Dark lumen MR colonography based on fecal tagging for detection of colorectal masses: accuracy and patient acceptance.

BACKGROUND: Magnetic resonance colonography (MRC) with fecal tagging has recently been investigated in clinical studies for the detection of polyps. We assessed fecal tagging MRC in a field trial. METHODS: Forty-two patients in a private gastroenterologic practice underwent MRC with barium-based fecal tagging (150 mL of 100% barium at each of 6 main meals before MRC) and conventional colonoscopy. Diagnostic accuracy of MRC and patient acceptance were assessed and compared with the respective results of conventional colonoscopy. RESULTS: Eighteen percent of all MRC examinations showed a remaining high stool signal in the colon that impeded a reliable inclusion or exclusion of polyps. On a lesion-by-lesion basis, sensitivities for polyp detection were 100% for polyps larger than 2 cm (n = 1), 40% for polyps between 10 and 19 mm, 16.7% for polyps between 6 and 9 mm, and 9.1% for polyps smaller than 6 mm. The main reason for the low acceptance of MRC was the barium preparation, which was rated worse than the bowel cleaning procedure with conventional colonoscopy. CONCLUSION: MRC with fecal tagging must be further optimized. The large amount of barium resulted in poor patient acceptance, and barium according to this protocol did not provide sufficient stool darkening. Other strategies, such as increasing the hydration of stool, must be developed.

Magnetic resonance colonography for the detection of inflammatory diseases of the large bowel: quantifying the inflammatory activity.

INTRODUCTION: The purpose of this study was to assess the diagnostic accuracy of magnetic resonance colonography (MRC) for its ability to detect and quantify inflammatory bowel disease (IBD) affecting the colon. Endoscopically obtained histopathology specimens were used as the standard of reference. MATERIALS AND METHODS: Fifteen normal subjects and 23 patients with suspected IBD of the large bowel underwent MRC. Three dimensional T1 weighted data sets were collected following rectal administration of water prior to and 75 seconds after intravenous administration of paramagnetic contrast (gadolinium-BOPTA). The presence of inflammatory changes in patients was documented based on bowel wall contrast enhancement, bowel wall thickness, presence of perifocal lymph nodes, and loss of haustral folds. All four criteria were quantified relative to data obtained from normal subjects and summarised in a single score. This MRC based score was compared with histopathological data based on conventional endoscopic findings. RESULTS: MRC correctly identified 68 of 73 segments found to reveal IBD changes by histopathology. All severely inflamed segments were correctly identified as such and there were no false positive findings. Based on the proposed composite score, MRC detected and characterised clinically relevant IBD of the large bowel with sensitivity and specificity values of 87% and 100%, respectively, for all investigated colonic segments. CONCLUSION: MRC may be considered a promising alternative to endoscopic biopsy in monitoring IBD activity or assessing therapeutic effectiveness.

[Cardiovascular whole-body MRI: possibilities and limitations in prevention]. / Kardiovaskuläre Ganzkörper-MRT: Möglichkeiten und Grenzen in der Früherkennung.

Cardiovascular disease is a major challenge to the healthcare with increasing prevalence in western societies. Hence, early detection of cardiovascular pathologies and preventative strategies will experience growing relevance in the future. Magnetic resonance imaging (MRI) nowadays allows a comprehensive analysis of the cardiovascular system. By combining separate examinations of brain, arterial vasculature, and heart the technique permits early detection of pathological changes with high diagnostic accuracy void of adverse events. Such a protocol has been proven feasible and technically robust and can be performed within 45 min. Inherent limitations are low spatial resolution of whole-body MR angiography and lack of functional stress testing of the heart. However, while being suitable as a fast and comprehensive imaging technique for cardiovascular screening purposes, medical consequences and socioeconomic relevance must further be elucidated.

Real time high resolution magnetic resonance imaging for the assessment of gastric motility disorders.

BACKGROUND: The aim of this study was to evaluate whether patients with increased or decreased gastric motility can be differentiated from healthy volunteers by means of real time magnetic resonance imaging (MRI). PATIENTS AND METHODS: Ten healthy volunteers, 10 patients with gastroparesis, and 10 patients with functional pylorospasm/peptic pyloric stenosis underwent real time MRI. All patients were examined on two separate days; once prior to therapy and once after adequate therapy. Antral motility was quantified by calculating the gastric motility index. RESULTS: Patients with gastroparesis showed a lower motility index compared with the reference volunteer group while the mean motility index of the patient group with pylorospasm was more than three times higher than that of the reference value of the volunteer group. However, the gastric motility index in the patient group with gastroparesis increased, and in the group with functional pylorospasm/peptic pyloric stenosis it decreased significantly after therapy. CONCLUSION: Real time MRI is a reliable tool for assessment of gastric motion. Furthermore, differences in gastric motility index in patients with increased or decreased gastric motility could be evaluated and quantified. Due to the non-invasive character of MRI, this imaging modality may be an attractive alternative to conventional invasive diagnostic tools for gastric motility disorders and therapeutic monitoring.

Fecal tagging: MR colonography without colonic cleansing.

Colorectal cancer, mostly arising (>90%) from preexisting adenomatous polyps, continues to be the second leading cause of cancer death. Magnetic resonance colonography (MRC) permits accurate detection of colonic polyps with a diameter larger than 10 mm. Because residual colonic stool cannot be differentiated from polyps, MRC requires a clean colon. However, the rigors associated with colonic cleansing considerably reduce patient acceptance. The need for colonic cleansing could be eliminated, if stool were to acquire a signal intensity different from polyps and identical to the enema used to fill and distend the colon. In principle, there are two approaches to this concept of fecal tagging: dark polyps surrounded by bright stool and a bright enema, and bright polyps surrounded by dark stool and a dark enema. The first approach has been evaluated with some success. Gadolinium (Gd)-DOTA was administered as an oral contrast agent with meals preceding MRC based on the administration of a Gd-based enema. The high cost of Gd-based contrast has limited the clinical utility of this technique. In the second approach patients are provided with barium as an oral fecal tagging agent to render stool dark, and barium for the enema is used to distend the colon during MRC. The colonic wall and polyps arising from it can be made visible after intravenous administration of Gd-based extracellular contrast. This method provides sufficient contrast between the darkened colonic lumen and the brightly enhanced colonic wall to permit virtual endoscopic rendering. Preliminary results showed an exact correlation with findings of conventional endoscopy and surgery. Fecal tagging obviates bowel cleansing and therefore should enhance patient acceptance for MR colonoscopy. Barium as the tagging agent is promising because it is inexpensive, commercially available, and characterized by an excellent safety profile.

[Contrast-enhanced 3D MR venography of central thoracic veins: preliminary experience]. / Kontrastmittelverstärkte 3D-MR-Venographie der oberen Thoraxapertur: Erste Erfahrungen.

PURPOSE: To evaluate the usefulness of three-dimensional (3D) gadolinium-enhanced magnetic resonance (MR) venography for evaluation of thoracic central veins. MATERIALS AND METHODS: Over a 4-month period, 14 patients with suspected central venous abnormalities were examined on a 1.5 T scanner (Magnetom Sonata, SIEMENS, Germany) by means of MR venography. A FLASH-3D sequence using the following parameters was employed: TR 1.6 ms, TE 0.6 ms, TA 3.74 s, flip: 15 degrees, slab thickness 110 mm, effective slice thickness: 2.75 mm, 40 partitions, FOV 360 mm, matrix 140 x 256. 10 s prior to imaging 20 ml of Gd-DOPTA (Multihance, BRACCO, Italy) were automatically injected (MEDRAD, Pittsburgh, USA) flushed by 20 ml of normal saline (flow 4 ml/s). Six 3D data sets were acquired in immediate succession in under 24 s. Results were corroborated with findings from duplex sonography. RESULTS: MR venograms were of diagnostic quality for all 14 patients. Compared to duplex sonography thromboses, post-thrombotic changes as well as functional compressions were reliably detected. Unsuspected findings were found in two patients. CONCLUSION: The outlined strategy allows for dynamic diagnostic imaging of central thoracic veins. Gadolinium-enhanced breath-hold 3D MR venography is easy to perform, well tolerated and highly accurate in assessing central venous pathology.

[Livedo reticularis, acral necroses and renal failure. Cholesterol crystal embolisms]. / Livedo reticularis, akrale Nekrosen und Niereninsuffizienz. Cholesterinkristallenembolien.

In a 67 year old patient with multiple cardiovascular risk factors a livedo reticularis, ischemic acral lesions as well as deterioration of renal function five weeks after cardiac catheterism and aorto-coronary bypass surgery led to suspicion of cholesterol embolism. Fundoscopy revealed cholesterol crystals in retinal vascular branches thus delivering important diagnostic information. Atheromatous lesions of the entire aorta and the ilio-femoral arteries were possible sources for embolism. The outcome was favorable. The lesions of the toes regressed and renal failure did not progress to dialysis. The diagnostic steps taken, the clinical picture of cholesterol embolism, the use of imaging and therapeutic options are discussed.

Contrast-enhanced, ultrafast 3D pulmonary MR angiography in a single breath-hold: initial assessment of imaging performance.

An ultrafast three-dimensional (3D) sequence was developed, enabling the acquisition of 44 contiguous 2.0- to 2.2-mm thin sections, during intravenous application of paramagnetic contrast, in a single breath-hold. To estimate the potential clinical usefulness, images were assessed qualitatively and quantitatively with regard to visibility of main, lobar, segmental, and subsegmental pulmonary arteries. Five volunteers were examined using a 192 x 192 matrix with an imaging time of 23 seconds and five other volunteers with a 160 x 160 matrix (18 seconds). Each volunteer was imaged in apnea and during shallow respiration. The breath-held 23-second scans revealed excellent image quality and near complete visualization of central and segmental, as well as 81% of subsegmental, pulmonary arteries. Imaging time can be shortened to 18 seconds with only marginal loss in visualization performance (P < .05). Respiratory motion was found to cause significant worsening of image quality and vessel detectability. To maintain relevance in a clinical setting, imaging time can be minimized at the cost of a reduction in spatial resolution.