T2-FLAIR Mismatch Sign and Response to Radiotherapy in Diffuse Intrinsic Pontine Glioma.

PURPOSE: The T2-fluid-attenuated inversion recovery (FLAIR) mismatch sign was previously reported as a diagnostic indicator of diffuse astrocytoma, isocitrate dehydrogenase-mutant, and 1p/19q noncodeletion. Subsequently, it was reported that the same findings were observed in diffuse intrinsic pontine glioma (DIPG). We investigated the clinical significance of T2-FLAIR mismatch sign in DIPG. METHODS: Twenty-one patients with DIPG (Male: Female = 12:9) were treated at our institute between 2004 and 2019. All patients were treated with local radiotherapy of 54 Gy/30 fractions. The positive T2-FLAIR mismatch sign was defined if it fulfilled the following criteria: (1) T2-FLAIR mismatch volume was >50% of T2 high volume at nonenhanced area, (2) the FLAIR low lesion is not associated with gadolinium enhancement (inside of enhancement or just outside of enhancement defined as edema), and (3) signal-intensity of FLAIR lowest lesion at tumor is lower than the normal cerebellar cortex. RESULTS: In our patient series, T2-FLAIR mismatch sign was found in 5 out of 21 patients. Objective response rate of radiotherapy was 100% in patients positive for T2-FLAIR mismatch, while it was 25.0% in patients negative for T2-FLAIR mismatch, and this difference was statistically significant (p < 0.01, Fisher's exact test). In patients under the age of 18-years, T2-FLAIR mismatch positive had a slightly better prognosis (p < 0.05, Wilcoxon test). CONCLUSION: T2-FLAIR mismatch sign in DIPG may be an indicator for better response to radiotherapy and a better prognostic factor.

T2-FLAIR mismatch sign in dysembryoplasticneuroepithelial tumor.

PURPOSE: T2-FLAIR mismatch sign was reported as specific imaging marker in non-enhancing diffuse astrocytoma, IDH-mutant & 1p/19q non-codeleted. However, most of the previous studies for T2-FLAIR mismatch sign were confirmed only among lower grade glioma. The aim of this study is to assess the T2-FLAIR mismatch sign in dysembryoplastic neuroepithelial tumor (DNET) and unveil the exception rules of the sign. METHOD: Eleven patients with histopathologically confirmed DNET were included in this study. The MR images were evaluated by 2 independent reviewers to assess (i) the presence or absence of T2-FLAIR mismatch sign and (ii) the presence or absence of gadolinium enhancement. CT was also performed to evaluate calcification and localized thinning of the skull bone. Inter-reviewer agreement with Cohen's kappa (κ) was calculated. RESULTS: The T2-FLAIR mismatch sign was present in 8 cases (72.7 %) and absent in 3 cases (27.3 %). None of them showed contrast enhancement on initial MR images. The inter-reviewer agreement for T2-FLAIR mismatch and CT characteristics was excellent (κ = 1.00). All of the DNET without T2-FLAIR mismatch presented with calcification on CT. All of the DNET adjacent to skull vault (5 cases) presented with localized bone thinning overlying the tumor. CONCLUSIONS: The T2-FLAIR mismatch sign was observed in more than half of the DNET and the sign is not specific for diffuse astrocytoma, IDH-mutant & 1p19q non-codeleted. The localized skull bone thinning overlying the tumor might help for diagnosis of DNET in some cases.

Utility of dual-energy CT for predicting the vascularity of meningiomas.

PURPOSE: Dual-energy computed tomography (DECT) can provide iodine, electron density (ED), and effective atomic number Z (Zeff) maps, facilitating the identification of tissue types. We investigated whether DECT parameters can predict the vascularity of meningiomas. METHOD: We acquired DECT and perfusion CT (PCT) images in 24 patients with histologically diagnosed meningioma. Regions of interest (ROIs) were placed at the tumor in iodine, ED, and Zeff maps derived from DECT and in a blood volume (BV) map derived from PCT. To normalize these parameters' values, we divided them by the values of contralateral normal-appearing white matter, i.e., the relative (r)ED, rZeff, and rBV. The vascular density of the tumor specimens was immunohistochemically analyzed by calculating the von Willebrand factor-positive vessel wall. We calculated Pearson's correlation coefficients to determine the correlation with PCT/DECT parameters and an immunohistopathological index. RESULTS: Contrast rZeff (r = 0.7020, p = 0.0001) and iodine (r = 0.5814, p = 0.0029) both had positive correlations with rBV derived from PCT. The rED values were negatively correlated with the rBV values (r = -0.4735, p = 0.0194), and the vascular density results confirmed positive correlations with rBV (r = 0.6909, p = 0.0002) and contrast rZeff (r = 0.4982, p = 0.0132) and a negative correlation with rED (r = -0.4265, p = 0.0377). Regarding the radiation exposure, the mean estimated volume CT dose index (CTDIvol) of DECT was 33.1 ± 1.72 mGy, much lower than that of PCT (103.3 ± 4.65 mGy). CONCLUSIONS: DECT predicted vascular density with lower radiation exposure compared to PCT. DECT could potentially replace PCT for evaluating the vascularity of meningiomas.

Clinical staging of upper urinary tract urothelial carcinoma for T staging: Review and pictorial essay.

Upper urinary tract urothelial carcinoma is staged using the TNM classification of malignant tumors. Preoperative TNM is important for treatment planning. Computed tomography urography is now widely used for clinical survey of upper urinary tract carcinoma because of its diagnostic accuracy. Computed tomography urography is recommended as the first-line imaging procedure in several guidelines. Several reports stated that computed tomography urography is also useful for staging. However, no educational and practical reviews detailing the T staging of upper urinary tract urothelial carcinomas using imaging are available. We discuss the scanning protocol, T staging using computed tomography urography, limitations, magnetic resonance imaging, computed tomography comparison and pitfalls in imaging of upper urinary tract urothelial carcinoma. A recent study reported the high diagnostic accuracy of computed tomography urography with respect to T3 or higher stage tumors. To date, images that show a Tis-T2 stage have not been reported, but various studies are ongoing. Although magnetic resonance imaging has lower spatial resolution than computed tomography urography, magnetic resonance imaging can be carried out without radiation exposure or contrast agents. Magnetic resonance imaging also offers the unique ability of diffusion-weighted imaging without contrast agent use. Some researchers reported that diffusion-weighted imaging is useful not only for detecting lesions, but for predicting the T stage and tumor grade. We recommend the appropriate use of computed tomography and magnetic resonance while considering the limitations of each modality and the pitfalls in upper urinary tract urothelial carcinoma imaging.

Usefulness of Histogram-Profile Analysis in Ring-Enhancing Intracranial Lesions.

BACKGROUND: Several intracranial pathologies present as a ring-enhancing lesion on conventional magnetic resonance imaging (MRI), creating diagnostic difficulty. We studied the characteristics of the anatomical border of gadolinium enhancement on T1-weighted imaging (WI) and hypointensity on T2WI to employ a simple technique of histogram-profile analysis of MRI for differentiation of various ring-enhancing intracranial lesions. METHODS: After approval from the institutional review board, preoperative MRI (T2WI, postcontrast T1WI) scans were analyzed retrospectively in 18 patients with histologically confirmed brain abscess, 66 glioblastomas, 46 brain-metastases, and 16 tumefactive multiple sclerosis (MS). T2WI and postcontrast T1WI were overlapped, and histogram-profile analysis was performed with in-house image-fusion software. The pattern of differential-peaks in histogram-profile was assessed visually. Kaplan-Meier survival analysis incorporating histogram-profile patterns was performed in patients with glioblastoma. RESULTS: The histogram-profile study revealed 4 distinct patterns. Pattern 1 showed no differential T2-hypointensity trough, pattern 2 had T2-hypointensity trough inside, whereas pattern 3 had T2-hypointensity trough overlapping the enhanced margin. Pattern 4 had T2-hypointensity trough immediately external to the enhanced margin. Pattern 1 was specific for tumefactive MS (93.3%), whereas pattern 4 was specific for glioblastoma (40.7%). Pattern 4 glioblastoma was subdivided into rim (T2-hypointensity ≥50% of circumference of contrast-enhanced tumor) and arc (T2-hypointensity <50% of circumference of contrast-enhanced tumor). Pattern 4 glioblastoma was further subdivided into group A (edema: T2-hyperintensity ≥50% of circumference of contrast-enhanced tumor) and group B (less edema: T2-hyperintensity <50% of circumference of contrast-enhanced tumor). Patients with pattern 3 glioblastoma (37.6%) had better survival compared with others (P = 0.0341) and pattern 4B had decreased survival compared with pattern 4A (P = 0.0001) and others (P = 0.0003). CONCLUSIONS: Tumefactive MS and a subset of glioblastomas show specific patterns in histogram-profile analysis. The difference in anatomical border also determines difference in survival in glioblastoma. Histogram-profile analysis is a simple and efficient technique to differentiate these pathologies.

Improved differentiation between high- and low-grade gliomas by combining dual-energy CT analysis and perfusion CT.

The purpose of this study was to investigate the value of the cerebral blood volume (CBV) obtained with perfusion computed tomography (CT) and the electron density (ED) measured by dual-energy CT for differentiating high- from low-grade glioma (HGG, LGG).The CBV and ED were obtained in 9 LGG and 7 HGG patients. The CBV and ED of LGGs and HGGs were compared. Receiver operating characteristic (ROC) curves were generated for CBV, ED, and CBV plus ED. The correlation between CBV, ED, and the MIB-1 labeling index of the tumors was examined. All of these analyses were also performed using relative CBV (rCBV) and ED (rED) (the value of tumors/the value of contralateral white matter).The mean CBV, ED, rCBV, and rED values were significantly higher in HGG than LGG (P < .05). By ROC analysis, the combination of rCBV plus rED as well as CBV plus ED were more accurate than CBV, ED, rCBV, rED alone. There was a significant correlation between ED and MIB-1 (P = .04).ED improved diagnostic accuracy of perfusion CT for differentiating HGG from LGG.

Introduction to the Technical Aspects of Computed Diffusion-weighted Imaging for Radiologists.

Diffusion-weighted (DW) imaging is a magnetic resonance (MR) imaging method. It is an indispensable sequence for the diagnosis of acute cerebral infarction and is recognized as a standard tool in oncologic imaging. Computed DW imaging refers to the synthesizing of arbitrary b-value DW images from a set of measured b-value images by voxelwise fitting. Computed DW imaging is advantageous because it generates DW images with a higher diffusion effect than that achievable by using the MR imaging units in use today. Additionally, computed DW imaging can reduce imaging time while producing images characterized by a higher signal-to-noise ratio than what the acquired DW images would display at the corresponding b values. By fitting input images acquired at a lower b value and correspondingly a shorter echo time, the signal intensity of the resulting computed DW image is closer to the ideal case. Computed DW images are generated by employing mathematical models that use mono-, bi-, or triexponential equations. To generate accurate computed DW images, the appropriate model must be selected, and the image parameters for the input data must be chosen accordingly. In addition, to reduce artifacts on computed DW images, the misalignment of input data must be corrected with the aid of image registration techniques. ©RSNA, 2018.

Imaging features of papillary renal cell carcinoma with cystic change-dominant appearance in the era of the 2016 WHO classification.

PURPOSE: Papillary renal cell carcinoma (P-RCC) typically exhibits a homogeneous, solid hypovascular mass; P-RCC with a cystic appearance is atypical. Tubulocystic RCC (TC-RCC), a newly proposed entity for renal tumors in the 2016 WHO classification, and cystic papillary RCC, may yield similar imaging findings. Therefore, we investigated the incidence of papillary RCC with cystic changes and compared its CT and pathologic features to differentiate between two entities. METHODS: We retrospectively evaluated 26 consecutive patients diagnosed with P-RCC. Two radiologists consensually identified dominant masses indicative of cystic changes on CT scans and recorded their Bosniak classification. In addition, two pathologists inspected the whole area of tumors macroscopically, labeled them as solid- or cystic change-dominant tumors, determined the pathogenesis of the cystic components (necrosis or hemorrhage), and recorded their inherent cystic characteristics (with/without TC-RCC components). We defined masses with cystic changes involving more than 50% of the entire tumor as cystic change-dominant tumors. RESULTS: Of the 26 tumors, 7 (27%) were diagnosed cystic change-dominant based on imaging and pathologic findings, of these, 2 were classified as Bosniak type III and 5 as Bosniak type IV. The pathologists confirmed that two type IV tumors demonstrated extensive necrosis and one type IV tumor revealed extensive hemorrhage. Four P-RCCs (type III and IV, 2 each) were of a mixed type harboring both solid and cystic components. Only one tumor exhibited a multilocular cystic appearance. All 7 cystic change-dominant P-RCCs were pathologically diagnosed as a pure P-RCC without TC-RCC components. CONCLUSION: While P-RCCs may contain cystic features, the multilocular type of cystic P-RCC is rare.

Diffusion-weighted MR imaging of non-complicated hepatic cysts: Value of 3T computed diffusion-weighted imaging.

PURPOSE: To investigate the utility of computed 3T diffusion-weighted imaging (c-DWI) for the diagnosis of non-complicated hepatic cysts with a focus on the T2 shine-through effect. MATERIALS AND METHODS: In 50 patients with non-complicated hepatic cysts we acquired one set of DWIs (b-value 0 and 1000 s/mm(2)) at 1.5T, and two sets at 3T (b-value 0 and 1000 s/mm(2), TE 70 ms; b-value 0 and 600 s/mm(2), TE 60 ms). We defined the original DWIs acquired with b = 1000 s/mm(2) at 1.5T and 3T as "o-1.5T-1000" and "o-3T-1000". c-DWIs were calculated with 3T DWI at b-values of 0 and 600 s/mm(2). c-DWI with b = 1000 and 1500 s/mm(2) were defined as "c-1000" and "c-1500". Radiologists evaluated the signal intensity (SI) of the cysts using a 3-point score where 1 = not visible, 2 = discernible, and 3 = clearly visible. They calculated the contrast ratio (CR) between the cysts and the surrounding liver parenchyma on each DWIs and recorded the apparent diffusion coefficient (ADC) with a b-value = 0 and 1000 s/mm(2) on 1.5T- and 3T DWIs. RESULTS: Compared with o-1.5T-1000 DWI, the visual scores of all but the c-1500 DWIs were higher (p = 0.07 for c-1500- and p < 0.01 for the other DWIs). The CR at b = 1000 s/mm(2) was higher on o-3T-1000- than on o-1.5T-1000- (p < 0.01) but not higher than on c-1500 DWIs (p = 0.96). The CR at b = 0 s/mm(2) on 3T images with TE 70 ms was higher than on 1.5T images (p < 0.01). The ADC value was higher for 3T- than 1.5T images (p < 0.01). CONCLUSIONS: Non-complicated hepatic cysts showed higher SI on o-3T-1000- than o-1.5T-1000 DWIs due to the T2-shine through effect. This high SI was suppressed on c-1500 DWIs.

Radiation dose reduction for coronary artery calcium scoring at 320-detector CT with adaptive iterative dose reduction 3D.

To assess the possibility of reducing the radiation dose for coronary artery calcium (CAC) scoring by using adaptive iterative dose reduction 3D (AIDR 3D) on a 320-detector CT scanner. Fifty-four patients underwent routine- and low-dose CT for CAC scoring. Low-dose CT was performed at one-third of the tube current used for routine-dose CT. Routine-dose CT was reconstructed with filtered back projection (FBP) and low-dose CT was reconstructed with AIDR 3D. We compared the calculated Agatston-, volume-, and mass scores of these images. The overall percentage difference in the Agatston-, volume-, and mass scores between routine- and low-dose CT studies was 15.9, 11.6, and 12.6%, respectively. There were no significant differences in the routine- and low-dose CT studies irrespective of the scoring algorithms applied. The CAC measurements of both imaging modalities were highly correlated with respect to the Agatston- (r = 0.996), volume- (r = 0.996), and mass score (r = 0.997; p < 0.001, all); the Bland-Altman limits of agreement scores were -37.4 to 51.4, -31.2 to 36.4 and -30.3 to 40.9%, respectively, suggesting that AIDR 3D was a good alternative for FBP. The mean effective radiation dose for routine- and low-dose CT was 2.2 and 0.7 mSv, respectively. The use of AIDR 3D made it possible to reduce the radiation dose by 67% for CAC scoring without impairing the quantification of coronary calcification.

Iterative decomposition of water and fat with echo asymmetry and least-squares estimation (IDEAL) magnetic resonance imaging as a biomarker for symptomatic multiple myeloma.

INTRODUCTION: To evaluate the effectiveness of iterative decomposition of water and fat with echo asymmetry and least-squares estimation (IDEAL) magnetic resonance imaging (MRI) to discriminate between symptomatic and asymptomatic myeloma in lumbar bone marrow without visible focal lesions. MATERIALS AND METHODS: The lumbar spine was examined with 3-T MRI in 11 patients with asymptomatic myeloma and 24 patients with symptomatic myeloma. The fat-signal fraction was calculated from the ratio of the signal intensity in the fat image divided by the signal intensity of the corresponding ROI in the in-phase IDEAL image. The t test was used to compare the asymptomatic and symptomatic groups. ROC curves were constructed to determine the ability of variables to discriminate between symptomatic and asymptomatic myeloma. RESULTS: Univariate analysis showed that ß2-microglobulin and bone marrow plasma cell percent (BMPC%) were significantly higher and fat-signal fraction was significantly lower with symptomatic myeloma than with asymptomatic myeloma. Areas under the curve were 0.847 for ß2;-microglobulin, 0.834 for fat-signal fraction, and 0.759 for BMPC%. CONCLUSION: The fat-signal fraction as a biomarker for multiple myeloma enables discrimination of symptomatic myeloma from asymptomatic myeloma. The fat-signal fraction offers superior sensitivity and specificity to BMPC% of biopsy specimens.

Cerebral blood flow in transient hypothyroidism after thyroidectomy: Arterial spin labeling magnetic resonance study.

OBJECTIVE: Our purpose was to apply arterial spin labeling (ASL) magnetic resonance imaging (MRI) to characterize regional cerebral blood flow (rCBF: the CBF values at each voxel / the subject's mean global flow) in patients with transient hypothyroidism after thyroidectomy. METHODS: Our study included 27 patients who had undergone total thyroidectomy due to thyroid cancer and pre-131I therapy and 24 controls. Patients were evaluated at two points in time: before and after thyroxine replacement. The assessments for the patients and controls consisted of evaluation of ASL of the brain and the severity of depression using 21-question Beck Depression Inventory (BDI). The assessments for the patients also included thyroid hormone lebel. We performed the comparison of rCBF between patients and controls, and investigated the association between rCBF in hypothyroid patients and thyroid hormone level and BDI score. RESULTS: Hypothyroid patients showed a significantly lower rCBF in the cerebellum, the left thalamus and some regions, and showed a significantly higher rCBF in the bilateral frontal gyri and some regions. After thyroxine replacement, patients showed a significantly lower rCBF mostly in the right frontal lobe, and showed a significantly higher rCBF in the left frontal and parietal lobes, although the degree of rCBF changes was lower after thyroxine replacement. In the hypothyroid patients, significant positive relationships were found between free T3 and the rCBF (p<0.05 corrected for FDR). CONCLUSIONS: This study revealed alterations of rCBF in patients with transient hypothyroidism. ASL is helpful for understanding of the effects of hypothyroidism on the brain.

Multidetector computed tomography-based microstructural analysis reveals reduced bone mineral content and trabecular bone changes in the lumbar spine after transarterial chemoembolization therapy for hepatocellular carcinoma.

PURPOSE: It is well recognized that therapeutic irradiation can result in bone damage. However, long-term bone toxicity associated with computed tomography (CT) performed during interventional angiography has received little attention. The purpose of this study was to determine the prevalence of osteoporosis and trabecular microstructural changes in patients after transarterial chemoembolization (TACE) for hepatocellular carcinoma therapy using an interventional-CT system. MATERIALS AND METHODS: Spinal microarchitecture was examined by 64-detector CT in 81 patients who underwent TACE, 35 patients with chronic hepatitis, and 79 controls. For each patient, the volumetric CT dose index (CTDIv) during TACE (CTDIv (TACE)), the dose-length product (DLP) during TACE (DLP (TACE)), and CTDIv and DLP of routine dynamic CT scans (CTDIv (CT) and DLP (CT), respectively), were calculated as the sum since 2008. Using a three dimensional (3D) image analysis system, the tissue bone mineral density (tBMD) and trabecular parameters of the 12th thoracic vertebra were calculated. Using tBMD at a reported cutoff value of 68 mg/cm3, the prevalence of osteoporosis was assessed. RESULTS: The prevalence of osteoporosis was significantly greater in the TACE vs. the control group (39.6% vs. 18.2% for males, P<0.05 and 60.6% vs. 34.8% for females, P<0.01). Multivariate regression analysis demonstrated that sex, age, and CTDIv (CT) significantly affected the risk of osteoporosis. Of these indices, CTDIv (CT) had the highest area under the curve (AUC) (0.735). Correlation analyses of tBMD with cumulative radiation dose revealed weak correlations between tBMD and CTDIv (CT) (r2 = 0.194, P<0.001). CONCLUSION: The prevalence of osteoporosis was significantly higher in post TACE patients than in control subjects. The cumulative radiation dose related to routine dynamic CT studies was a significant contributor to the prevalence of osteoporosis.

A longitudinal computed tomography study of lenalidomide and bortezomib treatment for multiple myeloma: trabecular microarchitecture and biomechanics assessed using multidetector computed tomography.

BACKGROUND: Bone disease is a common feature in patients with multiple myeloma. In this study, we investigated whether lenalidomide, similar to bortezomib, affects the microarchitecture and biomechanics of bones using clinical CT-based FEM. MATERIALS AND METHODS: Bone lesions were evaluated using whole-body 64-section multidetector CT scan. For microstructural- and CT/FEM analyses, the volume of interest was defined as a 10-mm thickness of the central part of the L3 vertebral body. Microstructural parameters and mechanical properties were calculated using a 3-D image analysis system. The changes from baseline to the second examination within groups were calculated. Relationships between baseline disease characteristics and percent changes of trabecular parameters were assessed using Spearman correlation analysis. RESULTS: Thirty-two patients were treated with bortezomib and 18 patients were treated with lenalidomide. At the second CT scan, apparent trabecular number, failure load, and stiffness were decreased in the bortezomib group and failure load and stiffness were increased significantly in the lenalidomide group. In the lenalidomide group, response to chemotherapy was positively associated with increases in failure load (ρ = 0.57; P < .05) and stiffness (ρ = 0.50; P < .05). CONCLUSION: Lenalidomide treatment resulted in significant increases in CT/FEM-derived estimates of bone strength. Response to chemotherapy predicted lenalidomide-induced bone changes and good responders had increased bone strength.

Measurement of electron density and effective atomic number by dual-energy scan using a 320-detector computed tomography scanner with raw data-based analysis: a phantom study.

We evaluated the accuracy of the electron densities and effective atomic numbers determined by raw data-based dual-energy analysis on a 320-detector computed tomography scanner. The mean (SD) errors between the measured and true electron densities and between the measured and true effective atomic numbers were 1.3% (1.5%) and 3.1% (3.2%), respectively. Electron densities and effective atomic numbers can be determined with high accuracy, which may help to improve accuracy in radiotherapy treatment planning.

Magnetic resonance evaluation of multiple myeloma at 3.0 Tesla: how do bone marrow plasma cell percentage and selection of protocols affect lesion conspicuity?

PURPOSE: To compare various pulse sequences in terms of percent contrast and contrast-to-noise ratio (CNR) for detection of focal multiple myeloma lesions and to assess the dependence of lesion conspicuity on the bone marrow plasma cell percent (BMPC%). MATERIALS AND METHODS: Sagittal T1-weighted FSE, fat-suppressed T2-weighted FSE (FS- T2 FSE), fast STIR and iterative decomposition of water and fat with echo asymmetry and least-squares estimation (IDEAL) imaging of the lumbar spine were performed (n = 45). Bone marrow (BM)-focal myeloma lesion percent contrast and CNR were calculated. Spearman rank correlation coefficients were obtained between percent contrast, CNR and BMPC%. Percent contrasts and CNRs were compared among the three imaging sequences. RESULTS: BM-focal lesion percent contrasts, CNRs and BMPC% showed significant negative correlations in the three fat-suppression techniques. Percent contrast and CNRs were significantly higher for FS- T2 FSE than for STIR (P<0.01, P<0.05, respectively), but no significant differences were found among the three fat-suppression methods in the low tumor load BM group. CONCLUSION: The higher BMPC% was within BM, the less conspicuous the focal lesion was on fat-suppressed MRI. The most effective protocol for detecting focal lesions was FS- T2 FSE. In the high tumor load BM group, no significant differences in lesion conspicuity were identified among the three fat-suppression techniques.