Twei-Shiun Jaw

Effect of intravenous gadolinium-DTPA on diffusion-weighted magnetic resonance images for evaluation of focal hepatic lesions.

Objective: Diffusion-weighted imaging (DWI) is usually performed before administration of intravenous contrast agents. Repetition of DWI is occasionally necessary after contrast administration, but the effects of contrast material on DWI and apparent diffusion coefficient (ADC) values in the abdomen have not yet been fully examined. The purpose of this work is to assess whether administration of gadolinium-based contrast material significantly affects DWI and ADC values at the focal hepatic lesions. Methods: The results of DWI at 3.0 T (Signa VH3; GE Medical Systems, Milwaukee, WI) were examined in 20 patients (age range: 33-86 years, mean age = 68 years) who were evaluated by means of a hepatic protocol at our hospital. Among the 20 patients studied, a total of 57 lesions were detected. Diffusion-weighted imaging was obtained using single-shot echo planar imaging with a b value of 500 s/mm2. Patients were injected with 0.1 mmol/kg gadopentetate dimeglumine. The signal-to-noise ratio (SNR) of the liver and the hepatic lesions was examined, and the contrast-to-noise ratio (CNR) of each lesion was evaluated. In addition, the ADC values calculated from the DWI were compared before and after administration of contrast agent. The statistical significance of differences between precontrast and postcontrast administration was determined by use of a paired t test. Results: The SNR and CNR of the DWI were not significantly different before and after administration of contrast agent. The ADC values tended to decrease after administration of contrast agent for each focal hepatic lesion and the liver, although they did not reach statistical significance. Conclusion: There was no significant difference before and after administration of contrast agent in the SNR or CNR of DWI. This indicates the feasibility of postcontrast DWI as a substitute for an unsuccessful precontrast-enhanced study in clinical practice.

Comparison of radiographic landmarks and the echocardiographic SVC/RA junction in the positioning of long-term central venous catheters

Background:  When implanting a permanent central venous catheter, the usual aim is to place the tip at the superior vena cava/right atrial (SVC/RA) junction. However, data validating radiographic landmarks of the SVC/RA junction are limited. This investigation was undertaken to compare the radiographic landmarks with the SVC/RA junction as determined by transesophageal echocardiography (TEE).

Muscle metabolism in Duchenne muscular dystrophy assessed by in vivo proton magnetic resonance spectroscopy.

To investigate the correlation between muscle function and metabolism in muscle tissue of Duchenne muscular dystrophy (DMD) patients by in vivo proton magnetic resonance spectroscopy. Materials and Methods: In this prospective study, we enrolled 8 boys with DMD and 8 healthy volunteers. In vivo proton magnetic resonance spectroscopy of the soleus muscles was performed using a whole-body 3.0-Tesla imaging unit and a knee coil. The levels of trimethyl ammonium (TMA) and total creatine (tCr) were measured. We compared TMA/water, tCr/water, and TMA/tCr ratios, and scores for muscle function in the legs by using a t test. Results: Fat infiltrated the leg muscles in all patients but no volunteers. All patients had elevated creatine kinase levels. Magnetic resonance spectra of patients and volunteers showed TMA and tCr peaks. Ratios of TMA/water (P = 0.0015), tCr/water (P = 0.0167), and TMA/tCr (P = 0.0017), and muscle function scores (P = 0.0028) were significantly lower in patients than in volunteers. All patients had impaired muscle function, whereas all volunteers had normal function. Muscle function in the legs was negatively correlated with the TMA/tCr ratio (r2 = 0.878). Conclusions: Metabolite ratios and muscle function scores were significantly decreased in patients with DMD when compared with normal control subjects. A statistically significant decrease in TMA/tCr ratio in patients with DMD as compared with control subjects was found to correlate with decreased muscle function.

MRI manifestations of gastrointestinal lymphoma

The magnetic resonance (MR) images of 11 cases of gastrointestinal lymphoma are presented. The findings include irregularly thickened mucosal folds, irregular submucosal infiltration, annular constricting lesion, exophytic tumor growth, mesenteric masses, and mesenteric/retroperitoneal lymphadenopathy. The tumors were homogeneous and intermediate in signal intensity on T1-weighted images. Heterogeneously increased signal intensities were noted on T2-weighted images. There was mild to moderate enhancement after intravenous administration of gadolinium dimeglumine (Gd-DTPA). The submucosal tumor infiltration might be outlined between the strongly GD-DTPA-enhanced mucosa and the low-intensity muscular layer. In one case that received tumor resection, the pathological examination showed destruction of most parts of the muscular layer, and the MR images did not disclose the low intensity muscular zone.

Widespread White Matter Alterations in Patients with End-Stage Renal Disease: A Voxelwise Diffusion Tensor Imaging Study

Hemodyalisis may not prevent brain damage resulting from accumulation of urea and other metabolites as previously believed. These investigators used voxelwise DTI to assess the white matter of 28 patients with end-stage renal disease. All DTI parameters were abnormal, especially in the callosum, sagittal stratum, and pons. BACKGROUND AND PURPOSE: ESRD results in excessive accumulation of urea and toxic metabolites. Hemodialysis is usually performed to maintain health in patients with ESRD; however, it may cause silent white matter alterations in the earlier stages. Hence, this study aimed to perform voxelwise diffusion tensor analysis for global detection of subtle white matter alterations in patients with ESRD. MATERIALS AND METHODS: Twenty-eight patients with ESRD and 25 age-matched control subjects were enrolled in this study. Each subject underwent CASI assessment and DTI. After spatial normalization of DTI images, voxelwise statistical analyses were performed to compare DTI parameters between the 2 groups. RESULTS: In patients with ESRD, AD, RD, and MD values were significantly increased, whereas the FA value was significantly decreased, mostly in the corpus callosum, bilateral sagittal stratum, and pons. Multiple regression analysis further revealed that both RD and MD were positively correlated with the duration of hemodialysis in the pons; however, no significant correlation was observed with FA. Negative correlations of RD and MD and a positive correlation of FA with the CASI score were observed in the corona radiata. CONCLUSIONS: We concluded that voxelwise DTI analysis is helpful in the detection of white matter alterations caused by hemodialysis.

MRI manifestations of gastrointestinal wall thickening

The appearance of gastrointestinal wall thickening of various entities is demonstrated on magnetic resonance imaging (MRI). The entities include benign gastric ulcer, gastric carcinoma, pancreatic carcinoma with direct invasion of stomach, duodenal leiomyoma, radiation enteritis, peritonitis, colonic carcinoma, recurrent carcinoma at the gastrojejunal anastomosis with direct extension to the transverse colon, colocolic intussusception, sigmoid diverticulitis with pericolonic abscess and fistula into the urinary bladder, and lymphoma of the stomach, duodenum, small bowel, and colon. Air was introduced antegradedly or retrogradedly into the alimentary tract to act as a contrast agent. When the bowel was distended by air, the normal bowel wall was barely visible or even invisible. Abnormal focal or segmental wall thickening was outlined between the intraluminal air and extraluminal fat. In some instances, the thickenings were better demonstrated on coronal or sagittal sections. The proper muscular layer of the bowel has a low-signal intensity and was delineated between the thickened mucosa—submucosa and extramural fat. Interruption of this low-intensity zone might represent tumor invasion through the muscular layer.

Differentiation between Malignant and Benign Gastric Ulcers: CT Virtual Gastroscopy versus Optical Gastroendoscopy

PURPOSE To retrospectively compare computed tomographic virtual gastroscopy (VG) and conventional optical gastroendoscopy for the differentiation of malignant and benign gastric ulcers. MATERIALS AND METHODS The institutional review board approved this study and confirmed that informed consent was not required. Gastric ulcers in 115 patients (mean age, 64.7 years; range, 31-86 years; 61 men, 54 women) were evaluated by using endoscopy and VG. Ulcer shape, base, and margin and periulcer folds were evaluated by two independent reviewers. Malignant gastric ulcers were identified by irregular, angulated, or geographic shape; uneven base; irregular or asymmetric edges; and disrupted or moth-eaten appearance of periulcer folds near the crater edge and/or clubbed or fused folds. Benign gastric ulcers were identified by smooth and regular shapes, even bases, clearly demarcated and regular edges, and folds that tapered and converged toward the ulcer. The performance of VG and endoscopy for the diagnosis of benign and malignant gastric ulcers was evaluated by using histopathologic results as the reference standard. The McNemar test was used to compare VG and endoscopic data. A P value less than .05 was considered to indicate a significant difference. RESULTS At histopathologic examination, 39 gastric ulcers were benign, while 76 were malignant. VG and endoscopy had sensitivities of 92.1% (70 of 76) and 88.2% (67 of 76), respectively, for overall diagnosis of malignant gastric ulcers, and specificities of 91.9% (34 of 37) and 89.5% (34 of 38), respectively, for overall diagnosis of malignant gastric ulcers. Endoscopy was more sensitive in depicting malignancy according to ulcer base (85.5% [65 of 76] vs 68.4% [52 of 76]) (P = .034), and VG was more specific in depicting malignancy according to ulcer margin (78.4% [29 of 37] vs 63.2% [24 of 38]) (P = .034). CONCLUSION VG and endoscopy were almost equally useful in distinguishing between malignant and benign gastric ulcers. SUPPLEMENTAL MATERIAL http://radiology.rsnajnls.org/cgi/content/full/2522081249/DC1.

Development of Adenoids:A Study by Measurement with MR Images

Magnetic resonance (MR) imaging, which is able to demonstrate the actual size of adenoids by differentiating them from other soft-tissue structures, can be effectively used to study the normal development of adenoids. To assess the normal development of adenoids and to understand their role in the nasopharyngeal airway compromise, the adenoids of 290 children who had MR examination for other reasons were measured by midsagittal T1-weighted spin-echo MR image. The maximal thickness of adenoids (A), anteroposterior depth of the nasopharynx (N) and the adenoid-nasopharynx (A/N) ratios were obtained using this method. The results showed that of the infants under the age of 3 months only 2 out of 11 adenoids (18%) could be identified. By 4 months of age, adenoids could be identified in 6 of 8 infants (75%). After 5 months of age, all adenoids were well demonstrated by MR imaging. The adenoids developed rapidly during infancy and reached a plateau between 2- and 14 years of age with a mean thickness ranging from 10.7 to 12.2 mm. Finally, the adenoids regressed rapidly after 15 years old. The A/N ratios, which could be used to assess the airway compromise, had a plateau between 2- and 7 years of age. After that, with the steady growth of the nasopharynx, the possible role of adenoid in airway compromise will become increasingly less significant in later childhood.

MRI demonstration of peritoneal implants

The magnetic resonance imaging (MRI) findings of 12 proven cases of peritoneal implants, mainly carcinomatosis, were reviewed for evidence of peritoneal seedings. The seeded sites include the pouch of Douglas, the ileocecal and retrocecal regions, the right and left paracolic gutters, Morisons pouch, the right subdiaphragmatic parietal peritoneum, the greater and lesser omentum, the gastrocolic, gastrosplenic, and phrenicocolic ligaments, the small bowel mesentery, the sigmoid and transverse mesocolons, and the small and large bowel walls. Sizes varied from less than 1 cm to omental cake and bulky tumors. The findings include linear or tiny nodular infiltrations of the omentum and subperitoneal fat (ligamentous, mesenteric, and mesocolic), focal or segmental wall thickenings, loss of unilateral colonie haustration with sacculation on the contralateral side, and nodular soft tissue masses along different locations of the peritoneal surfaces. Air was introduced via an antegrade or retrograde method to act as a gastrointestinal contrast agent and was found to be useful for delineating the seedings. As is true with computed tomography scan, miliary implants are also not detectable with MRI. The sensitivity and specificity of MRI in detecting peritoneal implants remain to be determined.

Split-Bolus Portal Venous Phase Dual-Energy CT Urography: Protocol Design, Image Quality, and Dose Reduction

OBJECTIVE The purpose of this study is to evaluate the image quality of split-bolus portal venous phase urography and the potential reduction of radiation dose by using a second-generation dual-source dual-energy CT (DECT) scanner. MATERIALS AND METHODS DECT urography was performed in 84 patients. Unenhanced CT was performed 20 minutes after drinking 800 mL of water. The split-bolus protocol consisted of a sequence of injections, as follows: 200 mL of normal saline (2.0 mL/s), 50 mL of contrast medium (2.5 mL/s) at 0 second, 70 mL of contrast medium (2.5 mL/s) at 360 seconds, and a saline flush of 25 mL. The scan was started at 420 seconds. Virtual unenhanced images were reconstructed from contrast-enhanced images. The mean CT density and signal-to-noise ratio (SNR) of the renal parenchyma, vessels, upper urinary tract, normal reference tissues, and tumors were measured for image quantitative analysis. Image quality and opacification of the collecting systems were rated by two radiologists using 3- or 4-point scales. RESULTS The SNR of all measured sites, except the renal pelvis, showed a statistically significant correlation (p < 0.001) between the true unenhanced and virtual unenhanced images. The overall sensitivity of stone detection was 87.5% (28/32) in virtual unenhanced images. Image quality of the renal parenchyma, arteries, and veins was excellent in 59.5%, 75.0%, and 97.6% of cases, respectively. Opacification of the intrarenal collecting systems, proximal, middle, and distal ureters, and bladder was complete in 92.9%, 83.9%, 78.6%, 77.4%, and 26.2% of patients, respectively. Omitting the unenhanced scan can reduce the mean radiation dose from 15.6 to 6.7 mSv. CONCLUSION Portal venous phase split-bolus DECT urography provides sufficient image quality with potential to reduce radiation exposure.