Invasion of small cell lung cancer into the limbic system from leptomeningeal metastases.

The diagnosis of leptomeningeal metastases is sometimes difficult when the cytology of cerebrospinal fluid is negative. We report a rare case of leptomeningeal metastases that required differentiation from paraneoplastic limbic encephalitis. A 67-year-old man with extensive-stage small cell lung cancer was admitted for a sudden decrease in the level of consciousness. He suffered memory disturbances that began the day before admission. Diffusion-weighted and fluid-attenuated inversion recovery images of brain magnetic resonance imaging (MRI) showed bilateral symmetric areas of hyperintensity in the hippocampus, amygdala, insular cortex, and medial temporal lobe; contrast enhancement was positive. Cytology of the cerebrospinal fluid (CSF) was negative. Anti-N-methyl-d-aspartate receptor antibody and herpes simplex virus DNA were not detected in the CSF. Paraneoplastic Limbic encephalitis was suspected due to his symptoms and brain MRI scan. The patient developed generalized seizures after admission. High-dose methylprednisolone and intravenous immune globulin were administered, but his condition did not improve. Uncontrollable seizures persisted and he died in the hospital at day 13. Autopsy revealed leptomeningeal metastasis and invasion of cancer cells into the limbic system. Contrast-enhanced MRI should be performed even if limbic encephalitis is suspected, and leptomeningeal metastases should be suspected if the lesions are enhanced.

Evaluation of Fibrous Cap Rupture of Atherosclerotic Carotid Plaque with Thin-Slice Source Images of Time-of-Flight MR Angiography.

OBJECTIVE: To investigate the ability of source image of time-of-flight magnetic resonance angiography (TOF-MRA) in the detection of fibrous cap rupture of atherosclerotic carotid plaques. MATERIALS AND METHODS: From the database of radiological information in our hospital, 35 patients who underwent carotid MR imaging and subsequent carotid endoarterectomy within 2 weeks were included in this retrospective study. MR imaging included thin-slice time-of-flight MR angiography, black-blood T1- and T2-weighted imaging. Sensitivity, specificity and accuracy were calculated for the detection of fibrous cap rupture with source image of TOF-MRA. The Cohen k coefficient was also calculated to quantify the degree of concordance of source image of TOF-MRA with histopathological data. RESULTS: Sensitivity, specificity and accuracy in the detection of fibrous cap rupture were 90% (95%CI: 81-98), 69% (95%CI: 56-82) and 79% (95%CI: 71-87) with a k value of 0.59. The false positives (n = 15) were caused by partial-volume averaging between fibrous cap and lumen at the shoulder of carotid plaque. The false negatives (n = 5) were underestimated as partial thinning of fibrous cap. CONCLUSION: Source image of TOF-MRA can be useful in the detection of fibrous cap rupture with high sensitivity, but further technical improvement should be necessary to overcome shortcomings causing image degradation.

Targeted biopsy based on ADC map in the detection and localization of prostate cancer: a feasibility study.

PURPOSE: To investigate the feasibility of targeted biopsy based on an apparent diffusion coefficient (ADC) map in the detection and localization of prostate cancer. MATERIALS AND METHODS: This study included 288 consecutive patients with high or increasing serum prostate-specific antigen (PSA) levels who underwent prostatic magnetic resonance imaging (MRI) examination with an ADC map. Four core-targeted biopsies of low ADC lesions were performed under transrectal-ultrasound guidance with reference to ADC map. The positive predictive values (PPVs) of low ADC lesions were calculated and compared for the peripheral zone (PZ), transition zone (TZ), and anterior portion, respectively. Comparisons of ADC values and sizes between malignant and nonmalignant lesions were also performed. RESULTS: A total of 313 low ADC lesions were detected in 195 patients and sampled by targeted biopsies. The PPVs were 55.3% (95% confidence interval [CI]: 50-61) in total, 61.0% (95% CI: 53-69) for PZ, 50.6% (95% CI: 43-58) for TZ, and 90.9% (95% CI: 81-100) for the anterior portion. The most common nonmalignant pathology of low ADC lesions was hyperplasia, followed by chronic prostatitis. There were significant differences in ADC values and sizes between malignant and nonmalignant low ADC lesions. CONCLUSION: Targeted biopsies could be capable of detecting cancers well wherever they may be in the prostate, although the PPVs varied depending on the location of low ADC lesions.

Detection and localization of prostate cancer with the targeted biopsy strategy based on ADC map: a prospective large-scale cohort study.

PURPOSE: To investigate the usefulness of targeted biopsy strategy based on apparent diffusion coefficient (ADC) maps in the detection and localization of prostate cancer. MATERIALS AND METHODS: Institutional review board approval and informed consent from all participants were obtained. This study included 1448 consecutive patients suspected of having prostate cancer based on PSA level, who were divided into two groups: Group A included 890 patients with low-ADC lesions who underwent targeted and systematic biopsies; Group B included 558 patients with no low-ADC lesions who underwent only systematic biopsies. The cancer detection rates (CDR) of each group, positive predictive value (PPV), and negative predictive value (NPV) of ADC maps were calculated. RESULTS: The CDR was 70.1% for Group A, higher than those for overall patients (48.1%) and for Group B (13.1%) with significant difference (P < 0.001). In the serum, PSA range from 4 to 20 ng/mL, the CDR was higher for the Group A than for the Group B and overall patients with significant differences. PPV and NPV of MR findings were 70.1% and 86.9%, respectively. Especially, the PPV of the MR findings for the anterior portion was as high as 90.1%. Among the false negatives of MR findings, Gleason score proved 6 or smaller in 79.5%, and positive core number was merely one or two in 80.8%. CONCLUSION: The targeted biopsy strategy based on ADC maps can be useful in the detection and localization of prostate cancer with high PPV.

Diffusion-weighted magnetic resonance imaging in the detection of testicular torsion: feasibility study.

PURPOSE: To investigate the feasibility and usefulness of diffusion-weighted magnetic resonance imaging in the detection of testicular torsion. MATERIALS AND METHODS: Institutional Review Board approval and informed consent from all participants were obtained. Consecutive 28 patients with acute scrotal symptoms were included in this study. Fat-suppressed T2-weighted, dynamic subtraction contrast-enhanced, and diffusion-weighted images were obtained in the coronal plane with a 1.5 T MR unit. An apparent diffusion coefficient (ADC) map was reconstructed from the diffusion-weighted images obtained with b-factor of 0 and 800 s/mm(2). Comparisons of ADC values between the affected and nonaffected testes were performed with Mann-Whitney's U-test. RESULTS: Diffusion-weighted and ADC images with diagnostic quality were obtained in 23 out of the 28 patients (82%). In testicular torsion (n = 9), the mean ADC value of the twisted testes was significantly lower than that of the nonaffected testes (0.750 ± 0.297 vs. 1.017 ± 0.165 × 10(-3) mm(2)/sec, P < 0.05). In other scrotal disorders (n = 14), there was no significant difference in the mean ADC value of the testes between the affected and nonaffected side (P = 0.655). The affected-to-nonaffected ratio of ADC value was significantly lower in testicular torsion than that in other scrotal disorders (P < 0.05). CONCLUSION: Diffusion-weighted imaging of the scrotum with testicular ADC measurement can allow for the detection of testicular torsion without any use of contrast media.

Determination of the cutoff level of apparent diffusion coefficient values for detection of prostate cancer.

PURPOSE: The aim of this study was to determine the cutoff level of apparent diffusion coefficient (ADC) values for diagnosing prostate cancer. MATERIALS AND METHODS: A total of 45 consecutive patients with prostate cancer who underwent diffusion-weighted magnetic resonance imaging (MRI) with ADC maps before radical prostatectomy were included in this retrospective study. MRI findings were correlated retrospectively with histopathological results of surgical specimens. Comparisons of ADC values between cancer and noncancer areas were performed with the two-tailed unequal variance t-test. The cutoff ADC level was determined in a way to achieve the best accuracy for detecting prostate cancer. RESULTS: The mean ADC value of all the cancer lesions (n =60) was 1.04 ± 0.31 (×10(-3) mm(2)/s). In the peripheral zone, the mean ADC values of cancer lesions and noncancer areas were 1.07 ± 0.35 and 1.94 ± 0.31, respectively (P < 0.001). In the transition zone, the mean ADC values of cancer lesions and noncancer areas were 1.00 ± 0.22 and 1.56 ± 0.14, respectively (P<0.001). The cutoff level for the ADC value was determined to be 1.35×10(-3) mm(2)/s. It provided sensitivity, specificity, and accuracy of 88%, 96%, and 93%, respectively. CONCLUSION: The cutoff ADC level determined on the basis of the results obtained from radical prostatectomy specimens can help differentiate malignant from nonmalignant lesions.

MR plaque imaging of the carotid artery.

Atherosclerotic carotid plaque represents a major cause of cerebral ischemia. The detection of vulnerable plaque is important for preventing future cardiovascular events. The key factors in advanced plaque that are most likely to lead to patient complications are the condition of the fibrous cap, the size of the necrotic core and hemorrhage, and the extent of inflammatory activity within the plaque. Magnetic resonance (MR) imaging has excellent soft tissue contrast and can allow for a more accurate and objective estimation of carotid wall morphology and plaque composition. Recent advances in MR imaging techniques have permitted serial monitoring of atherosclerotic disease evolution and the identification of intraplaque risk factors for accelerated progression. The purpose of this review article is to review the current state of techniques of carotid wall MR imaging and the characterization of plaque components and surface morphology with MR imaging, and to describe the clinical practice of carotid wall MR imaging for the determination of treatment plan.

Characterization of atherosclerotic plaque of carotid arteries with histopathological correlation: vascular wall MR imaging vs. color Doppler ultrasonography (US).

PURPOSE: To investigate whether the vessel wall MRI of carotid arteries would differentiate at-risk soft plaque from solid fibrous plaque by identifying liquid components more accurately than color Doppler ultrasonography (US). MATERIALS AND METHODS: This study included 54 carotid arteries in 54 consecutive patients who underwent carotid endarterectomy. MRI was performed using black-blood fat-suppressed (FS) T1-and FS T2-weighted TSE sequences. A total of 68 major segments of the 54 carotid plaques were grouped into four MR categories based on signal intensity index (SII). MR criteria used for the diagnosis of plaque vulnerability were: at-risk soft plaque including a segment of liquid component (category A or B), solid fibrous plaque (category C or D). The MR and US findings were compared with histopathological findings of endarterectomy specimens. RESULTS: Intraoperative findings and microscopic examination of endarterectomy specimens revealed 24 at-risk soft plaques and 30 solid fibrous plaques. The sensitivity, specificity, and accuracy for diagnosing at-risk soft plaque are 96%, 93%, and 94% for MR, and 75%, 63%, and 69% for color Doppler US, respectively. The slice-by-slice MR evaluation of carotid wall also revealed detailed information of plaque segments and correlated well with the features of corresponding histologic sections. CONCLUSION: Vessel wall MRI with MRI category could have a potential to more accurately diagnose an at-risk soft plaque predominantly composed of liquid components in comparison with color Doppler US.

Assessment of time-resolved, dynamic, contrast-enhanced MRDSA using radial sliding-window reconstruction.

Sliding-window reconstruction (SWR) has been recently introduced for rapid imaging that improves temporal resolution while maintaining signal-to-noise ratio (SNR) and spatial resolution. We assessed the quantity of 2-dimensional contrast-enhanced magnetic resonance digital subtraction angiography (2D CE-MRDSA) with non-Cartesian radial SWR in phantom and clinical studies. In phantoms, we compared the quantitative properties of time-intensity curves (TIC) obtained with dynamic 2D CE-MRDSA using SWR in a radial acquisition with those obtained by Cartesian acquisition. We calculated the mean variance and standard deviation among signal intensities in TICs and used SWR to study 2D CE-MRDSA in 5 patients with angiographically proven arteriovenous malformations. Using a 3-point grading scale, we individually scored vascular visualization capability and calculated time delay (TD) from the TIC in the feeding artery (FA), nidus, and draining vein (DV). The maximum signal intensity variance in Cartesian SWR was 6.58 +/- 2.27% among time-intensity curves and was 0.87 +/- 0.77% radial SWR. Signal intensity in radial SWR decreased significantly (P<0.001) compared with the Cartesian SWR. In clinical study, the mean rating on 2D CE-MRA of the feeding artery was 2.3, nidus, 2.6, and draining vein, 2.6. Mean delay time between DV and FA was 1.8 s. The radial SWR technique is useful for demonstrating the hemodynamic features of vascular malformations in the head with 2D CE-MRDSA.

MR imaging features of solid-pseudopapillary tumor of the pancreas.

Solid-pseudopapillary tumor (SPT) of the pancreas is characterized as cystic, necrotic, and hemorrhagic degeneration. In this study, magnetic resonance (MR) findings of 4 cases were reviewed. Patchy or spotty areas of high intensity that suggested hemorrhagic degeneration were constantly detected on fat-suppressed T(1)-weighted images. Dynamic contrast-enhanced MR imaging revealed mild and gradual increase of contrast enhancement in solid portions. Multi-contrast MR imaging that included fat-suppressed T(1)-weighted imaging and dynamic contrast-enhanced imaging allowed accurate diagnosis of SPT and its differentiation from other tumors.

MR imaging of testicular torsion: features of testicular hemorrhagic necrosis and clinical outcomes.

PURPOSE: To determine whether emergency subtraction dynamic contrast-enhanced MR imaging (DCE-MRI) in combination with T2- and T2*-weighted imaging of the testis is useful in the evaluation of patients with testicular torsion. MATERIALS AND METHODS: Fourteen patients with surgically proven testicular torsion were examined using preoperative emergency MRI, including T2-weighted, T2*-weighted, and DCE-MRI. The affected testis was examined histologically in eight patients who underwent orchiectomy, and by postoperative follow-up MRI in six patients who underwent orchiopexy. The diagnostic criteria for testicular torsion and detection of hemorrhagic necrosis in the affected testis in emergency MRI were decreased or no perfusion in DCE-MRI and a spotty and/or streaky pattern of low or very low signal intensity in T2- and T2*-weighted images. The intraoperative findings and clinical outcomes were also compared. RESULTS: The histological findings and follow-up MR images revealed total or partial necrosis of the affected testis in 10 of the 14 patients. In the diagnosis of complete torsion, the sensitivities were 100% for DCE-MRI and 75% for T2- and T2*-weighted imaging. In the detection of testicular necrosis, T2- and T2*-weighted imaging showed the highest accuracy (100%), followed by 12-hour time from onset (93%), intraoperative findings (79%), and DCE-MRI (71%). CONCLUSION: Emergency MRI can help diagnose testicular torsion and detect testicular necrosis when DCE-MRI is used in combination with T2- and T2*-weighted images.

MR imaging of acute biliary disorders.

In patients with acute right-sided epigastric pain, jaundice, and a high fever, it is essential to accurately diagnose the cause of the symptoms, differentiate acute biliary disorders from nonbiliary disorders, and evaluate the severity of the disease. Gray-scale ultrasonography (US) and computed tomography (CT) are useful primary imaging modalities, but their results are not always conclusive. Magnetic resonance (MR) imaging, including MR cholangiopancreatography, can be a valuable complement to US and CT when additional information is needed. MR images have excellent tissue contrast and can provide more specific information, allowing diagnosis of complications that arise from acute cholecystitis, such as empyema, gangrenous cholecystitis, gallbladder perforation, enterocholecystic fistula, emphysematous cholecystitis, and hemorrhagic cholecystitis. In addition, causes of obstructive jaundice, acute suppurative cholangitis, and hemobilia can be clearly demonstrated with multisequence MR imaging. Single-section MR cholangiopancreatography and heavily T2-weighted imaging, in combination with fat-suppressed T1- and T2-weighted imaging, provide comprehensive and detailed information about the biliary system around the obstruction site, biliary calculi, inflammatory processes, purulent material, abscesses, gas, and hemorrhage. Contrast-enhanced MR imaging is useful for evaluation of the gallbladder wall; lack of enhancement and disruption of the wall may be findings specific for gangrenous cholecystitis and gallbladder perforation, respectively.

Quantification of left ventricular volumes from cardiac cine MRI using active contour model combined with gradient vector flow.

We investigated the feasibility of combining the active contour model with gradient vector flow (Snakes-GVF) to estimate left ventricular (LV) volumes from cardiac cine magnetic resonance imaging (MRI). MRI data were acquired from 27 patients, including 14 adults (9 men, 5 women, 55.0+/-23.3 years) and 13 children (10 boys, 3 girls, 2.7+/-2.1 years) using Gyroscan Intera (1.5 Tesla, Philips Medical Systems). LV volumes were calculated by adding the areas surrounded by the contour extracted by Snakes-GVF and compared with volumes estimated by manual tracing. Those estimated by Snakes-GVF [y (mL)] correlated well with those estimated by manual tracing [x (mL)]. In adult cases, the regression equation and correlation coefficient were y=1.008x - 0.517 and 0.996, respectively. In pediatric cases, they were y=1.174x - 2.542 and 0.992, respectively. In conclusion, Snakes-GVF is a powerful and useful tool for quantifying LV volumes using cardiac MRI.

Automatic motion correction for quantification of myocardial perfusion with dynamic magnetic resonance imaging.

Respiratory motion makes it difficult to quantify myocardial perfusion with dynamic magnetic resonance imaging (MRI). The purpose of this study was to evaluate an automatic registration method for motion correction for quantification of myocardial perfusion with dynamic MRI. The present method was based on the gradient-based method with robust estimation of displacement parameters. For comparison, we also corrected for motion with manual registration as the benchmark. The myocardial kinetic parameters, K1 (rate constant for transfer of contrast agent from blood to myocardium) and k2 (rate constant for transfer from myocardium to blood), were calculated from dynamic images with a two-compartment model. The images corrected by the present method were similar to those corrected by manual registration. The kinetic parameters obtained after motion correction with the present method were close to those obtained after motion correction with manual registration. These results suggest that the present method is useful for motion correction for quantification of myocardial perfusion with dynamic MRI.

High-resolution selective three-dimensional magnetic resonance coronary angiography with navigator-echo technique: segment-by-segment evaluation of coronary artery stenosis.

PURPOSE: To investigate the feasibility of high-resolution selective three-dimensional (3D) magnetic resonance coronary angiography (MRCA) in the evaluation of coronary artery stenoses. MATERIALS AND METHODS: In 12 patients with coronary artery stenoses, MRCA of the coronary artery groups, including the coronary segments with stenoses of 50% or greater based on conventional x-ray coronary angiography (CAG), was performed with double-oblique imaging planes by orienting the 3D slab along the major axis of each right coronary artery-left circumflex artery (RCA-LCX) group and each left main trunk-left anterior descending artery (LMT-LAD) group. Ten RCA-LCX and five LMT-LAD MR angiograms were obtained, and the results were compared with those of conventional x-ray angiography. RESULTS: Among 70 coronary artery segments expected to be covered, a total of 49 (70%) segments were fully demonstrated in diagnostic quality. The identification of segmental location of stenoses showed as high an accuracy as 96%. The retrospective analysis for stenosis of 50% or greater yielded the sensitivity, specificity, and accuracy of 80%, 85%, and 84%, respectively. CONCLUSION: Selective 3D MRCA has the potential for segment-by-segment evaluation of major portions of the right and left coronary arteries with high accuracy.

Fast MR imaging in obstetrics.

Ultrasonography (US) is the initial imaging modality of choice for evaluation of patients in obstetrics. However, the results of US are not always sufficient. Magnetic resonance (MR) imaging, which uses no ionizing radiation, may be an ideal method for further evaluation. Although MR imaging is not recommended during the first trimester and use of contrast material is not recommended in pregnant patients, fast MR imaging is useful in various obstetric settings and can provide more specific information with excellent tissue contrast and multiplanar views. In pregnant patients with acute conditions, various diseases (eg, red degeneration of a uterine leiomyoma) may be diagnosed. MR imaging allows characterization of pelvic masses discovered during pregnancy and diagnosis of postpartum complications (eg, abscess, hematoma, ovarian vein thrombosis). In pregnant patients with hydronephrosis, MR urography can demonstrate the site of obstruction and the cause (eg, a ureteral stone). MR pelvimetry may be beneficial in cases of breech presentation. Contrast material-enhanced dynamic MR imaging allows one to evaluate the vascularity of a placental polyp, detect the viable component of a gestational trophoblastic tumor, and diagnose a uterine arteriovenous malformation. MR imaging enables diagnosis of rare forms of ectopic pregnancy and early diagnosis of ectopic pregnancy.