Carmofur-induced leukoencephalopathy: MRI

Carmofur, a derivative of 5-fluorouracil, has recently been noted to have an infrequent but serious association with leukoencephalopathy. To our knowledge, there has been no report of early MRI findings in this leukoencephalopathy. We describe a case in which diffuse high signal intensity of the entire cerebral white matter, including the corpus callosum, was seen on T2-weighted magnetic resonance images. Although similar findings can be seen in many other diseases, carmofur-induced leukoencephalopathy should be suspected in a patient treated with carmofur. It is important to know the clinical and MRI characteristics of this condition, for early diagnosis and better prognosis.     

Diffusion-weighted MR imaging of thyroid nodules

Introduction  The purpose of our study was to determine the diagnostic role of diffusion-weighted imaging (DWI) in the differentiating of malignant and benign thyroid nodules by using fine needle aspiration biopsy cytology criteria as a reference standard. The apparent diffusion coefficient (ADC) values of the normal-looking thyroid parenchyma were also evaluated both in normal patients and in patients with nodules. Methods  Between March 2007 and February 2008, 76 consecutive patients with ultrasound-diagnosed thyroid nodules and 20 healthy subjects underwent diffusion-weighted MR imaging by using single-shot spin echo, echo planar imaging. A total of 93 nodules were included in the study using the following b factors 100, 200, and 300 mm²/s. ADC values of thyroid nodules and normal area in all subjects were calculated and compared using suitable statistical analysis. Results  Mean ADC values for malignant and benign nodules were and for b-100 factor, and for b-200, and and , for b-300, respectively. Mean ADC values of malignant nodules were lower than benign nodules. There were significant differences in ADC values between benign and malignant nodules. ADC values among normal-appearing thyroid parenchyma of patients and normal-appearing thyroid parenchyma of healthy subjects were insignificant at all b factors. Conclusion  Benign nodules have higher ADC values than malignant ones. DWI may be helpful in differentiating malign and benign thyroid nodules.     

Diffusion-weighted MR imaging in the early diagnosis of periventricular leukomalacia

Diffusion-weighted imaging (DWI) has been shown to be highly sensitive in detecting acute cerebral infarction, but its use in detecting hypoxic–ischemic encephalopathy (HIE) in neonates is still controversial. Moreover, few reports concern pre-term infants with possible periventricular leukomalacia (PVL). We examined the ability of this technique to detect cerebral changes in the acute phase of PVL. Fifteen MR examinations were performed in 11 pre-term infants (mean age 3.4 days, range 2–6 days). Conventional DWI sequences, apparent diffusion coefficient (ADC) maps, and US obtained in the acute phase were compared. All the neonates underwent US follow-up up to 4 months after delivery; those with suspected PVL also underwent MRI follow-up for up to 2 months. Qualitative and quantitative evaluations were performed to assess the presence of DW changes compatible with PVL. Diffusion-weighted MRI showed signal hyperintensity associated with decreased ADC values in 3 subjects (27%). In these patients conventional MRI sequences were interpreted as normal and US (performed at the same time) as doubtful in 2 and compatible with PVL in 1 subject. The MRI and US follow-up confirmed severe damage in all these patients. In 1 neonate hemorrhages involving the germinative matrix were identified. In 8 neonates MRI was considered normal. In these subjects US follow-up (up to 4 months) confirmed no signs of PVL. Diffusion-weighted imaging may have a higher correlation with later evidence of PVL than does conventional MR imaging and US when performed in the acute phase of the disease.     

Diffusion-weighted MR imaging of the normal fetal lung

To quantify apparent diffusion coefficient (ADC) changes in fetuses with normal lungs and to determine whether ADC can be used in the assessment of fetal lung development. In 53 pregnancies (20–37th weeks of gestation), we measured ADC on diffusion-weighted imaging (DWI) in the apical, middle, and basal thirds of the right lung. ADCs were correlated with gestational age. Differences between the ADCs were assessed. Fetal lung volumes were measured on T2-weighted sequences and correlated with ADCs and with age. ADCs were 2.13 ± 0.44 μm²/ms (mean ± SD) in the apex, 1.99 ± 0.42 μm²/ms (mean ± SD) in the middle third, and 1.91 ± 0.41 μm²/ms (mean ± SD) in the lung base. Neither the individual ADC values nor average ADC values showed a significant correlation with gestational age or with lung volumes. Average ADCs decreased significantly from the lung apex toward the base. Individual ADCs showed little absolute change and heterogeneity. Lung volumes increased significantly during gestation. We have not been able to identify a pattern of changes in the ADC values that correlate with lung maturation. Furthermore, the individual, gravity-related ADC changes are subject to substantial variability and show nonuniform behavior. ADC can therefore not be used as an indicator of lung maturity.     

Diffusion-weighted MR imaging and MR spectroscopy in glutaric aciduria type 1

Although conventional magnetic resonance imaging (MRI) findings of glutaric aciduria type 1 (GA-1) have been well established, diffusion weighted MR imaging (DWI) and proton MR spectroscopy (MRS) findings are limited. We report widespread restricted diffusion in the white matter and increased diffusion in bilateral putamen in a case of GA-1. The MRS showed decreased N-acetyl-aspartate (NAA)/creatine (Cr) ratio compared with a sex and age-matched control with no significant change in choline (Cho)/Cr ratio. The presence of the lactate peak reflecting disturbed mitochondrial functions in this disease has never been reported.     

Diffusion-weighted MR imaging of uterine endometrial cancer

PURPOSE: To determine the feasibility of diffusion-weighted (DW) MRI of uterine endometrial cancer and to investigate whether the apparent diffusion coefficient (ADC) values of endometrial cancer differ from those of normal endometrium and whether they differ according to the histologic grade of the tumor. MATERIALS AND METHODS: Study population included 18 consecutive females with surgically proven endometrial cancer and 12 females with pathologically confirmed normal endometrium in cervical cancer patients. Visual evaluation and ADC measurement were performed in endometrial cancer and normal endometrium. RESULTS: All endometrial cancer and the normal endometrium appeared hyperintense on DW images. The mean ADC value (10(-3) mm(2)/second) of endometrial cancer was 0.88 +/- 0.16, which was significantly lower (P < 0.01) than that of normal endometrium (1.53 +/- 0.10). The mean ADC value for each histologic grade was 0.93 +/- 0.16 (G1), 0.92 +/- 0.13 (G2), and 0.73 +/- 0.09 (G3). CONCLUSION: The present study showed that DW imaging is feasible in demonstrating uterine endometrial cancer and ADC measurement has a potential ability to differentiate between normal and cancerous tissue of the endometrium. The ADC values of endometrial cancers of higher grade show tendency to decrease compared to those of lower grade, although estimation of histologic grade based on ADC values seems difficult because of considerable overlap.     

Diffusion-weighted MR imaging (DWI) in spinal cord ischemia

Introduction Spinal cord infarction is a rare clinical diagnosis characterized by a sudden onset of paralysis, bowel and bladder dysfunction, and loss of pain and temperature perception, with preservation of proprioception and vibration sense. Magnetic resonance imaging (MRI) usually demonstrates intramedullary hyperintensity on T2-weighted MR images with cord enlargement. However, in approximately 45% of patients, MR shows no abnormality. Diffusion-weighted MR imaging (DWI) has been widely used for the evaluation of a variety of brain disorders, especially for acute stroke. Preliminary data suggest that DWI has the potential to be useful in the early detection of spinal infarction.Methods We performed DWI, using navigated, interleaved, multishot echo planar imaging (IEPI), in a series of six patients with a clinical suspicion of acute spinal cord ischemia.Results In all patients, high signal was observed on isotropic DWI images with low ADC values (0.23 and 0.86×10⁻³ cm²/s), indicative of restricted diffusion.Conclusion We analyzed the imaging findings from conventional MR sequences and diffusion-weighted MR sequences in six patients with spinal cord infarction, compared the findings with those in published series, and discuss the value of DWI in spinal cord ischemia based on current experience. Although the number of patients with described DWI findings totals only 23, the results of previously published studies and those of our study suggest that DWI has the potential to be a useful and feasible technique for the detection of spinal infarction.     

Diffusion-weighted MR imaging of the breast: Advantages and pitfalls

The aim of this paper is to review all clinical applications of diffusion weighted MR imaging (DWI) for breast pathology. The challenge of DWI is to obtain the best compromise between lesion detection and characterization. Technical factors affecting lesion characterization and detection are detailed including the effect of contrast administration, the choice of number of b and of b_max, the variation of diagnostic performance according to the type and the size of lesion studied.     

Diffusion-weighted MR imaging of pyogenic intraventricular empyema

Introduction Pyogenic intraventricular empyema (PIE) is a potentially fatal CNS infection. However, it is sometimes difficult to diagnose PIE on the basis of clinical and conventional MRI findings. Diffusion-weighted imaging (DWI) has been accepted as a useful MR sequence for the diagnosis of various intracranial infections. The purpose of this study was to determine the DWI characteristics of PIE and the role of DWI in the diagnosis of PIE. Methods Eight patients with PIE underwent MRI including DWI. We assessed the presence and signal characteristics of PIE. In seven patients, the signal intensities of the PIE and cerebrospinal fluid (CSF) were measured and the contrast-to-noise ratio (CNR) percentage was calculated. ADC values of the PIE, CSF, and white matter were also determined. Results PIE was detected in all patients by DWI, in five (63%) by FLAIR imaging, and in two (25%) by T1- and T2-weighted imaging. The CNR percentages of the PIEs in relation to the CSF were highest for DWI, followed by FLAIR, T1-, and T2-weighted imaging. There were statistically significant differences between the images of each sequence. In all patients, PIE showed hyperintensities on DWI and hypointensities to the CSF and hypo- or isointensities to the white matter on ADC maps. The ADC values (mean±SD) of the PIE, CSF, and white matter were 0.60±0.27, 2.81±0.04, and 0.79±0.08 (×10⁻³ mm²/s). There was a statistically significant difference between PIE and the CSF. Conclusion PIE shows a bright intensity on DWI, and DWI is a sensitive MR sequence for the diagnosis of PIE.     

Diffusion-weighted MR imaging of viral encephalitis

Introduction The aim of this study was to evaluate the role of diffusion-weighted imaging (DWI) in the diagnosis of viral encephalitis and its relationship with the stage of the illness.Methods We performed conventional magnetic resonance imaging (MRI) including T1-W, T2-W and fluid attenuated inversion recovery (FLAIR) sequences and DWI in 18 patients with viral encephalitis diagnosed on the basis of laboratory, clinical and radiologic findings. Based on the qualitative and quantitative comparison of the conventional MRI and DWI, the patients were divided into three groups. Apparent diffusion coefficient (ADC) values of the involved and contralateral normal brain tissues were computed and compared for each group. The degree of correlation between the time (TI) from the onset of neurologic symptoms to the MR examination and ADC values was determined.Results In group I (n=11) DWI was superior to conventional MRI in detecting the encephalitic involved sites and in depicting the borders of the encephalitic lesions. In group II (n=4) DWI was similar to conventional MRI. In group III (n=3) conventional MRI was superior to DWI. Mean ADC values of affected versus contralateral normal brain tissues were 0.458±0.161×10⁻³ versus 0.86±0.08×10⁻³ in group I, 0.670±0.142×10⁻³ versus 0.93±0.07×10⁻³ in group II, and 1.413±0.211×10⁻³ versus 1.05±0.06×10⁻³ in group III. Patients in group I had significantly lower ADC values than those in group II, while patients in group III had the highest ADC values (P<0.05). The ADC values were significantly lower in the affected sites than in the unaffected sites of patients in groups I and II, but were significantly higher in the affected sites than in the unaffected sites of patients in group III (P<0.05). There was an excellent correlation between ADC values and duration of the disease (r=0.874, P=0.01).Conclusion DWI is superior to other conventional diagnostic MR sequences in the detection of early viral encephalitic lesions and depiction of the lesion borders and, in combination with other sequences, DWI may contribute to the determination of the disease phase.     

Diffusion-weighted MR imaging for urinary bladder carcinoma: initial results

The aim of this study was to demonstrate the feasibility of using diffusion-weighted (DW) magnetic resonance (MR) imaging under free breathing for the detection of a urinary bladder carcinoma. In 15 patients with 17 urinary bladder carcinomas, DW images were obtained in the axial plane under free breathing scanning with a multisection spin-echo type single-shot echo planar sequence with a body coil. DW images were evaluated based on cystoscopic findings. Moreover, the apparent diffusion coefficient (ADC) value was measured in a circular region of interest (ROI) within the carcinoma, urine, normal bladder wall, prostate and seminal vesicle. In the results, on the DW images, all 17 carcinomas were clearly shown as high signal intensity relative to the surrounding structure. The ADC value (×10⁻³ mm²/s) in the carcinoma was 1.18±0.19, which was significantly lower compared with that of urine (3.28±0.20), the normal bladder wall (2.27±0.24), prostate (transition zone: 1.57±0.09, peripheral zone:1.85±0.22) and seminal vesicle (2.01±0.22). In conclusion, DW images under free breathing enabled the clear detection of the urinary bladder carcinoma, whose ADC values were lower compared with those of the surrounding structure. The DW images may be useful in evaluating tumors invading to the surrounding structures.     

Reversible posterior leukoencephalopathy after combination chemotherapy

We describe a young woman with Burkitt's lymphoma, treated with intravenous adriamycine and cyclophosphamide and intrathecal cytarabine. She developed a reversible posterior leukoencephalopathy syndrome (RPLS) with typical MRI findings. Diffusion-weighted images during the first days after the onset of symptoms predicted a small irreversible lesion in the frontal lobe, verified on T2-weighted images 1 month later. The patient showed full recovery after high-dose steroid treatment. Received: 4 April 2000/Accepted: 17 May 2000     

Diffusion-weighted imaging in patients with progressive multifocal leukoencephalopathy

Progressive multifocal leukoencephalopathy (PML) is a severe demyelinating disease of the central nervous system due to JC polyoma virus infection of oligodendrocytes. PML develops in patients with impaired T-cell function as occurs in HIV, malignancy or immunosuppressive drugs users. Until now no imaging methods have been reported to correlate with clinical status. Diffusion-weighted imaging (DWI) is a robust MRI tool in investigating white matter architecture and diseases. The aim of our work was to assess diffusion abnormalities in focal white matter lesions in patients with PML and to correlate the lesion load measured with conventional MRI and DWI to clinical variables. We evaluated eight patients with a biopsy or laboratory-supported diagnosis of PML. All patients underwent MRI including conventional sequences (fluid attenuated inversion recovery-FLAIR) and DWI. Mean diffusivity (MD) maps were used to quantify diffusion on white matter lesions. Global lesion load was calculated by manually tracing lesions on FLAIR images, while total, central core and peripheral lesion loads were calculated by manually tracing lesions on DWI images. Lesion load obtained with the conventional or DWI-based methods were correlated with clinical variables such as disease duration, disease severity and survival. White matter focal lesions are characterized by a central core with low signal on DWI images and high MD (1.853 × 10⁻³ mm2/s), surrounded by a rim of high signal intensity on DWI and lower MD (1.1 × 10⁻³ mm2/s). The MD value of normal-appearing white matter is higher although not statistically significant (0.783 × 10⁻³ mm2/s) with respect to control subjects (0.750 × 10⁻³ mm2/s). Inter-rater correlations of global lesion load between FLAIR (3.96%) and DWI (3.43%) was excellent (ICC =0.87). Global lesion load on FLAIR and DWI correlates with disease duration and severity (respectively, p = 0.037, p = 0.0272 with Karnofsky scale and p = 0.0338 with EDSS on FLAIR images; p = 0.043, p = 0.0296 with Karnofsky scale and p = 0.0365 with EDSS on DW images). Central core lesion load on DWI correlates with disease duration and severity (respectively p = 0.043, p = 0.0103 with Karnofsky scale and p = 0.0112 with EDSS), while peripheral lesion load does not correlate with any clinical variable. The global lesion load in PML correlates with disease duration and severity. DWI images, which can distinguish within lesions a central core from a peripheral rim, reveal that a larger central core component correlates to a worsened clinical status and longer disease duration. On the other hand the peripheral rim lesion load visualized on DWI images does not correlate with clinical variables and does not achieve obtaining further prognostic information with respect to conventional imaging.     

Optimizing joint imaging: MR imaging techniques

For optimizing MR of the joints, a sophisticated knowledge of MR system hard-and software condition, and coil technologies, sequence and contrast preparation techniques, and the use of paramagnetic contrast agents is necessary. This review article discusses the basic principles of the appropriate use of surfacecoilsas well as the different conventional and fast imagingsequences, including three-dimensional (3D)MR imaging. In addition, the applications of contrast agents as well as the most important contrast prepaation techniques are reviewed.     

儿童脑室周围白质软化症的MR扩散张量成像研究

目的应用MR扩散张量成像对脑室周围白质软化症(PVL)患儿和正常婴幼儿进行比较。方法对15例正常志愿者和15例PVL患儿进行了扩散张量成像扫描,测量双侧内囊后肢、双侧视放射和胼胝体膝部、压部的部分各向异性(FA)值,并对结果进行统计学比较。结果对照组和PVL组的右侧内囊后肢的FA值分别为0682±0399和0555±0087、左侧内囊后肢的FA值分别为0673±0043和0557±0030,右侧和左侧视放射的FA值分别为0437±0675、0429±0052、0351±0051、0339±0064,胼胝体膝部、压部的FA值分别为0696±0579、0756±0454、0564±0080、0586±0100,差异均有统计学意义(P<001)。结论扩散张量成像能提示纤维束的髓鞘化过程的延迟,反映儿童发育中脑白质微观结构的改变,在PVL的随访观察中具有较大的潜力。     

Diffusion-weighted echo-planar MR imaging of CNS involvement in systemic lupus erythematosus

RATIONALE AND OBJECTIVES: The purpose of this study was to determine the range of findings at diffusion-weighted magnetic resonance (MR) imaging in patients with systemic lupus erythematosus (SLE) and central nervous system involvement. MATERIALS AND METHODS: Diffusion-weighted MR images were reviewed in 20 patients with SLE and correlated with clinical symptoms and findings at computed tomography, conventional MR imaging, MR angiography, or conventional angiography. RESULTS: Diffusion-weighted MR imaging showed acute or subacute lesions in nine of 20 patients (45%). In the other 11, it showed no abnormal findings or chronic lesions. In four of the nine patients with lesions, diffusion-weighted imaging primarily showed hyperintense lesions with decreased apparent diffusion coefficient (ADC), which indicates acute or subacute infarcts. In four other patients, it primarily showed iso- or slightly hyperintense lesions with increased ADC, suggesting vasogenic edema. In two of these four patients, the findings were consistent with hypertensive encephalopathy. In the other two, small hyperintense foci on diffusion-weighted images with decreased ADC were seen within the vasogenic edema. These foci presumably represent microinfarcts associated with SLE vasculopathy. In the ninth patient, diffusion-weighted imaging showed a small linear hyperintense lesion with normal ADC in the left parietooccipital region. CONCLUSION: Diffusion-weighted imaging shows primarily two patterns of acute or subacute parenchymal lesions in patients with SLE: acute or subacute infarction and vasogenic edema with or without microinfarcts.     

MR imaging: acronyms and clinical applications

The intention of this article is to provide an overview of all MR imaging techniques that are accessible on most of commercially available scanners and have the potential to be used in routine clinical applications. The techniques implemented by the major vendors are briefly explained, including a comparison of the commonly used acronyms. A classification scheme is introduced which provides a reasonable illustration of similarities and differences between various techniques. The imaging techniques are divided into two main groups, the spin-echo and gradient-echo sequences. Within each group is the basic sequence, those which require a preparation of the magnetization, those which use multiple echoes to fill the k-space and those which are performed in a single shot. For each technique the typical clinical applications are listed or the potential applications which have been published. Received: 18 August 1998; Revision received: 3 November 1998; Accepted: 4 November 1998     

Diffusion-weighted MR imaging in transient ischaemic attacks

The purpose of this study was to determine frequency and the characteristics of diffusion-weighted imaging (DWI) abnormalities in patients with transient ischaemic attack (TIA). We analysed data of 98 consecutive patients (mean age: 60.6±15.4 years, 56 men) admitted between January 2003 and April 2004 for TIA. Age, gender, symptom type and duration, delay from onset to magnetic resonance imaging (MRI), probable or possible TIA and cause of TIA were compared in patients with (DWI+) and without (DWI−) lesions on DWI. Volume and apparent diffusion coefficient (ADC) values of DWI lesions were computed. DWI revealed ischaemic lesions in 34 patients (34.7%). Lesions were small (mean volume: 1.9 cm³±3.3), and ADC was moderately decreased (mean ADC ratio: 79.5%). The diagnosis of TIA was considered as probable in all DWI+ patients. A multiple logistic regression model demonstrated that TIA duration greater than or equal to 60 min (OR, 7.6; 95% CI, 2.3–25.7), aphasia (OR, 9.2; 95% CI, 2.7–31.4) and motor deficit (OR, 5.1; 95% CI, 1.5–17.8) were independent predictors of DWI lesions. Prolonged TIA duration, aphasia and motor deficits are associated with DWI lesions. More than half of TIA patients with symptoms lasting more than 60 min have DWI lesions.     

Diffusion-weighted MR imaging of posterior reversible leukoencephalopathy syndrome: a pictorial essay

Posterior reversible leukoencephalopathy syndrome is characterized by reversible white matter lesions. However, ischemic injury with irreversible damage may occur. This pictorial essay illustrates MR features associated with posterior reversible leukoencephalopathy syndrome. We will emphasize the role of diffusion-weighted imaging for the discrimination of irreversible ischemic injury from reversible vasogenic edema.