OBJECTIVE: To evaluate the visibility of hepatomesenteric vascular segments by 3D gadolinium-enhanced magnetic resonance (MR) angiography and to compare the method effectiveness between two different gadolinium doses (single and double doses). MATERIALS AND METHODS: A prospective study was performed with 36 schistosomiasis patients who were submitted to 3D contrast-enhanced MR angiography. Scans were performed in a high-field equipment (1.5 T), with body coil and power injector for intravenous contrast administration. Contrast double doses (Gd-DTPA 0.2 mmol/kg) and single doses (0.1 mmol/kg) were randomly used respectively in 21 and 15 patients. Studies were interpreted by consensus between two observers who have rated the visualization degree of 25 proximal vascular segments without knowing the dose used. RESULTS: Proximal and calibrous vascular segments have presented higher visualization degree in the greatest part of the sample studied. The celiac trunk, common hepatic artery, splenic artery, proximal and medium third of superior mesenteric artery, portal vein, splenic vein and superior mesenteric vein have presented grade 2 visualization in more than 70% of the sample studied. As regards comparison between different doses, there was no significant difference (p < 0.05) in the visualization degree of several structures evaluated, between double dose and single dose groups, except for an isolate case of evaluation of right hepatic artery (p = 0.008) in which the single dose group has presented a higher frequency of grade 2 visualization with statistical significance. CONCLUSION: The visualization degree of hepatomesenteric vascular segments by 3D gadolinium-enhanced MR angiography is high, especially in the proximal and calibrous segments. The comparison between groups using single and double contrast doses has demonstrated similar results.

Keywords: Magnetic resonance angiography, Schistosomiasis, Gadolinium

Early magnetic resonance angiography techniques used flow-sensitive sequences to obtain contrast of the vascular structures. Three techniques are based on this approach: phase-contrast, time-of-flight and black blood techniques. However, these acquisition methods are time-consuming and more susceptible to movement artifacts, flow-related artifacts and signal loss due to stenotic lesions. They also present low sensitivity for slow flow detection. The use of paramagnetic contrast medium in magnetic resonance angiography studies provides a simple and quick way of obtaining vascular enhancement. Image contrast is based on vascular enhancement in opposition to background suppression. Important factors for the technical improvement of gadolinium-enhanced magnetic resonance angiography include modern techniques of central k-space ordering that are responsible for high image contrast, and implementation of appropriate timing injection. Gadolinium-enhanced magnetic resonance angiography is a useful diagnostic tool for investigation of anatomical anomalies, stenotic and occlusive disease, and surgical complications, particularly in patients with organ transplants. Gadolinium-enhanced magnetic resonance angiography has the advantage of a noninvasive method since it does not require ionizing radiation or an iodine contrast medium, and allows the evaluation of parenchymatous structures for additional diagnostic information.

Keywords: Angiography, Magnetic resonance imaging, Gadolinium

OBJECTIVE: To qualitatively and quantitatively evaluate the morphological changes of the liver and spleen using magnetic resonance imaging (MRI) in patients with chronic infection by Schistosoma mansoni and the reproducibility of MRI findings in the hepatosplenic evaluation of these patients. MATERIALS AND METHODS: We prospectively studied 28 schistosomotic patients submitted to MRI of the upper abdomen. The scans were performed using a high field equipment (1.5 T), a body coil and a power injector for administration of intravenous contrast. The scans were interpreted by two independent examiners who evaluated the presence of morphological changes in the liver and spleen. Interobserver and intraobserver agreement were measured using the kappa and intraclass correlation tests. RESULTS: Qualitative variables presented good interobserver and intraobserver agreement (kappa > 0.65 and r > 0.66, respectively). The best interobserver agreement was for the anteroposterior diameter of the spleen (r = 0.98). The observers identified reduction of the right hepatic lobe, enlargement of the left hepatic lobe and caudate lobes associated with splenomegaly in almost all patients, and also identified fissure widening, heterogeneity of hepatic parenchyma, irregularity of hepatic contours, presence of peripheral hepatic vessels and periportal fibrosis in almost all patients. CONCLUSION: Hepatic morphological changes are characterized by reduction of the right lobe and enlargement of the caudate and left lobes, and morphological changes in the spleen are characterized by the presence of splenomegaly and siderotic nodules. MRI presents high reproducibility for the evaluation of these changes in patients with chronic infection by Schistosoma mansoni.

Keywords: Parasitic liver disease, Spleen, Schistosomiasis mansoni, Magnetic resonance imaging

OBJECTIVE: To evaluate the role of the equilibrium phase in abdominal computed tomography. MATERIALS AND METHODS: A retrospective, cross-sectional, observational study reviewed 219 consecutive contrast-enhanced abdominal computed tomography images acquired in a three-month period, for different clinical indications. For each study, two reports were issued - one based on the initial analysis of non-contrast-enhanced, arterial and portal phases only (first analysis), and a second reading of these phases added to the equilibrium phase (second analysis). At the end of both readings, differences between primary and secondary diagnoses were pointed out and recorded, in order to measure the impact of suppressing the equilibrium phase on the clinical outcome for each of the patients. The extension of the exact Fisher's test was utilized to evaluate the changes in the primary diagnosis (p < 0.05 as significant). RESULTS: Among the 219 cases reviewed, the absence of the equilibrium phase determined change in the primary diagnosis in only one case (0.46%; p > 0.999). As regards secondary diagnoses, changes after the second analysis were observed in five cases (2.3%). CONCLUSION: For clinical scenarios such as cancer staging, acute abdomen and investigation for abdominal collections, the equilibrium phase is dispensable and does not offer any significant diagnostic contribution.

Keywords: X-ray computed tomography; Ionizing radiation; Neoplasm staging; Acute abdomen.

OBJECTIVE: To evaluate the necessity of the non contrast-enhanced phase in abdominal computed tomography scans. MATERIALS AND METHODS: A retrospective, cross-sectional, observational study was developed, evaluating 244 consecutive abdominal computed tomography scans both with and without contrast injection. Initially, the contrast-enhanced images were analyzed (first analysis). Subsequently, the observers had access to the non-contrast-enhanced images for a second analysis. The primary and secondary diagnoses were established as a function of the clinical indications for each study (such as tumor staging, acute abdomen, investigation for abdominal collection and hepatocellular carcinoma, among others). Finally, the changes in the diagnoses resulting from the addition of the non-contrast-enhanced phase were evaluated. RESULTS: Only one (0.4%; p > 0.999; non-statistically significant) out of the 244 reviewed cases had the diagnosis changed after the reading of non-contrast-enhanced images. As the secondary diagnoses are considered, 35 (14%) cases presented changes after the second analysis, as follows: nephrolithiasis (10%), steatosis (3%), adrenal nodule (0.7%) and cholelithiasis (0.3%). CONCLUSION: For the clinical indications of tumor staging, acute abdomen, investigation of abdominal collections and hepatocellular carcinoma, the non-contrast-enhanced phase can be excluded from abdominal computed tomography studies with no significant impact on the diagnosis.

Keywords: Computed tomography; Ionizing radiation; Abdomen; Contrast media.

OBJECTIVE: To assess the reduction of estimated radiation dose in abdominal computed tomography following the implementation of new scan protocols on the basis of clinical suspicion and of adjusted images acquisition parameters. MATERIALS AND METHODS: Retrospective and prospective review of reports on radiation dose from abdominal CT scans performed three months before (group A - 551 studies) and three months after (group B - 788 studies) implementation of new scan protocols proposed as a function of clinical indications. Also, the images acquisition parameters were adjusted to reduce the radiation dose at each scan phase. The groups were compared for mean number of acquisition phases, mean CTDI_vol per phase, mean DLP per phase, and mean DLP per scan. RESULTS: A significant reduction was observed for group B as regards all the analyzed aspects, as follows: 33.9%, 25.0%, 27.0% and 52.5%, respectively for number of acquisition phases, CTDI_vol per phase, DLP per phase and DLP per scan (p < 0.001). CONCLUSION: The rational use of abdominal computed tomography scan phases based on the clinical suspicion in conjunction with the adjusted images acquisition parameters allows for a 50% reduction in the radiation dose from abdominal computed tomography scans.

Keywords: Computed tomography; Abdomen; Contrast media; Radiation dose; Radiation protection.