Fungal versus bacterial brain abscesses: is diffusion-weighted MR imaging a useful tool in the differential diagnosis?

Introduction The aim of this study was to investigate the appearance of fungal brain abscesses on diffusion-weighted (DW) images, and to evaluate whether the imaging characteristics and apparent diffusion coefficient (ADC) values associated with fungal abscesses were distinct from those of bacterial abscesses. Methods We retrospectively reviewed the MR images from nine patients with fungal brain infections, and 17 patients with pyogenic brain abscesses. All patients underwent conventional MR sequences and DW imaging on 1.5-T clinical MR scanners. ADC values of 20 fungal and 20 bacterial brain abscesses were calculated and compared using a random factor analysis of variance. Results Multiple lesions were present in 6 of 9 patients (67%) with fungal abscesses and in 5 of 17 patients (29%) with bacterial abscesses. On DW images, all but one bacterial brain abscess showed a homogeneous high signal, whereas the appearance of fungal abscesses on DW images was more variable: in five of nine patients with fungal abscesses, the lesions were homogeneously hyperintense, while in the remaining four patients, the lesions were of mixed signal intensity. Mean ADC values were 0.74 × 10⁻³ mm²/s in the fungal group and 0.486 × 10⁻³ mm²/s in the bacterial group (P≤0.05). Conclusion Our results indicate that there is a trend towards higher ADC values in fungal lesions. Additional findings that support fungal rather than bacterial cerebral infection are multiplicity, signal heterogeneity on T2-weighted and DW imaging, and involvement of deep grey-matter nuclei.     

Magnetic resonance imaging features of nasopharyngeal carcinoma and nasopharyngeal non-Hodgkin's lymphoma: Are there differences?

Purpose

To describe differences in the primary tumour and distribution of cervical lymphadenopathy for cases of nasopharyngeal carcinoma (NPC) and nasopharyngeal non-Hodgkin's lymphoma (NPNHL) using magnetic resonance (MR) imaging.

Materials and methods

MR images of patients with NPC (n = 272) and NPNHL (n = 118) were independently reviewed by two experienced radiologists.

Results

NPC had a higher incidence of tumour invasion associated with the levator and tensor muscles of the velum palatine, the longus colli and medial pterygoid muscles, the base of the pterygoid process, the clivus, the base and greater wing of the sphenoid bone, the petrous apex, the foramen lacerum, the foramen ovale, the hypoglossal canal, and intracranial infiltration. In contrast, NPNHL had a higher incidence of tumour invasion associated with the hypopharynx, the palatine and lingual tonsils, as well as the ethmoid and maxillary sinuses. NPNHL also had a higher incidence of extensive and irregular bilateral lymphadenopathy, and lymphadenopathy in the parotid.

Conclusions

NPC more often involved an unsymmetrical tumour with a propensity to invade both widely and deeply into muscle tissue, the fat space, the neural foramen, and the skull base bone. In contrast, NPNHL tended to be a symmetrical and diffuse tumour with a propensity to spread laterally through the fat space and along the mucosa to the tonsils of the oropharynx and hypopharynx. These differences facilitate a differentiation of these diseases using MR images, and enhance our understanding of the biological behavior of these malignant tumours of the nasopharynx.     

Magnetic resonance imaging of pulmonary nodules: accuracy in a granulomatous disease–endemic region

Objective

To estimate the diagnostic accuracy of signal intensity of the lesion-to-spinal cord ratio (LSR) and apparent diffusion coefficient (ADC) in diffusion-weighted (DW) magnetic resonance imaging of pulmonary nodules suspicious for lung cancer in granulomatous lung disease-endemic regions.

Methods

Forty-nine patients with indeterminate solitary pulmonary nodules detected by chest computed tomography and histopathologically confirmed diagnoses were included in the study. DW images were analysed semiquantitatively by focusing regions of interest on the lesion and spinal cord at the same level (for LSR calculation). ADCs were estimated from ratios of the two image signal intensities. Ratios of T1 and T2 signal intensity between nodules and muscle were calculated for comparison.

Results

Mean ADCs?±?standard deviations for lung cancer and benign lesions were 0.9?±?0.2 and 1.3?±?0.2?×?10^-3 mm²/s, respectively. Mean LSRs were 1.4?±?0.3 for lung cancer and 1?±?0.1 for benign lesions. ADCs and LSRs differed significantly between malignant and benign lesions (P?<?0.001). Mean T2 signal intensity ratios also differed significantly between benign and malignant lesions (0.8?±?0.2 vs. 1.6?±?0.2; P?<?0.05).

Conclusions

DWI can help to differentiate malignant from benign lesions according to ADC and the LSR with good accuracy.

Key Points

? DW imaging can help differentiate malignant from benign pulmonary nodules. ? ADC and LSR signal intensities had only small overlap between malignant and benign pulmonary nodules. ? Mean T2 signal intensity ratios differed significantly between benign and malignant lesions.

     

Is magnetic resonance diffusion-weighted imaging superior in the diagnosis of pancreatic adenocarcinoma and does it have a prognostic value?

Aim

To assess how beneficial is adding Magnetic Resonance Diffusion-Weighted Imaging (DWI) to conventional MRI in the identification, characterization, and prognostic assessment of pancreatic duct adenocarcinoma (PDAC).

Diffusion-weighted imaging of solid or predominantly solid gynaecological adnexial masses: is it useful in the differential diagnosis?

Objectives

This study investigated whether diffusion-weighted imaging (DWI) and apparent diffusion coefficient (ADC) values provide specific information that allows the diagnosis of solid or predominantly solid gynaecological adnexial lesions, especially whether they can discriminate benign and malignant lesions.

Methods

DWI was performed in 37 patients with histologically proven solid or predominantly solid adnexial lesions (22 malignant and 15 benign neoplasms). The lesions in our data set were divided into two groups, all adnexial lesions or lesions of ovarian origin, for evaluation. The areas of the highest signal intensity on DWI (b = 800 s mm⁻²) and the lowest ADC values within the lesions were evaluated.

Results

On DWI, high signal intensity was observed more often in malignant than in benign lesions (p<0.0001). There was no significant difference between the ADC values of the malignant and benign lesions in either the adnexial (0.88±0.16 vs 0.84±0.42; p = 0.96) or the ovarian (0.85±0.14 vs 1.05±0.2; p = 0.133) lesions. When signal intensities on DWI were compared, however, malignant lesions had higher values than the benign lesions in both the adnexial (0.69±0.21 vs 0.29±0.13; p<0.0001) and the ovarian lesions (0.75±0.14 vs 0.37±0.24; p = 0.003).

Conclusion

On DWI, high signal intensity was observed more frequently with the malignant lesions.MRI plays an important role in the diagnosis of gynaecological adnexial lesions [1-4]. It provides useful information for the characterisation of various ovarian, uterine and tubal masses. Some morphological and signal intensity features of the lesions on MRI are very important for the differential diagnosis [5], but this information may sometimes be non-specific. Many studies have looked at the utility of diffusion-weighted MRI in the differential diagnosis of benign and malignant gynaecological lesions [6]. In particular, the contributions of diffusion-weighted imaging (DWI) and apparent diffusion coefficient (ADC) values in differentiating between cystic benign lesions and malignant ovarian and uterine lesions have been evaluated [6]. Only one investigation used DWI to assess the solid components of ovarian lesions in a wide study population [11]. To our knowledge, the utility of DWI and ADC values in assessing solid or predominantly solid gynaecological adnexial masses has not been investigated previously.In this study, our goal was to investigate whether DWI and ADC values provide specific information that can diagnose solid or predominantly solid gynaecological adnexial lesions, in particular, whether these parameters can discriminate benign and malignant lesions.     

Liver diffusion-weighted MR imaging: the tower of Babel?

There is a growing amount of literature regarding diffusion-weighted imaging (DWI) of the liver. The apparent diffusion coefficient (ADC) was introduced in 1986 and is used extensively in studies. However, methods for calculating ADC vary considerably and the value of the ADC strongly depends on the b values chosen for its calculation. Indeed, the ADC incorporates the effects of both diffusion and perfusion, which can vary independently. Since signal attenuation as a function of b follows a bi-exponential pattern, other diffusion/perfusion coefficients can be calculated using DWI, and these may provide more meaningful measurements than the ADC. The absence of standardization for both the terminology and the methodology in DWI of the liver makes it difficult for readers to understand the technique used and strongly limits comparisons between studies. Here, we review the main principles of DWI of the liver, the limits of the ADC, and the exciting capabilities of multi-parametric DWI. We also insisted on the need for a common language for DWI of the liver.     

Magnetic resonance fistulography for the demonstration of anovaginal fistula: an alternative imaging technique?

Anovaginal fistulae (AVF) are frequently seen in patients with inflammatory bowel disease, especially in Crohn disease with active colonic inflammation. Herein, we report a 21-year-old woman with Crohn disease suffering from vaginal discharge and anal pain. Although clinical presentation was very suggestive of AVF, physical examination and colonoscopy were inconclusive. We used an alternative technique and performed magnetic resonance fistulography by applying rectal contrast for the demonstration of AVF.     

Magnetic resonance imaging of the proximal tibial epiphysis: could it be helpful in forensic age estimation?

There is an increasing demand for age estimations of living persons who are involved in civil and criminal procedures but lack a valid birth certificate indicating their date of birth. Several studies have recommended the application of magnetic resonance imaging (MRI) and assessment of the stage of epiphyseal fusion in age estimation. This study involved retrospective MRI analysis of 335 cases (217 males and 118 females) whose ages ranged from 8 to 28 years (yrs). We assessed the degree of ossification of the proximal tibial epiphysis depending on the classifications of Schmeling and Kellinghaus used for the main stages (I, II, III, IV & V) and substages (IIa, b, c & IIIa, b, c). Significant differences between males and females at stages IIIc, IV and V (p < 0.001) were observed. Additionally, the ossification of the proximal tibial epiphyses occurred earlier in females than in males (2–4 yrs). The mean of ages in stage IV was approximately 18.6 yrs. in females and 22.5 yrs. in males, meaning that stage IV can be used as a valuable forensic marker to determine whether the person in question has reached the age of 18 yrs. We concluded that the application of MRI in the assessment of the ossification status of the proximal tibial epiphysis could be helpful in age estimation for various forensic purposes.     

Detection of liver metastasis: is diffusion-weighted imaging needed in Gd-EOB-DTPA-enhanced MR imaging for evaluation of colorectal liver metastases?

Purpose

We compared diagnostic ability for detecting hepatic metastases between gadolinium ethoxy benzyl diethylenetriamine pentaacetic acid (Gd-EOB-DTPA)-enhanced magnetic resonance imaging (MRI) and diffusion-weighted imaging (DWI) on a 1.5-T system, and determined whether DWI is necessary in Gd-EOB-DTPA-enhanced MRI for diagnosing colorectal liver metastases.

Materials and methods

We assessed 29 consecutive prospectively enrolled patients with suspected metachronous colorectal liver metastases; all patients underwent surgery and had preoperative Gd-EOB-DTPA-enhanced MRI. Overall detection rate, sensitivity for detecting metastases and benign lesions, positive predictive value, and diagnostic accuracy (Az value) were compared among three image sets [unenhanced MRI (DWI set), Gd-EOB-DTPA-enhanced MRI excluding DWI (EOB set), and combined set].

Results

Gd-EOB-DTPA-enhanced MRI yielded better overall detection rate (77.8?C79.0?%) and sensitivity (87.1?C89.4?%) for detecting metastases than the DWI set (55.9?% and 64.7?%, respectively) for one observer (P?<?0.001). No statistically significant difference was seen between the EOB and combined sets, although several metastases were newly detected on additional DWI.

Conclusions

Gd-EOB-DTPA-enhanced MRI yielded a better overall detection rate and higher sensitivity for detecting metastases compared with unenhanced MRI. Additional DWI may be able to reduce oversight of lesions in Gd-EOB-DTPA-enhanced 1.5-T MRI for detecting colorectal liver metastases.     

Rare breast neoplasms: is there any peculiar feature on magnetic resonance mammography?

PURPOSE: The purpose of this study is to describe the semiological features of rare breast neoplasms at magnetic resonance mammography (MRM). MATERIALS AND METHODS: Out of 468 MRMs of patients with a histological diagnosis of breast malignancy, 27 (5.7%) cases of rare breast neoplasms, confirmed by definitive histological analysis on surgical specimens, were selected: four (0.9%) intracystic papillary neoplasms, four (0.9%) intraductal papillary neoplasms, five (1.0%) invasive papillary neoplasms, two (0.4%) medullary carcinomas, seven (1.5%) mucinous carcinomas, three (0.6%) tubular carcinomas, one (0.2%) tubulo-lobular carcinoma and one (0.2%) desmoid tumour. Two radiologists evaluated the MRM images according to Fischer criteria and indicated a level of diagnostic suspicion. In particular, MRM lesion morphology and enhancement characteristics were analysed. RESULTS: No semiologic features of malignancy or peculiar appearances indicating rare breast neoplasm were identified. On the contrary, MRM appearance was nonspecific and often suggestive of probably benign (Breast Imaging Reporting and Data System-BI-RADS 3) (40%) or benign lesions (BI-RADS 2) (7.5%), or lesions were undetectable at MRM (BI-RADS 1) (7.5%). CONCLUSIONS: Frequently, rare breast neoplasms show low suspicious morphologic and kinetic patterns at MRM, and they are often classified as indeterminate lesions. This is probably due to their high grade of differentiation and their histological features.     

Magnetic resonance imaging of active sacroiliitis: Do we really need gadolinium?

Introduction

Magnetic resonance imaging (MRI) of active inflammatory changes of the sacroiliac joint (SIJ) in spondyloarthritis (SpA) is performed with short tau inversion recovery (STIR) sequences and fat-saturated T1-weighted fast spin-echo (FSE) sequences after administration of gadolinium-based contrast medium (T1/Gd). The aim of the present study was to compare these two pulse sequences in terms of diagnosis, diagnostic confidence, and quantification of inflammatory changes.

Materials and methods

The study included 105 patients with suspected SpA; 72 patients developed clinical SpA over time. All patients were examined with STIR and T1/Gd and each of the two sequences was analyzed separately in conjunction with unenhanced T1 FSE images. For quantitative estimation of inflammatory changes, each sacroiliac joint (SIJ) was divided into 4 quadrants (and severity per quadrant was assigned a score of 0-4, resulting in a maximum sum score of 16 per SIJ). Diagnostic confidence was assessed on a visual analogue scale ranging from 0 to 10.

Results

Active sacroiliitis was diagnosed in 46 patients and ruled out in 34 using STIR, whereas findings were inconclusive in 25 patients. The corresponding numbers for T1/Gd were 47, 44, and 14. Diagnostic confidence was significantly lower for STIR (7.3 ± 2.6) compared with T1/Gd (8.7 ± 1.9) (p < 0.001).The sum scores were 2.5 (±3.3) for STIR and 2.2 (±3.2) for T1/Gd for the right SIJ and 2.2 (±2.9) (STIR) and 1.9 (±3.1) (T1/Gd) for the left SIJ. Agreement was high with intraclass correlation coefficient (ICC) values of 0.86 for the right SIJ and 0.90 for the left SIJ and positive correlation (r = 0.62 right, 0.60 left).

Summary

STIR sequences alone are sufficient for establishing a reliable diagnosis and quantify the amount of inflammation in active sacroiliitis. A contrast-enhanced study is dispensable in patients with established disease or in the setting of clinical follow-up studies. However, a contrast-enhanced MR sequence is beneficial to ensure maximum diagnostic confidence when patients with early sacroiliitis are examined.     

Magnetic resonance imaging of acute “wiiitis” of the upper extremity

We present the first reported case of acute “wiiitis”, documented clinically and by imaging, of the upper extremity, caused by prolonged participation in a physically interactive virtual video-game. Unenhanced magnetic resonance imaging (MRI) demonstrated marked T2-weighted signal abnormality within several muscles of the shoulder and upper arm, without evidence of macroscopic partial- or full-thickness tearing of the muscle or of intramuscular hematoma.     

Does combined imaging of the pre- and postsynaptic dopaminergic system increase the diagnostic accuracy in the differential diagnosis of parkinsonism?

Purpose We hypothesized that combining pre- and postsynaptic quantitative information about the dopaminergic system would provide a higher diagnostic accuracy in the differential diagnosis of parkinsonism than specific striatal D₂ receptor binding alone. Therefore, the aim of the study was to introduce new semi-quantitative parameters and evaluate their ability to discriminate between Parkinson’s disease (IPS) and non-idiopathic parkinsonian syndromes (non-IPS). Methods In 100 patients (69 IPS, 31 non-IPS), postsynaptic [¹²³I]IBZM and presynaptic [¹²³I]FP-CIT SPECT scans were evaluated by observer-independent techniques. The diagnostic performances of striatal dopamine transporter (DAT) and D₂ receptor binding, their respective asymmetries, and a combination of pre- and postsynaptic asymmetry were evaluated with ROC analyses. A logistic regression model was generated combining factors to calculate the probability for each patient of belonging to either diagnostic group. Results D₂ receptor binding provided a sensitivity of 87.1% and a specificity of 72.5% with an area under the curve (AUC) of 0.866. The AUCs of other single parameters were lower than that of D₂ binding. A gain of diagnostic power (p = 0.026) was reached with a model combining pre- and postsynaptic asymmetries and D₂ binding (sensitivity 90.3%, specificity 73.9%, AUC 0.893). Conclusion The combination of quantitative parameters of presynaptic DAT and postsynaptic D₂ receptor binding demonstrates superior diagnostic power in the differentiation of patients with IPS and non-IPS than the established approach based on D₂ binding alone. Striatal D₂ receptor binding and the combination of DAT and IBZM binding asymmetries are the factors contributing most in separating these diagnostic groups.