Pathological fracture in paediatric bone tumours and tumour-like lesions: A predictor of benign lesions?

Objective:To determine the incidence and causes of pathological fractures in paediatric bone tumours and tumour-like lesions, and to determine if they are predictive of benign lesions.Methods and materials:Retrospective review of children with suspected bone tumours referred to a specialist musculoskeletal oncology service between September 2019 and August 2020. Data recorded included patient age and gender, lesion location, the presence of a pathological fracture on the initial plain radiograph, and the final diagnosis made either by image-guided biopsy/curettage or based on typical imaging features.Results:231 patients were included with 233 lesions (138 males and 93 females with mean age 10.5 years, range 3 months–18 years). Final diagnosis was based on histology in 85 (36.5%) cases and imaging in 148 (63.5%) cases, 52 (22.3%) lesions classed as non-neoplastic, 139 (59.7%) as benign and 42 (18%) as malignant. Pathological fractures were seen in 41 cases (17.6%) at presentation, involving the humerus in 19 (46.3%), the femur in 14 (34.1%), the tibia in 3 (7.3%), the fibula and radius in two each (4.9%) and the second toe proximal phalanx in 1 (2.4%) (p < 0.001). The commonest underlying lesions included simple bone cyst (n = 17; 41.5%) and non-ossifying fibroma (n = 10; 24.4%). Only 4 cases (9.75%) were malignant, one case each of osteosarcoma, Ewing sarcoma, leukaemia and BCOR undifferentiated round cell sarcoma. Pathological fracture occurred in 27.7% of non-malignant lesions and 9.5% of malignant lesions, this difference being statistically significant (p < 0.001).Conclusion:Pathological fractures were seen in 17.6% of paediatric bone tumours, tumour-like lesions, being significantly associated with humeral location and non-malignant diagnosis.Advances in knowledge:Demonstrates the frequency, location and underlying diagnosis of pathological fractures in paediatric bone tumour and tumour-like lesions.     

Malignancy rates and diagnostic performance of the Bosniak classification for the diagnosis of cystic renal lesions in computed tomography – a systematic review and meta-analysis

Objective

To systematically review the literature on the Bosniak classification system in CT to determine its diagnostic performance to diagnose malignant cystic lesions and the prevalence of malignancy in Bosniak categories.

Methods

A predefined database search was performed from 1 January 1986 to 18 January 2016. Two independent reviewers extracted data on malignancy rates in Bosniak categories and several covariates using predefined criteria. Study quality was assessed using QUADAS-2. Meta-analysis included data pooling, subgroup analyses, meta-regression and investigation of publication bias.

Results

A total of 35 studies, which included 2,578 lesions, were investigated. Data on observer experience, inter-observer variation and technical CT standards were insufficiently reported. The pooled rate of malignancy increased from Bosniak I (3.2 %, 95 % CI 0–6.8, I²?=?5 %) to Bosniak II (6 %, 95 % CI 2.7–9.3, I²?=?32 %), IIF (6.7 %, 95 % CI 5–8.4, I²?=?0 %), III (55.1 %, 95 % CI 45.7–64.5, I²?=?89 %) and IV (91 %, 95 % CI 87.7–94.2, I²?=?36). Several study design-related influences on malignancy rates and subsequent diagnostic performance indices were identified.

Conclusion

The Bosniak classification is an accurate tool with which to stratify the risk of malignancy in renal cystic lesions.

Key points

? The Bosniak classification can accurately rule out malignancy.? Specificity remains moderate at 74?% (95?% CI 64–82).? Follow-up examinations should be considered in Bosniak IIF and Bosniak II cysts.? Data on the influence of reader experience and inter-reader variability are insufficient.? Technical CT standards and publication year did not influence diagnostic performance.

     

CT and histopathological correlation of congenital cystic pulmonary lesions: a common pathogenesis?

AIM: To determine whether similarities exist in both the imaging and histopathological features of congenital cystic lung lesions and whether a more appropriate classification would be to adopt the theory of "malinosculation". MATERIAL AND METHODS: From the histopathology and computed tomography (CT) database, 24 patients (16 male, median age 3 years) with congenital cystic lung lesions were identified. CT studies were reviewed for site and characteristics of the lesions, parenchymal features, bronchial anatomy, and the presence of a feeding systemic vessel. Individual histopathological parameters were also correlated with CT data. RESULTS: There were five type 1 congenital cystic adenomatoid malformations (CCAMs), six type 2 CCAMs, one type 4 CCAM, one bronchial atresia, four pleuropulmonary blastomas (PPBs), and seven sequestrations. CCAMs (types 1, 2 and 4), sequestrations and PPBs appeared as cystic lesions, with cyst size less than 2cm in type 2 CCAMs. Sequestrations were distinguished radiologically from CCAMs by systemic vessels. Reduced pulmonary attenuation was seen in bronchial atresia, type 2 CCAMs and in sequestrations. Histopathology showed an overlap in entities with sequestrations demonstrating CCAM type 2 histology and segmental atresia noted in both type 2 CCAMs and sequestrations. PPBs showed histological and imaging overlap with type 4 CCAMs and were distinguished on histology by the presence of blastematous proliferation. CONCLUSIONS: This study demonstrates overlap in the CT appearances of congenital cystic lesions. The similarity in CT and histopathology findings across the spectrum of developmental lesions supports the hypothesis of a common aetiology.     

Association between FDG uptake, CSF biomarkers and cognitive performance in patients with probable Alzheimer’s disease

Purpose  Brain imaging of FDG uptake and cerebrospinal fluid (CSF) concentration of amyloid-beta 1–42 (Aβ_1-42) or tau proteins are promising biomarkers in the diagnosis of Alzheimer’s disease (AD). There is still uncertainty regarding any association between decreased FDG uptake and alterations in CSF markers. Methods  The relationship between FDG uptake, CSF Aβ_1-42 and total tau (T-tau), as well as the Mini-Mental State Examination (MMSE) score was investigated in 34 subjects with probable AD using step-wise linear regression. FDG uptake was scaled to the pons. Results  Scaled FDG uptake was significantly reduced in the probable AD subjects compared to 17 controls bilaterally in the precuneus/posterior cingulate area, angular gyrus/inferior parietal cortex, inferior temporal/midtemporal cortex, midfrontal cortex, and left caudate. Voxel-based single-subject analysis of the probable AD subjects at p < 0.001 (uncorrected) revealed a total volume of significant hypometabolism ranging from 0 to 452 ml (median 70 ml). The total hypometabolic volume was negatively correlated with the MMSE score, but it was not correlated with the CSF measures. VOI-based step-wise linear regression revealed that scaled FDG uptake in the precuneus/posterior cingulate was negatively correlated with CSF Aβ_1-42. Scaled FDG uptake in the caudate was positively correlated with CSF T-tau. Conclusion  The extent and local severity of the reduction in FDG uptake in probable AD subjects are associated with cognitive impairment. In addition, there appears to be a relationship between local FDG uptake and CSF biomarkers which differs between different brain regions.     

Differential diagnosis of tumours and tumour-like lesions of the infrapatellar (Hoffa’s) fat pad: pictorial review with an emphasis on MR imaging

A variety of intrinsic and extrinsic tumours and tumour-like conditions may affect the infrapatellar (Hoffas) fat pad (IFP). MR imaging is the technique of choice in evaluating these conditions, but correlation with radiographs is important to identify those lesions producing mineralization. This pictorial review illustrates the spectrum of mass-like lesions that can affect the IFP, emphasizing the radiographic and MR findings that suggest a specific diagnosis.     

Radiologic–pathologic correlations of intratumoral tissue components in the most common solid and cystic renal tumors. Pictorial review

This paper describes the correlation between US-CT images and pathologic findings in the most common solid and cystic renal tumors, to better differentiate malignant and benign renal masses. Several intratumoral tissue components present correlation with US-CT images. Macroscopic components, corresponding to necrotic, hemorrhagic and cystic changes, are identified by visual analysis of the gross specimen, while microscopic components are identified by histopathologic analysis. Microscopic components are classified as cellular [(1) high cellularity with poor extracellular stroma, ±high nucleus–cytoplasm ratio±high uniformity in tumoral cells dimensions; (2) low cellularity with large extracellular stroma±low nucleus–cytoplasm ratio±low uniformity in tumoral cells dimensions], stromal [(1) fibrotic; (2) fibrovascular; (3) fibromyxoid], vascular related to neoangiogenesis, necrotic [(1) coagulative; (2) colliquative; (3) hemorrhagic], calcific, and adipose.Presented as educational exhibit in EPOS 2004 and awarded by Cum Laude at ECR 2004     

‘Hot’ and ‘cold’ lesions detected by gallium-67 scintigraphy in a pyogenic liver abscess

Most pyogenic liver abscesses appear to be not in a ⁶⁷Ga-citrate study; rarely, a warm or cold area may also be seen. We present a patient with a pyogenic liver abscess that had both cold and hot areas in the ⁶⁷Ga-citrate study. This striking finding is probably related to the different stages of evolution of the abscess.     

The relationship between educators’ and children's physical activity and sedentary behaviour in early childhood education and care

ObjectivesThe early childhood education and care (ECEC) environment has a significant role to play in the promotion of physical activity and reduction of sedentary behaviour in young children. Educators may be an important social factor influencing children's physical activity and sedentary behaviour, however limited evidence exists on this relationship. The primary aim was to examine the relationships between educators’ and children's physical activity and sedentary behaviours within ECEC settings.DesignA cross sectional study.MethodsThe study involved 11 ECEC centres from NSW, Australia (n = 110 educators; n = 490 children). Data for each centre were collected over five consecutive days. Objectively measured physical activity and sedentary behaviour were collected from children using Actigraph accelerometers and were analysed using STATA 13c. Linear regression was used to examine relationships between children and educators, adjusted for centre clustering.ResultsA significant association was reported between educators’ sedentary behaviour and children's sedentary behaviour (p = 0.047). Educators spent 61% of their work day in sedentary behaviour. No significant associations were reported between educators’ physical activity and children's physical activity, for any intensity of physical activity.ConclusionsThe positive relationship between educators’ sedentary behaviours and children's sedentary behaviour in this study highlights a novel area to target in future interventions. Improving physical activity and sedentary behaviours of educators will likely improve children's physical activity levels and thus health and wellbeing outcomes.     

Correlation between morphological expansion and impairment of intra- and prelesionary motility in inflammatory small bowel lesions in patients with Crohn's disease – Preliminary data

Introduction

The aim of this study is to investigate if alterations of intra- and prelesionary motility in inflamed small-bowel segments correlate with length, wall-thickness and prelesionary dilatation of inflammatory small bowel lesions in patients suffering from Crohn's disease assessed with MRI.

Methods and materials

This retrospective IRB approved study included 25 patients (12 males, 18–77y) with inflammatory lesions examined using (MRE) magnetic resonance imaging enterography. Cine MRE was performed using a coronal 2D steady-state free precession sequence (TR 2.9, TE 1.25) on a 1.5T MRI scanner. Small bowel motility was examined using a dedicated MR-motility assessment software (Motasso, Vers. 1.0, Sohard AG, Bern, Switzerland). Motility patterns (contraction frequency, relative occlusion rate and mean diameter) were assessed in correlation to wall thickness, length and prelesionary dilatation of the lesions. Statistical analysis was performed by calculation of the Pearson's-Correlation coefficient.

Results

The length of the inflammatory segments, the wall thickening and prelesionary dilatation did not correlate with the frequency of the contractions (r = 0.17, p = 0.477; r = 0.316, p = 0.123; r = 0.161, p = 0.441) or the impairment of luminal occlusion (r = 0.274, p = 0.184; r = 0.199, p = .0339; r = 0.015, p = 0.945) and only the prelesionary dilatation (r = 0.410, p = 0.042) correlated to the mean luminal diameter of the segment.

Conclusion

The degree of motility impairment within inflammatory small bowel lesions does not significantly correlate with the extent of the lesion but with the motility measured in prelesionary, non-affected segments, suggesting an interdependent functional aspect of inflammation even in morphologically non-affected small bowel segments.     

Correlation between pathology and neuromelanin MR imaging in Parkinson’s disease and dementia with Lewy bodies

Introduction

Direct correlation between neuropathological findings and postmortem neuromelanin MR imaging (NmMRI) was performed in the substantia nigra pars compacta (SNc) to clarify the pathological background of the signal changes in normal, Parkinson’s disease (PD), and dementia with Lewy bodies (DLB) cases.

Methods

NmMRI of 10 % formalin-fixed autopsied midbrains was performed in three cases (normal control, DLB, and PD) with a 3T imaging system, using a 3D gradient echo T1-weighted sequence with a magnetization transfer contrast pulse. Neuropathological examinations of the midbrains were performed, and the density of neuromelanin-positive neurons (number per square millimeter) was determined. The extent of iron deposition in the midbrain was also evaluated using ferritin immunohistochemistry. Furthermore, we directly correlated the contrast signal ratio in the SNc and the density of neuromelanin-containing neurons.

Results

Diffuse hyperintense areas in the SNc reflected well-preserved neuromelanin-containing neurons in the normal control case, whereas an iso-intense area in the SNc showed severe loss of neuromelanin-containing neurons in the DLB and PD cases. Increased signal intensity in the SNc was apparently not influenced by iron deposition. Furthermore, a significant positive correlation between signal intensity and the density of neuromelanin-containing neurons was seen in the SNc.

Conclusion

Based on the direct correlation between postportem NmMRI and neuropathological findings, signal intensity in the SNc is closely related to the quantity of neuromelanin-containing neurons but is not influenced by iron deposition.     

Exploring associations between neuromuscular performance,hypermobility, and children’s motor competence

ObjectivesTo evaluate if neuromuscular performance and hypermobility are factors associated with children’s motor competence.DesignCross-sectional observation study.MethodsData was collected on 60 children aged 6–12 years; motor competence was determined using the Movement Assessment Battery for Children-2 test, with children classified into 3 groups (Typically Developing n = 30; ‘At Risk’ of low motor competence (LMC) n = 9; LMC n = 21). Neuromuscular performance was determined utilising the Resistance Training Skills Battery for Children (RTSBc), 5-repetition maximum (5RM) leg press and Biodex dynamometry to assess isometric and isokinetic peak torque of the knee flexors and extensors. Hypermobility was measured using the Beighton and Lower Limb Assessment Score.ResultsBetween-groups MANCOVA revealed typically developing children scored significantly higher on the RTSBc than those ‘at risk’ of LMC (p = 0.021) and those in the LMC group (p < 0.001). 5RM scores also differed between groups, with typically developing children achieving significantly higher scores than the LMC group. No differences were found between groups for isometric or isokinetic measures of strength. Sequential regression analysis revealed neuromuscular performance variables explained 44.7% of the variance in motor competence, with RTSBc (p < 0.001) and 5RM (p = 0.019) emerging as positive significant predictors. Hypermobility failed to explain significant variance in motor competence beyond that explained by neuromuscular performance.ConclusionsNeuromuscular performance of children varies according to levels of motor competence, with those with LMC performing poorly on tasks requiring multi-joint movement. Furthermore, neuromuscular performance predicted almost half the variance observed in motor competence and highlights a novel intervention strategy.     

‘Haste makes waste’: The tradeoff between walking speed and target-stepping accuracy

BackgroundWhen environmental conditions require accurate foot placement during walking (e.g., on a rough path), we typically walk slower to avoid tripping, slipping or stumbling. Likewise, hurrying too much is a common situational circumstance of walking-related falls. This suggests a tradeoff between walking speed and stepping accuracy in situations that demand precise foot placement.Research questionHow can this expected tradeoff between walking speed and stepping accuracy best be parameterized?MethodsIn Experiment 1, participants (n = 20) walked at five different speeds over an irregularly spaced sequence of projected stepping targets. Participants were instructed to place their feet accurately onto the targets, while following a constant-speed cue running alongside the walkway. Stepping accuracy was parameterized as overall (RMSE, root mean square error), variable (VE) and constant (CE) stepping errors, quantified over targets as well as per target. In Experiment 2, we determined preferred walking speed and stepping accuracy for regularly and irregularly spaced stepping targets.ResultsRepeated-measures ANOVAs revealed that RMSE and VE grew linearly with increasing speeds, both over targets as well as per target. Per target CE varied in magnitude and sign with variations in inter-target spacing: for shorter inter-target spacing targets were overshot (CE > 0), while for longer inter-target spacing targets were undershot (CE < 0). This effect was stronger for faster speeds and for targets preceded by the shortest and longest inter-target spacing. Preferred walking speed and per-target VE did not differ between regularly and irregularly spaced targets.SignificanceParticipants stepped less precisely when walking faster. The linear increase in VE with faster speeds was consistent with Schmidt’s law regarding the speed-accuracy tradeoff. The systematic comparison of stepping errors over regularly and irregularly spaced stepping-target conditions further provided important clues on how to best parameterize stepping accuracy: per stepping target using VE (i.e., stepping inconsistency), complemented with CE (i.e., stepping bias) in case of irregular inter-target spacing.     

A comparative study of the accuracy of Ranawat’s and Pierchon’s methods to determine the centre of rotation in bilateral coxopathy

Objective. The objective of the study was to compare two methods (Ranawat’s and Pierchon’s) used to determine the centre of rotation of the hip and establish which method calculates a position nearer to the real centre of rotation. Patients and design. We selected 24 patients with unilateral osteoarthritis of the hip. The centre of rotation of the healthy hip was determined in two consecutive radiographic studies by superimposing a template of circles and using two axes as the reference lines (X-axis=teardrop line; Y-axis=a line perpendicular to the X-axis, drawn from the intersection of the ilio-ischiatic line and the teardrop line). After ensuring the stability of these references, both methods were applied to the same radiograph to determine which one established a centre of rotation nearer to the anatomical centre identified by the template of circles. Results. When the values for the healthy hip are compared with those obtained using Ranawat’s method, highly significant differences are observed for both X (P<0.0001) and Y (P<0.0001). When the results for the healthy hip are compared with the values obtained using Pierchon’s method, neither the X (P=0.722 ) nor the Y values (P=0.112) show any significant differences. It would be advisable to use Pierchon’s method to determine the centre of rotation during the preoperative planning for a total hip arthroplasty when the anatomical alteration is bilateral. Received: 16 March 2000 Revision requested: 16 June 2000 Revision received: 31 July 2000 Accepted: 10 August 2000     

Accuracy in contouring of small and low contrast lesions: Comparison between diagnostic quality computed tomography scanner and computed tomography simulation scanner—A phantom study

To evaluate the accuracy in detection of small and low-contrast regions using a high-definition diagnostic computed tomography (CT) scanner compared with a radiotherapy CT simulation scanner. A custom-made phantom with cylindrical holes of diameters ranging from 2–9 mm was filled with 9 different concentrations of contrast solution. The phantom was scanned using a 16-slice multidetector CT simulation scanner (LightSpeed RT16, General Electric Healthcare, Milwaukee, WI) and a 64-slice high-definition diagnostic CT scanner (Discovery CT750 HD, General Electric Healthcare). The low-contrast regions of interest (ROIs) were delineated automatically upon their full width at half maximum of the CT number profile in Hounsfield units on a treatment planning workstation. Two conformal indexes, CI_in, and CI_out, were calculated to represent the percentage errors of underestimation and overestimation in the automated contours compared with their actual sizes. Summarizing the conformal indexes of different sizes and contrast concentration, the means of CI_in and CI_out for the CT simulation scanner were 33.7% and 60.9%, respectively, and 10.5% and 41.5% were found for the diagnostic CT scanner. The mean differences between the 2 scanners' CI_in and CI_out were shown to be significant with p < 0.001. A descending trend of the index values was observed as the ROI size increases for both scanners, which indicates an improved accuracy when the ROI size increases, whereas no observable trend was found in the contouring accuracy with respect to the contrast levels in this study. Images acquired by the diagnostic CT scanner allow higher accuracy on size estimation compared with the CT simulation scanner in this study. We recommend using a diagnostic CT scanner to scan patients with small lesions (<1 cm in diameter) for radiotherapy treatment planning, especially for those pending for stereotactic radiosurgery in which accurate delineation of small-sized, low-contrast regions is important for dose calculation.     

Differences in striatal dopamine transporter density between tremor dominant and non-tremor Parkinson’s disease

Purpose

Parkinson’s disease (PD) can manifest with a tremor-dominant or a non-tremor (akinetic-rigid) phenotype. Although the tremor-dominant subtype may show a better prognosis, there is limited information on the phenotypic differences regarding the level of striatal dopamine transmission. The present study investigated striatal dopamine transporter (DAT) binding characteristics in a large sample of patients with and without tremor.

Methods

[¹²³I]FP-CIT SPECT scans of 231 patients with a clinical diagnosis of PD and abnormal FP-CIT binding (157 with tremor, 74 without tremor) and 230 control patients with normal FP-CIT binding (148 with tremor, 82 without tremor) were analysed using an automated region-of-interest analysis of the scans (BRASS). Specific striatal binding ratios were compared between phenotypes and groups using age, sex, and symptom duration, predominant side of symptoms, dopaminergic medications and scanner as covariates.

Results

Patients with PD had 28.1 – 65.0 % lower binding in all striatal regions compared to controls (p?p?Conclusion The motor phenotype is associated with the extent of caudate dopamine terminal loss in PD, as dopamine function is relatively more preserved in tremor patients. Symptom type is related to caudate dopamine function only in association with Parkinsonian dopaminergic degeneration, not in intact dopamine systems in patients with non-PD tremor.     

Diagnosis,management, and outcome of obstructed hemivagina and ipsilateral renal agenesis (OHVIRA syndrome): Is there a correlation between MRI findings and outcome?

AimTo review the experience of a single tertiary center with obstructed hemivagina and ipsilateral renal agenesis (OHVIRA syndrome) and evaluate if MRI findings correlate with outcome.MethodsPatients (n = 32) diagnosed with OHVIRA syndrome between 2001 and 2019 were analyzed. Presenting symptoms, age of menarche, age at operation, MRI findings, management, and outcome were reviewed. In sagittal MRI planes, distance from hematocolpos to perineum was measured. Measurements were compared among patients who underwent single-stage vaginoplasty and hemihysterectomy.ResultsMean age at diagnosis and mean age of menarche was 16.8 ± 6.4 (10−33) and 12.8 ± 1.0 (10–15). Main presenting complaints were abdominal pain/dysmenorrhea. Eighteen anomalies (56.3%) were on right side. Twenty-eight had ipsilateral renal agenesis, 3 patients had normal renal anatomy and one had unilateral multicystic dysplastic kidney. In MRI, 21 patients had hematocolpos, 11 patients had both hematocolpos and hematometra. 28 patients underwent single-stage vaginoplasty and vaginal septum resection. One had hemihysterectomy due to sepsis at presentation. Three patients had hemihysterectomy due to proximal vaginal septum and impossibility of vaginoplasty. During follow-up, 7 cases (21.9%) had married and 5 of these (71.4%) were pregnant or had delivered. Five patients had reoperation during follow-up. MRI images of 19 patients indicated mean distances from hematocolpos to perineum whom underwent vaginoplasty or hemihysterectomy were 33.9 ± 18.1 mm (10–79 mm) and 87.3 ± 11.0 mm (80–100), respectively (p = .009).ConclusionsGold standard treatment of OHVIRA syndrome is single-stage vaginoplasty. Distance from hematocolpos to perineum in MRI may correlate with surgical outcome. Hemihysterectomy may be an alternative for extreme proximal vaginal septum or infectious complications.     

Does supplementation of contrast MR imaging with thallium-201 brain SPECT improve differentiation between benign and malignant ring-like contrast-enhanced cerebral lesions?

Objective To determine whether thallium-201 (²⁰¹Tl) brain single photon emission computed tomography (SPECT) could supplement magnetic resonance (MR) imaging diagnostic information by visual comparison of two separate data sets from patients with ring-like contrast-enhanced cerebral lesions. Methods A combination of MR imaging and ²⁰¹Tl brain SPECT sets obtained from 13 patients (10 men, 3 women) ranging in age from 26 years to 86 years (mean 61.0 years) were retrospectively reviewed. A total of 12 patients had a solitary lesion, and the others had multiple lesions. All but two intracranial foci were pathologically confirmed. The final diagnoses were six glioblastomas, two cerebral metastases from lung cancer, and one each of abscess, resolving hematoma, primary central nervous system lymphoma, toxoplasmosis, and radiation necrosis. The two separate image formats (MR images and SPECT) were shown to ten readers with practical experience. All of the MR images for each patient were shown to each reader first. After interpreting them, the readers were shown the SPECT images. Images were scored in terms of how benign or malignant the foci were on a 5-point scale from “definitely benign” to “definitely malignant.” Results The improvement in the performance of all ten readers was from 67.7% to 93.8% in mean accuracy (P = 0.0028) and from 0.730 to 0.971 in mean Az value (P = 0.0069) after they were shown the ²⁰¹Tl brain SPECT images. Conclusions ²⁰¹Tl brain SPECT should substantially increase confidence in the diagnosis of intracranial lesions with ring-like contrast enhancement when MR imaging does not permit differentiation between benign and malignant disease.