5 ml s(-1)). Arterial and portal venous phase contrast enhancement (HU) of the vessels, organs, and pancreatic masses were measured and a qualitative image assessment was performed by two independent readers. In the arterial phase, Iomeprol 400 led to a significantly greater enhancement in the aorta, superior mesenteric artery, coeliac trunk, pancreas, pancreatic carcinomas, kidneys, spleen and wall of the small intestine than Iomeprol 300. Portal venous phase enhancement was significantly greater in the pancreas, pancreatic carcinomas, wall of the small intestine and portal vein with Iomeprol 400. The two independent readers considered Iomeprol 400 superior over Iomeprol 300 concerning technical quality, contribution of the contrast agent to the diagnostic value, and evaluability of vessels in the arterial phase. No differences were found for tumour delineation and evaluability of infiltration of organs adjacent to the pancreas between the two iodine concentrations. In conclusion the higher iodine concentration leads to a higher arterial phase contrast enhancement of large and small arteries in MSCT of the pancreas and therefore improves the evaluability of vessels in the arterial phase.

Numerical simulation of airflow patterns and air temperature distribution during inspiration in a nose model with septal perforation

BACKGROUND

The most typical symptoms of patients with nasal septal perforation (SP) are crusting and recurrent nosebleed. The objective of the study was to determine the influence of SP on intranasal temperature profile and airflow patterns during inspiration by means of numerical simulation.

METHODS

Two realistic bilateral models of the human nose with and without SP were reconstructed based on computed tomography (CT). A numerical simulation was performed. The intranasal air temperature distribution and airflow patterns during inspiration were displayed, analyzed, and compared.

RESULTS

SP causes a highly disturbed airflow in the area of perforation. A spacious vortex within the perforation including various localized vortices was detected. A disturbed intranasal temperature distribution between the right and left nasal cavities developed.

CONCLUSIONS

The numerical simulation demonstrates the interaction between airflow patterns and heating of respiratory air. The disturbed airflow causes reduced air conditioning. This fact may contribute to crusting and recurrent nosebleed.

[CT colonography --"virtual colonoscopy"--a current review]

This article reviews published data regarding CT colonography and discusses both technical and medical aspects of its development over the last 10 years. Although colonography can be performed using MRI instead of CT, mainly CT aspects are dealt with. The technical development of CT to the current generation of Multi-detector-row-CT is explained, and the influence of various factors (slice thickness, dose, patient preparation, post processing) is discussed. The method has a high sensitivity and specificity as well as a high negative predictive value for the detection of polyps > or = 1 cm, but is currently still insufficient in the detection of polyps < 5 mm. It is a valid alternative after incomplete optical colonoscopy and an alternative in patients with "high-risk" for conventional endoscopy. In the future it may become an alternative for conventional endoscopy in screening programs for colorectal cancer.

Multislice CT imaging of anomalous coronary arteries

The purpose of the present study was to evaluate the role of 16 multislice computed tomography (MSCT) to identify the origin of anomalous coronary arteries and to confirm their anatomic course in relation to the great vessels. Accuracy of coronary artery disease (CAD) detection was a secondary aim and was tested with conventional angiograms (CA) serving as standard of reference. Two hundred and forty-two consecutive patients referred for noninvasive coronary CT imaging were reviewed for the study. Sixteen patients (6.6%) with anomalous coronary arteries were detected and included as the study group. MSCT and CA images were analyzed in a blinded fashion for accuracy of anomalous artery origin and path detection. Results were compared in a secondary consensus evaluation. Accuracy ratios to detect CAD with MSCT in all vessels were calculated. Coronary anomalies for all 16 patients were correctly displayed on MSCT. CA alone achieved correct identification of the abnormality in only 53% (P=0.016). Sensitivity and specificity of MSCT to detect significantly stenosed vessels was 90 and 92%. 16-MSCT is accurate to delineate abnormally branching coronary arteries and allows sufficiently accurate detection of obstructive coronary artery disease in distal branches. It should therefore be considered as a prime non-invasive imaging tool for suspected coronary anomalies.

[Abdominal trauma. Injury oriented management]

Successful management of abdominal trauma is characterized by efficient emergency-room work-up aimed at immediate determination of the prognosis by rational use of diagnostic techniques. The purposes of any conservative and/or surgical procedures are the preservation of organ function and low mortality and morbidity in multiply injured patients. State-of-the-art computed tomography with fast trauma scanning has become well accepted among patients with multiple trauma. Organ resections are becoming less common, except in the case of bowel injuries. The surgical treatment of hepatobiliary, splenic and large-vessel trauma is still challenging, as it involves the risk of life-threatening bleeding, while in the case of pancreatic and bowel injuries the challenge lies in the avoidance of septic complications. Interdisciplinary management of complex injuries with application of the "damage control" concept contributes to high-quality results in abdominal trauma.

Minimally invasive intervention for acute bleeding from a pseudoaneurysm after revision hip arthroplasty

After multiple revisions of her right hip arthroplasty, an 83-year-old woman developed deep infection with a chronic draining sinus. In August 2002 severe acute bleeding occurred through this fistula. Angiography revealed a pseudoaneurysm of the right external iliac artery. Because of the multiple pathologies affecting this ASA grade IV patient, conventional surgical treatment was considered to be contra-indicated, and a stent was placed percutaneously under fluoroscopic control to seal the vascular laceration. No haematoma and no further bleeding was observed on the control CT-scan or at angiography. However the patient died with terminal renal failure forty days later. The case reported shows a rare complication of total hip arthroplasty. The method used in this case to seal the leakage, using a covered stent, is uncommon but effective in cases where conventional surgery is contra-indicated.

Comparison of MR imaging sequences for liver and head and neck interventions

RATIONALE AND OBJECTIVES

To compare the appropriate pulse sequences for interventional device guidance during magnetic resonance (MR) imaging at 0.2 T and to evaluate the dependence of sequence selection on the anatomic region of the procedure.

MATERIALS AND METHODS

Using a C-arm 0.2 T system, four interventional MR sequences were applied in 23 liver cases and during MR-guided neck interventions in 13 patients. The imaging protocol consisted of: multislice turbo spin echo (TSE) T2w, sequential-slice fast imaging with steady precession (FISP), a time-reversed version of FISP (PSIF), and FISP with balanced gradients in all spatial directions (True-FISP) sequences. Vessel conspicuity was rated and contrast-to-noise ratio (CNR) was calculated for each sequence and a differential receiver operating characteristic was performed.

RESULTS

Liver findings were detected in 96% using the TSE sequence. PSIF, FISP, and True-FISP imaging showed lesions in 91%, 61%, and 65%, respectively. The TSE sequence offered the best CNR, followed by PSIF imaging. Differential receiver operating characteristic analysis also rated TSE and PSIF to be the superior sequences. Lesions in the head and neck were detected in all cases by TSE and FISP, in 92% using True-FISP, and in 84% using PSIF. True-FISP offered the best CNR, followed by TSE imaging. Vessels appeared bright on FISP and True-FISP imaging and dark on the other sequences.

CONCLUSION

In interventional MR imaging, no single sequence fits all purposes. Image guidance for interventional MR during liver procedures is best achieved by PSIF or TSE, whereas biopsies in the head and neck are best performed using FISP or True-FISP sequences.