T2-weighted Fast Spin-echo Magnetic Resonance Imaging Research Articles

Feasibility of salt pads to improve fat suppression in low-field MRI systems

IntroductionFat-suppressed images are essential in clinical practice but are often affected by magnetic field inhomogeneity, resulting in poor image quality. We hypothesized that salt (99% sodium chloride [NaCl]) could be used as a magnetic field uniformity assist pad and verified whether salt pads improve magnetic field uniformity and the fat suppression effect in low-field magnetic resonance imaging (MRI) systems. MethodsWe conducted a small clinical study where coronal 2D fast spin-echo T2-weighted MRI with fat suppression was performed. The subjects were 10 healthy volunteers (six men and four women) with no surgical history, with a mean age of 20.5 years (range, 20–30 years). In the clinical study, we performed physical and visual evaluation by imaging a subject's knee with and without salt pads. ResultsThe results of the clinical study indicated that the use of salt pads improved the magnetic field uniformity, thus increasing the fat suppression effect. ConclusionsSalt pads improved the homogeneity of the magnetic field and the fat suppression effect in low-field MRI systems. Implications for practiceThe use of salt pads in low-field MRI systems could provide more accurate fat suppression images.

Tumor grade estımatıon of clear cell and papıllary renal cell carcınomas usıng contrast-enhanced MDCT and FSE T2 weıghted MR ımagıng: radıology-pathology correlatıon.

Discrimination of low grade (grade 1-2) renal tumors from high grade (grade 3-4) ones carries crucial importance in terms of the management of these patients and also in the decision-making of appropriate treatment strategies. Our aim was to investigate whether contrast-enhanced multidetector computed tomography (MDCT) and T2 weighted fast spin echo (FSE) magnetic resonance imaging (MRI) could play a specific role in the discrimination of low grade versus high grade tumors in clear cell renal cell carcinoma (ccRCC) and papillary renal cell carcinoma (pRCC) patients. In this study, we retrospectively evaluated 66 RCC patients based on histopathologic findings who had underwent either partial or total nephrectomies. Our cohort consisted of 52 ccRCC and 14 pRCC patients, of whom 50 were male (%76) and 16 were female (%24). Among the 52 ccRCC patients, 18 had both cortico-medullary phase contrast-enhanced CT and MRI, 15 had only cortico-medullary phase CT and 19 had only MRI examination. In the pRCC group, 8 patients had both cortico-medullary phase contrast-enhanced CT and MRI, 3 had only cortico-medullary phase CT and 3 had only MRI. We both calculated mean tumor attenuation values on cortico-medullary phase MDCT images as HU (hounsfield unit) and also tumor mean signal intensity values on FSE T2 weighted MR images, using both region of interest and whole lesion measurements including normal renal cortex. The obtained values were compared with the grading results of the ccRCC and pRCC tumors according to the WHO/International Society of Urological Pathology grading system. A significant positive correlation was found between the mean attenuation values of both tumor subtypes on cortico-medullary phase contrast-enhanced CT and their grades (p < 0.001). High grade tumors exhibited higher mean attenuation values (74.3 ± 22.3 HU) than the low grade tumors (55.2 ± 23.7 HU) in both subtypes. However, a statistically significant correlation was not found between the mean signal intensity values of the two tumor subtypes on FSE T2 weighted MR images and their grades (p > 0.05). Low grade tumors had a mean signal intensity value of 408.9 ± 44.6, while high grade tumors showed a value of 382.1 ± 44.2. The analysis of the ccRCC group patients, yielded a statistically significant correlation between the mean signal intensity values on T2 weighted images and tumor grading (p < 0.001). Low grade (grade 1-2) ccRCC patients exhibited higher mean signal intensity values (475.7 ± 51.3), as compared to those of high grade (grade 3-4) (418.5 ± 45.7) tumors. On the other hand, analysis of the pRCC group patients revealed that there was a significant correlation between the mean attenuation values of tumors on cortico-medullary phase contrast-enhanced CT and their grades (p < 0.001). High grade papillary subtype tumors (54.2 ± 25.2) showed higher mean attenuation values than the low grade (35.5 ± 18.8) ones. Contrast-enhanced MDCT and T2 weighted FSE MRI can play a considerable role in the discrimination of low grade versus high grade tumors of both subtype RCC patients. Thus, these non-invasive evaluation techniques may have positive impact on the determination of the management and treatment strategies of these patients.

Distribution of Bone Contusion Patterns in Acute Noncontact Anterior Cruciate Ligament–Torn Knees

Background: Bone contusions are commonly observed on magnetic resonance imaging (MRI) in individuals who have sustained a noncontact anterior cruciate ligament (ACL) injury. Time from injury to image acquisition affects the ability to visualize these bone contusions, as contusions resolve with time. Purpose: To quantify the number of bone contusions and their locations (lateral tibial plateau [LTP], lateral femoral condyle [LFC], medial tibial plateau [MTP], and medial femoral condyle [MFC]) observed on MRI scans of noncontact ACL-injured knees acquired within 6 weeks of injury. Study Design: Cross-sectional study; Level of evidence, 3. Methods: We retrospectively reviewed clinic notes, operative notes, and imaging of 136 patients undergoing ACL reconstruction. The following exclusion criteria were applied: MRI scans acquired beyond 6 weeks after injury, contact ACL injury, and previous knee trauma. Fat-suppressed fast spin-echo T2-weighted MRI scans were reviewed by a blinded musculoskeletal radiologist. The number of contusions and their locations (LTP, LFC, MTP, and MFC) were recorded. Results: Contusions were observed in 135 of 136 patients. Eight patients (6%) had 1 contusion, 39 (29%) had 2, 41 (30%) had 3, and 47 (35%) had 4. The most common contusion patterns within each of these groups were 6 (75%) with LTP for 1 contusion, 29 (74%) with LTP/LFC for 2 contusions, 33 (80%) with LTP/LFC/MTP for 3 contusions, and 47 (100%) with LTP/LFC/MTP/MFC for 4 contusions. No sex differences were detected in contusion frequency in the 4 locations (P > .05). Among the participants, 50 (37%) had medial meniscal tears and 52 (38%) had lateral meniscal tears. Conclusion: The most common contusion patterns observed were 4 locations (LTP/LFC/MTP/MFC) and 3 locations (LTP/LFC/MTP).

High resolution hemodynamic profiling of murine arteriovenous fistula using magnetic resonance imaging and computational fluid dynamics

BackgroundArteriovenous fistula (AVF) maturation failure remains a major cause of morbidity and mortality in hemodialysis patients. The two major etiologies of AVF maturation failure are early neointimal hyperplasia development and persistent inadequate outward remodeling. Although hemodynamic changes following AVF creation may impact AVF remodeling and contribute to neointimal hyperplasia development and impaired outward remodeling, detailed AVF hemodynamics are not yet fully known. Since murine AVF models are valuable tools for investigating the pathophysiology of AVF maturation failure, there is a need for a new approach that allows the hemodynamic characterization of murine AVF at high resolutions.MethodsThis methods paper presents a magnetic resonance imaging (MRI)-based computational fluid dynamic (CFD) method that we developed to rigorously quantify the evolving hemodynamic environment in murine AVF. The lumen geometry of the entire murine AVF was reconstructed from high resolution, non-contrast 2D T2-weighted fast spin echo MRI sequence, and the flow rates of the AVF inflow and outflow were extracted from a gradient echo velocity mapping sequence. Using these MRI-obtained lumen geometry and inflow information, CFD modeling was performed and used to calculate blood flow velocity and hemodynamic factors at high resolutions (on the order of 0.5 μm spatially and 0.1 ms temporally) throughout the entire AVF lumen. We investigated both the wall properties (including wall shear stress (WSS), wall shear stress spatial gradient, and oscillatory shear index (OSI)) and the volumetric properties (including vorticity, helicity, and Q-criterion).ResultsOur results demonstrate increases in AVF flow velocity, WSS, spatial WSS gradient, and OSI within 3 weeks post-AVF creation when compared to pre-surgery. We also observed post-operative increases in flow disturbances and vortices, as indicated by increased vorticity, helicity, and Q-criterion.ConclusionsThis novel protocol will enable us to undertake future mechanistic studies to delineate the relationship between hemodynamics and AVF development and characterize biological mechanisms that regulate local hemodynamic factors in transgenic murine AVF models.

Association Between Infrapatellar Fat Pad Volume and Knee Structural Changes in Patients with Knee Osteoarthritis.

The function of the infrapatellar fat pad (IPFP) in knee osteoarthritis (OA) remains uncertain. This study aimed to examine cross-sectional associations between IPFP volume and knee structures in patients with knee OA. The study included 174 patients with clinical knee OA (mean age, 55.5 yrs). Fat-suppressed 3-D T1-weighted spoiled gradient recall magnetic resonance imaging (MRI) was used to measure the IPFP and cartilage volume. T2-weighted fast spin echo MRI was used to assess cartilage defects and bone marrow lesions (BML). Radiographic knee osteophytes and joint space narrowing (JSN) were assessed using the Osteoarthritis Research Society International atlas. After adjustment for potential confounders, greater IPFP volume was associated with greater tibial and patellar cartilage volume (all p < 0.05), and fewer cartilage defects at all sites (OR 0.88-0.91, all p < 0.05). IPFP volume was associated with presence of BML at lateral tibial and medial femoral sites (OR 0.88-0.91, all p < 0.05) and osteophytes at lateral tibiofemoral compartment (OR 0.88, p < 0.05). IPFP volume was not significantly associated with JSN. Greater IPFP volume was associated with greater knee cartilage volume and fewer structural abnormalities, suggesting a protective role of IPFP size in knee OA.

High Sensitivity of Diffusion-weighted MR Imaging for the Detection of Liver Metastases from Neuroendocrine Tumors: Comparison with T2-weighted and Dynamic Gadolinium-enhanced MR Imaging

To compare the sensitivity and specificity of diffusion-weighted (DW) magnetic resonance (MR) imaging for identifying liver metastases from neuroendocrine tumor (NET) to those of T2-weighted fast spin-echo (FSE) and three-dimensional dynamic gadolinium-enhanced MR imaging, with surgical and histopathologic findings as the reference standard. This retrospective study was approved by institutional review board, and informed consent was waived. Fifty-nine patients with NETs (41 patients with 162 liver metastases, and 18 control subjects with no liver metastases) underwent MR imaging that included DW, T2-weighted FSE, and dynamic gadolinium-enhanced MR sequences. Images were retrospectively reviewed by two abdominal radiologists, independently, for the detection and characterization of liver metastases. MR findings were compared with histopathologic and intraoperative ultrasonography findings for metastasis on a lesion-by-lesion basis to determine the sensitivity of each MR sequence alone and combined. Specificity was calculated by using the control population. Interreader agreement for each MR sequence and McNemar test were also calculated. There was excellent agreement between observers 1 and 2 for characterizing liver metastases at per-lesion analysis (κ coefficient: 0.86-1.00). DW MR was more sensitive (observer 1: sensitivity, 71.6% [116 of 162], 95% confidence interval [CI]: 64.2%, 78.0%; observer 2: sensitivity, 71.0% [115 of 162], 95% CI: 63.6%, 77.4%) than T2-weighted FSE (observer 1: sensitivity, 55.6% [90 of 162], 95% CI: 47.9%, 63.0%; observer 2: sensitivity, 55.6% [90 of 162], 95% CI: 47.9%, 63.0%) and dynamic gadolinium-enhanced MR (observer 1: sensitivity, 47.5% [77 of 162], 95% CI: 34.0%, 55.2%; observer 2: sensitivity, 48.1% [78 of 162], 95% CI: 40.6%, 55.8%) (P < .001 for both, McNemar test). The specificity of these sequences ranged from 88.9% to 100% (DW MR vs T2-weighted FSE MR: P > .99, DW MR vs dynamic gadolinium-enhanced MR: P = .61, and T2-weighted FSE MR vs dynamic gadolinium-enhanced MR: P = .61, McNemar test). DW MR imaging was more sensitive for the detection and characterization of liver metastases from NETs than T2-weighted FSE and dynamic gadolinium-enhanced MR imaging and should be systematically performed.

Renal angiomyolipoma with pseudocapsule mimicking renal cell carcinoma

We present a case of renal angiomyolipoma with pseudocapsule mimicking renal cell carcinoma. Axial in-phase and opposed-phase gradient-echo magnetic resonance (MR) images showed that the signal intensity of the lesion is hypointense on the opposed-phase image compared with that on the in-phase image, confirming the presence of lipid in the lesion. Axial T2-weighted fast spin–echo MR imaging showed the lesion as slightly hyperintense relative to adjacent renal parenchyma. On T2-weighted MR imaging, a hypointense rim surrounded the lesion.

Exophytic renal masses: angular interface with renal parenchyma for distinguishing benign from malignant lesions at MR imaging.

To retrospectively determine whether benign exophytic renal masses can be distinguished from renal cell carcinoma (RCC) on the basis of angular interface at single-shot fast spin-echo (SE) T2-weighted magnetic resonance (MR) imaging. This retrospective study was compliant with HIPAA and was approved by the institutional review board. Patient informed consent was waived. A total of 162 exophytic (2 cm or greater) renal masses in 152 patients (103 men, 49 women; mean age, 58 years; age range, 23-85 years) were included. Two radiologists independently recorded the mass size and angular interface on single-shot fast SE T2-weighted MR images. Surgical pathologic report and MR follow-up were used as reference standards. Logistic regression analysis was used to examine the usefulness of these variables for differentiating benign masses from RCCs. Diagnostic performance was analyzed by comparing values for area under receiver operating characteristic curve (A(z)). Sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of angular interface for diagnosing benign masses were calculated. Reader agreement was assessed with kappa-weighted statistics and intraclass correlation coefficients (ICCs). Of 162 masses, 65 were benign, and 97 were RCCs. The sensitivity, specificity, PPV, NPV, and A(z) of angular interface for diagnosing benign masses were 78%, 100%, 100%, 87%, and 0.813, respectively. Angular interface (P < .001) was a significant predictor of benign renal mass but mass size (P = .66) was not. There was almost perfect interobserver agreement for mass size (ICC = 0.96) and angular interface (kappa = 0.91). The presence of an angular interface with the renal parenchyma at single-shot fast SE T2-weighted MR imaging is a strong predictor of benignity in an exophytic renal mass 2 cm or greater in diameter with high specificity and diagnostic accuracy.

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.

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.

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.

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.

Anterior Cruciate Ligament Reconstruction Grafts: MR Imaging Features at Long-term Follow-up—Correlation with Functional and Clinical Evaluation

To assess the presence of increased intrasubstance signal intensity within anterior cruciate ligament (ACL) grafts and to assess whether such signal intensity changes are correlated to clinical assessments of graft instability and patient function 4-12 years after ACL reconstruction. Ethical permission and written informed patient consent were obtained. The study was HIPAA compliant. Forty-seven patients were included and underwent 1.5-T magnetic resonance (MR) imaging of the knee that was treated surgically. Signal intensity characteristics of the ACL graft were evaluated on sagittal intermediate-weighted and sagittal and axial T2-weighted fast spin-echo MR images. The amount of signal intensity change, femoral and tibial graft tunnel position, and orientation of ACL graft in the coronal plane were assessed. Objective index of graft stability or laxity was performed with arthrometric testing, and subjective function was assessed by using International Knee Documentation Committee (IKDC) scoring. Increased intrasubstance graft signal intensity was found in 70 % (33 of 47) and in 64% (30 of 47) of patients on intermediate-weighted MR images and T2-weighted MR images, respectively. When present, intrasubstance graft signal intensity changes involved less than 25% of the maximal cross-sectional area of the graft in 70% (23 of 33) of cases on intermediate-weighted acquisitions and in 70% (21 of 30) of cases on T2-weighted acquisitions. No significant association was seen between graft signal intensity changes on intermediate-weighted and T2-weighted images and IKDC score (P = .667 and .698, respectively), arthrometric testing (P = .045-.99), and time since surgery (P = .592 and .610, respectively). Small amounts of increased intrasubstance graft signal intensity on intermediate- and T2-weighted images can be seen after ACL reconstruction at long-term follow-up of 4 years or longer and do not necessarily correlate with findings of joint instability or functional limitations in patients after ACL repair.

Nodal Metastasis in Non–Small Cell Lung Cancer: Accuracy of 3.0-T MR Imaging

To prospectively evaluate the diagnostic accuracy of 3.0-T magnetic resonance (MR) imaging in the detection of non-small cell lung cancer nodal metastasis, with histopathologic analysis as the reference standard. Institutional review board approval and informed consent were obtained. From July 2005 to May 2006, 113 patients (91 men, 22 women; age range, 34-82 years; mean age, 61 years) with non-small cell lung cancer underwent thoracic 3.0-T MR imaging followed by surgery or mediastinoscopy. The lymph node-to-tumor ratios (LTRs) of signal intensity and nodal morphologic characteristics (such as eccentric cortical thickening or obliteration of the fatty hilum) were assessed on T2-weighted triple-inversion black-blood fast spin-echo images. Nodal short-axis diameter was assessed on T1-weighted three-dimensional fast field-echo images. Receiver operating characteristic and multivariate logistic regression analyses were used for statistical evaluation. The cutoff value (LTR > 0.84) proved to be most appropriate (area under the receiver operating characteristic curve = 0.735, P < .001) in the detection of a nodal metastasis. Of the various parameters examined, morphologic characteristics appeared to be the most significant (P < .001) parameters for depicting a malignant node (multivariate logistic regression analyses; odds ratio, 7.5). Nodal morphology was analyzed, and diagnostic sensitivity, specificity, and accuracy were 53% (39 of 74 nodal stations), 91% (453 of 496 nodal stations), and 86% (492 of 570 nodal stations), respectively. Morphologic details of lymph nodes on T2-weighted triple-inversion black-blood fast spin-echo MR images are significant for detection of mediastinal or hilar nodal metastasis at 3.0-T MR imaging.

Hepatic Metastases: Diffusion-weighted Sensitivity-encoding versus SPIO-enhanced MR Imaging

To retrospectively compare accuracy of diffusion-weighted (DW) single-shot echo-planar imaging with sensitivity encoding (SENSE) with that of superparamagnetic iron oxide (SPIO)-enhanced magnetic resonance (MR) imaging in the evaluation of hepatic metastases due to extrahepatic malignancies. Patients provided informed consent; ethics committee approval was not required. The data of 24 patients (16 men, eight women; age range, 41-68 years; mean age, 61.9 years) with 40 resected hepatic metastases were retrospectively reviewed. Before SPIO administration, DW SENSE imaging and T2-weighted fast spin-echo (SE) and T1-weighted dual-echo fast field-echo (FFE) MR imaging were performed. After SPIO administration, T2-weighted fast SE, T1-weighted dual-echo, and T2*-weighted FFE MR examinations were performed. Images were divided into two sets: The SPIO-enhanced MR image set consisted of pre- and postcontrast T2-weighted fast SE and dual-echo T1-weighted FFE images and postcontrast T2*-weighted FFE images. The DW SENSE image set included DW SENSE images and precontrast T2-weighted fast SE and dual-echo T1-weighted FFE images. Three radiologists individually interpreted these images and sorted the confidence levels for presence of hepatic metastasis in each section into five grades. Area under the receiver operating characteristic (ROC) curve (A(z)) was calculated for each image set. Hepatic metastases showed higher signal intensity on DW SENSE images than on T2-weighted fast SE images. Conversely, signals from vessels and cysts were suppressed with DW SENSE imaging. ROC analysis showed higher A(z) values when the DW SENSE image set was interpreted (0.90) than when the SPIO-enhanced MR image set was interpreted (0.81). The sensitivity and specificity, respectively, of total cases were 0.66 and 0.90, for the SPIO-enhanced MR image set and 0.82 and 0.94 for the DW SENSE image set. During SPIO-enhanced MR image interpretation, lesions 1 cm in diameter or smaller showed significantly lower sensitivity than lesions larger than 1 cm in diameter. During both interpretation sessions, left lobe lesions showed significantly lower sensitivity than right lobe lesions. Combined reading of DW SENSE images and T2-weighted fast SE and dual-echo T1-weighted FFE MR images showed higher accuracy in the detection of hepatic metastases than did reading of SPIO-enhanced MR images.

Accuracy of Liver Fat Quantification at MR Imaging: Comparison of Out-of-Phase Gradient-Echo and Fat-saturated Fast Spin-Echo Techniques—Initial Experience

To retrospectively determine the relative accuracy of liver fat quantification with out-of-phase gradient-echo magnetic resonance (MR) imaging and fat-saturated fast spin-echo MR imaging in patients with and without cirrhosis, with histologic analysis as the reference standard. Committee on Human Research approval was obtained. Patient consent was not required. Data collection ended before HIPAA regulations were implemented, but patient anonymity was maintained. Twenty-seven patients, 16 with cirrhosis, were retrospectively identified who underwent MR imaging before histopathologic evaluation of liver fat at biopsy or surgery. The patient population consisted of 15 male and 12 female patients (mean age, 55 years; range, 16-75 years). One radiologist blinded to the histopathologic results recorded mean signal intensity derived from three regions of interest placed in the right and left lobes of the liver on three sections and signal intensity of the spleen from one region of interest within the same section. Liver fat was quantified with the relative loss of signal intensity on out-of-phase images compared with that on in-phase T1-weighted gradient-echo images and with relative loss of signal intensity on T2-weighted fast spin-echo MR images obtained with fat saturation compared with those obtained without fat saturation. Hotelling t test was used to compare correlation coefficients between relative signal intensity differences and histopathologically determined percentage of fat. In patients without cirrhosis, liver fat quantification with fat-saturated fast spin-echo MR imaging was significantly better than it was with out-of-phase gradient-echo MR imaging (r = 0.92 vs 0.69, P < .01). In patients with cirrhosis, liver fat quantification was correlated only with fat-saturated fast spin-echo MR imaging (r = 0.76, P < .01); the relative signal intensity loss on out-of-phase gradient-echo MR images was not correlated with histopathologically determined percentage of fat (r = 0.25, P = .36). Preliminary results suggest liver fat may be more accurately quantified with fat-saturated fast spin-echo MR imaging than with out-of-phase gradient-echo MR imaging, especially in patients with cirrhosis.

Staging Prostate Cancer with Dynamic Contrast-enhanced Endorectal MR Imaging prior to Radical Prostatectomy: Experienced versus Less Experienced Readers

To prospectively determine the accuracy of experienced and less experienced readers in the interpretation of combined T2-weighted fast spin-echo (SE) magnetic resonance (MR) images and dynamic contrast material-enhanced MR images compared with T2-weighted fast SE alone, with respect to differentiation of stage T2 versus stage T3 prostate carcinoma, with histologic analysis serving as the reference standard. Institutional review board approval and informed consent were obtained, and 124 consecutive men (age range, 42-74 years; median age, 63 years) with biopsy-proved prostate cancer underwent MR imaging and were candidates for radical prostatectomy. T2-weighted fast SE MR images and multisection dynamic contrast-enhanced MR images with a 2-second time resolution for the whole prostate were obtained. The T2-weighted and fused color-coded parametric dynamic contrast-enhanced MR images with T2-weighted images were evaluated prospectively and scored with regard to local extent by one experienced reader and evaluated retrospectively by two less experienced readers working in consensus by using a five-point scale; images with a score greater than or equal to four were considered indicative of T3 disease. Results were correlated with whole-mount section histopathologic findings, and receiver operating characteristics analysis was performed. Twenty-five patients were excluded because of positive findings in the lymph nodes (n = 16), preoperative biopsy-proved seminal vesicle invasion (n = 5), and an absent dynamic dataset (n = 4). Ninety-nine patients were included in this study. The overall sensitivity, specificity, and accuracy of MR staging performance in prostate cancer with dynamic contrast-enhanced MR imaging was 69% (24 of 35 patients), 97% (62 of 64 patients), and 87% (86 of 99 patients), respectively, for the experienced reader. This difference was not significant (P = .48) when results were compared with results from the T2-weighted images. Staging performance for the less experienced readers with parametric dynamic contrast-enhanced MR imaging, however, resulted in significant improvement of the area under the receiver operating characteristics curve (A(z)) compared with T2-weighted MR imaging alone (A(z) = .66 and .82, respectively; P = .01). The use of multisection dynamic contrast-enhanced MR imaging in staging prostate cancer showed significant improvement in staging performance for the less experienced readers but had no benefit for the experienced reader.

Prenatal diagnosis of hemifacial microsomia by magnetic resonance imaging

We present a case of hemifacial microsomia, first detected by prenatal sonography and confirmed by ultrafast magnetic resonance (MR) imaging. A 26-year-old patient was referred to our hospital at 20 weeks of gestation because of unilateral right-sided ventriculomegaly and of a possible ventriculoseptal defect (VSD). Our sonographic examination suggested a right orbital hypoplasia and a hemiatrophy of the nose. The ultrafast T2-weighted single-shot fast-spin echo MR imaging, demonstrated a right ear hypoplasia (microtia), a right orbital hypoplasia, and a right renal hypoplasia. Epibulbar dermoid or conjunctival lipodermoid were not recognized. The fetus was prenatally diagnosed as hemifacial microsomia. Termination of pregnancy was performed at 21 weeks gestation, and a male baby weighing 342g was stillborn. The baby showed facial asymmetry, including hemiatrophy of the right nose, and right ear hypoplasia. Autopsy revealed a 2mm area of VSD, agenesis of the right kidney and ureter, pancreatic and renal aberration into right adrenal gland, thymus hypoplasia and an unfixed ascending colon without intestinal malrotation. To the best of our knowledge, this is the first report of prenatal diagnosis for hemifacial microsomia using fetal MR imaging. In our case, fetal MR imaging has evolved into a powerful diagnostic tool, for the accurate prenatal diagnosis.

High-b-value diffusion-weighted MR imaging for pretreatment prediction and early monitoring of tumor response to therapy in mice.

To evaluate the use of diffusion-weighted magnetic resonance (MR) imaging with standard and high b values for pretreatment prediction and early detection of tumor response to various antineoplastic therapies in an animal model. Mice bearing C26 colon carcinoma tumors were treated with doxorubicin (n = 25) and with aminolevulinic acid-based photodynamic therapy (n = 23). Fourteen mice served as controls. Conventional T2-weighted fast spin-echo and diffusion-weighted MR images were acquired once before therapy and at 6, 24, and 48 hours after treatment. Pretreatment and early (1-2 days) posttreatment water diffusion parameters were calculated and compared with later changes in tumor volumes measured on conventional MR images by using the Pearson correlation test. In chemotherapy-treated tumors, a significant correlation (P <.002, r = 0.6) was observed between diffusion parameters that reflected tumor viability, measured prior to treatment, and changes in tumor volumes after therapy. This correlation implies that tumors with high pretreatment viability will respond better to chemotherapy than more necrotic tumors. In tumors treated with photodynamic therapy, no such correlation was found. Changes observed in water diffusion 1-2 days after treatment significantly correlated with later tumor growth rate for both therapies (P <.002, r = 0.54 for photodynamic therapy; P <.0003, r = 0.61 for chemotherapy). High-b-value diffusion-weighted MR imaging has potential use for the early detection of response to therapy and for predicting treatment outcome prior to initiation of chemotherapy.

MRI of coronary artery atherosclerosis in rabbits: Histopathology-MRI correlation and atheroma characterization

Background and objectivesWe report in vivo magnetic resonance imaging (MRI) characteristics and histopathology correlation of the thrombus formation in atherosclerosis the rabbit animal model.Design and methodsAtherosclerosis was induced in white male rabbits with vegetable ghee followed oxidized diet. Baseline MRI of atherosclerosis-recruited rabbits was done and later animals were used for atheroma histopathology characterization. Contiguous cross-sectional T2-weighted fast spin echo MRI images were compared by coronary histopathology. In all animals, coronary aortic wall thickening and atheroma size was measured using MRI.ResultsMRI images and digitized histological sections confirmed intraluminal thrombus in 6 (67%) of the 9 animals. MRI data showed correlation with the histopathology for aortic wall thickness (R2 = 0.82, P < 0.0001), lumen area (R2 = 0.88, P < 0.0001) and plaque size (R2 = 0.77, P < 0.0001). Optimized TE and TR parameters and multicontrast enhancement generated better MRI visibility of vulnerable plaque components. The MRI data evaluated % stenosis, plaque burden. Frequency of plaques, plaque height in aorta and coronary artery atheroma was also assessed by histology. In vivo, MRI determined the presence and size of the thrombus in this animal model of atherosclerosis and histopathology defined the plaque disruption.ConclusionThe combination of in vivo MRI and comparison with histopathology images of rabbit coronary thrombus may be a research tool for understanding of the pathogenesis of acute coronary plaques.