Oral distension methods for small bowel MRI: comparison of different agents to optimize bowel distension.

Background Different methods for bowel distension prior to magnetic resonance imaging (MRI) examinations were described in recent years. Purpose To compare orally administered psyllium or locust bean gum / mannitol (LBM) with tylose administered through a duodenal catheter for bowel distension in patients undergoing MRI examination of the small bowel. Material and Methods Three different methods of bowel distension prior to MRI were compared: tylose applied through a duodenal catheter and orally administered psyllium and LBM in three groups with 15 patients each. Datasets were blinded and reviewed independently by two experienced radiologists, who assessed the diagnostic value and the maximum luminal diameter. Results Tylose was superior to psyllium and LBM in the examination of the duodenum and proximal jejunum. LBM was superior to the other methods for distension of the ileum and terminal ileum. The greatest luminal diameter of the duodenum was achieved after tylose and distension of the terminal ileum was the best in patients receiving LBM. The psyllium group was inferior to the other two groups in all segments. Conclusion By using LBM as an oral method of bowel distension, many patients can avoid the unpleasant placement of a duodenal catheter without compromising the diagnostic value of the examination.

Diffusion-weighted MR imaging in comparison to integrated [¹8F]-FDG PET/CT for N-staging in patients with lung cancer.

PURPOSE: The purpose of this study was to prospectively determine the diagnostic accuracy of diffusion-weighted imaging (DWI) using MRI in the staging of thoracic lymph nodes in patients with lung cancer, and to compare the performance to that of PET/CT. PATIENTS AND METHOD: 20 consecutive patients (pts) with histologically proven lung cancer were included in this study. In all pts FDG-PET/CT was routinely performed to stage lung carcinoma. Additionally, MRI (1.5T) was performed including native T1w, T1w post contrast medium, T2w, and DWI sequences. Regarding the N stage based on the results of the PET/CT there were 5 patients with N0, 3 patients with N1, 5 patients with N2 and 7 patients with N3. Image analysis was performed by two radiologists (R1 and R2), respectively. The reviewers had to chose between 1 (at least one lymph node within a station is malignant) or 0 (no lymph nodes suspicious for malignancy). First the T1 post contrast sequence was analyzed. In a second step the DWI sequence (b=800) was analyzed. Both steps were performed in a blinded fashion. RESULTS: MR imaging with or without DWI only agreed with the results of the PET/CT regarding the N stage in 80% of the patients-15% were understaged and 5% overstaged. There was excellent interobserver agreement; the N-staging result only differed in 1 patient for DWI, resulting in correlation coefficients of 0.98 for DWI and 1.0 for MRI. Compared to PET-CT MRI overstaged one and understaged 4 patients, while DWI overstaged one and understaged 3 patients. This resulted in correlation coefficients of 0.814 (R1 and R2) for MRI and 0.815 (R1) and 0.804 (R2) for DWI. Regarding the ADC values there were no significant differences between ipsilateral hilar (1.03 mm(2)/s ± 0.13), subcarinal (0.96 mm(2)/s±0.24), ipsilateral mediastinal (1.0mm(2)/s ± 0.18), contralateral mediastinal (0.93 mm(2)/s ± 0.23) and supraclavicular (0.9 mm(2)/s ± 0.23) lymph nodes. CONCLUSION: Diffusion-weighted imaging does not show a clear advantage over conventional MR protocols in the N-staging of lung cancer. MRI with or without DWI shows a moderately correlation with PET/CT with a tendency for understaging.

Cisterna chyli in patients with malignancy--influence of cardiovascular disease on the prevalence of the cisterna.

UNLABELLED: The purpose of this study was to investigate the potential correlation between the presence and size of the cisterna chyli (CC) on computed tomography (CT) and the presence of cardiovascular disease. MATERIALS AND METHODS: Out of a 3000-patient cohort 2599 patients who received a CT examination of the chest and/or abdomen with measurable inferior vena cava and azygos vein were included in this retrospective study. To assess the presence of cardiovascular disease the following parameters were recorded from the PACS or clinical information system: diameter of vena cava and azygos vein, presence of ascitis, serum creatinine, history of congestive heart failure, coronary artery disease or arterial hypertension and medication (diuretics, beta-blocker). In addition the volume of the CC and the presence or absence of malignant disease were recorded. Mean values (vessel diameters, creatinine) or percentages were calculated and compared for the groups with (n=416) and without (n=2183) a cisterna. Multivariate logistic regression analysis was performed for all parameters to identify the potential association with the presence and size of a cisterna. In addition the simultaneous influence of the parameter malignancy, cardiovascular disease and age on presence and size of the CC was analyzed in a logistic regression model. RESULTS: The presence or absence of a CC was not associated with any of the measured parameter. Regarding the size of the CC, there was a positive correlation with the diameter of the azygos vein, the presence of ascitis and diuretic medication. The influences of malignancy, elevated central venous pressure and age on the development of a CC proved to be highly significant but could not be separated or quantified. CONCLUSION: The volume of the cisterna chyli is influenced by pathologic states with an increased central venous pressure, while the presence or absence of the cisterna seems to be independent of those factors.

Pitfalls in abdominal diffusion-weighted imaging: how predictive is restricted water diffusion for malignancy.

OBJECTIVE: As diffusion-weighted imaging is increasingly implemented into routine protocols of abdominal MRI, abnormal findings in expected and unexpected locations become more common. The aim of our retrospective study was to investigate the specificity of restricted diffusion in differentiation of benign from malignant abdominal disease. MATERIALS AND METHODS: Two hundred thirty consecutively registered patients underwent abdominal MRI including diffusion-weighted imaging (single-shot spin-echo echo-planar sequence) with b values of 0, 150, 500, and 1,000 s/mm(2). Lesions were detected by two blinded readers using only the images with a b value of 1,000 s/mm(2), and representative apparent diffusion coefficients were measured. Lymph nodes were not documented. RESULTS: Fifty-two of the 230 patients had a total of 55 lesions with restricted diffusion (23.9%). The mean apparent diffusion coefficient was 809 mm(2)/s. Forty-three lesions (78.2%) were malignant. The 12 benign lesions were liver hemangioma, liver adenoma, autoimmune pancreatitis, pancreatic teratoma, two abscesses, three cases of inflammatory bowel wall thickening due to Crohn's disease, Bartholin cyst, hemorrhagic ovarian cyst, and renal Rosai-Dorfman disease. CONCLUSION: Restricted diffusion is generally considered to be associated with malignant tumors because of the high cellularity of these tumors. However, in interpretation of diffusion-weighted images, it should be kept in mind that a number of benign lesions, as many as 22% in our cohort, can exhibit restricted diffusion on images with high b values, thus mimicking malignant lesions.

Multidetector computed tomography coronary angiography: sublingual nitroglycerine improves image quality significantly because of peripheral coronary vasodilatation.

PURPOSE: In this study, we investigated the influence of sublingual nitroglycerine (NTG) on the peripheral diameter, intraluminal contrast agent density, and image quality of coronary arteries during computed tomography coronary angiography (CTCA). MATERIALS AND METHODS: Thirty patients with sublingual NTG application were matched to 30 patients without NTG. The diameters of the left anterior descending coronary artery (LAD), the left circumflex coronary artery and the right coronary artery were measured at 1-, 4-, and 8-cm length of each vessel as well as the intraluminal contrast agent density along the LAD. Vessel diameters and contrast attenuation at 4 and 8 cm were referenced against the values at 1 cm and processed as percentage reduction. Image quality of the posterior descending artery was assessed subjectively by 2 independent observers. RESULTS: The percentage of peripheral vessel diameter reduction and the peripheral attenuation of contrast agent density for all measured coronary arteries was significantly smaller in the group with NTG administration. The image quality of the posterior descending artery was significantly higher in the group with NTG. CONCLUSIONS: Sublingual administration of NTG before CTCA results in improved diagnostic image quality because of a significant dilatation and improved intraluminal contrast agent density of the peripheral vessels.

Coronary MR imaging: navigator echo biofeedback increases navigator efficiency--initial experience.

RATIONALE AND OBJECTIVES: The aim of this study was to investigate whether a respiratory biofeedback system could increase navigator efficiency and maintain image quality compared to conventional respiratory-gated magnetic resonance coronary angiography (MRCA). MATERIALS AND METHODS: Eighteen healthy volunteers underwent MRCA using three different respiratory-gating protocols. A conventional expiratory free-breathing (FB) sequence was compared to two approaches using navigator echo biofeedback (NEB), a midinspiratory approach (NEBin) and an expiratory approach (NEBex). Navigator data reflecting the position of the diaphragm relative to a 3-mm gating window were made available to the subject using a video projector in combination with a Plexiglas screen and mirror goggles. Image quality was graded by two radiologists in consensus using a visual score ranging from 1 (not visible) to 4 (excellent vessel depiction). RESULTS: The NEB approaches improved navigator efficiency (71.1% with NEBex and 68.0% with NEBin vs 42.2% with FB), thus reducing total imaging time. This difference was statistically significant (P(NEBin)=.007; P(NEBex)=.001). Image quality in the NEBex group was comparable to that in the FB group (median score, 2.44 vs 2.52), but it proved to be significantly lower (median score, 1.94 vs 2.52) for the right coronary artery and the left anterior descending coronary artery in the NEBin group. CONCLUSION: NEB maintains image quality and significantly increases navigator efficiency, thereby decreasing total imaging time by about 40% compared to a conventional FB acquisition strategy.

Prospectively gated axial CT coronary angiography: preliminary experiences with a novel low-dose technique.

To assess image quality and radiation exposure with prospectively gated axial CT coronary angiography (PGA) compared to retrospectively gated helical techniques (RGH). Forty patients with suspected coronary artery disease (CAD) and a stable heart rate below 65 bpm underwent CT coronary angiography (CTCA) using a 64-channel CT system. The patient cohort consisted of 20 consecutive patients examined using a PGA technique and 20 patients examined using a standard RGH technique. Both groups were matched demographically according to age, gender, body mass index, and heart rate. For both groups, two independent observers assessed image quality for all coronary segments on an ordinal scale from 1 (nonassessable) to 5 (excellent quality). Image quality and radiation exposure were compared between patient groups. There were no significant differences in vessel-based image quality between the two groups (P > 0.05). Mean (+/- SD) effective radiation exposure in the PGA group was 3.7 +/- 0.8 mSv compared to 18.9 +/- 3.8 mSv in the RGH group without ECG-based tube current modulation (P < 0.001). Preliminary experience shows PGA technique to be a promising approach for CTCA resulting in a substantial reduction in radiation exposure with image quality comparable to that of standard RGH technique.

Electronic colon-cleansing for CT colonography: diagnostic performance.

BACKGROUND: The purpose of this study was to evaluate whether an electronic-colonic-cleansing (ECC) algorithm is beneficial for the diagnostic performance compared to a CT colonography (CTC) evaluation without electronic cleansing in tagged datasets. METHODS: Two blinded readers evaluated CTC datasets from 79 patients with 153 colorectal polyps confirmed by optical colonoscopy. Cases were read in a randomized order with and without the use of electronic colon-cleansing software. Per-polyp sensitivity, per-polyp/per-patient specificity and reading times (with and without ECC) have been calculated and reported. RESULTS: Per-polyp sensitivity for polyps >6 mm without using ECC was 60.4% (Reader 1: 59.7%, Reader 2: 61.1%), while polyps >10 mm were detected with a sensitivity of 58.3% (Reader 1: 66.7%, Reader 2: 50%). On electronically cleansed datasets, the sensitivity was 73.6% (Reader 1: 76.4%; Reader 2: 70.8%) for polyps >6 mm and 83.3% (Reader 1: 83.3%; Reader 2: 83.3%), respectively. Per-patient specificity was 75% without using cleansing (Reader 1: 68%, Reader 2: 82%) and 81.5% using ECC (Reader 1: 86%, Reader 2: 77%). CONCLUSION: Reading CTC cases using ECC software improves sensitivity in detecting clinically relevant colorectal polyps.

The cisterna chyli: prevalence, characteristics and predisposing factors.

The purpose of this study was to determine the prevalence and characteristics of the cisterna chyli (CC) in a large 3,000-patient cohort and to identify potential predisposing factors for the development of a CC. Three thousand consecutive contrast-enhanced CT examinations (1,261 women, 1,739 men, mean age 61.0 years) of the chest and/or abdomen were included in this retrospective study. Imaging characteristics of the CC (size, attenuation, location) were documented as well as clinical information (malignant disease, pattern of metastasis). A CC was found in 16.1% of the patients with an average volume of 302 microl. The mean attenuation was 4.8 Hounsfield units (HU). Twenty percent of the CC showed CT densities of 15 HU and higher. Patients with malignancies showed a significantly (p < 0.001) higher prevalence of CC (340/1,757, 19.4%) than patients with benign conditions (144/1,243, 11.6%). Especially the finding of a large CC (>1,000 microl) represents an elevated relative risk for malignancy of 1.7 (p = 0.0017). We found a significant association between malignant disease and the presence and size of a cisterna chyli. Identifying the continuity between the CC and the thoracic duct is a safer method to distinguish a CC from retrocrural lymph nodes than near-water CT attenuation alone.

Multienergy photon-counting K-edge imaging: potential for improved luminal depiction in vascular imaging.

The purpose of this study was to investigate whether spectral computed tomography (CT) has the potential to improve luminal depiction by differentiating among intravascular gadolinium-based contrast agent, calcified plaque, and stent material by using the characteristic k edge of gadolinium. A preclinical spectral CT scanner with a photon-counting detector and six energy threshold levels was used to scan a phantom vessel. A partially occluded stent was simulated by using a calcified plaque isoattenuated to a surrounding gadolinium chelate solution. The reconstructed images showed an effective isolation of the gadolinium with subsequent clear depiction of the perfused vessel lumen. The calcified plaque and the stent material are suppressed.

Strongyloides stercoralis: a rare cause of obstructive duodenal stenosis.

BACKGROUND: Strongyloidiasis is a rare helminthic infection in Europe, and it may cause duodenal obstruction. METHODS: We report a patient who was admitted to our Medical Department with nausea and repeated vomiting since 10 years until food intake became impossible. Subsequent investigations revealed a duodenal obstruction at the upper third of the duodenum, as well as enterocolitis of the terminal ileum with eosinophils dispersed throughout the mucosa. Since food intake was still not possible after treatment with a course of i.v. PPI and prokinetic applications, we decided to perform a resection of the upper duodenum with Y-Roux reconstruction. RESULTS: The histopathological examination of the resected specimen revealed strongyloidiasis. CONCLUSION: Parasite infections such as strongyloidiasis represent a rare differential diagnosis of duodenal obstruction especially if patients originate from endemic regions.

Computer-aided detection in computer tomography colonography: a review.

BACKGROUND: Colorectal cancer is one of the most common causes of death from cancer. Computer tomography colonography (CTC) - also known as 'virtual colonoscopy' - is a minimally invasive, CT-based procedure that can simulate conventional colonoscopy using three-dimensional computerized reconstructions. In an attempt to improve the method further, a lot of research emphasis has been put on computer-aided detection (CAD) to overcome potential limitations of this examination. OBJECTIVE: This review recapitulates basic principles of CTC and CAD and highlights the importance of this method as a tool for screening for colorectal cancer. METHODS: This article reviews the current literature on CAD used with CT colonography. RESULTS/CONCLUSION: CAD potentially helps to improve the detection rate for adenomas, decrease interobserver variability and data set interpretation time.

Monitoring gastric filling, satiety and gastric emptying in a patient with gastric balloon using functional magnetic resonance imaging-a feasibility report.

BACKGROUND: Intragastric balloons are used for short term weight loss therapy in obese. It is possible to monitor the ballon with sonography, however this method is sometimes insufficient in obese patients. Therefore MRI seems to be a potential therapy-monitoring option. PURPOSE: In this feasibility report we want to demonstrate the potential use of functional MRI in monitoring gastric filling, patient satiation and gastric emptying in a obese patient who previously received intragastric balloon placement. MATERIAL AND METHODS: We selected one patient (male, 178 cm, 127 kg, BMI = 40,5 kg/m(2)) who recently received a gastric balloon and visualized gastric motility in presence of the gastric balloon before and after food intake. Fast cross-sectional images in one breathhold spin echo or gradient echo sequences were aquired. Real-time gastric motion was performed with cine mode. RESULTS: MRI offers perfect visualisation of gastric balloons in obese patients. Gastric filling and emptying can be monitored in correlation to patient satiety sensation. MRI can visualize the gastric balloon with degree of filling and possible leakages. Cine mode sequences demonstrate gastric motility and gastric wall peristalsis. CONCLUSION: MR is a valuable imaging alternative for patients with intragastric balloons.

CT colonography: an update.

Computed tomographic (CT) colonography (CTC)--also known as "virtual colonoscopy"--was first described more than a decade ago. As advancements in scanner technology and three-dimensional (3D) postprocessing helped develop this method to mature into a potential option in screening for colorectal cancer, the fundamentals of the examination remained the same. It is a minimally invasive, CT-based procedure that simulates conventional colonoscopy using 2D and 3D computerized reconstructions. The primary aim of CTC is the detection of colorectal polyps and carcinomas. However, studies reveal a wide performance variety in regard to polyp detection, especially for smaller polyps. This article reviews the available literature, discusses established indications as well as open issues and highlights potential future developments of CTC.

Bowel preparation for CT-colonography: comparison of two different cleansing protocols.

OBJECTIVE: Comparison of cleansing effects and colonic distension observed with two polyethyleneglycol-solution (PEG) containing bowel preparation techniques prior to CT-colonography (CTC). MATERIALS AND METHODS: One hundred and three patients that received CTC in our institution were retrospectively evaluated. Fifty-one patients received preparation 1 (BP1; based on a GoLytely formulation+bisacodyl), 52 preparation 2 (BP2; based on a NuLytely formulation+bisacodyl). On multi-planar-reformatted (MPR) images, fluid residuals and colon distension were assessed in five colonic segments, from the ascending colon to the rectum. RESULTS: On average, significantly (p<0.001) lower fluid residuals were assesses when using BP2 regardless of the patient position. In prone position, a significantly lower fluid level was observed in the sigmoid using bowel preparation 2. The average maximum diameter measured for the whole colon was 5.2+/-0.6 cm in prone position and 4.8+/-0.6 cm in the supine position in BP1 (p<0.01). In BP2 the average maximum diameter measured for the whole colon was 5.3+/-0.6 cm in prone position and 4.7+/-0.5 cm in supine position, respectively (p<0.001). CONCLUSION: Overall, lower fluid residuals were scored using BP2. In both preparation groups we achieved better colonic distension in prone position. We were not able to distend the sigmoid better when insufflating air during patient repositioning.

Nasal air temperature and airflow during respiration in numerical simulation based on multislice computed tomography scan.

BACKGROUND: Adequate nasal air-conditioning is of greatest importance. Because detailed processes of nasal air-conditioning still are not completely understood, numerical simulations of intranasal temperature distribution and airflow patterns during inspiration and expiration were performed. METHODS: A three-dimensional model of the human nose based on computed tomography scans was reconstructed. A computational fluid dynamics application was used displaying temperature and airflow during respiration based on time-dependent boundary conditions. RESULTS: Absolute air temperature and velocity values vary depending on detection site and time of detection. Areas of low velocities and turbulence show distinct changes in air temperature. The turbinate areas prove to be the main regions for heat exchange. The numerical results showed excellent comparability to our in vivo measurements. CONCLUSION: Numerical simulation of temperature and airflow based on computational fluid dynamics is feasible providing entirely novel information and an insight into air-conditioning of the human nose.

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.

Numerical simulation of intranasal airflow after radical sinus surgery.

PURPOSE: Radical sinus surgery disturbs intranasal humidification and heating of inspired air, resulting in reduced air conditioning mainly caused by a disturbed airflow. Therefore, the aim of this study was to simulate the intranasal airflow after radical sinus surgery during inspiration by means of numerical simulation. MATERIAL AND METHODS: A bilateral model of the human nose with maxillectomy, ethmoidectomy, and resection of the lateral nasal wall and the turbinates on one side based on a multislice computed tomographic scan was reconstructed. An unsteady numerical simulation displaying the intranasal airflow patterns applying the computational fluid dynamics solver Fluent 6.1.22 was performed. RESULTS: Spacious vortices throughout the entire nasal cavity and the paranasal sinuses caused by the radical resections occurred, causing a less-intense contact between air and the surrounding nasal wall. An enlargement of the nasal cavity volume and a reduction of the nasal surface area in ratio to the nasal cavity volume could be observed. CONCLUSIONS: Aggressive sinus surgery leads to disturbed intranasal air conditioning caused by disturbed intranasal airflow patterns and a reduction of the surface area in relation to the nasal volume. The presented numerical simulation demonstrates the close relation between air conditioning and intranasal airflow. It can be helpful to understand and interpret in vivo measured data of intranasal temperature and humidity.

Numerical simulation of intranasal air flow and temperature after resection of the turbinates.

BACKGROUND: Radical surgical resection of the turbinates leads to a reduced intranasal air conditioning. The aim of this study was to determine the effect of turbinate resection on intranasal heating and airflow patterns using a numerical simulation. METHODS: A bilateral model of the human nose with resection of the turbinates on one side based on a CT-scan was reconstructed. A numerical simulation applying the computational fluid dynamics (CFD) solver Fluent 6.1.22 was performed displaying inspiratory intranasal air temperature and airflow patterns. RESULTS: Due to resection of the turbinates the airflow pattern is disturbed resulting in a spacious vortex throughout the entire nasal cavity. Hence, contact between air and surrounding nasal wall is less intense. Consequently, intranasal heating of the inspired air is relevantly reduced. CONCLUSIONS: Surgical resection of the turbinates leads to a disturbed intranasal air conditioning. The presented numerical simulation demonstrates the close relation between airflow patterns and heating.