T2-weighted Fast Spin-echo Images Research Articles

Is CT Still Useful in the Study Protocol of Retinoblastoma?

Intralesional calcium deposition is considered a key element for differentiating retinoblastoma from simulating lesions. Our aim was to assess whether MR imaging associated with ophthalmologic investigations (ophthalmoscopy and ultrasonography) could replace CT in the detection of diagnostic intralesional calcifications in retinoblastoma. Ophthalmoscopic findings, MR images, CT scans, and histologic examination of 28 retinoblastomas from 23 consecutive children (11 males, 12 females; age range at admission, 1-35 months; mean age, 11 months; median age, 9 months) were retrospectively evaluated. Ultrasonography was performed in 18 patients with 21 retinoblastomas. MR imaging included T2-weighted spin-echo and gradient-echo images, fluid-attenuated inversion recovery images, and T1-weighted spin-echo images with and without contrast enhancement. Clinical data were integrated with MR imaging data to evaluate the utility of both approaches to discover calcifications; particularly, a correlation between intralesional signal-intensity void spots on MR imaging and hyperattenuating areas on CT scans was performed. Ophthalmoscopy detected calcifications in 12 of 28 eyes (42.85%). Ultrasonography detected calcifications in 20 of 21 eyes (95.23%). CT showed hyperattenuating intralesional areas consistent with calcifications in 27 of 28 eyes (96.42%). MR imaging showed intralesional signal-intensity void spots in 25 of 28 eyes (89.28%). All spots detected with MR imaging matched the presence of calcifications on CT scans. Gradient-echo T2*-weighted and fast spin-echo T2-weighted images showed the highest degree of correlation with CT. When we put together ophthalmoscopy, ultrasonography, and MR imaging data, no calcifications detected on CT were missed, and the differential diagnosis was thorough. A combination of clinical data and MR images may remove potentially harmful ionizing radiation from the study protocol of retinoblastoma.

T2 at MR Imaging Is an Objective Quantitative Measure of Cerebral White Matter Signal Intensity Abnormality in Preterm Infants at Term-equivalent Age

To compare quantitative T2 relaxometry of cerebral white matter (WM) with qualitative assessment of conventional T2-weighted magnetic resonance (MR) images, to assess the relationship between cerebral WM T2 and region-specific apparent diffusion coefficient (ADC), and to examine WM T2 regional variation in preterm infants at term. The local ethical committee granted ethical permission for this study; informed parental consent was obtained for each infant. Sixty-two preterm infants born at less than 32 weeks gestation and nine control infants were examined at 1.5 T; T2-weighted fast spin-echo MR images, T2 relaxometry data, and diffusion-weighted MR images were acquired. Conventional T2-weighted MR images were assessed by a pediatric neuroradiologist for diffuse excessive high signal intensity (DEHSI) in WM. Regions of interest were positioned in frontal WM, central WM, and posterior WM at the level of the centrum semiovale. In preterm infants at term, T2 was longer in all WM regions than in control infants; in infants with DEHSI, T2 was longer than in infants without DEHSI and control infants, with posterior WM T2 being longer than central or frontal WM T2. In control infants, T2 was similar in all WM regions. Frontal and posterior WM ADCs were higher in preterm infants at term than in control infants. Cerebral WM T2 is an objective quantitative measurement that can easily and rapidly be obtained during clinical MR imaging in preterm infants at term.

Diffusion-Weighted and Gd-EOB-DTPA-Contrast-Enhanced Magnetic Resonance Imaging for Characterization of Tumor Necrosis in an Animal Model

To evaluate the role of diffusion-weighted magnetic resonance imaging (MRI) in determining tumor necrosis and contrast-enhanced MRI using gadoxetic acid disodium (Gd-EOB-DTPA) in determining maximum tumor size measurement and tumor delineation compared with criterion-standard histologic measurements in the rabbit VX2 liver tumor model. VX2 tumors were implanted in the livers of 13 rabbits. Magnetic resonance imaging was performed using a 1.5-T MRI scanner and an extremity coil. The imaging protocol included T2-weighted fast spin-echo images, 3-dimensional T1-weighted spoiled gradient-echo with and without fat suppression after administration of Gd-EOB-DTPA, and diffusion-weighted echo planar images. Rabbits were killed, and the tumor was harvested and sliced at 4-mm intervals in the axial plane. The MRI parameters evaluated were tumor size, tumor delineation, and tumor apparent diffusion coefficient (ADC) values. Histologic sections were evaluated to quantify tumor necrosis. On contrast-enhanced MRI (obtained from 11 rabbits), the mean tumor sizes were 20, 19, and 20 mm in the arterial, portal venous, and delayed phases, respectively. Tumor delineation was most distinguishable in the delayed phase. On diffusion-weighted MRI (acquired in 13 rabbits), the mean tumor ADC value was 1.84 x 10 mm/s. The mean tumor size at pathology was 16 mm. The mean percent necrosis at the tumor's pathologic condition was 36%. The correlation between ADC value and percent necrosis showed an R value of 0.68. Contrast-enhanced MRI using Gd-EOB-DTPA may provide additional information about tumor outline in the liver. Moreover, we showed a remarkable correlation between ADC values and tumor necrosis. Thus, diffusion-weighted imaging may be useful to assess tumor necrosis; nevertheless, the search for new modalities remains important.

Intermuscular adipose tissue (IMAT): Association with other adipose tissue compartments and insulin sensitivity

To quantify intermuscular adipose tissue (IMAT) of the lower leg as well as to investigate associations with other adipose tissue (AT) compartments. The relationship between IMAT and insulin sensitivity was also examined. Standardized quantification of IMAT was performed in a large cohort (N = 249) at increased risk for type 2 diabetes in the right calf by T1-weighted fast spin-echo imaging at 1.5T (Magnetom Sonata; Siemens Healthcare). Additionally, whole-body AT distribution was assessed. Insulin sensitivity was determined by glucose clamp. Males showed significantly more IMAT than females (2.1 +/- 1.1 cm(2) vs. 1.5 +/- 0.9 cm(2); P < 0.001). IMAT correlated well with other AT depots, especially with visceral AT (VAT; r(females) = 0.52, P < 0.0001 vs. r(males) = 0.42, P < 0.0001). Moreover, IMAT showed a negative correlation with the glucose infusion rate (GIR; r(females) = -0.43, P = 0.0002 vs. r(males) = -0.40, P = 0.0007). Quantification of IMAT is possible by standard MR techniques. AT distribution of the lower leg is comparable to the visceral compartment with males having higher IMAT/VAT but lower subcutaneous AT (SCAT). IMAT seems to be involved in the pathogenesis of insulin resistance, as shown by the significant negative correlation with GIR.

Another Dimension in Magnetic Resonance Cholangiopancreatography

The purpose of this study was to compare 2-dimensional (2D) and 3D magnetic resonance cholangiopancreatography (MRCP) for image quality and diagnostic performance in the evaluation of pathologically verified intraductal papillary mucinous neoplasm (IPMN) of the pancreas. In this institutional review board-approved retrospective review, 21 patients (14 women and 7 men; mean age, 69 years; range, 43-93 years) who underwent 2D and 3D MRCPs on a 1.5-T system for pathologically confirmed IPMN were studied. Two-dimensional MRCP protocol included multiplanar thin- and thick-slab single-shot fast spin-echo imaging, coronal single-shot fast spin-echo, and transverse T2-weighted fast spin-echo imaging. Three-dimensional MRCP was performed using a fast-recovery fast spin-echo sequence with single-volume acquisition and maximum intensity projection reconstructions. Using a 5-point scale, 2 readers independently evaluated MRCPs for (1) image quality, (2) visualization of the pancreatic duct (PD), and (3) visualization of the cystic lesions. Intraductal papillary mucinous neoplasm's morphological features (septa, mural nodules, and duct communication) were also graded similarly to predict benignity or malignancy. Surgical and pathological data served as reference standard. A pancreatic surgeon reviewed the 21 MRCPs to determine the usefulness of 3D MRCP compared with that of 2D MRCP for surgical planning. Of the 21 IPMNs, 11 were side-branch IPMNs and 10 were main-duct-lesions IPMNs with side-branch involvement. A statistically significant improvement in image quality and visualization of the PD and cystic lesion was demonstrated with 3D MRCP in comparison with that demonstrated with 2D MRCP (P < or = 0.002). The morphological details of IPMN were also identified, with higher confidence with 3D MRCP in comparison with that using 2D MRCP. Two-dimensional and 3D MRCPs performed similarly for predicting benign and malignant lesions, with sensitivity ranging from 50.0% to 66.7% and specificity ranging from 86.7% to 93.3%. The pancreatic surgeon preferred 3D to 2D MRCP for surgical evaluation and planning in 14 of 21 cases. Compared with 2D MRCP, 3D MRCP provides better image quality, offers superior evaluation of the PD and morphological details of IPMN, and is preferred for surgical planning.

Locally Advanced Rectal Cancer: MR Imaging for Restaging after Neoadjuvant Radiation Therapy with Concomitant Chemotherapy Part II. What Are the Criteria to Predict Involved Lymph Nodes?

To prospectively determine diagnostic performance of predictive criteria for nodal restaging after radiation therapy with concomitant chemotherapy by using ultrasmall superparamagnetic iron oxide (USPIO)-enhanced magnetic resonance (MR) imaging in patients with rectal cancer. After institutional review board approval and informed consent were obtained, 39 patients (24 men, 15 women; mean age, 64 years) with rectal cancer underwent USPIO-enhanced two-dimensional (2D) T2-weighted fast spin-echo, three-dimensional (3D) T1-weighted gradient-echo, and 3D T2*-weighted MR for restaging. Two observers evaluated nodes for border irregularity, short- and long-axis diameters, and estimated percentage of white region (<30%, 30%-50%, or >50%) within the node (3D T2*-weighted images). Ratio of the measured surface area of the white region within the black node to the measured surface area of the total node (Ratio(A)) was calculated. Signal intensity (SI) in gluteus muscle (SI(GM)) and in total node (SI(TN)) were used to calculate SI(TN)/SI(GM) ratio. Histopathologic findings were reference standard. Receiver operating characteristic (ROC) curves were compared and interobserver agreement was determined. Lesion-by-lesion analysis was feasible in 201 lymph nodes. Area under the ROC curve (AUC) of border and short- and long-axis diameters for observer 1 were 0.85, 0.87, and 0.88 and for observer 2 were 0.70, 0.89, and 0.87, respectively. AUC for estimated percentage of white region within the node, Ratio(A), and SI(TN)/SI(GM) ratio for observer 1 were 0.98, 0.99, and 0.62 and for observer 2 were 0.97, 0.98, and 0.65, respectively. AUC for USPIO-enhanced MR criteria was significantly better than AUC for conventional MR criteria (P < .01). All criteria except border irregularity and SI(TN)/SI(GM) ratio showed high interobserver agreement (kappa > 0.79). The most reliable predictors for identifying benign nodes after radiation therapy with concomitant chemotherapy by using USPIO-enhanced MR imaging for restaging in patients with rectal cancer were estimated percentage of white region within the node and Ratio(A). Measurements on standard 2D T2-weighted fast spin-echo images versus primary staging results offer reasonably good accuracy to identify benign lymph nodes after therapy.

MRI of the Spine: Image Quality and Normal–Neoplastic Bone Marrow Contrast at 3 T Versus 1.5 T

The objectives of our study were to compare image quality of the spine and visualization of spine abnormalities at 3 T and 1.5 T as well as to evaluate differences in quantitative assessment of normal and neoplastic vertebral bone marrow. One hundred nine MR examinations of the spine were performed at 1.5 T and 3 T in the same patients within a time interval of less than 3 months. Visualization of anatomic and pathologic structures was analyzed by two radiologists. Normal and pathologic bone marrow was assessed on T1-weighted fast spin-echo (FSE) sequences. The signal intensity contrast of neoplastic bone marrow versus normal vertebral bone marrow was measured at 1.5 T versus 3 T. Sensitivity, specificity, and accuracy with 95% CIs were computed to assess the performance of muscle and disk as standards to differentiate between neoplastic and normal bone marrow on T1-weighted sequences at 1.5 T and 3 T. For all anatomic structures evaluated, image quality was rated significantly higher at 3 T than at 1.5 T, with 71.6% of the studies overall being superior at 3 T. The contrast between normal and pathologic bone marrow was significantly larger at 3 T (mean +/- SD, 0.33 +/- 0.13) than at 1.5 T (0.27 +/- 0.11). The highest accuracy was found using muscle signal at 3 T to differentiate between normal and pathologic bone marrow. The use of 3-T MRI improves visualization of anatomic structures in the spine over 1.5-T MRI. As an internal standard on T1-weighted FSE images, skeletal muscle can be used to differentiate between infiltrative and normal bone marrow with higher accuracy at 3 T than at 1.5 T.

Multiple myeloma in a liver transplant recipient: Diagnostic value of MR imaging

Multiple myeloma is a rare complication in a liver transplant patient. In this case report, we present a 54-year-old man who received an orthotopic liver transplantation for HCC in HBV/HDV-related cirrhosis; about ten months after liver transplant, patient was admitted to our hospital complaining of asthenia and low grade fever with an accompanying costal, dorsal and lumbar pain. MRI of thoracic and lumbar spine was performed; T1-, T2-weighted fast spin-echo and short time inversion recovery (STIR) images showed scattered focal lesions diffusely involving vertebral bodies and an expansive mass at the level of T10–T12 right paravertebral soft tissues. The excisional biopsy of the paravertebral soft tissue mass leaded to the final diagnosis of multiple myeloma. The presented case shows that the multiple myeloma can represent a rare complication in liver transplant recipient as part of the spectrum of post-transplant lympho-proliferative disease. Although the biopsy is necessary to make the definitive diagnosis of multiple myeloma, in our opinion MRI is the best technique to determine the exact location, size and local compressive effects of the focal lesions.

Early Radiation-induced Bone Marrow Injury: Serial MR Imaging During Initial 4 Weeks After Irradiation 1

Magnetic resonance (MR) imaging has been widely used to detect bone marrow (BM) changes after radiotherapy. However, little information about the dynamic MR appearance of early radiation-induced BM injury is available. This experimental study was designed to determine the MR appearance of irradiated BM during the initial 4 weeks after irradiation. After focal BM irradiation (20 Gy, single dose, x-ray), 12 of 20 rabbits underwent serial MR studies weekly from days 7 to 28; eight rabbits were used for histologic investigation on days 7, 14, 21, and 28 after irradiation. Under microscopy, early BM changes after irradiation consisted of sinusoid dilatation and congestion, followed by a progressive decrease in cellularity and later fat degeneration. All irradiated BM showed relative hyperintensity on short-inversion time inversion recovery (STIR) imaging from days 7 to 21 after irradiation and increased enhancement with gadolinium diethylenetriamine pentaacetic acid (DTPA) administration from days 7 to 28 after irradiation. However, on STIR imaging and gadolinium DTPA enhancement, the relative signal intensity of irradiated BM appeared to decline in a time-dependent way. On fast spin-echo (FSE) T1-weighted imaging, relative hyperintensity was detected in irradiated BM from day 21 after irradiation. On fat-suppressed FSE T1-weighted imaging, a slight increase in signal intensity was shown in some irradiated BM (in five of 12 rabbits) on day 7 after irradiation. STIR imaging was sensitive to early BM congestion and sinusoidal dilatation, spin-echo T1-weighted imaging was effective in detecting later fatty degeneration in irradiated BM, and gadolinium DTPA enhancement may contribute to the evaluation of BM vascular injury in response to irradiation.

MR Imaging-guided Percutaneous Cryoablation of the Prostate in an Animal Model: In Vivo Imaging of Cryoablation-induced Tissue Necrosis with Immediate Histopathologic Correlation

To evaluate the feasibility of magnetic resonance (MR) imaging-guided percutaneous cryoablation of normal canine prostates and to identify MR imaging features that accurately predict the area of tissue damage at a microscopic level.Six adult male mixed-breed dogs were anesthetized, intubated, and placed in a 0.5-T open MR imaging system. A receive-only endorectal coil was placed, and prostate location and depth were determined on T1-weighted fast spin-echo (FSE) MR imaging. After placement of cryoprobes and temperature sensors, three freezing protocols were used to ablate prostate tissue. Ice ball formation was monitored with T1-weighted FSE imaging. Tissue necrosis area was assessed with contrast-enhanced weighted MR imaging and compared with histopathologic findings.A total of 12 cryolesions (mean size, 1.2 cm) were bilaterally created in six prostates. Ice ball formation was oval and signal-free on T1-weighted FSE sequences in all cases. Postprocedural contrast-enhanced MR imaging typically showed a nonenhancing area of low signal intensity centrally located within the frozen area, surrounded by a bright enhancing rim in all cases. On histopathologic examination, two distinct zones were identified within cryolesions. Centrally, a necrotic zone with complete cellular destruction and hemorrhage was found. Between this necrotic zone and normal glandular tissue, a zone of fragmented and intact glands, interstitial edema, and rare acute inflammatory cells was seen. Correlation between nonenhancement on contrast-enhanced weighted MR images and tissue necrosis on pathologic examination was consistent within all six dogs.MR imaging-guided cryoablation of the prostate is technically feasible. The nonenhancing area on postablation contrast-enhanced weighted MR imaging accurately predicts the area of cryoablation-induced tissue necrosis on pathologic analysis.

Unresectable Hepatocellular Carcinoma: Serial Early Vascular and Cellular Changes after Transarterial Chemoembolization as Detected with MR Imaging

To prospectively assess serial changes in contrast material-enhanced and diffusion-weighted (DW) magnetic resonance (MR) imaging values within 1 month after transarterial chemoembolization (TACE) in patients with unresectable hepatocellular carcinoma (HCC). Institutional review board approval was obtained for this prospective HIPAA-compliant study. MR imaging was performed before and within 24 hours after TACE in 24 patients with HCC (21 male, three female; mean age, 59 years and 62 years, respectively). Serial MR imaging was subsequently performed 1, 2, 3, and 4 weeks after therapy. The imaging protocol included fast spin-echo T2-weighted MR imaging, breath-hold DW echo-planar MR imaging, and breath-hold unenhanced and contrast-enhanced T1-weighted three-dimensional fat-suppressed gradient-recalled-echo MR imaging in the arterial and portal venous phases. Tumor size, enhancement, and apparent diffusion coefficient (ADC) values were recorded before and sequentially after treatment. Regression models for the correlated data were used to assess changes in these parameters over time after TACE. Mean tumor size was 7.5 cm and was unchanged up to 4 weeks after therapy. Reduction in tumor enhancement in the arterial phase occurred immediately after TACE, with a consistent reduction occurring 1-3 weeks after therapy (P = .001). Reduction in tumor enhancement in the portal venous phase also occurred immediately after TACE, with a consistent reduction occurring 1-3 weeks after therapy (P = .0003). The increase in tumor ADC value was significant 1-2 weeks after therapy (P = .004), borderline significant 3 weeks after therapy, and insignificant 24 hours and 4 weeks after therapy. Significant reduction in tumor enhancement occurred within 24 hours after TACE and persisted up to 4 weeks after TACE. Lesser changes in the ADC value appeared 1 week after TACE, persisted through 2 weeks after TACE, and became less apparent 3 and 4 weeks after TACE. No change in tumor size was recorded during the follow-up period.

MR Imaging Findings of the Uveal Schwannoma

Uveal schwannoma is a rare benign neoplastic proliferation of pure Schwann cells. The purpose of this study was to describe MR imaging features of uveal schwannoma. MR images in 6 female patients with uveal schwannoma confirmed by pathologic examination were retrospectively reviewed. MR imaging was performed in all 6 patients, with postcontrast T1-weighted imaging (T1WI) completed in all 6 patients and dynamic contrast-enhanced MR imaging, in 5. MR imaging findings of the tumor were evaluated with emphasis on the location, size, shape, margin, signal intensity, and pattern of enhancement. The lesions appeared as solitary well-defined ovoid masses in the ciliochoroidal region in 5 patients and in the choroid in 1. With respect to the vitreous body, uveal schwannoma was hyperintense on T1WI spin-echo (SE) images in all 6 patients. The tumors were hypointense to the vitreous body on fast SE (FSE) T2-weighted images (T2WI) in 4 patients and isointense in 1. However, with respect to the brain, uveal schwannoma demonstrated isointensity on T1WI SE images in all 6 patients, isointensity on FSE T2WI images in 5 patients, and hyperintensity on T2WI SE images in 1. On postcontrast T1WI images, 3 patients showed markedly heterogeneous enhancement, and 3 showed markedly homogeneous enhancement. Uveal schwannoma should be included in the differential diagnosis when an oval isointense mass relative to brain is seen in the ciliochoroidal region.

Hepatocellular lesions with increased iron uptake on superparamagnetic iron oxide-enhanced magnetic resonance imaging in cirrhosis or chronic hepatitis: comparison of four magnetic resonance sequences for lesion conspicuity

The aim of this study was to determine the adequate MR sequence for the lesion conspicuity of hepatocellular lesions with increased iron uptake on superparamagnetic iron oxide (SPIO)-enhanced MRI. SPIO-enhanced MRI was performed using a 1.5-T system. Among 25 patients with hypovascular hepatocellular nodules on contrast-enhanced dynamic CT (no early enhancement at arterial phase and hypoattenuation at equilibrium phase), 39 lesions with increased iron uptake on SPIO-enhanced MRI were evaluated. SPIO-enhanced MRI included (1) T1-weighted in-phase gradient recalled echo (GRE) images, (2) T2-weighted fast spin echo (FSE) images, (3) T2*-weighted GRE with moderate TE (7 ms) and (4) long TE (12 ms). The lesion-to-liver contrast-to-noise ratios of the hepatocellular nodule and the signal-to-noise ratio (SNR) of the hepatic parenchyma were calculated by one radiologist for a quantitative assessment. MR images were reviewed retrospectively by two independent radiologists to compare the subjective lesion conspicuity in each image set based on a four-point rating scale. The mean lesion-to-liver contrast-to-noise ratios with T2*-weighted GRE with moderate TE (7 ms) was highest (5.79+/-3.71) and was significantly higher than those with T1-weighted, in-phase images (3.79+/-3.23, P<.01), T2-weighted images (2.72+/-1.52, P<.001) and T2*-weighted GRE with long TE (12 ms) (3.93+/-2.69, P<.05). The subjective rating of lesion conspicuity was best on the T2*-weighted GRE with moderate TE (7 ms), followed by that on the T2*-weighted GRE with moderate TE (7 ms; P<.05). T2*-weighted GRE sequence with moderate TE (7 ms) showed high lesion-to-liver contrast-to-noise ratios in hepatocellular lesions with increased iron uptake on SPIO-enhanced MRI, indicating better lesion conspicuity of hypointense hepatocellular nodules in cirrhosis or chronic hepatitis.

A Study of Diffusion-Weighted Magnetic Resonance Imaging in Men with Untreated Localised Prostate Cancer on Active Surveillance

BackgroundMarkers that predict the behaviour of localised prostate cancer are needed to identify patients that require treatment. ObjectiveWe have analysed the apparent diffusion coefficient (ADC) generated from diffusion-weighted magnetic resonance imaging (DW-MRI) with respect to repeat biopsy findings and time to radical treatment in patients in a prospective study of active surveillance. Design, setting, and participantsSome 86 men recruited between 2002 and 2006 were followed for a median of 29 mo. Patients had clinical stage T1/T2a N0/Nx M0/Mx adenocarcinoma of the prostate, prostate-specific antigen (PSA) level <15 ng/ml, Gleason score ≤7, primary Gleason grade ≤3, and positive biopsy cores (pbc) ≤50%. MeasurementsAll patients had DW-MRI in addition to standard MRI sequences. Tumour regions of interest (ROIs) were identified using T2-weighted fast-spin echo images as focal areas of restricted diffusion. Univariate analyses including all clinical variables and tumour ADC data were performed with respect to repeat biopsy findings and time to radical treatment. Receiver operating curves (ROC) compared predictive variables. Results and limitationsPatients in the study had a median age of 66 yr and a median initial PSA level of 6.7 ng/ml. Some 39 patients (45%) received deferred radical treatment, and 34 patients (40%) had adverse histology on repeat biopsy. According to univariate analysis, tumour ADC was a significant predictor of both adverse repeat biopsy findings (p<0.0001; hazard ratio [HR]: 1.3; 95% confidence interval [CI]: 1.1–1.6), and time to radical treatment (p<0.0001; HR: 1.5; 95% CI: 1.2–1.8). ROC curves for ADC showed an area under the curve (AUC) of 0.7 for prediction of adverse repeat biopsy findings and an AUC of 0.83 for prediction of radical treatment. ConclusionsIn patients with low-risk, localised disease, tumour ADC on DW-MRI may be a useful marker of prostate cancer progression and may help to identify patients who stand to benefit from radical treatment. This possibility warrants further study.

Evaluating the severity of nonalcoholic steatohepatitis with superparamagnetic iron oxide‐enhanced magnetic resonance imaging

To evaluate the utility of noninvasive assessment of human nonalcoholic fatty liver disease (NAFLD) patients using superparamagnetic iron oxide (SPIO)-enhanced MRI. Nineteen NAFLD patients underwent SPIO-enhanced MRI. The values of tau, a time constant for an exponential approximation, were calculated using gradient-echo echo-planar imaging, and the values of %T2, a marker of the T2 relaxation effect of SPIO, were calculated using T2-weighted fast spin-echo images. Correlations between these values and the histological NAFLD activity scores were evaluated. The study protocol was approved by our Institutional Review Board and all patients gave informed consent. There was a statistically significant relationship between the NAFLD activity scores and the tau values (r = 0.66, P = 0.002). The %T2 values were also significantly correlated with the NAFLD activity score (r = -0.58, P = 0.009). A cutoff tau value of 42.8 predicted "definitive NASH" (NAFLD activity score >or=5) with a specificity of 66.7% and a sensitivity of 99.9%, whereas a cutoff %T2 value of 32.5 predicted "definitive NASH" with a specificity of 72.7% and a sensitivity of 87.5%. Noninvasive SPIO-enhanced MRI may be helpful for identifying NASH patients among patients suspected of having NAFLD.

Diffusion-weighted Imaging in Cervical Cancer with an Endovaginal Technique: Potential Value for Improving Tumor Detection in Stage Ia and Ib1 Disease

To establish apparent diffusion coefficients (ADCs) of invasive cervical carcinoma compared with nontumor cervical epithelium and determine sensitivity and specificity of diffusion-weighted (DW) magnetic resonance (MR) imaging used in conjunction with T2-weighted MR imaging to help detect invasive cervical carcinoma in patients with stage Ia and Ib1 disease. Local research ethics committee approval was obtained with written consent from each subject. Group 1 comprised patients (mean age, 38.7 years +/- 13.2 [standard deviation]) with histologically confirmed cervical intraepithelial neoplasia (CIN) found on smear (n = 20) or stage Ib1 cervical tumors (n = 18). Patients were imaged with endovaginal T2-weighted fast spin-echo and single-shot DW echo-planar MR imaging of the cervix. ADCs from invasive cervical carcinoma and nontumor regions were compared within (t test) and between (U test) patients. A derived threshold ADC level indicative of invasive cervical carcinoma was used with T2-weighted imaging by two independent observers to identify possible invasive cervical carcinoma in group 2, patients with suspected disease (n = 21; mean age, 42.0 years +/- 16.4). Surgical specimens were the reference standard. Interobserver agreement was assessed. In group 1, ADCs from cervical carcinoma (757 x 10(-6) mm(2)/sec +/- 110) and adjacent epithelium (1331 x 10(-6) mm(2)/sec +/- 159) or CIN (1291 x 10(-6) mm(2)/sec +/- 156) were significantly different (P < .0001). In group 2, respective sensitivity and specificity to help detect invasive cervical carcinoma on T2-weighted images were 55.6% and 75% for observer 1 and 66.7% and 41.7% for observer 2, and 88.9% and 66.7% for observer 1 and 77.8% and 58.3% for observer 2 when ADC maps with a threshold level of 1100 x 10(-6) mm(2)/sec were added. Interobserver agreement was fair (kappa = 0.37) for T2-weighted images alone and good (kappa = 0.80) with ADC included. ADCs from invasive cervical carcinoma are significantly lower than those from nontumor epithelium; good interobserver agreement by using T2-weighted and DW MR imaging makes this technique potentially useful to help detect early-stage disease.

Pediatric MR Cholangiopancreatography: Principles, Technique, and Clinical Applications

High-quality magnetic resonance (MR) cholangiopancreatographic images are difficult to obtain in children due to the small caliber of the pediatric bile ducts and to motion artifacts. However, there has been ongoing improvement in image quality, thanks to better coil technology, increased speed of acquisition, refinement in respiratory compensation techniques, and newer sequences. Heavily T2-weighted fast spin-echo (FSE) and single-shot FSE MR imaging sequences with long echo times are used to image the biliary and pancreatic ducts. Secretin has been shown to improve the visualization of the pancreatic duct and pancreaticobiliary junction. Factors that affect image quality in pediatric MR cholangiopancreatography include sedation, negative oral contrast material, radiofrequency coil selection, respiratory compensation techniques, echo time, echo train length, section-slab thickness, planes of scanning, field of view, and number of signals acquired. However, giving proper attention to these factors and tailoring the study to the body size of the patient (which varies considerably) can lead to high-quality diagnostic MR cholangiopancreatographic images. Use of MR cholangiopancreatography in children is limited by the need for sedation or anesthesia, high cost, limited availability, and long scanning times. Nonetheless, this modality can be a viable alternative to endoscopic retrograde cholangiopancreatography (ERCP) in the evaluation of various entities such as choledochal cyst, recurrent pancreatitis, primary sclerosing cholangitis, and a transplanted liver, and may obviate ERCP.

Interexaminer Reliability of T2-Weighted Magnetic Resonance Imaging for Lumbar Bright Facet Sign

Objective The aims of this study were to characterize the bright facet response within the lumbar spine, to identify a constellation of findings associated with the response, and to quantify the interexaminer agreement on the previous objectives. Methods A retrospective study of lumbar magnetic resonance images obtained on 105 (N = 105) adult subjects (62 men and 43 women; age range, 18-84 years; mean age, 46.51 ± 16.01 years) were reviewed by 2 musculoskeletal radiologists for the presence of high signal within the facet articulations (bright facet response) on fast spin echo T2-weighted images. Results Of the 630 lumbar facet articulations imaged (L3/L4 through L5/S1), 340 (54%) and 346 (55%) respectively, per examiner, did show a bright facet response. Interexaminer agreement with respect to the level and grading of a bright facet response was almost perfect with κ ranging from 0.85 to 0.91 (SE, 0.06). Prevalence of bright facet responses averaged 40.5% at L5/S1, 56.5% at L3/L4, and 66.5% at the L4/L5 level. There was an association with degenerative facet and disk changes. Conclusion The bright facet response was a common phenomenon on T2-weighted magnetic resonance imaging of the lumbar spine in these cases. There was sufficient agreement with respect to the presence and extent of the bright facet response to conclude that the examiners' determinations were not made by random chance. There exist sufficient repeatability and reliability that a single descriptive term can be applied to unify the bright facet response, the bright facet sign.

Tolosa–Hunt syndrome: MRI appearances

A review of MRI findings in seven patients with Tolosa-Hunt syndrome was carried out. Seven patients presented with unilateral painful ophthalmoplegia. Magnetic resonance imaging studies were carried out to evaluate the cavernous sinuses and orbits. Coronal fast spin-echo T2-weighted images and fat-saturated T1-weighted coronal and transverse images with and without contrast enhancement were obtained for the cavernous sinuses and orbits. All patients showed focal-enhancing masses expanding the ipsilateral cavernous sinus. In one patient the mass was extending to the orbital apex and intraorbitally. All patients recovered on corticosteroid therapy and resolution of the masses was documented on follow-up MRI studies in five patients. One patient had a relapse of symptoms after discontinuing therapy. Magnetic resonance imaging studies of the cavernous sinus and orbital apex show high sensitivity for the detection and follow up of inflammatory mass lesions in Tolosa-Hunt syndrome. Magnetic resonance imaging should be the initial screening study in these patients.

Carr-Purcell-Meiboom-Gill imaging of prostate cancer: quantitative T2 values for cancer discrimination

Quantitative, apparent T(2) values of suspected prostate cancer and healthy peripheral zone tissue in men with prostate cancer were measured using a Carr-Purcell-Meiboom-Gill (CPMG) imaging sequence in order to assess the cancer discrimination potential of tissue T(2) values. The CPMG imaging sequence was used to image the prostates of 18 men with biopsy-proven prostate cancer. Whole gland coverage with nominal voxel volumes of 0.54 x 1.1 x 4 mm(3) was obtained in 10.7 min, resulting in data sets suitable for generating high-quality images with variable T(2)-weighting and for evaluating quantitative T(2) values on a pixel-by-pixel basis. Region-of-interest analysis of suspected healthy peripheral zone tissue and suspected cancer, identified on the basis of both T(1)- and T(2)-weighted signal intensities and available histopathology reports, yielded significantly (P<.0001) longer apparent T(2) values in suspected healthy tissue (193+/-49 ms) vs. suspected cancer (100+/-26 ms), suggesting potential utility of this method as a tissue specific discrimination index for prostate cancer. We conclude that CPMG imaging of the prostate can be performed in reasonable scan times and can provide advantages over T(2)-weighted fast spin echo (FSE) imaging alone, including quantitative T(2) values for cancer discrimination as well as proton density maps without the point spread function degradation associated with short effective echo time FSE sequences.