Genitourinary applications of diffusion-weighted MR imaging in the pelvis

Diffusion-weighted (DW) magnetic resonance (MR) imaging has a large number of potential clinical applications in the female and male pelvis and can easily be added to any routine MR protocol. In the female pelvis, DW imaging allows improvement of staging in endometrial and cervical cancer, especially in locally advanced disease and in patients in whom contrast medium administration should be avoided. It can also be helpful in characterizing complex adnexal masses and in depicting recurrent tumor after treatment of various gynecologic malignancies. DW imaging shows promising results in monitoring treatment response in patients undergoing radiation therapy of cervical cancer. An increase in apparent diffusion coefficient (ADC) values of responders precedes changes in size and may therefore allow early assessment of treatment success. In the male pelvis, the detection of prostate cancer in the peripheral zone is relatively easier than in the central gland based on the underlying ADC values, whereas overlapping values reported in the central gland still need further research. DW imaging might also be applied in the noninvasive evaluation of bladder cancer to differentiate between superficial and muscle-invasive tumors. Initial promising results have been reported in differentiating benign from malignant pelvic lymph nodes based on the ADC values; however, larger-scale studies will be needed to allow the detection of lymph node metastases in an individual patient. Prerequisites for successfully performing DW imaging of the female and male pelvis are standardization of the DW imaging technique, including the choice of b values, administration of an antiperistaltic drug, and comparison of DW findings with those of morphologic MR imaging.

Diffusion-weighted MR imaging in the head and neck

Extracranial applications of diffusion-weighted (DW) magnetic resonance (MR) imaging are gaining increasing importance, including in head and neck radiology. The main indications for performing DW imaging in this relatively small but challenging region of the body are tissue characterization, nodal staging, therapy monitoring, and early detection of treatment failure by differentiating recurrence from posttherapeutic changes. Lower apparent diffusion coefficients (ADCs) have been reported in the head and neck region of adults and children for most malignant lesions, as compared with ADCs of benign lesions. For nodal staging, DW imaging has shown promise in helping detect lymph node metastases, even in small (subcentimeter) nodes with lower ADCs, as compared with normal or reactive nodes. Follow-up of early response to treatment is reflected in an ADC increase in the primary tumor and nodal metastases; whereas nonresponding lesions tend to reveal only a slight increase or even a decrease in ADC during follow-up. Optimization and standardization of DW imaging technical parameters, comparison of DW images with morphologic images, and increasing experience, however, are prerequisites for successful application of this challenging technique in the evaluation of various head and neck pathologic conditions.

Low-field Mri and arthroscopy of meniscal lesions in ten dogs with experimentally induced cranial cruciate ligament insufficiency

Little is known about the magnetic resonance imaging (MRI) appearance of canine meniscal lesions. The aim of this study is to describe the MR appearance of meniscal lesions in dogs with experimentally induced cranial cruciate ligament (CCL) deficiency. The pilot study revealed dogs weighing approximately 10 kg to be too small for meniscal evaluation on low-field MRI. In the main study, dogs weighing approximately 35 kg were used. The left CCL was transected and low-field MRI was performed regularly until 13 months post-surgery. Normal menisci were defined as grade 0. Intrameniscal lesions not reaching any surface corresponded to grade 1 if focal and to grade 2 if linear or diffuse. Grade 3 lesions consisted in linear tears penetrating a meniscal surface. Grade 4 lesions included complex signal changes or meniscal distortion. Between 2 and 13 months post-surgery, all dogs developed grade 4 lesions in the medial meniscus. Most of them corresponded to longitudinal or bucket handle tears on arthroscopy and necropsy. Two dogs showed grade 3 lesions reaching the tibial surface of the lateral meniscus on MRI but not in arthroscopy. Such tears are difficult to evaluate arthroscopically; MRI provides more accurate information about the tibial meniscal surface. Grades 1 and 2 lesions could not be differentiated from presumably normal menisci with our imaging technique. An MRI grading system better adapted to canine lesions has yet to be developed. MRI is a helpful tool for the diagnosis of complete tears in the canine meniscus, especially in larger dogs.

Postmortem unenhanced magnetic resonance imaging of myocardial infarction in correlation to histological infarction age characterization

AIMS: Postmortem magnetic resonance (MRI) imaging is currently evaluated as alternative to traditional autopsy and myocardial infarction plays a key role therein. The aim of this study is to determine the suitability of postmortem MRI in infarction age staging. METHODS AND RESULTS: In eight human forensic corpses presenting with a total of 11 myocardial infarcted areas, short-axis, transversal, and longitudinal long-axis images (T1, T2, stir, flair) were acquired in situ on a 1.5 T system. During subsequent autopsy, the section technique was adapted to short-axis images. Histological investigations were performed along the entire circumference of the left ventricle to correlate the signal alteration in MR to the histological appearance. Two peracute infarctions were not detected in MRI and autopsy. Four acute infarcted areas presented with decreased signal in necrotic centres and increased signal in marginal myocardial regions (T2-weighted). T1-weighted images showed local hyperintensities when intramyocardial haemorrhage occurred. Four cases showed subacute infarctions with hyperintense regions in T2-weighted images and no signal alteration in T1-weighted images. Four chronic myocardial infarctions showed distinctively decreased signals in all applied sequences. CONCLUSION: Postmortem MRI demonstrates myocardial infarction in situ and allows for an infarction age estimation based on the signal behaviour.

Postmortem radiology of fatal hemorrhage: measurements of cross-sectional areas of major blood vessels and volumes of aorta and spleen on MDCT and volumes of heart chambers on MRI

OBJECTIVE: Autopsy determination of fatal hemorrhage as the cause of death is often a difficult diagnosis in forensic medicine. No quantitative system for accurately measuring the blood volume in a corpse has been developed. MATERIALS AND METHODS: This article describes the measurement and evaluation of the cross-sectional areas of major blood vessels, of the diameter of the right pulmonary artery, of the volumes of thoracic aorta and spleen on MDCT, and of the volumes of heart chambers on MRI in 65 autopsy-verified cases of fatal hemorrhage or no fatal hemorrhage. RESULTS: Most cases with a cause of death of "fatal hemorrhage" had collapsed vessels. The finding of a collapsed superior vena cava, main pulmonary artery, or right pulmonary artery was 100% specific for fatal hemorrhage. The mean volumes of the thoracic aorta and of each of the heart chambers and the mean cross-sectional areas of all vessels except the inferior vena cava and abdominal aorta were significantly smaller in fatal hemorrhage than in no fatal hemorrhage. CONCLUSION: For the quantitative differentiation of fatal hemorrhage from other causes of death, we propose a three-step algorithm with measurements of the diameter of the right pulmonary artery, the cross-sectional area of the main pulmonary artery, and the volume of the right atrium (specificity, 100%; sensitivity, 95%). However, this algorithm must be corroborated in a prospective study, which would eliminate the limitations of this study. Quantitative postmortem cross-sectional imaging might become a reliable objective method to assess the question of fatal hemorrhage in forensic medicine.

Postmortem imaging of blood and its characteristics using MSCT and MRI

The rapid development of computed tomography (CT) and magnetic resonance imaging (MRI) led to the introduction and establishment in postmortem investigations. The objectives of this preliminary study were to describe the imaging appearances of the early postmortem changes of blood after cessation of the circulation, such as sedimentation, postmortem clotting, and internal livores, and to give a few first suggestions on how to differentiate them from other forensic findings. In the Virtopsy project, 95 human corpses underwent postmortem imaging by CT and MRI prior to traditional autopsy and therefore 44 cases have been investigated in this study. Postmortem alterations as well as the forensic relevant findings of the blood, such as internal or subcutaneous bleedings, are presented on the basis of their imaging appearances in multislice CT and MRI.

[MRI-based diagnosis of giant cell arteritis]

The giant cell arteritis and its symptoms are usually non-specific and accompanied with symptoms of polymyalgia rheumatica. As complications of the giant cell arteritis ischemia, infarction or rupture of the damaged vessel can occur. We report on a 56-year-old female patient, who suffered for one year about weight loss, tiredness and intolerance as well as symptoms of polymyalgia rheumatica. Gastroscopy and colonoscopy showed normal findings. In the context of the malignancy search we made a computer tomography and magnet resonance tomography. The data showed an enlargement and an enhancement of the aorta, which led us to the suspicion of a giant cell arteritis. We started immediately with a medical treatment. The biopsy of the arteries temporales supported histological the diagnosis.

Functional evaluation of transplanted kidneys with diffusion-weighted and BOLD MR imaging: initial experience

PURPOSE: To prospectively evaluate feasibility and reproducibility of diffusion-weighted (DW) and blood oxygenation level-dependent (BOLD) magnetic resonance (MR) imaging in patients with renal allografts, as compared with these features in healthy volunteers with native kidneys. MATERIALS AND METHODS: The local ethics committee approved the study protocol; patients provided written informed consent. Fifteen patients with a renal allograft and in stable condition (nine men, six women; age range, 20-67 years) and 15 age- and sex-matched healthy volunteers underwent DW and BOLD MR imaging. Seven patients with renal allografts were examined twice to assess reproducibility of results. DW MR imaging yielded a total apparent diffusion coefficient including diffusion and microperfusion (ADC(tot)), as well as an ADC reflecting predominantly pure diffusion (ADC(D)) and the perfusion fraction. R2* of BOLD MR imaging enabled the estimation of renal oxygenation. Statistical analysis was performed, and analysis of variance was used for repeated measurements. Coefficients of variation between and within subjects were calculated to assess reproducibility. RESULTS: In patients, ADC(tot), ADC(D), and perfusion fraction were similar in the cortex and medulla. In volunteers, values in the medulla were similar to those in the cortex and medulla of patients; however, values in the cortex were higher than those in the medulla (P < .05). Medullary R2* was higher than cortical R2* in patients (12.9 sec(-1) +/- 2.1 [standard deviation] vs 11.0 sec(-1) +/- 0.6, P < .007) and volunteers (15.3 sec(-1) +/- 1.1 vs 11.5 sec(-1) +/- 0.5, P < .0001). However, medullary R2* was lower in patients than in volunteers (P < .004). Increased medullary R2* was paralleled by decreased diffusion in patients with allografts. A low coefficient of variation in the cortex and medulla within subjects was obtained for ADC(tot), ADC(D), and R2* (<5.2%), while coefficient of variation within subjects was higher for perfusion fraction (medulla, 15.1%; cortex, 8.6%). Diffusion and perfusion indexes correlated significantly with serum creatinine concentrations. CONCLUSION: DW and BOLD MR imaging are feasible and reproducible in patients with renal allografts.

Subsecond fluorine-19 MRI of the lung

Minimal scan times in rapid fluorine-19 MRI using sulfur hexafluoride (SF6) have been on the order of 10 s. Because of the very short T1 relaxation time of SF6 (T1 = 1.65 ms), high receiver bandwidths are necessary to allow for a high number of excitations. Since high bandwidths cause high levels of electronic noise, SNR per acquisition has been too low to further reduce scan time. The purpose of this study was to investigate whether scan times could be reduced using hexafluoroethane (C2F6), a gas with a longer T1 (T1 = 7.9 ms) at a relatively low bandwidth of 488 Hz/pixel. Gradient-echo images were acquired during and after completion of the wash-in of a 70% C2F6- 30% O2 mixture. Peak SNR values of 16 and 7.9 were observed for coronal projection images acquired within 2 s and 260 ms, respectively. These results demonstrate that subsecond imaging is feasible using C2F6.

Brain atrophy in pure and complicated hereditary spastic paraparesis: a quantitative 3D MRI study

Hereditary spastic paraparesis (HSP) is a heterogeneous group of neurodegenerative disorders with progressive lower limb spasticity, categorized into pure (p-HSP) and complicated forms (c-HSP). The purpose of this study was to evaluate if brain volumes in HSP were altered compared with a control population. Brain volumes were determined in patients suffering from HSP, including both p-HSP (n = 21) and c-HSP type (n = 12), and 30 age-matched healthy controls, using brain parenchymal fractions (BPF) calculated from 3D MRI data in an observer-independent procedure. In addition, the tissue segments of grey and white matter were analysed separately. In HSP patients, BPF were significantly reduced compared with controls both for the whole patient group (P < 0.001) and for both subgroups, indicating considerable brain atrophy. In contrast to controls who showed a decline of brain volumes with age, this physiological phenomenon was less pronounced in HSP. Therefore, global brain parenchyma reduction, involving both grey and white matter, seems to be a feature in both subtypes of HSP. Atrophy was more pronounced in c-HSP, consistent with the more severe phenotype including extramotor involvement. Thus, global brain atrophy, detected by MRI-based brain volume quantification, is a biological marker in HSP subtypes.

Hip pain in renal transplant recipients: symptomatic gluteus minimus and gluteus medius tendon abnormality as an alternative MRI diagnosis to avascular necrosis

OBJECTIVE: The purpose of this study was to review the diagnosis on MRI and radiography of 24 renal transplant recipients with hip pain suspicious for avascular necrosis and to investigate whether there is an association between kidney transplant patients with end-stage renal disease and symptomatic gluteus minimus and medius tendon abnormality. CONCLUSION: Symptomatic gluteus minimus and medius tendon lesions and abnormalities can occur in renal allograft recipients. The MRI findings of this entity allow an alternative diagnosis in this patient population.