Ultrasound and magnetic resonance imaging assessmentof active bowel segments in Crohn's disease.

AIM: Determining bowel disease activity in Crohn's patients can be difficult on clinical and laboratory assessment. Endoscopy is invasive and barium studies use ionising radiation. The aim of this study was to compare ultrasound and magnetic resonance imaging (MRI) in detecting Crohn's disease activity in the small or large bowel. MATERIALS AND METHODS: Thirty patients, previously diagnosed with Crohn's disease, had bowel ultrasound and MR imaging, and were deemed active or inactive on each test. The 'gold standard' was based on clinical assessment and one or more of the following: endoscopy, barium studies or surgery. RESULTS: For determining Crohn's disease activity, the sensitivities and specificities of bowel ultrasound and MRI were 87 percent and 100 percent, and 87 percent and 71 percent, respectively. Significant parameters that defined disease activity were bowel wall thickening on ultrasound and MRI, and contrast enhancement of the bowel wall and mesenteric vascularity/stranding on MRI. CONCLUSION: Ultrasound and MRI were both sensitive for determining Crohn's disease activity in the bowel, but MRI with gadolinium enhancement was less specific.

MR imaging evaluation of the activity of Crohn's disease.

OBJECTIVE: The purpose of this study was to evaluate the sensitivity and specificity of MR imaging in assessing the activity of Crohn's disease. SUBJECTS AND METHODS: Thirty symptomatic patients with Crohn's disease but uncertain disease activity were prospectively examined using MR imaging. Twenty-nine patients were scored using the Crohn's disease activity index. Six hundred milliliters of water orally and 1 mg of glucagon intramuscularly were given before imaging. Breath-hold images were obtained using T2-weighted turbo spin-echo, T1-weighted fast low-angle shot, and fat-suppressed gadolinium-enhanced T1-weighted fast low-angle shot sequences. Images were assessed by two radiologists who were unaware of the patient's symptoms, clinical scoring, and other imaging tests, and who reached a consensus about the imaging findings (bowel wall thickening, bowel wall enhancement, and perienteric changes) and determined the absence or presence of active disease in each patient. MR imaging findings were correlated with endoscopy and surgery. RESULTS: Twenty-three patients had active disease and seven patients had inactive disease. One hundred twenty-four of a total of 168 bowel segments were examined with both MR imaging and endoscopy or surgery. On a per patient basis, MR imaging had an overall sensitivity of 91% and a specificity of 71% for active disease. The Crohn's disease activity index had a sensitivity of 92% and a specificity of 28%. On a per segment basis, MR imaging had a sensitivity of 59% and a specificity of 93%. Bowel wall thickening of greater than 4 mm, bowel wall enhancement (ratio of signal intensity of abnormal to normal bowel > 1.3:1), and increased mesenteric vascularity were useful in identifying active disease. A layered enhancement pattern after the IV administration of gadolinium was highly specific for active inflammation. CONCLUSION: MR imaging is useful in assessing the activity of Crohn's disease and may be helpful when clinical scoring is equivocal.

Uterine fibroleiomyoma: MR imaging appearances before and after embolization of uterine arteries.

PURPOSE: To evaluate the magnetic resonance (MR) imaging appearances of uterine fibroleiomyoma before and after embolization and to determine whether there are preembolization MR imaging characteristics that are predictive of a successful outcome. MATERIALS AND METHODS: MR imaging was performed in 18 patients (32 fibroleiomyomas) before and at 2 and 6 months after embolization of the uterine arteries. On each occasion, fibroleiomyoma signal intensity and gadolinium enhancement characteristics were assessed in comparison with those of myometrium on T1-weighted and gadolinium-enhanced images or with those of skeletal muscle on T2-weighted images. Fibroleiomyoma volume was measured by using the ellipsoid formula. RESULTS: The mean fibroleiomyoma volume before embolization was 340 cm3 (range, 15-1,383 cm3). The mean reduction in fibroleiomyoma volume was 43% at 2 months and 59% at 6 months. Before embolization, high signal intensity on T1-weighted images was predictive of a poor response (P = .008), and high signal intensity on T2-weighted images was predictive of a good response (P = .007). The degree of gadolinium enhancement was not correlated with fibroleiomyoma volume reduction (P = .46). CONCLUSION: MR imaging was useful for evaluation of changes in fibroleiomyoma volume after uterine arterial embolization. MR imaging characteristics of fibroleiomyomas before embolization can help predict subsequent response to treatment.

Three-dimensional computed tomography bronchoscopy using clinical datasets: a comparison with fibreoptic bronchoscopy.

OBJECTIVE: To assess three-dimensional computed tomography 'bronchoscopic' (3-DCTB) reconstruction of routine CT data as a non-invasive method of airway visualization, and compare it with fibreoptic bronchoscopy (FOB). METHODS: Fourteen datasets were acquired from 13 patients undergoing both FOB and CT examination of the chest. Standard continuous volume CT using 6 mm collimation and clinical FOB techniques were employed. Images were obtained from 3-DCTB reconstructions by segmentation and surface recognition algorithms generating surface rendered 'bronchoscopic views'. These were scored for technical quality and anatomical detail. The most distal bronchi seen in left upper and right lower lobes were recorded for FOB and 3-DCTB. RESULTS: On FOB, the subsegmental bronchi were seen in right lower and in left upper lobe in 10/14 cases and 4/14 cases, respectively. Visualization of the subsegmental airways was not achieved with 3-DCTB, as they could not be identified with confidence. 3-DCTB never achieved a more distal view than obtained by FOB. Using 3-DCT, the right, lower lobe segmental bronchi were seen in 10/14 cases, and lobar bronchus in 14/14 cases (two occluded). In the left upper lobe, 3-DCT showed segmental bronchi in 6/14 cases, lobar bronchus in 11/14 cases (one occluded) and the left main bronchus appeared occluded in 3/14 cases. Overall, technical quality and anatomical detail scores of the carina and proximal bronchi ranked significantly higher than views of segmental bronchi. CONCLUSIONS: 3-DCTB cannot routinely replace FOB for inspection of major and segmental bronchi. Subsegmental bronchi cannot be adequately demonstrated by 3-DCTB using 6 mm collimation datasets.

Proton MRS and quantitative MRI assessment of the short term neurological response to antiretroviral therapy in AIDS.

OBJECTIVE: To investigate MRI and proton spectroscopy changes in five patients with HIV associated dementia complex (HADC) treated with antiretroviral therapy. METHODS: Three markers were evaluated: (1) CSF/intracranial volume ratio; (2) T2 weighted signal ratio between parieto-occipital white and subcortical grey matter; and (3) metabolite ratios from long echo time (TE=135 ms) single voxel proton spectra of parieto-occipital white matter. RESULTS: Spectroscopic changes indicated initial increases in N-acetyl/(N-acetyl + choline + creatine) ratio (NA/(NA+ Cho+Cr)) and progression of atrophy after initiation of antiretroviral therapy in four of five patients. When the neurological status of the patients subsequently deteriorated (two of five patients), the NA/(NA+Cho+Cr) ratio also declined. CONCLUSIONS: Spectroscopic changes mirror reversible neuronal dysfunction. These objective, non-invasive techniques may be used for monitoring the neurological effects of antiretroviral drug therapy in patients with HADC.

Comparison of magnetic resonance imaging with neuropathological findings in the diagnosis of HIV and CMV associated CNS disease in AIDS.

OBJECTIVES: To compare the results of clinical assessment and MRI with neuropathological findings in the diagnosis of HIV and cytomegalovirus (CMV) associated CNS disease. METHODS: A retrospective study of 35 patients infected with HIV who were examined at necropsy between four and 70 (median 20) days after neurological assessment and MRI. RESULTS: Of the 35 patients, 19 had diffuse white matter hyperintensity on T2 weighted MRI, six of whom also had focal lesions. Nine other patients had focal white matter lesions and seven had changes in cortical atrophy only. Necropsy in the 19 with diffuse white matter hyperintensity showed HIV leukoencephalopathy (HIVLEP) with encephalitis in 10, CMV encephalitis in three, both HIVLEP/HIV encephalitis and CMV encephalitis in one, lymphoma in three, and non-specific inflammation in two. Necropsy in the 16 other patients without diffuse white matter hyperintensity showed CMV encephalitis in six, HIV encephalitis (without HIVLEP) in two, CMV encephalitis and HIVLEP/HIV encephalitis in one, non-HIV associated abnormalities in five, herpes simplex encephalitis in one, and lymphoma in one. CMV DNA was detected in CSF of five of seven patients with CMV encephalitis and in two of two with CMV associated polyradiculopathy but without CMV encephalitis. Diffuse white matter hyperintensity on MRI had a sensitivity of 100%, a specificity of 66.6%, and a positive predictive value of 58% for diagnosis of HIVLEP. CONCLUSION: Diffuse white matter hyperintensity on MRI can be due to either HIV or CMV associated pathology or non-specific abnormalities.

Cerebral proton magnetic resonance spectroscopy in asymptomatic HIV infection.

OBJECTIVE: To determine whether proton magnetic resonance spectroscopy (MRS) demonstrates central nervous system abnormalities in asymptomatic HIV-1-infected individuals. DESIGN: Both prospective and retrospective cross-sectional analyses of MRS in asymptomatic HIV-infected individuals. SETTING: Two specialists HIV/AIDS outpatient facilities in London. PARTICIPANTS: Eighty-four HIV-1 seropositive asymptomatic men; 29 HIV-1 antibody-negative homosexual men at high-risk for HIV infection and 48 HIV-1 antibody-negative men at low-risk for HIV infection as controls. MAIN OUTCOME MEASURES: Single voxel, gradient-localized proton MRS performed at 1.5 T with 135 msec echo-time and 1,600 msec repeat-time in an 8 ml volume of interest positioned in the parieto-occipital white matter. Spectroscopic results were expressed as ratios between the areas under the N-acetyl (NA), creatine (Cr) and choline (Cho) resonance peaks. RESULTS: There were no differences between those controls at high and those at low-risk for HIV infection. Comparing the combined control groups with the asymptomatic seropositive patients there were statistically significant differences in NA/Cho, NA/Cr (both P < 0.05) and NA/(NA + Cho + Cr) (P < 0.01). CONCLUSION: Abnormalities in cerebral biochemistry may be demonstrated by proton MRS during asymptomatic HIV-1 infection.

Correlation of MRI and neuropathology in AIDS.

OBJECTIVE: To assess the correlation between findings on radiological and neuropathological examinations of the brain. METHODS: The formalin fixed brains of 19 patients who had died of AIDS were examined by MRI and neuropathology. RESULTS: The rate of identification of cerebral atrophy was similar radiologically and neuropathologically. However, only in half of these cases were the two examinations concordant in the diagnosis. Furthermore, in the 15 brains which had radiological diffuse white matter lesions, the underlying pathology was heterogeneous. CONCLUSIONS: The possible reasons for the inconsistencies, and their relevance to the interpretation of imaging studies, are discussed. The study suggests that the qualitative identification of atrophy in the postmortem brain is problematical and that diffuse white matter lesions seen on MRI are not indicative of a specific pathological process.

Magnetic resonance imaging of the brain and cerebral proton spectroscopy in patients with systemic lupus erythematosus.

OBJECTIVE: To investigate the prevalence and extent of cerebral changes in patients with systemic lupus erythematosus (SLE) by magnetic resonance imaging (MRI) and magnetic resonance spectroscopy (MRS). METHODS: SLE patients (47 women) and controls (25 women) underwent 1.5T MRI. A semiautomated segmentation technique calculated cerebrospinal fluid (CSF) and brain volumes. Proton MRS of the frontal and parieto-occipital white matter yielded metabolite ratios of N-acetyl groups (NA), choline, and creatine. RESULTS: Compared with the control group, the SLE patients more often had cerebral atrophy on MRI (32% versus 0%), confirmed by an increase in the CSF to intracranial volume ratio. The patients also had old infarcts and hemorrhages (8.5% versus 0%) and more small white matter lesions (23% versus 8% had > 5 such lesions). MRS showed relative reduction of NA peaks. Although no patient was studied when acutely ill, prior neurologic involvement was related to abnormal findings. CONCLUSION: MRI and MRS are helpful in the investigation of cerebral complications of SLE. There are chronic changes which may be ischemic in nature. Their precise cause, consequences, and prevention are current challenges.

Cerebral volumes and spectroscopic proton metabolites on MR: is sex important?

One of the factors that may influence the selection of appropriate controls for MR studies of the brain is gender. This study compared calculated intracranial volumes and proton spectroscopic metabolite ratios obtained from male and female volunteers. Thirty-two males (mean age = 36; range = 30-53 yr) and 19 females (mean age = 39; range = 26-53 yr) underwent investigation at 1.5T. Brain, cerebrospinal fluid (CSF), and intracranial (ICV = brain + CSF) volumes were measured by the CLASS technique on data acquired using an axial dual spin-echo imaging sequence (TE = 20/90 ms, TR = 3500 ms). Proton spectra (TE = 135 ms, TR = 1600 ms) were acquired from an 8 ml cubic region placed in parieto-occipital white matter. The mean male and female brain, CSF and ICV were significantly different (p < .005). However, the mean CSF/ICV ratios of the two groups were not significantly different. The N-acetyl/choline and choline/creatine metabolite ratios of the two groups were significantly different (p < .05). When comparing proton metabolite ratios and absolute brain volumes between groups, gender is an important factor. CSF/ ICV ratios do not appear to depend on gender.

Proton Spectroscopy in a Cross-Section of HIV-Positive Asymptomatic Patients Receiving Immediate Compared with Deferred Zidovudine (Concorde Study).

The purpose of this study was to examine by proton spectroscopy for any difference in cerebral metabolites in patients taking part in the Concorde study (comparing the efficacy of immediate versus deferred treatment with zidovudine on asymptomatic HIV infected individuals). Forty seven HIV positive male patients [29 immediate, 18 deferred zidovudine] were examined in the last 9 months of the therapeutic trial. Magnetic resonance imaging and proton spectroscopy were performed at 1.5 Tesla using a single voxel placed in the parieto-occipital white matter. No significant difference was found in metabolite ratios comparing immediate versus deferred zidovudine (NA/NA+Cho+Cr 0.52 vs. 0.52). High quality spectra were acquired in relatively large numbers of patients and logistically spectroscopy may be applied to clinical therapeutic studies.

Cranial MR imaging in Wilson's disease.

OBJECTIVE: The purpose of the study was to describe the range of abnormalities seen on cranial MR images of patients with Wilson's disease and correlate the findings with clinical severity, duration of disease, and duration of neurologic signs and symptoms before treatment. In those patients with serial studies, the changes on MR images were compared with the clinical response. SUBJECTS AND METHODS: Twenty-five patients with Wilson's disease underwent MR imaging of the brain using conventional spin-echo sequences (n = 25), phase maps (n = 8), and partially refocused interleaved multiple-echo sequences (n = 5). RESULTS: MR imaging findings were abnormal in 22 patients and normal in three patients. The basal ganglia were interpreted as abnormal in 19 (86%) of 22 patients, involving the putamen in 19 (86%), the thalami in 12 (54%), the caudate head in 10 (45%), and the globus pallidus in nine (41%). We found a predilection for involvement of the outer rim of the putamen and the ventral nuclear mass of the thalami. The claustrum was abnormal in three patients. The midbrain was abnormal in 17 (77%) of these 22 patients, affecting predominantly the tegmentum but also the substantia nigra, red nuclei, inferior tectum, and crura. The pons was abnormal in 18 (82%) of 22 patients, and the cerebellum was abnormal in 11 patients (50%), with involvement of the superior and middle cerebellar peduncles. Atrophy was present in 18 (82%) of 22 patients, and cortical white matter changes were apparent in 13 (59%) of 22 patients. The scan of one untreated patient revealed shortening of the T1 relaxation time in the thalami, which was consistent with the paramagnetic effects of copper. Phase maps and partially refocused interleaved multiple-echo sequences performed in eight and five patients, respectively, and used to reveal a susceptibility change induced by iron or copper showed normal findings. We found a significant inverse relationship between severity, but not extent, of change in signal intensity and the length of untreated disease (p = .030) and the total duration of disease (p = .015). The study group was too small to show a correlation with clinical findings. Changes seen on MR images matched the clinical response to treatment in only two of the seven patients who underwent follow-up studies. CONCLUSION: MR imaging revealed abnormalities in the basal ganglia, cerebral white matter, midbrain, pons, and cerebellum. The paramagnetic effects of copper were detected only in untreated patients. Patients with a longer duration of disease had less severe changes in signal intensity. MR imaging was of limited value in follow-up.

Sub-cortical white-grey matter contrast on MRI as a quantitative marker of diffuse HIV-related parenchymal abnormality.

White matter change occurs in human immunodeficiency virus (HIV) encephalopathy, which may be difficult to assess subjectively especially in the early stages of disease. This study applies a quantitative approach to the assessment of this finding. Sixty-three HIV seropositive subjects, 47 seronegative blood donors and 17 seronegative homosexual men underwent axial T2 weighted MRI of the brain at 1.5T. Quantitative analysis was performed by obtaining the pixel contrast between parieto-occipital white matter and head of caudate grey matter (Cwg). Highest values of Cwg were found in a subgroup of subjects with AIDS who had diffuse/patchy white matter abnormalities and atrophy on qualitative image assessment. Statistically significant differences were found in Cwg between subjects with high (> or = 200 x 10(6)/I) and low (< 200 x 10(6)/I) CD4 lymphocyte counts (P < 0.05) and between subjects with and without HIV-1 associated cognitive/motor complex (P < 0.05). This technique provides an objective measure of diffuse HIV-related parenchymal abnormality seen on T2 weighted MRI.

Blood-Brain Barrier Integrityin HIV Infection:Evaluation by Contrast-EnhancedMagnetic Resonance Imaging.

This study assesses the integrity of the blood-brain barrier (BBB) in human immunodeficiency virus (HIV) seropositive individuals to magnetic resonance imaging (MRI) contrast agent Gd-DTPA. Twelve HIV seropositive patients and six control subjects had T2-weighted and serial pre- and post-contrast TI-weighted MRI. Ten of the twelve seropositive patients demonstrated white matter hyperintensity with or without atrophy on T2-weighted MRI and 8/10 who underwent neurological examination demonstrated neurological abnormalities. No statistically significant differences of trends in white matter pixel values were observed between pre- and post-contrast scans in any of the patients or controls. Serial T1-weighted MRI does not demonstrate any change in the integrity of the BBB to Gd-DTPA in HIV seropositive patients, regardless of the presence or absence of white matter hyperintensity with or without atrophy on T2-weighted MRI or clinical signs of HIV-I associated with cognitive/motor complex.

Cerebral magnetic resonance relaxometry in HIV infection.

A prospective, cross-sectional study was designed to determine the magnetic resonance relaxation times of cerebral white matter in human immunodeficiency virus (HIV) infected individuals. T1 and T2 were estimated at 1.5 T using four-point methods. Seventy-five HIV-1 seropositive subjects, 48 seronegative blood donors, and 17 seronegative homosexual men were studied. Associations between relaxometry and clinical classification, neurological status, immunological status, and qualitative MRI were investigated. Statistically significant differences in white matter T1 relaxation time were found comparing low-risk control and AIDS groups (p < .005), seropositive subjects with neurological signs and those without (p < .005), and subjects with low (CD4 < or = 200 x 10(6)/l) and high (CD4 > 200 x 10(6)/1) CD4 cell counts (p < .05). These findings add to the body of information that reveals no HIV-related change in the brain before the onset of symptomatic immunosuppression and go someway to validating the previous visually rated, qualitative findings. Statistically significant difference in white matter T2 relaxation time were also found comparing the two control groups (p < .005) highlighting the need for appropriate controls.

Toxoplasmosis and primary central nervous system lymphoma in HIV infection: diagnosis with MR spectroscopy.

PURPOSE: To differentiate intracranial lymphoma from Toxoplasma gondii lesions in patients infected with the human immunodeficiency virus, by means of localized spin-echo proton magnetic resonance (MR) spectroscopy. MATERIALS AND METHODS: Twenty-seven lesions were studied (18 T gondii lesions, nine lymphoma lesions) at 1.5 T. Spectra were acquired at an echo time of 135 msec from voxels centered on the lesions. Both visual analysis and spectral fitting were used to obtain metabolite ratios for choline (Cho), creatine (Cr), N-acetyl (NA), lactate, and lipids. RESULTS: Three spectral categories were seen. One had large lipid peaks with suppression of other metabolites. Another had an elevated Cho/Cr ratio with relatively diminished NA. The third had features of the other two. Examples of each spectrum type were acquired from both T gondii and lymphoma lesions. Neither method of analysis allowed differentiation between lesion types. MR spectroscopy showed an overlap of spectra. CONCLUSION: The authors conclude that toxoplasmosis and lymphoma cannot be differentiated with spin-echo proton MR spectroscopy at 135 msec.

Short echo time proton spectroscopy of the brain in HIV infection/AIDS.

Short echo time proton spectra have been acquired from the brains of 30 male homosexual Acquired Immunodeficiency Syndrome (AIDS) patients and 12 age-matched control subjects on a 1.5 T MR system. The acquisition protocol used stimulated acquisition voxel localisation with a voxel size of 8 ml and repeat, echo, and mixing times of 5000, 20, and 30 ms, respectively. A single 25.6-ms Gaussian water suppression pulse was used with 128 spectral acquisitions and the data were eddy current corrected using a water reference. Baseline-corrected spectra were nonlinearly least squares fitted to a model function consisting of Gaussian functions representing the major metabolites reported in short echo proton spectra. Results indicate that the N-acetyl/creatine (NA/Cr) ratio is significantly reduced by 20% in AIDS patients [NA/Cr = 1.91 (0.51)] compared to control subjects [NA/Cr = 2.37 (0.25)] at short echo times.