Atypical retroperitoneal fibrosis: MRI findings

A case of retroperitoneal fibrosis with an unusual perirenal involvement diagnosed at MR imaging is reported. Other conditions, such as metastatic disease or lymphoma, may be considered especially when the initial presentation is not typical. Imaging modalities in this condition are discussed. Received: 6 May 1998; Revision received: 3 August 1998; Accepted: 28 August 1998     

特发性腹膜后纤维化的MRI诊断

目的：探讨特发性腹膜后纤维化（IRPF）的MRI表现。方法：回顾性分析8例经穿刺活检病理证实的IRPF患者的MRI图像资料。所有患者均行腹部MRI常规扫描,其中5例同时行增强扫描,4例行DWI检查,5例行MRU检查。结果：IRPF呈类圆形或不规则形软组织信号,包绕腹膜后大血管及输尿管等腹膜后器官,早期病变呈稍长T1、稍长T2信号,动态增强扫描动脉期示病灶明显强化,DWI上呈稍高信号;中晚期病变T2WI信号逐渐减低,呈等信号或低信号,动态增强扫描动脉期及静脉期无明显强化,延迟期呈轻度不均匀强化,DWI上呈不均匀稍低信号。当病变包绕输尿管时,MRU检查可见一侧或双侧输尿管变细,病变段以上输尿管积水及肾盂积水。结论：MRI多序列检查有助于IRPF的诊断及鉴别诊断,有较大的临床应用价值。     

CT findings in circumscribed upper abdominal idiopathic retroperitoneal fibrosis

Idiopathic retroperitoneal fibrosis (IRF) is a rare condition of unknown etiology. An unusual case of IRF exclusively located at the peripancreatic area without extension below the lower renal poles is reported.     

MRI findings of treated bacterial septic arthritis

Introduction

The purpose of this study was to report the MRI findings that can be encountered in successfully treated bacterial septic arthritis.

Materials and methods

The study included 12 patients (8 male and 4 female; mean age 38?years, range 9–85) with 13 proven cases of bacterial septic arthritis. The joints involved were hip (n?=?3), knee (n?=?3), shoulder (n?=?2), sacroiliac (n?=?2), ankle (n?=?1), wrist (n?=?1), and elbow (n?=?1). MRI examinations following surgical debridement and at initiation of antibiotic therapy and after successful treatment were compared for changes in effusion, synovium, bone, and periarticular soft tissues. Imaging findings were correlated with microbiological and clinical findings.

Results

Joint effusions were present in all joints at baseline and regressed significantly at follow-up MRI (p?=?0.001). Abscesses were present in 5 cases (38?%), and their sizes decreased significantly at follow-up (p?=?0.001). Synovial enhancement and thickening were observed in all joints at both baseline and follow-up MRI. Myositis/cellulitis was present in 10 cases (77?%) at baseline and in 8 cases (62?%) at follow-up MRI. Bone marrow edema was present in 10 joints (77?%) at baseline and persisted in 8 joints (62?%). Bone erosions were found in 8 joints (62?%) and persisted at follow-up MRI in all cases.

Conclusion

The sizes of joint effusions and abscesses appear to be the factors with the most potential for monitoring therapy for septic arthritis, since both decreased significantly following successful treatment. Synovial thickening and enhancement, periarticular myositis/cellulitis, and bone marrow edema can persist even after resolution of the infection.     

Diffusion-weighted MRI in evaluating liver fibrosis: a feasibility study in cirrhotic patients

PURPOSE: This study was designed to establish whether the measurement of apparent diffusion coefficients (ADCs) is clinically accurate in diagnosing liver fibrosis in a selected series of cirrhotic patients. MATERIALS AND METHODS: Twenty-eight cirrhotic patients (mean age 58.1 years) with histologically proven liver fibrosis and 29 healthy controls (mean age 43.8 years) underwent liver diffusion-weighted magnetic resonance (MR) using a 1.5-Tesla (T) magnet equipped with a phased-array coil. Diffusion studies with parallel imaging [generalized autocalibrating partially parallel acquisitions (GRAPPA)] were performed within a single breath-hold using a single-shot spin-echo echo-planar sequence (TE 74 ms) using four b values: b=0, 150, 250 and 400 s/mm(2). A unidirectional diffusion gradient was applied. ADCs were measured on ADC maps. RESULTS: Mean ADC was significantly lower in cirrhotic livers than in controls (1.11+/-0.16 vs. 1.54+/-0.12.10(-3)mm(2)/s) (p<0.0001). Receiver operating characteristic (ROC) analysis showed an area under the curve (AUC) of 0.96 [confidence interval (CI) 95%:(0.87; 0.94)], demonstrating higher sensitivity and specificity (92.9% and 100%, respectively) for an ADC cutoff of 1.31.10(-3)mm(2)/s. Positive predictive value (PPV), negative predictive value (NPV) and overall accuracy were 100%, 99.9% and 96.4%, respectively. CONCLUSIONS: Diffusion-weighted MRI is an accurate tool in evaluating advanced liver fibrosis if an optimised single-shot spin-echo echo-planar sequence with maximum intermediate b value is used. The ADC threshold for liver fibrosis was 1.31.10(-3)mm(2)/s.     

Diffusion-weighted MRI of fatty liver

Purpose:

To investigate the effect of fat infiltration on the apparent diffusion coefficient (ADC) of liver, and assess the relationship between ADC and hepatic fat fraction (HFF).

Materials and Methods:

MRI scans of 120 consecutive patients were included in this retrospective study. Of these, 42 patients were included in the fatty liver group and 78 in the control group. ADC values were measured from a pair of diffusion‐weighted (DW) images (b = 0 mm²/s and 1000 mm²/s). HFFs were measured using T1W GRE dual‐echo images. The difference between the ADCs of the two groups was assessed with the t‐test. The relationship between HFF and ADC was determined using linear regression analysis and the Pearson correlation coefficient (r).

Results:

Mean HFFs were 0.85 ± 2.86 and 13.67 ± 8.62 in the control and fatty liver groups, respectively. The mean ADC of fatty liver group 1.20 ± 0.22 × 10^?3 mm²/s was significantly lower than that of the control group 1.32 ± 0.23 × 10^?3 mm²/s (P = 0.02). Linear regression analysis revealed an inverse relationship between ADC and HFF (r = ?0.39, P < 0.0001).

Conclusion:

ADC significantly decreases in patients with >5% HFF, and ADC and HFF exhibit an inverse relationship. J. Magn. Reson. Imaging 2012;35:1109‐1111. © 2011 Wiley Periodicals, Inc.

     

FDG-PET/CT findings of autoimmune pancreatitis associated with idiopathic retroperitoneal fibrosis

We report the fluorodeoxyglucose positron emission tomography (FDG-PET)/computed tomography (CT) findings of autoimmune pancreatitis (AIP) associated with idiopathic retroperitoneal fibrosis. A 69-year-old male patient was admitted to our hospital with obstructive jaundice. Six months prior to this admission, he was treated with steroid therapy for retroperitoneal fibrosis. Laboratory data showed that elevated T-bil, C-reactive protein, amylase and immunoglobulin 4, and antinuclear antibodies were positive. Clinical history, laboratory data, CT image, and magnetic resonance imaging led to a diagnosis of autoimmune pancreatitis. To investigate the inflammatory activity, FDG-PET/CT was undertaken. FDG-PET/CT demonstrated diffuse intense FDG uptake in the enlarged pancreas and diffuse mild uptake in the region of the abdominal aorta-bilateral iliac arteries. A dilated right renal pelvis and upper ureter, corresponding to hydronephrosis probably caused by retroperitoneal fibrosis, were shown. An FDG-PET/CT was useful to evaluate inflammatory activity and morphological imaging, and supported our diagnosis of AIP and retroperitoneal fibrosis.     

Alveolar echinococcosis of the liver: Diffusion-weighted MRI findings and potential role in lesion characterisation

Purpose

To report the diffusion-weighted MRI findings in alveolar echinococcosis (AE) of the liver and evaluate the potential role of apparent diffusion coefficients (ADCs) in the characterisation of lesions.

Materials and methods

We retrospectively included 22 patients with 63 AE liver lesions (≥1 cm), examined with 3-T liver MRI, including a free-breathing diffusion-weighted single-shot echo-planar imaging sequence (b-values = 50, 300 and 600 s/mm²). Two radiologists jointly assessed the following lesion features: size, location, presence of cystic and/or solid components (according to Kodama's classification system), relative contrast enhancement, and calcifications (on CT). The ADC_total, ADC_min and ADC_max were measured in each lesion and the surrounding liver parenchyma.

Results

Three type 1, 19 type 2, 17 type 3, three type 4 and 21 type 5 lesions were identified. The mean (±SD) ADC_total, ADC_min and ADC_max for all lesions were 1.73 ± 0.50, 0.76 ± 0.38 and 2.63 ± 0.76 × 10⁻³ mm²/s, respectively. The mean ADC_total for type 1, type 2, type 3, type 4 and type 5 lesions were 1.97 ± 1.01, 1.76 ± 0.53, 1.73 ± 0.41, 1.15 ± 0.42 and 1.76 ± 0.44 × 10⁻³ mm²/s, respectively. No significant differences were found between the five lesion types, except for type 4 (p = 0.0363). There was a significant correlation between the presence of a solid component and low ADC_min (r = 0.39, p = 0.0016), whereas an inverse correlation was found between the relative contrast enhancement and ADC_total (r = −0.34, p = 0.0072).

Conclusion

The ADCs of AE lesions are relatively low compared to other cystic liver lesions, which may help in the differential diagnosis. Although ADCs are of little use to distinguish between the five lesion types, their low value reflects the underlying solid component.     

Riedel's thyroiditis and retroperitoneal fibrosis in multifocal fibrosclerosis: positron emission tomographic findings

PURPOSE: The authors describe F-18 fluorodeoxyglucose positron emission tomographic (FDG PET) imaging features of Riedel's thyroiditis and retroperitoneal fibrosis in a patient with multifocal fibrosclerosis. MATERIALS AND METHODS: A 41-year-old woman in whom Riedel's thyroiditis had been diagnosed 7 months earlier was examined for fatigue, anorexia, and lower back pain, irradiating to the abdomen. Abdominal sonography and computed tomography showed a retroperitoneal mass. A biopsy of this mass showed histopathologic findings of retroperitoneal fibrosis. FDG PET was performed to evaluate the activity of the retroperitoneal fibrosis and to screen for other areas of fibrosclerosis. RESULTS: The FDG-PET images showed an intense hypermetabolic abdominal mass surrounding the aorta and increased glucose metabolism in the thyroid. No other sites of abnormal FDG metabolism were noted. These abnormalities disappeared after 4 months of steroid therapy. CONCLUSIONS: Sites of multifocal fibrosclerosis can be demonstrated by FDG PET, probably as a result of active inflammation involving lymphocytes, plasma cells, and fibroblast proliferation. FDG PET can help to establish the diagnosis of multifocal fibrosclerosis and evaluate the activity and patient response to corticosteroid therapy.     

Diffusion-weighted MRI of the prostate

Diffusion-weighted magnetic resonance imaging (DWI) can complement MRI of the prostate in the detection and localization of prostate cancer, particularly after previous negative biopsy. A total of 13 original reports and 2 reviews published in 2010 demonstrate that prostate cancer can be detected by DWI due to its increased cell density and decreased diffusiveness, either qualitatively in DWI images or quantitatively by means of the apparent diffusion coefficient (ADC). In the prostate, the ADC is influenced by the strength of diffusion weighting, localization (peripheral or transitional zone), presence of prostatitis or hemorrhage and density and differentiation of prostate cancer cells. Mean differences between healthy tissue of the peripheral zone and prostate cancer appear to be smaller for ADC than for the (choline + creatine)/citrate ratio in MR spectroscopy. Test quality parameters vary greatly between different studies but appear to be slightly better for combined MRI and DWI than for MRI of the prostate alone. Clinical validation of DWI of the prostate requires both increased technical conformity and increased numbers of patients in clinical studies.     

Diffusion-weighted MRI in cervical cancer

The purpose was to investigate the potential value of apparent diffusion coefficient (ADC) measurement with MRI in the assessment of cervix cancer. Diffusion-weighted MRI was performed in 47 patients with cervical carcinoma undergoing chemoradiation therapy and 26 normal controls on a 1.5-T system with a b-value of 600 s/mm². FIGO stage, tumor volume, nodal status, interstitial fluid pressure (IFP) and oxygen measurements were recorded. Response was defined as no visible tumor 3–6 months following completion of therapy. The average median ADC (mADC) of cervical carcinomas (1.09±0.20×10⁻³ mm²/s) was significantly lower than normal cervix (2.09±0.46×10⁻³ mm²/s) (P<0.001). There was no correlation between mADC, nodal status, tumor volume, IFP or oxygen measurements. mADC was significantly lower in FIGO stages T1b/T2a (0.986 × 10⁻³ mm²/s) compared to T2b (1.21×10⁻³ mm²/s) and T3/T4 (1.10×10⁻³ mm²/s) (P<0.001). In patients with squamous carcinomas the 90th percentile of ADC values was lower in responders than non-responders (P<0.05). Median ADC in cervix carcinoma is significantly lower compared to normal cervix. ADC may have predictive value in squamous tumors, but further long-term study will determine the ultimate clinical utility.     

Diffusion-weighted MRI of subdural and epidural empyemas

We reviewed diffusion-weighted images (DWI) from eight patients with subdural and four with epidural empyemas to assess the possibility of differentiating between these lesions by DWI. The signal intensities of the empyemas on DWI, and maps of the apparent diffusion coefficient (ADC) were analysed in seven patients. In seven of the eight patients with subdural empyema, the lesions appeared as areas of high signal. The ADC maps confirmed that these areas were the result of restricted diffusion. (In the remaining patient, the lesion showed a mixture of high and low signal.) The epidural empyemas contained areas of low signal in all four patients; part of the empyema was isointense or gave high signal in two. DWI may be an adjunct to conventional sequences for differentiating between subdural and epidural empyemas.     

Perirenal involvement by retroperitoneal fibrosis: The usefulness of MRI to establish diagnosis

A case of retroperitoneal fibrosis (RPF) with rare, extensive involvement of the perirenal area is reported. Magnetic resonance imaging (MRI) signal intensities were helpful in distinguishing benign from malignant disease.     

Diffusion-weighted MRI of cerebral toxoplasma abscess

OBJECTIVE: This retrospective study reports the diffusion-weighted MRI appearance of Toxoplasma abscesses, rim-enhancing cerebral masses resulting from toxoplasmosis infection. In all patients, the signal intensity of the abscess core on diffusion-weighted MRI was equal to or less than that of normal, unaffected cerebral white matter and the measured apparent diffusion coefficient was greater than that of unaffected white matter. Histopathology revealed necrotic tissue in the center of these abscesses but no purulent fluid. CONCLUSION: Unlike pyogenic abscesses, the core tissue of rim-enhancing Toxoplasma abscesses shows no restriction of water diffusion.     

Diffusion-weighted MRI in cortical ischaemia

We carried out MRI on 16 male and three female comatose patients, aged 2 days to 79 years, with suspected cortical ischaemia referred from our intensive care units. Using a head coil, and following standard imaging, including coronal fluid-attenuated inversion-recovery images, we performed diffusion-weighted imaging (DWI) using a whole-brain multislice single-shot echo-planar sequence with b 0 and 1000 s/mm²: 5-mm slices covering the whole brain, TR 7000 TE 106 ms, 128×128 pixels, field of view 250 mm, one excitation. Maps of apparent diffusion coefficients (ADC) were generated automatically. DWI showed cortical, basal ganglia and watershed-area high signal in all cases, associated with a decrease in ADC to 60– 80% of normal. DWI showed lesions not seen (40%) or underestimated (40%) on conventional T2-weighted imaging. Within 24 h of the onset of symptoms, DWI showed changes not readily detectable on T2-weighted images. The cortical high signal on DWI and the ADC changes, suggesting severe ischaemia rather than oedema, was found in areas known to be affected by cortical laminar necrosis. Extension to the brain stem and white matter was associated with a higher likelihood of death.