Qualitative Imaging Features Research Articles

Imaging parameters of high grade gliomas in relation to the MGMT promoter methylation status: the CT, diffusion tensor imaging, and perfusion MR imaging

We hypothesized that methyl-guanine methyl transferase (MGMT) promoter methylation status, a predictor of the chemosensitivity for high grade gliomas (HGGs), may be associated with computed tomography (CT)/magnetic resonance (MR) imaging variables. Out of 38 consecutive patients with HGGs, 24 patients whose MGMT promoter methylation status was available [12 men and 12 women; median age, 49years; age range, 22-79years; WHO grade III (n = 7), WHO grade IV (n = 17)] were enrolled retrospectively. CT attenuation, apparent diffusion coefficient (ADC), fractional anisotropy (FA), and relative cerebral blood volume (rCBV) were measured for enhancing tumors. Qualitative imaging features were also analyzed. Mann-Whitney and Fisher's exact tests were used to evaluate relationships between MGMT promoter methylation status and imaging variables. Maximum CT attenuation was significantly lower in the methylated MGMT promoter group than that in the unmethylated MGMT promoter group (30.3 ± 9.5HU versus 39.2 ± 4.7HU, respectively, p = 0.009). While ADC values tended to be higher in the methylated group than in the unmethylated group (p = 0.055), ADC ratio was significantly higher, and the FA and FA ratios were significantly lower in the methylated group than in the unmethylated group (p = 0.032, p = 0.006 and p = 0.007, respectively). In contrast, rCBV ratio did not differ between the two groups (p = 0.380). Regarding imaging features, only ill-defined margin was seen more frequently in the methylated group than in the unmethylated group (45.5% versus 7.7%, respectively, p = 0.048). Preoperative imaging can predict MGMT promoter methylation status, which is of paramount importance for predicting treatment response to chemotherapy with an alkylating agent.

MRI Features of Renal Oncocytoma and Chromophobe Renal Cell Carcinoma

The purpose of this study was to retrospectively describe the MRI features of the pathologically related entities renal oncocytoma and chromophobe renal cell carcinoma (RCC). Twenty-eight cases of histologically proven renal oncocytoma and 15 of chromophobe RCC evaluated with preoperative MRI from January 2003 through June 2009 at our institution were independently reviewed for an array of MRI features by two radiologists blinded to the final histopathologic diagnosis. These features were tabulated and compared between chromophobe RCC and renal oncocytoma by use of the Mann-Whitney test and binary logistic regression. Renal oncocytoma and chromophobe RCC showed no significant difference in size or any of 16 qualitative imaging features (p = 0.0842-1.0, reader 1; p = 0.0611-1.0, reader 2). Microscopic fat, hemorrhage, cysts, infiltrative margins, perinephric fat invasion, renal vein invasion, enhancement homogeneity, and hypervascularity were each observed in less than 20% of cases by both readers. A central scar and segmental enhancement inversion (a recently described finding in which early contrast-enhanced images show relatively more enhanced and less enhanced intralesional components with inversion of their relative enhancement on later images) were observed by both readers in at least 10% of cases of both renal oncocytoma and of chromophobe RCC with no significant difference between the two entities (p = 0.2092-0.2960). We have presented the largest series to date of the MRI features of both renal oncocytoma and chromophobe RCC. These related entities exhibited similar findings, and no MRI features were reliable in distinguishing between them.

High-resolution MR imaging of the skin: normal imaging features [in French

The purpose of this study was to describe the qualitative and quantitative MR imaging features of normal skin.

IRM haute résolution de la peau : aspects normaux

To describe the qualitative and quantitative MR imaging features of normal skin. Thirty-one normal subjects underwent MR evaluation on a 1.5 Tesla magnet using a dedicated coil. Several skin sites were evaluated (back at the scapular level, posterior calf and inferior heel). Two pulse sequences were acquired: a SE T1W and a gradient-echo sequence (FIESTA). Qualitative and quantitative analysis was performed for all three sites. In normal subjects, the different skin layers (callus, epidermis, dermis, hypodermis and pilosebaceous follicles) can be separated and measured on MR. Epidermis and hypodermis are hyperintense whereas dermis is hypointense. Our results confirm the presence of qualitative and quantitative variations between different skin regions. In some cases, a differentiation between papillary and reticular dermis can be achieved. Pilosebaceous follicles and the deep vascular network were clearly depicted on the FIESTA sequence. Measurements for each skin layer were compared based on sex, site and MR pulse sequence. MRI provides evaluation of the different skin layers, epidermis, dermis, and hypodermis, and their different components.