Magnetic resonance coronary angiography with 3D TrueFISP: breath-hold versus respiratory gated imaging.

To compare the diagnostic accuracy of coronary magnetic resonance angiography with three-dimensional (3D) trueFISP breath-hold and respiratory gated techniques for the detection of significant coronary artery stenosis. 15 patients who recently underwent elective coronary angiogram were studied and a total of 60 arteries and 48 arteries were assessed by breath-hold and respiratory gated 3D trueFISP techniques, respectively. The image quality, length of artery visualized and the presence or absence of significant coronary artery stenosis were recorded. 83.3% and 81.7% of the arteries obtained with the respiratory gated and the breath-hold techniques, respectively, had an image quality suitable for further analysis. There was no significant difference in the length of artery visualized. Sensitivity and specificity of 80%, 100% and 75% and 100%, respectively, were obtained with the breath-hold and respiratory gated techniques in detecting significant stenosis in the coronary arteries. Both techniques have moderate sensitivity and high specificity in detection of significant stenosis in the visualized segments of the major coronary arteries. However, they cannot replace conventional coronary angiogram for diagnosing coronary artery disease at present. Further studies are required to evaluate whether breath-hold approach is more efficient, therefore should be performed first and respiratory gated approach reserved for those who cannot breath-hold.

Magnetic resonance cholangiography in children.

Magnetic resonance cholangiography has been shown to be useful in the evaluation of hepatobiliary problems in paediatric patients. Its clinical application in biliary atresia, choledochal cyst, cholelithiasis, bile plug syndrome and liver transplant are illustrated by the following cases.

Computer-assisted detection as a second reader in symptomatic Asian women with palpable breast cancer.

PURPOSE: To determine the potential role of a computer-assisted detection (CAD) algorithm as a second reader for experienced and inexperienced radiologists in mammography reading in Asian women. MATERIAL AND METHODS: Two-view mammograms performed in 124 consecutive patients who presented with palpable breast cancer masses were retrospectively evaluated by two experienced breast radiologists (7 and 10 years' experience). The original reports of the session radiologists with variable experience of reading mammograms (2 to more than 10 years) were also evaluated. The number of suspicious masses and microcalcification clusters detected in each patient by both groups of radiologists were recorded. The radiologists then re-evaluated the films with the CAD system as a second reader. Any improvement in the detectability of breast pathology by either the experienced radiologists and/or by the session radiologists was then assessed. A total of 127 breasts had biopsy-proven carcinoma; 74 breasts had mastectomy performed. All the imaging results were correlated with tru-cut biopsy or mastectomy histology. RESULTS: With CAD-aided interpretation, there were altogether 95 visible masses and 77 suspicious microcalcification clusters in 109 mammographically detectable cancers correlated with histology results. There was a 7.4% (7/95) and 10.4% (8/77) increase in the number of masses and microcalcification clusters detected, respectively, by the experienced radiologists after application of CAD, whereas the increase was 13.7% (13/95) and 27.3% (21/77) for detection of masses and microcalcifications by the session radiologists, respectively. In 9 patients, a secondary focus detected by CAD was confirmed by histology. Three patients had contralateral breast tumors, 1 had a satellite invasive tumor while 5 had ductal carcinoma in situ on the same breast. Based on the biopsies and 74 mastectomies, the true-positive and false-positive detection rate of CAD was 92.6% and 31.8% for detection of carcinomas. The true-positive and false-positive detection rates were 100% and 58.8% for microcalcification clusters. CONCLUSION: The current generation CAD algorithm helped to improve the detection rate of carcinomas, calcifications and multifocality in Asian breasts.

Plaque volume measurement by magnetic resonance imaging as an index of remodeling of middle cerebral artery: correlation with transcranial color Doppler and magnetic resonance angiography.

BACKGROUND: The feasibility of a noninvasive evaluation of remodeling of the middle cerebral artery (MCA) by magnetic resonance imaging (MRI) was assessed. The results were correlated with magnetic resonance angiography (MRA) and transcranial color Doppler (TCD) findings. METHODS: 26 patients (13 male and 13 female, age ranged from 46 to 82 years) who presented with symptoms of cerebrovascular accidents had TCD, MRA and MRI assessment of the MCA. The TCD and MRA findings of 40 MCAs accessible by TCD were correlated with the ratio of cross-sectional area of the vessel (VA), luminal area of the vessel (LA) and plaque load (PL). RESULTS: The VA ratio and LA showed no correlation with TCD or MRA results. PL however was shown to be associated with both TCD and MRA. CONCLUSIONS: MRI could be used to assess remodeling in MCAs. PL was found to be associated with TCD and MRA findings.

Imaging features of hepatocellular carcinoma.

This pictorial review concentrates on the imaging features of hepatocellular carcinoma as revealed by ultrasonography, computed tomography, magnetic resonance imaging and angiography. Understanding of the pathomorphological characteristics of the disease is important to precise image interpretation.

Magnetic resonance imaging in ischaemic heart disease.

Magnetic resonance imaging has an increasing role in the assessment of ischaemic heart disease. Its superb spatial and temporal resolution currently allows accurate assessment of cardiac function, regional wall motion, and the extent of myocardial infarction. Regional myocardial perfusion can also be assessed, most commonly by a first-pass technique. Non-invasive imaging of the coronary arteries by various magnetic resonance imaging techniques represents a major advance in recent years. In the foreseeable future, magnetic resonance imaging may become a single, comprehensive examination for the assessment of ischaemic heart disease.

Feasibility study of using air as a contrast medium in MR colonography.

AIM: To evaluate the feasibility of using air as intraluminal contrast medium in magnetic resonance (MR) colonography. MATERIALS AND METHODS: Twenty-two patients underwent MR colonography (MRC) using air before colonoscopy. All patients were imaged in prone and supine positions. Each colon was divided into five segments. Two radiologists reviewed the images for the degree of colonic distension, image quality and colonic lesions. The colonic lesions identified using MR were compared with those identified on colonoscopy. RESULTS: Eight men and 14 women with mean age of 55.5 years were studied. All patients completed the MR examination. One hundred and five out of 110 (95.5%) colonic segments were well distended in both prone and supine positions. Image quality was good in all cases. Colonoscopy detected 16 lesions: three > or = 1 cm, one 7 mm lesion and 12 lesions < or = 5 mm. All lesions 1 cm or larger were detected by MRC. CONCLUSION: MRC using air and the single-shot half-Fourier rapid acquisition with refocused echoes (RARE) technique is feasible. But in this small pilot study, it had low sensitivity for the detection of polyps less than 1 cm in diameter.

Hyperintense middle cerebral artery sign using MRI.

AIM: To assess whether the presence of the hyperintense middle cerebral artery (MCA) sign, detected using magnetic resonance imaging (MRI), has any prognostic value in subacute infarction. The results were also compared with computed tomography (CT). MATERIALS AND METHODS: Twenty-five consecutive patients with suspected subacute ischaemic stroke (6-48 h after onset of symptoms) underwent MRI and CT assessment. The incidence of intraluminal thrombus demonstrated by conventional T1 and T2-weighted images was assessed. The results were correlated with National Institutes of Health Stroke Scale (NIHSS). RESULTS: Hyperintense MCA was identifiable on T1-weighted images in 77.8% patients, on T2-weighted images in 61.1% patients, and in 38.9% patients using CT. Patients with intraluminal thrombus identified by MRI had more severe stroke (mean NIHSS of 12.2+/-8.0 versus 4+/-3.2 respectively, p=0.003). CONCLUSIONS: The presence of hyperintense MCA by MRI is associated with higher NIHSS and may therefore have a prognostic value.

B0 images obtained from diffusion-weighted echo planar sequences for the detection of intracerebral bleeds.

BACKGROUND AND PURPOSE: To evaluate the accuracy of B0 echo planar imaging (EPI) sequences for the detection of intracerebral bleeds. METHODS: One hundred patients with acute strokes had magnetic resonance imaging and computed tomography (CT) examinations performed within 48 hours after the onset of symptoms. The detectability of intracerebral bleeds by the B0 EPI sequences was assessed. The results were compared to the gradient echo (GRE) sequence and CT brain examinations. The results of the GRE sequences were used as the gold standard. RESULTS: The B0 EPI sequences detected 11 out of 11 acute, intracerebral hematomas; 6 out of 8 acute hemorrhagic strokes; 2 out of 2 acute, intraventricular hemorrhages; 8 out of 8 old hemorrhagic infarcts; 1 out of 1 subarachnoid hemorrhages; and 11 out of 22 patients with microbleeds. For the detection of acute, intracerebral hematomas and acute, hemorrhagic infarcts, B0 EPI sequences had a sensitivity of 89.5%, a specificity of 100%, and an accuracy of 98%. CT had a sensitivity of 57.9%, a specificity of 100%, and an accuracy of 92%. B0 EPI sequences did not miss any acute or chronic hemorrhages detected by CT examinations. CONCLUSIONS: B0 EPI sequences could not replace GRE images for the detection of both acute and chronic hemorrhages. Their sensitivity for the detection of acute and chronic blood products, however, was comparable, if not superior, to that of CT examinations.

Carotid intima-media thickness in patients with head and neck irradiation for the treatment of nasopharyngeal carcinoma.

AIM: Intima-media thickness (IMT) has been shown to be useful in the evaluation and monitoring of carotid artery atherosclerosis in patients at risk of cardiovascular events. In this study, we aimed to examine the IMT in patients with nasopharyngeal carcinoma (NPC) who received irradiation to the carotid arteries during radiotherapy, and compared them with a control group. MATERIALS AND METHODS: Fifty-one NPC patients (aged between 39 and 69 years) and a group of 51 age-and sex-matched controls were studied by ultrasound. The IMT at the far wall of the common carotid artery was measured three times and the average value taken in each subject. The IMT of both groups were compared. Risk factors for IMT thickness, including hypertension, smoking, hyperglycaemia, hypercholesterolaemia, history of cerebrovascular accidents and cardiovascular disease, were also studied. RESULTS: The mean carotid IMT of patients in the NPC group (2.2+/-1.5 mm) was statistically greater than that in normal controls (0.7+/-0.15 mm) (P < 0.05). There was no statistically significant difference between the IMT in the right and left common carotid arteries within each group of patients. CONCLUSION: The findings suggest that patients with irradiation have increased arterial IMT. As they are asymptomatic the clinical relevance is not clear.

Sonographic characterisation of radiation-induced carotid artery stenosis.

BACKGROUND AND PURPOSE: To study the distribution, extent and sonographic characterisation of radiation-induced carotid artery stenosis in nasopharyngeal carcinoma (NPC) patients. METHODS: The distribution of plaques, the extent of stenosis, and the sonographic characterisation of the plaque at maximum stenosis were recorded in 71 NPC patients. The results were compared with the ultrasound results of a control group of 142 patients presenting with symptoms of cerebrovascular disease or carotid bruit. RESULTS: NPC patients had a higher incidence of carotid stenosis (77 vs. 50.7%). The common carotid arteries were most commonly affected by radiation-induced stenosis (93/142 vs. 37/284 in the control group), whereas the carotid bulb was the most commonly affected (56/284) site in the control group. Significantly more NPC patients had moderate-to-severe stenosis (21/71 vs. 27/142). Analysis of the sonographic appearance of radiation-induced and atherosclerotic plaques showed more diffuse involvement in the post-radiation group. Non-calcified plaques and intraplaque hypoechoic foci were also more frequent in the post-radiation group. CONCLUSIONS: Radiation-induced carotid stenosis is more diffuse in distribution, is associated with more severe luminal stenosis and has different sonographic plaque characterisation compared with carotid stenosis without radiation exposure.

Biliary drainage for obstructive jaundice enhances hepatic energy status in humans: a 31-phosphorus magnetic resonance spectroscopy study.

BACKGROUND: Biliary obstruction impairs liver function although the pathophysiological mechanism is incompletely understood. AIMS: The aim of this study was to examine serial changes in liver metabolism in patients with obstructive jaundice using image guided in vivo 31-phosphorus magnetic resonance spectroscopy ((31)P MRS). This technique allows repeated and non-invasive assay of organ energy metabolism and phospholipid biochemistry. PATIENTS: We studied 10 patients presenting with obstructive jaundice secondary to extrahepatic localised malignancy. There were eight men and two women, median age 72 years (range 54-94), six with cholangiocarcinoma (all Bismuth type 1) and four with carcinoma of the head of the pancreas. Ten healthy volunteers (median age 24 years (range 21-26)) were studied for comparison. METHODS: Hepatic metabolism in jaundiced patients was measured by (31)P MRS at presentation and again after a one week period of biliary drainage. Conventional liver function tests were also recorded. RESULTS: Compared with controls, liver spectra from jaundiced patients contained an excess of phosphomonoester (PME) metabolites (PME/total phosphate median 10.3% (interquartile range 8.7-11.5) in controls, 15.4% (13.1-17.7) in jaundiced cases; p<0.01). Biliary decompression was achieved in all patients (five with internal stents and five by external drainage catheters), and plasma biochemistry improved predictably (bilirubin 176 micromol/l (158-351) at presentation, 110 micromol/l (42-241) after drainage for one week; p<0.01). Enhancement of hepatic energy status, measured by the ratio of adenosine triphosphate (ATP) to inorganic phosphate (Pi), was observed in all cases after relief of biliary obstruction (ATP/Pi 1.4 (1.17-1.69) at presentation, 1.97 (1.4-2.48) after drainage; p<0.01) and was independent of the route of bile drainage. Hepatic phosphodiester (PDE) content was decreased after relief of obstruction (PDE/total phosphate 25.2% (20.5-27.4) at presentation, 19.8% (16.6-24.5) after drainage; p<0.01). This change was probably due to a reduction in the contribution from bile contents to this resonance as a strong PDE signal was also detectable in spectra obtained from separate bile specimens. CONCLUSIONS: Obstructive jaundice produces alterations in liver phosphoester biochemistry, most likely reflecting disturbances in phospholipid metabolism. Relief of biliary obstruction is associated with a measurable increase in hepatic energy status. Bile may contribute to the phosphodiester signal of the 31-phosphorus liver spectrum and changes in these resonances must therefore be interpreted with caution and in relation to the clinical situation. Monitoring of liver metabolism by (31)P MRS may allow clinicians to refine the selection and timing of therapeutic options in jaundiced patients.