Intraspinal epidermoid cyst: diffusion-weighted MRI

We report a 7-year-old boy who presented with two-month history of worsening low back and right leg pain. Conventional MR images demonstrated a poorly outlined intradural mass recognized by the displacement of the conus medullaris and the nerve roots of the cauda equina at the L2–3 level. The signal intensity of the lesion was similar to CSF. There was no contrast enhancement of the lesion. Diffusion-weighted images and ADC values revealed restricted diffusion within the mass. Myelography confirmed the mass as an intradural filling defect with myelographic block at the L2–3 level. The patient underwent total surgical excision of the mass. Pathologic examination revealed the diagnosis of epidermoid cyst. Received: 11 July 2000 Accepted: 1 December 2000     

MR扩散加权成像鉴别颅内囊性病变的价值

目的探讨MR扩散加权成像（DWI）在颅内囊性病变中的鉴别诊断价值。方法对76例经临床及手术病理证实的颅内囊性病变患者，行常规MR、DWI及增强MR检查，其中脑脓肿19例，原发性脑胶质瘤20例，小脑血管母细胞瘤4例，脑转移瘤10例，蛛网膜囊肿7例，表皮样囊肿16例。回顾性分析颅内囊性病变的DWI信号特征，定量测定囊性变区表观扩散系数（ADC）值。结果DWI上19例脑脓肿呈高信号；34例脑肿瘤患者中，除3例脑胶质瘤呈高信号、1例呈等信号，1例脑转移瘤呈高信号外，其余29例均呈低信号。各种病变ADC值分别为：脑脓肿（0．62±0．15）×10^-3 mm^2／s、脑胶质瘤（2．39±0．78）×10^-3 mm^2／s、脑血管母细胞瘤（2．68±0．40）×10^-3 mm^2／s、脑转移瘤（2．79±0．79）×10^-3 mm^2／s。脑脓肿与脑胶质瘤、脑血管母细胞瘤、脑转移瘤的囊变坏死区ADC值比较，差异均有统计学意义（P〈0．01）；脑胶质瘤与脑血管母细胞瘤、脑转移瘤的囊变坏死区ADC值比较，差异均无统计学意义（P〉0．05）。7例颅内蛛网膜囊肿的DWI呈低信号；16例表皮样囊肿DWI呈明显高信号。颅内蛛网膜囊肿和表皮样囊肿的ADC值分别为（2．96±0．36）×10^-3 mm^2／s和（0．94±0．13）×10^-3 mm^2／s，二者之间差异有统计学意义（P〈0．01）。结论DWI及ADC值对鉴别脑脓肿和囊性或坏死性脑肿瘤具有重要的价值，DWI表现为低信号的颅内囊性病变可除外脑脓肿。     

颅内不典型表皮样囊肿MR表现和病理对照分析

目的 探讨颅内不典型表皮样囊肿的MR表现及其与病理所见的关系.方法 回顾性分析7例颅内不典型表皮样囊肿的MR表现,并与手术病理所见对照.全部病例均行MR平扫检查,2例行MR增强扫描,1例行CT扫描.结果 4例表皮样囊肿位于小脑半球实质,2例位于大脑半球实质,1例位于小脑周围.T1WI 6例表皮样囊肿呈高信号,1例呈等信号,T2WI 5例呈很低信号,2例呈高信号.增强扫描囊肿不强化.病理检查镜下可见囊肿内大量蛋白物质.结论 颅内表皮样囊肿呈短T1和等T1信号主要与囊肿内存在大量蛋白物质有关,需要与颅内短T1信号的病变鉴别.     

Characterization of head and neck lesions with diffusion-weighted MR imaging and the apparent diffusion coefficient values

Purpose

The aim of this study was to determine the role of diffusion-weighted MR imaging (DWI) and the apparent diffusion coefficient (ADC) in characterization of head and neck lesions.

Patients and methods

MR imaging including diffusion-weighted sequences was performed on 43 patients presented with head and neck lesions. Images were obtained with a diffusion-weighted factor (b factor) of 100, 500, and 1000 s/mm². ADC maps were reconstructed, and the ADC value of the lesions was calculated.

Results

The mean ADC value of malignant tumors was (1.02 ± 0.22) × 10⁻³ mm²/s (n = 31). The mean ADC value of benign tumors was (1.62 ± 0.27) × 10⁻³ mm²/s (n = 12). The mean ADC of lymphomas was significantly lower than that of carcinomas. The difference in the ADC value between the malignant tumors and benign lesions was statistically significant (p < 0.001). Selection of (1.2) × 10⁻³ mm²/s as a threshold value of ADC for differentiating benign from malignant tumors yielded the best result, with an accuracy of 94%, sensitivity of 95%, specificity of 92%, positive predictive value of 92% and negative predictive value of 94%.

Conclusion

DWI and the ADC measurement are promising, non-invasive imaging approach that can be used for characterization of head and neck lesions. It can help differentiate malignant tumors from benign lesions.     

骶管内脊膜囊肿的MR诊断

目的　探讨骶管内脊膜囊肿的临床表现、MR诊断及鉴别诊断。方法　 2 5例骶管内脊膜囊肿 ,均经手术病理证实。其中男 9例 ,女 16例 ,年龄 18～ 56岁 ,平均 40 .3岁。所有病例均行MR检查。结果　囊肿位于骶管内 ,呈卵圆形 19例 ,长条状囊袋形 3例 ,不规则形 1例 ,串珠形 2例。囊肿境界清楚 ,囊壁菲薄 ,囊液信号与脑脊液信号相似 ,T1WI囊液呈均质性低信号 ,T2 WI囊液呈高信号 ,8例T2 WI囊液信号较脑脊液信号更高。其中 7例囊肿内于T1WI和T2 WI可见细条状神经根影。 8例增强扫描囊液、囊壁无增强。结论　MR是骶管内脊膜囊肿最佳的检查方法之一 ,正确认识其MR征象不仅能够准确诊断 ,而且可以指导临床治疗方案的选择。     

Detection and classification of focal liver lesions in patients with colorectal cancer: retrospective comparison of diffusion-weighted MR imaging and multi-slice CT

Objectives

To compare the diagnostic performance of diffusion-weighted MR imaging (DWI) with multi-slice CT (MS-CT) in the detection and classification of focal liver lesions in patients with colorectal cancer.

Methods

In a retrospective study 68 patients who underwent DWI at 1.5 T (b-values of 50, 300 and 600 s/mm²) and contrast-enhanced MS-CT were analysed by two radiologists blinded to the clinical results. Imaging results were correlated with intraoperative surgical and ultrasound findings (n = 24), imaging follow-up or PET (n = 44). Sensitivity of DWI and MS-CT in detection of focal liver lesions was compared on a per-lesion and a per-segment basis. Receiver operator-characteristic (ROC) curves to determine the diagnostic performance and the sensitivities of correctly identifying liver metastases on a segmental base were calculated.

Results

For lesion detection, DWI was significantly superior to MS-CT both on a per-lesion (difference in sensitivities for reader 1 and 2 22.65% and 19.06%, p < 0.0001) and a per-segment basis (16.86% and 11.76%, p < 0.0001). Especially lesions smaller than 10 mm were better detected with DWI compared to MS-CT (difference 41.10% and 29.45%, p < 0.0001). ROC-analysis showed superiority for lesions classification (p < 0.0001) of DWI (AUC: 0.949 and 0.951) as compared to MS-CT (AUC: 0.879 and 0.892, p < 0.0001 and p = 0.005). DWI was able to filter out metastatic segments with a higher sensitivity (88.2 and 86.5%) compared to MS-CT (68.0 and 67.4%, p < 0.0001 and p = 0.005, respectively).

Conclusion

Compared to MS-CT DWI is both more sensitive in the detection of liver lesions and more accurate in determining the extent of metastatic disease in patients with colorectal cancer and therefore might help to optimize therapeutic management in those patients.     

MR imaging of metronidazole-induced encephalopathy: lesion distribution and diffusion-weighted imaging findings

BACKGROUND AND PURPOSE: MR imaging features of metronidazole-induced encephalopathy (MIE) have not been fully established. This study was undertaken to determine the topographic distributions and diffusion-weighted imaging (DWI) findings of MIE. MATERIALS AND METHODS: We retrospectively evaluated the initial MR images (n = 7), including DWI (n = 5), and follow-up MR images (n = 4) after drug discontinuation in 7 patents with clinically diagnosed MIE. The topographic distributions of lesions were evaluated on MR images, and DWI signal intensities and apparent diffusion coefficient (ADC) values of the lesions were assessed. RESULTS: MR images demonstrated bilateral symmetric T2 hyperintense lesions in the cerebellar dentate nucleus (n = 7), midbrain (n = 7), dorsal pons (n = 6), medulla (n = 4), corpus callosum (n = 4), and cerebral white matter (n = 1). Brain stem lesions involved the following: tectum (n = 5), tegmentum (n = 4), red nucleus (n = 3) of the midbrain, vestibular nucleus (n = 6), and a focal tegmental lesion involving the superior olivary nucleus (n = 6) and abducens nucleus (n = 4) of the pons and vestibular nucleus (n = 4) and inferior olivary nucleus (n = 1) of the medulla. DWI (n = 5) showed isointensity or hyperintensity of lesions, and the decreased ADC value was found only in the corpus callosum lesions (n = 2). All detected lesions were completely reversible at follow-up except for the single corpus callosum lesion with an initial low ADC value. CONCLUSION: Brain lesions were typically located at the cerebellar dentate nucleus, midbrain, dorsal pons, medulla, and splenium of the corpus callosum. According to DWI, most of the lesions in MIE probably corresponded to areas of vasogenic edema, whereas only some of them, located in the corpus callosum, corresponded to cytotoxic edema.     

The added value of diffusion-weighted MR imaging to MR cholangiopancreatography in differentiating malignant from benign extrahepatic biliary strictures

Purpose

To investigate the added value of diffusion-weighted imaging (DWI) to magnetic resonance cholangiopancreatography (MRCP) in differentiating benign from malignant extrahepatic biliary strictures.

Methods

Magnetic resonance examination including, T2-weighted imaging, MRCP and DWI using different b-values (0,500,800 s/mm²) were performed in 38 patients with suspicious extrahepatic biliary strictures. Apparent diffusion coefficient (ADC) value was calculated. The signal intensity of the lesions on DWI using b = 500 and 800 s/mm² was examined. Analysis of the DWI and MRCP images for the cause of the extrahepatic biliary stricutre was performed. Patients were further confirmed by histopathological diagnosis and follow up. Sensitivity, specificity, accuracy, positive predictive and negative predictive values were calculated for both the MRCP images and DWI.

Results

Of the 38 cases, 23 cases had malignant extrahepatic biliary strictures and 15 had benign strictures. DWI detected 21 out of the 23 malignant biliary strictures and 14 out of 15 benign biliary strictures. Malignant strictures more frequently appeared hyperintense than benign strictures on DWI using b-values of 500 and 800 s/mm². There was a significant difference in sensitivity (91.3% vs. 73%), specificity (93.3% vs. 64.7%), accuracy (92.1% vs. 73.6%), positive predictive value (95.4% vs. 81%), and negative predictive value (87.5% vs. 64.7%) between DWI and MRCP in differentiating biliary strictures.

Conclusion

Combined evaluation using DWI added to MRCP improves the differentiation of malignant from benign extrahepatic biliary strictures.     

High b-value diffusion-weighted MR imaging of normal brain at 3T

Introduction

The purpose of this study was to determine the normative apparent diffusion coefficient (ADC) values at 3 T using high b-value (3000 s/mm²) diffusion-weighted images (DWI) and compare the signal characteristics of the high b value with standard b-value (1000 s/mm²) DWI.

Methods

Institutional review board approval was obtained for this prospective study which included 20 volunteers (10 M, 10 F, mean age: 38.7 ± 14.9) without any known clinical disease or radiological findings. All brain examinations were performed with 3 T MR by using similar parameters of b1000 and b3000 DWI sequences. DWI and ADC maps were obtained. Signal intensity, noise, signal to noise ratio (SNR), contrast to noise (CNR), contrast ratio (CR), and ADC values of bilateral posterior limb of internal capsule, frontal white matter, parietal gray matter, pons, thalamus, splenium of corpus callosum were measured on b1000 and b3000 DW images.

Results

In all anatomic locations, MR signal intensity, SNR and ADC values of b3000 images were significantly lower than MR signal intensity, SNR and ADC values of b1000 images (p < 0.001). The CNR and CR values at the posterior limb of internal capsule and pons were significantly increased on b3000 images (p < 0.001) and decreased in the other regions measured.

Conclusion

The ADC values calculated from standard b-value DWI were significantly higher than those calculated from high b-value DWI. These results agree with the previous studies. In the regions where CNR values increase with high b value, b3000 DWI images may provide additional clinical information.     

The value of single-shot turbo spin-echo diffusion-weighted MR imaging in the detection of middle ear cholesteatoma

Introduction Single-shot (SS) turbo spin-echo (TSE) diffusion-weighted (DW) magnetic resonance imaging (MRI) is a non echo-planar imaging (EPI) technique recently reported for the evaluation of middle ear cholesteatoma. We prospectively evaluated a SS TSE DW sequence in detecting congenital or acquired middle ear cholesteatoma and evaluated the size of middle ear cholesteatoma detectable with this sequence. The aim of this study was not to differentiate between inflammatory tissue and cholesteatoma using SS TSE DW imaging. Methods A group of 21 patients strongly suspected clinically and/or otoscopically of having a middle ear cholesteatoma without any history of prior surgery were evaluated with late post-gadolinium MRI including this SS TSE DW sequence. Results A total of 21 middle ear cholesteatomas (5 congenital and 16 acquired) were found at surgery with a size varying between 2 and 19 mm. Hyperintense signal on SS TSE DW imaging compatible with cholesteatoma was found in 19 patients. One patient showed no hyperintensity due to autoevacuation of the cholesteatoma sac into the external auditory canal. Another patient showed no hyperintensity because of motion artifacts. Conclusion This study shows the high sensitivity of this SS TSE DW sequence in detecting small middle ear cholesteatomas, with a size limit as small as 2 mm.     

Quantitative diffusion-weighted MR imaging in the differential diagnosis of breast lesion

The role of diffusion-weighted magnetic resonance imaging (DWI) to differentiate breast lesions in vivo was evaluated. Sixty women (mean age, 53 years) with 81 breast lesions were enrolled. A coronal echo planar imaging (EPI) sequence sensitised to diffusion (b value=1,000 s/mm²) was added to standard MR. The mean diffusivity (MD) was calculated. Differences in MD among cysts, benign lesions and malignant lesions were evaluated, and the sensitivity and specificity of DWI to diagnose malignant and benign lesions were calculated. The diagnosis was 18 cysts, 21 benign and 42 malignant nodules. MD values (mean±SD ×10⁻³ mm²/s) were (1.48±0.37) for benign lesions, (0.95±0.18) for malignant lesions and (2.25±0.26) for cysts. Different MD values characterized different malignant breast lesion types. A MD threshold value of 1.1×10⁻³ mm²/s discriminated malignant breast lesions from benign lesions with a specificity of 81% and sensitivity of 80%. Choosing a cut-off of 1.31×10⁻³ mm²/s (MD of malignant lesions -2 SD), the specificity would be 67% with a sensitivity of 100%. Thus, MD values, related to tumor cellularity, provide reliable information to differentiate malignant breast lesions from benign ones. Quantitative DWI is not time-consuming and can be easily inserted into standard clinical breast MR imaging protocols.     

MR imaging of hypoglycemic encephalopathy: lesion distribution and prognosis prediction by diffusion-weighted imaging

Introduction

The aim of this study was to evaluate the patterns of hypoglycemic encephalopathy on diffusion-weighted imaging (DWI) and the relationship between the imaging patterns and clinical outcomes.

Methods

This retrospective study included 17 consecutive patients that had hypoglycemic encephalopathy with DWI abnormalities. The topographic distributions of the DWI abnormalities of the cortex, deep gray matter, and white matter structures were assessed. In addition, possible correlation between the patterns of brain injury on DWI and clinical outcomes was investigated.

Results

There were three patterns of DWI abnormalities: involvement of both gray and white matter (n?=?8), selective involvement of gray matter (n?=?4), and selective involvement of white matter (n?=?5). There was no significant difference in the initial blood glucose levels among patients for each of the imaging patterns. Most patients (16/17) had bilateral symmetrical abnormalities. Among patients with bilateral symmetrical gray and/or white matter injuries, one had moderate to severe disability and 14 remained in a persistent vegetative state. The two patients with a focal unilateral white matter abnormality and a localized splenial abnormality recovered without neurological deficits.

Conclusion

The results of this study showed that white matter was more sensitive to hypoglycemia than previously thought and there was no specific association between the patterns of injury and clinical outcomes whether the cerebral cortex, deep gray matter, and/or white matter were affected. Diffuse and extensive injury observed on the DWI predicts a poor neurologic outcome in patients with hypoglycemic injuries.     

Role of diffusion-weighted MR imaging in chest wall masses

Purpose

To determine the role of diffusion weighted MR imaging and apparent diffusion coefficient (ADC) in chest wall masses.

Materials and methods

This study included 62 patients with chest wall masses. They underwent routine MR imaging and diffusion MR weighted imaging on a 1.5 T MR unit (Symphony-Siemens). Diffusion MR imaging was done with diffusion factor b value of 0, 500, and 1000 s/mm². The apparent diffusion coefficient (ADC) map was reconstructed. The signal intensity was visually assessed on ADC maps and ADC value was measured in chest wall lesions. The mean ADC values correlated with histo-pathological results.

Results

Adequate ADC maps were obtained in 62 patients. The mean ADC values of chest wall lesions were 1.76 ± 0.08 × 10⁻³ mm²/s in inflammatory lesion, 3.21 ± 0.05 × 10⁻³ mm²/s in the cystic lesions, 1.67 ± 0.03 × 10⁻³ mm²/s in neurofibroma, 2.12 ± 0.07 × 10⁻³ in haemangioma, and 0.89 ± 0.06 × 10⁻³ mm²/s in malignant tumors. The mean ADC value of the malignant tumor was significantly different from that of benign chest wall tumors (P < 0.001).

Conclusion

Diffusion weighted MR imaging is a new imaging modality for differentiation malignant from benign chest wall masses. In addition, it has a role in characterization of different malignant and benign tumors.     

Coronal oblique turbo STIR imaging of the sacrum and sacroiliac joints at routine MR imaging of the lumbar spine

The objective of the study was to evaluate the clinical impact of coronal oblique imaging of the lumbrosacral junction and the sacrum at initial presentation for MR imaging of the lumbar spine in patients presenting with low back pain or sciatic pain. Two hundred and sixty consecutive patients attending for MRI of the lumbar spine underwent simultaneous coronal oblique turbo short tau inversion recovery (STIR; TR 2500, TE 40, TI 150, echo train length 7, number of scan acquisitions 2) imaging of the sacrum and the sacroiliac joints with a field of view of 30-cm and 3-mm slices (acquisition time 3 min and 20 s). Images were reviewed by two experienced radiologists to determine the cause of back pain, with and without images of the sacrum and sacroiliac joints. The added value of the additional sequence was assessed. Correlation was made with surgery, response to nerve root injection or clinical follow-up at 3 months. Subgroup analysis was performed to determine if patient stratification according to sex or symptoms would be useful. In total, in 19 of 260 patients (7.3%), abnormalities were identified at coronal STIR imaging. In 7 of 260 patients (2.7%), pathology was identified in the sacrum thought to account for back pain, altering the diagnosis made on the standard sequences. These diagnoses were sacroiliitis (n=2), sacral stress fracture (n=1), degenerative sacroiliac joints (n=1), degenerative accessory articulation between the lumbar spine and the sacrum (n=1), Tarlov cyst of nerve root (n=1) and retroverted uterus causing sciatic pain (n=1). Patient stratification according to sex or the presence or absence of sciatic symptoms was not useful in predicting the added benefit of the additional sequence. Routine coronal STIR imaging of the sacrum as part of lumbar spine MRI improves assessment of patients presenting with low back pain or sciatica in only a small number of patients.     

Role of diffusion-weighted MR imaging in discrimination between the intracranial cystic masses

Objective

Discriminating pyogenic brain abscesses from cystic or necrotic tumors is sometimes difficult with CT or conventional MR imaging. Diffusion MR imaging is a valuable diagnostic test in cases of intracranial cystic masses.

Methods

This work was conducted from July 2008 to June 2013 on 90 patients; 43 males and 47 females. Their ages range from 5 to 70 years. All patients were subjected to routine MRI examination and diffusion weighted imaging using 1.5 T MRI scanner. Gadolinium was given to some cases on routine MRI. Diffusion weighted imaging was performed with a single-shot spin-echo echo-planar pulse sequence (b = 0–1000 s/mm²). The apparent diffusion coefficient values and ratio were measured.

Results and conclusions

Patients in this study were categorized into three main groups; first group is brain abscesses (36 cases), 91.6% of them showed restricted diffusion, second group is malignant cystic or necrotic brain tumors, 28 cases of high grade necrotic glioma, 60.7% of them are free diffusion, and third group is benign cystic masses, arachnoid and epidermiod cysts (11 cases); all arachnoid cysts are free diffusion. From these results diffusion-weighted imaging is playing an important role in discrimination of cystic intracranial masses.     

Atypical idiopathic inflammatory demyelinating lesions (IIDL): Conventional and diffusion-weighted MR imaging (DWI) findings in 42 cases

Introduction

The purpose of this study was to evaluate MR imaging characteristics with conventional and advanced MR imaging techniques in patients with IIDL.

Methods

MR images of the brain in 42 patients (20 male, 22 female) with suspected or known multiple sclerosis (MS) from four institutions were retrospectively analyzed. Lesions were classified into five different subtypes: (1) ring-like lesions; (2) Balo-like lesions; (3) diffuse infiltrating lesions; (4) megacystic lesions; and (5) unclassified lesions.The location, size, margins, and signal intensities on T1WI, T2WI, and diffusion-weighted images (DWI), and the ADC values/ratios for all lesions, as well as the contrast enhancement pattern, and the presence of edema, were recorded.

Results

There were 30 ring-like, 10 Balo-like, 3 megacystic-like and 16 diffuse infiltrating-like lesions were detected. Three lesions were categorized as unclassified lesions.Of the 30 ring-like lesions, 23 were hypointense centrally with a hyperintense rim. The mean ADC, measured centrally, was 1.50 ± 0.41 × 10⁻³ mm²/s. The mean ADC in the non-enhancing layers of the Balo-like lesions was 2.29 ± 0.17 × 10⁻³ mm²/s, and the mean ADC in enhancing layers was 1.03 ± 0.30 × 10⁻³ mm²/s. Megacystic lesions had a mean ADC of 2.14 ± 0.26 × 10⁻³ mm²/s. Peripheral strong enhancement with high signal on DWI was present in all diffuse infiltrating lesions. Unclassified lesions showed a mean ADC of 1.43 ± 0.13 mm²/s.

Conclusion

Restriction of diffusion will be seen in the outer layers of active inflammation/demyelination in Balo-like lesions, in the enhancing part of ring-like lesions, and at the periphery of infiltrative-type lesions.     

Transient splenial lesion of the corpus callosum associated with antiepileptic drugs: evaluation by diffusion-weighted MR imaging

Transient focal lesions in the splenium of the corpus callosum have been reported in epileptic patients receiving antiepileptic drugs. The characteristic imaging features included an oval high signal lesion on T2-weighted images in the central part of the splenium, no enhancement on post-contrast MR images, and complete reversibility without specific treatment. We report identical MR imaging findings in a depressive patient who had received antiepileptic drugs. In addition, diffusion-weighted MR imaging findings are described in our case, which is the first report on this unique lesion associated with antiepileptic drugs. Although this lesion has been assumed to be vasogenic edema in the previous reports, diffusion-weighted MR imaging showed markedly restricted diffusion of the lesion in the present case, suggesting that cytotoxic edema was the main pathophysiological abnormality.