Frequency-selective Fat Suppression Research Articles

Collagen deposition in the liver is strongly and positively associated with T1rho elongation while fat deposition is associated with T1rho shortening: an experimental study of methionine and choline-deficient (MCD) diet rat model.

A number of questions concerning the histological mechanism of elongated T1rho in liver fibrosis remain unanswered. Using a rat model of non-alcoholic fatty liver disease (NAFLD) induced with methionine and choline-deficient (MCD) diet, the primary aim of this study is to clarify whether collagen deposition per se causes liver T1rho elongation. There were 45 rats in the NAFLD model group and 8 rats in the control group. NAFLD model rats were fed MCD diet for 1, 2, 4, 6, 8, or 10 weeks, respectively. At the endpoint, the rats had in vivo MRI at 3.0 T and followed by histology. For T1rho data acquisition, a rotary echo spin-lock pulse was implemented in a three-dimensional fast field echo sequence with frequency selective fat suppression. The spin-lock frequency was set to 500 Hz, and the spin-lock times of 5, 10, 40, and 50 ms were used. Liver specimens were processed with hematoxylin-eosin staining for steatosis and inflammation evaluation, and Masson's trichrome staining for collagen visualization. The semiquantitative histopathological evaluation was based on NASH Clinical Research Network criteria. Histomorphometric analysis calculated percentages of fat and collagen accumulations in the livers. A strong (r=0.82) and significant (P<0.0001) positive correlation between liver collagen content and liver T1rho was observed. Rats with no or minimal inflammation could have very long T1rho value. Among experimental rats without a positive fibrosis grading, five rats did not have an inflammation score (i.e., had minimal inflammation or no inflammation) while four had a positive inflammation score; the difference in liver T1rho between these two types of rats was minimal. Eight control rat livers and 15 stage-1 fibrosis rat livers were separated by liver T1rho completely. When four subgroups of experiment rats were selected where the liver collagen had a very narrow range within these subgroups, all these four subgroups showed a trend of negative correlation between liver fat and liver T1rho. Collagen deposition in the live strongly contributes to liver T1rho elongation, while fat deposition contributes to T1rho shortening. In a well-controlled experimental setting, T1rho measure alone allows separation of healthy livers and stage-1 liver fibrosis in the MCD rat liver model.

Assessment of the Quality of Breast MR Imaging Using the Modified Dixon Method and Frequency-Selective Fat Suppression: A Phantom Study.

To obtain objective and concrete data by physically assessing the quality of breast magnetic resonance images based on the fat-suppression effect by the modified Dixon method (mDixon) and frequency-selective fat suppression (e-Thrive) using an original lipid-content breast phantom that could easily reveal the influence of non-uniform fat suppression in breast magnetic resonance imaging. The fat-suppression uniformity was approximately seven times superior when using mDixon compared with when using e-Thrive. mDixon appears to have a significant advantage.

The Dixon technique and the frequency-selective fat suppression technique in three-dimensional T1 weighted MRI of the liver: a comparison of contrast-to-noise ratios of hepatocellular carcinomas-to-liver.

The use of three-dimensional T1 weighted gradient echo sequences such as the Dixon technique and the frequency-selective fat suppression (FS) technique is currently widely accepted method in MRI examinations of the liver. To assess the image qualities of the Dixon technique and the frequency-selective FS technique, the contrast-to-noise ratios (CNRs) of hepatocellular carcinoma (HCC)-to-liver and fat-to-liver were compared between the two techniques in the hepatobiliary phase (HBP) following administration of gadolinium-ethoxybenzyl-diethylenetriamine penta-acetic acid. MR images of 59 patients with a total of 86 HCCs were retrospectively evaluated. Images were consecutively obtained with the Dixon and frequency-selective FS methods in the HBP and their CNRs of HCC-to-liver and fat-to-liver were compared. CNRs and contrast ratios were calculated by the mean value of the liver parenchyma, HCC, fat and standard deviation of the liver parenchyma. The Wilcoxon signed-ranks test was used for statistical analysis. The median CNRs for the frequency-selective FS and Dixon techniques of HCC-to-liver were 4.3 and 5.4 (p < 0.01), mesenteric fat-to-liver were 9.9 and 12.8 (p < 0.01) and subcutaneous fat-to-liver were 9.9 and 13.2 (p < 0.01), respectively. The Dixon technique yielded higher CNRs of HCC-to-liver than that of the frequency-selective FS technique. There are a limited number of reports on quantitative analysis of the image qualities of the Dixon technique and the frequency-selective FS technique, particularly within the same patient and examination.

Improved frequency selective fat suppression in the posterior neck with tissue susceptibility matched pyrolytic graphite foam

To demonstrate improved frequency selective fat suppression in MRI using a magnetic susceptibility matching foam by reducing B0 inhomogeneities induced within the body by air-tissue interfaces. Flexible pyrolytic graphite (PG) composite foam was tailored to match the magnetic susceptibility of human tissue and was shaped to surround the cervical spine region. Field maps and frequency selective fat suppressed T1 -weighted FLASH images were acquired at 3 Tesla in both phantoms and six healthy necks. B0 field uniformity was shimmed to a target critical threshold of 1 ppm for fat suppression. The percentage of voxels in the phantom that did not achieve the critical threshold was reduced from 64% without the PG foam to only 1% with the foam. A similar decrease from 16% to 2% was observed in the in vivo region of interest. PG foam improved B0 field uniformity by moving air-tissue field gradients outside of the neck where they cannot cause MRI artifacts. The PG foams consistently mitigated signal dropout, improved overall SNR, and enabled more robust frequency selective fat suppression.

Frequency-Selective Fat Suppression Radiofrequency Pulse Train to Remove Olefinic Fats

CHESS pulse can suppress the signal originating from aliphatic fat protons but cannot suppress the signal from olefinic fat protons, which is near the resonance frequency of water protons. Adipose tissue contains various fat species; aliphatic fat comprises about 90 % and olefinic fat about 10 % of adipose tissue. Thus, CHESS pulse cannot be used to suppress the signal from adipose tissue completely. The purpose of this study was to find a method to suppress the signal from adipose tissue completely. The Fatsat train pulse, created with an arbitrary flip angle and insensitive to B1 inhomogeneity, was used. Because B1 inhomogeneity is larger on higher field magnetic resonance imaging, the fat suppression radiofrequency pulse needs to be B1-insensitive. To investigate a percentage of olefinic fat in adipose tissues, the excitation frequency of the Fatsat train pulse was varied from −240 to +400 Hz and the images and fat-suppressed images were obtained. The presence of olefinic fat comprising about 10 % of abdominal adipose tissue was identified. The result agreed with some previous papers. Complete fat suppression could be achieved by partial (10 %) inversion of longitudinal aliphatic fat magnetization and by canceling out the two fat magnetizations. The flip angle was identified to about 95°. In conclusion, the cause that the signal from adipose tissues cannot be suppressed completely has been found. Improved images that signals from adipose tissues were suppressed completely have been demonstrated. This technique can also be applied to several pulse sequences.

Diagnostic accuracy of MR sialography in sialolithiasis and salivary ductal stenosis

ObjectivesThe purpose of this study is to determine the diagnostic accuracy of MR sialography in the examination of patients with salivary duct disease. Patients and methodsTwenty-eight patients (twenty males and eight females, average age, 47years), with symptoms related to the salivary glands, underwent both conventional sialography and MR sialography. The latter was performed using heavily T2-weighted, two dimensional, fast spin-echo techniques and a neck coil. Contiguous 3-mm axial images with frequency-selective fat suppression were acquired through the symptomatic gland. The MR sialography findings were compared with the final diagnoses determined by conventional sialography, and with surgery in the case of those who underwent surgical intervention. Ultrasound examination was performed using 7.5MHz transducer. Conventional sialography was performed with the use of 0.012–0.021inch sialographic catheter and an injection of 0.3–1.5ml Ultravist 300mg/ml. ResultsFinal diagnosis included sialolithiasis in eleven cases, sialolithiasis and stenosis in four cases, stenosis without lithiasis in ten cases and normal salivary glands in three cases. (The normal cases were excluded from the study). ConclusionIt is concluded that MR sialography with a heavily T2-weighted sequence is highly successful in the noninvasive visualization of the ductal system of major salivary glands in cases that could not be examined by conventional sialogram. It is useful for diagnosing sialolithiasis and ductal stenosis. However, normal MR sialographic findings do not allow the exclusion of small calculi. Thus in patients with strong clinical suspicion of calculi and normal MR sialographic findings, conventional sialography should still be performed.

MRI of the ankle joint in healthy non-athletes and in marathon runners: image quality issues at 7.0 T compared to 1.5 T

To present imaging characteristics of the ankle at 7.0 T and to investigate the appearance and image quality of presumed pathologies of ankles without physical strain as well as of ankles after a marathon run in comparison to 1.5 T. Appearance of presumed pathologic findings and image quality of TSE (PD, T2, and STIR) and GRE sequences (MEDIC, DESS, and/or CISS) at 7.0 T and 1.5 T MRI were compared by two senior radiologists in consensus in two healthy controls without strain and in six marathon runners after a full-length marathon (eight males, mean age 49.1 years). Overall, 7.0 T MRI allowed for higher resolution images for most of the sequences while requiring comparable acquisition times and achieving high contrast images mainly in gradient echo sequences. Bursal or presumed peritendineal fluid and/or edematous tissue, which were found in seven of eight subjects, could be best appreciated with 7.0 T MEDIC. Other findings with sharper delineation at 7.0 T included cartilage defects (best: CISS), osseous avulsions, and osteophytes (best: DESS). Nevertheless, 1.5 T STIR imaging enabled assessment of a tibiotalar bone edema-like lesion in two runners, which was barely visible at 7.0 T using STIR, but not with any other sequence at 7.0 T including MEDIC (with frequency selective fat suppression). 7.0 T showed larger image quality variations with challenges especially in the TSE sequences. Our initial results of ultra-high-field ankle joint imaging demonstrate the improved depiction of ankle anatomy, fluid depositions, and cartilage defects. However imaging of edema-like bone lesions remains challenging at ultra-high magnetic field strength, and TSE coverage in particular is limited by the specific absorption rate.

Usefulness of IDEAL T2-weighted FSE and SPGR imaging in reducing metallic artifacts in the postoperative ankles with metallic hardware

The aim of this work is to prospectively compare the effectiveness of iterative decomposition of water and fat with echo asymmetry and least-squares estimation (IDEAL), T2-weighted fast spin-echo (FSE), and spoiled gradient-echo (SPGR) MR imaging to frequency selective fat suppression (FSFS) protocols for minimizing metallic artifacts in postoperative ankles with metallic hardware. The T2-weighted and SPGR imaging with IDEAL and FSFS were performed on 21 ankles of 21 patients with metallic hardware. Two musculoskeletal radiologists independently analyzed techniques for visualization of ankle ligaments and articular cartilage, uniformity of fat saturation, and relative size of the metallic artifacts. A paired t test was used for statistical comparisons of MR images between IDEAL and FSFS groups. IDEAL T2-weighted FSE and SPGR images enabled significantly improved visualization of articular cartilage (p < 0.05), the size of metallic artifact (p < 0.05), and the uniformity of fat saturation (p < 0.05). However, no significant improvement was found in the visibility of ligaments. IDEAL T2-weighted FSE and SPGR imaging effectively reduces the degree of tissue-obscuring artifacts produced by fixation hardware in ankle joints and improves image quality compared to FSFS T2-weighted FSE and SPGR imaging. However, visibility of ligaments was not improved using IDEAL imaging.

Whole-Body Diffusion-Weighted Imaging: The Added Value to Whole-Body MRI at Initial Diagnosis of Lymphoma

The objective of our study was to evaluate the diagnostic performance of conventional whole-body MRI without and with diffusion-weighted imaging (DWI) in the detection of known (18)F-FDG-avid lymphomas. The conventional whole-body MRI protocol consisted of a T2-weighted sequence and a T2-weighted spectral attenuated inversion recovery (SPAIR) sequence with frequency-selective fat suppression. The second protocol used the same sequences as the first protocol but also included DWI. Seventeen patients with pathologically confirmed, newly diagnosed, untreated lymphoma were recruited. T2-weighted and T2-weighted SPAIR images were evaluated first, separate from the DW images, and then were evaluated with the DW images. We used (18)F-FDG PET/CT as the standard of reference. True-positive, false-positive, and false-negative values were evaluated on a per-lesion basis. Tumor staging based on T2-weighted and T2-weighted SPAIR imaging without DWI and then with DWI was compared using the Ann Arbor staging system. True-positive lesions were increased from 89% to 97%, false-positive lesions were increased from 3% to 6%, and false-negative lesions were decreased from 11% to 3% by the addition of DWI. Diagnostic sensitivity was significantly increased (p = 0.002) by adding DWI. Lesions detected on DWI but not on T2-weighted and T2-weighted SPAIR imaging were located in renal (n = 1), paraaortic (n = 6), and pelvic (n = 3) lymph nodes. On DWI, 47% of the lesions (n = 55) were more conspicuous than on T2-weighted and T2-weighted SPAIR imaging; most of these lesions (58%, n = 32) were from lymph nodes in the pelvic or abdominal regions and bone marrow. No difference was found between T2-weighted and T2-weighted SPAIR imaging without DWI and T2-weighted and T2-weighted SPAIR imaging with DWI in lymphoma staging, being consistent with PET/CT in 88% of the patients (n = 15). The addition of DWI to conventional whole-body MRI sequences enhanced lesion conspicuity and improved diagnostic accuracy for lymphomas. With technical optimization, whole-body MRI with DWI, as a nonionizing imaging modality, may potentially be useful as an alternative method to PET/CT in the management of malignant lymphoma.

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We have developed a sequence for abdominal examination that fat suppressed 3D-T1W by a linear filling order using an adiabatic pulse for frequency selective fat suppression. We simulated the change in fat signal using a linear method and checked the starting point of data filling for the null point using a phantom of different T1 values. We then checked the contrast between the fat signal and liver. After checking by using simulation, a clinical evaluation was done. The change in fat signal was mostly the same after the fourth shot, and we were able to estimate the null point of the fat signal by the following parameters: TR, FA, TFE factor, and shot interval. Consequently, we could control the starting point of data filling in k-space for fat suppression. The contrast between fat and liver was improved because noise was reduced by the linear method. The sequence developed with the linear filling order using frequency selective fat suppression pulse proved to be useful.

Radiofrequency Ablation of Bone with Cooled Probes and Impedance Control Energy Delivery in a Pig Model: MR Imaging Features

To determine the coronal marrow ablation length and detect cortical thinning after radiofrequency ablation (RFA) of bone in a pig model. Twelve pigs underwent RFA with a 1- or 2-cm single internally cooled electrode placed at the mid-diaphyseal point of their long bones at 1, 7, or 28 days before euthanasia. Twelve minutes of impedance control radiofrequency energy was delivered at maximum output from a 200-W generator. Pigs were imaged with axial and coronal turbo spin-echo (SE) T1- and T2-weighted frequency-selective fat suppression sequences by using spectral presaturation with inversion recovery (SPIR). A radiologist blinded to the timing of the treatment and the results of other imaging sequences measured the coronal ablation zone length and cortical thickness. The pigs were euthanized, and the ablated bone underwent histologic examination. At SPIR imaging, the zone of marrow ablation was defined as an area of low signal intensity surrounded by a high-signal-intensity band. At T1-weighted imaging, the zone of marrow ablation was defined as a heterogeneously isointense area surrounded by a low-signal-intensity band. The mean (+/-standard deviation) coronal marrow ablation zone measurement with SPIR imaging at 28 days was 47 mm +/- 9 (range, 34-73 mm) for the 1-cm electrode and 51 mm +/- 7 (range, 33-67 mm) for the 2-cm electrode. Two humeral fractures occurred at 21 and 28 days after therapy. Thinning of the cortex adjacent to the electrode insertion site was identified in the humeral group only. The change in the marrow signal intensity with impedance-controlled RFA is larger than that reported for temperature-controlled protocols. RFA leads to bone weakening.

Identification of lipomatous metaplasia in old infarcted myocardium by cardiovascular magnetic resonance and computed tomography

Lipomatous metaplasia of myocardium after myocardial infarction (MI) is less reported, and the exact prevalence and clinical implications of this phenomenon are unclear. A case of lipomatous metaplasia after MI evaluated with cardiovascular magnetic resonance (CMR) and computed tomography (CT) is presented. The presence of lipomatous metaplasia could not be easily differentiated from scar simply by the delayed-enhanced images. Loss of signal on TrueFISP cine MRI can be a hint. A pre-contrast T1-weighted image with or without frequency-selective fat suppression is useful in order to verify the existence of lipomatous metaplasia on CMR.

Fast sequences with fat suppression in breath-hold mode: new standard in contrast-enhanced T1-weighted MR imaging of renal tumors?

Our purpose was to analyze detection, diagnostic characterization, and staging of renal solid lesions using different fast T1-weighted sequences with fat suppression in breath-hold mode compared with a gradient-echo sequence after contrast application. Twenty-five patients with focal renal lesions were examined with a T1-weighted ultrafast turbo spin-echo (UTSE) sequence with frequency selective fat suppression (SPIR), two different segmented echo-planar imaging (EPI) sequences - a spin-echo and a gradient-echo echo-planar sequence (SE-, FFE-EPI) combined with SPIR and a gradient-echo (fast field echo, FFE) sequence in a prospective study. The images of all sequences were visually evaluated and in addition to qualitative evaluation the contrast-to-noise ratio (CNR) for cyst and solid lesions was measured. Among the different T1-weighted sequences, the best detection and characterization of renal solid lesions were obtained with the UTSE SPIR and the SE-EPI sequence (sensitivity: 100 and 75%, respectively; specificity: 90 and 75%, respectively). The FFE and FFE-EPI sequences showed lower sensitivity (86%) and the same specificity (75%). The staging of renal tumors was best achieved with the UTSE SPIR and SE-EPI sequence (84 and 73%, respectively). The staging was correct in only 47% and 58 for the FFE and FFE-EPI sequences, respectively. The investigated sequences showed no significant differences in CNR. The combination of fat suppression and breath-hold mode improves detection, characterization, and staging of renal lesions. The UTSE SPIR and SE-EPI sequence in breath-hold mode showed specific image artifacts, but offered high sensitivity and specificity for detection and characterization of renal lesions compared with the FFE sequence. The results of this study suggest, for T1-weighted imaging of renal tumors, use of UTSE or SE-EPI sequences with fat suppression in breath-hold mode for renal imaging.

Optimization and validation of a rapid high-resolution T1-w 3D FLASH water excitation MRI sequence for the quantitative assessment of articular cartilage volume and thickness

In view of follow up, survey and development of therapeutic strategies for osteoarthritis where cartilage deterioration plays an important role, a non invasive, reliable and quantitative assessment of the articular cartilage is desirable. The currently available high resolution T1-weighted (T1-w) 3D FLASH pulse sequences with frequency selective fat suppression are very time consuming. We have 1) optimized a high resolution T1-w 3D FLASH water excitation (WE) sequence for short acquisition time and cartilage visualization, and 2) validated this sequence for cartilage volume and thickness quantification. The spectral fat presaturation was replaced by selective water excitation. The flip angle of the WE sequence was optimized for the contrast to noise (C/Ncart) ratio of cartilage. Sagittal datasets (voxel size: 0.31 × 0.31 × 2 mm3) of the knees of nine healthy volunteers were acquired both, with the 3D FLASH WE (17.2/6.6/30°) sequence (WE) and a previously validated 3D FLASH fat saturated (42/11/30°) sequence (FS). For validation of the WE sequence, cartilage volume, mean and maximal cartilage thickness of the two sequences were compared. Reproducibility was assessed by calculating the coefficient of variation (COV %) of 4 consecutive WE data sets in the volunteers. The acquisition time was reduced from 16′30″ (FS) down to 7′14″ for the WE sequence. Image contrast and visualization of the cartilage was very similar, but delineation of the basal layer of the cartilage was slightly improved with the WE sequence. A flip angle of 30° provided the best C/Ncart ratios (WE). Reproducibility (COV) was between 1.9 and 5.9%. Cartilage volume and thickness agreed within 4% between FS and WE sequence. The WE sequence allows for rapid, valid and reproducible quantification of articular cartilage volume and thickness, prerequisites for follow-up examinations. The reduced acquisition time (50% of FS) enables routine clinical application and thus may contribute to a broader assessment of osteoarthritis.

Spectroscopic imaging (1H-2D-CSI) of the prostate: sequence optimization and correlation with histopathological results

Methodological optimization of a 1H MR spectroscopic imaging sequence (1H-2D-CSI) and evaluation of its potential to diagnose prostate cancer as validated by histopathological maps. The prostates of 18 patients were evaluated by 1H-MR-CSI (voxel dimension: 1 cm3) at 1.5 Tesla. This sequence was additionally combined with a frequency selective fat suppression. It was possible to distinguish prostate carcinoma from prostate hyperplasia spectroscopically by the ratio of citrate/(choline + creatine). Differentiation of high-grade prostatic intraepithelial neoplasia (PIN, high-grade) from prostate carcinoma was not unambiguously possible. Prediction of tumor differentiation was not possible by the ratio of citrate/(choline + creatine) by our maximum spatial resolution of 1 cm3. 1H-2D-CSI is suitable for tumor detection. Tumor differentiation was not possible with the spatial resolution used.

Use of pelvic surface coil MR imaging for assessment of clinically localized prostate cancer with histopathological correlation

We evaluated the ability of magnetic resonance imaging (MRI) operating at 1.0 Tesla with a Helmholz pelvic surface coil to predict the pathological stage of prostate carcinoma. Radiological diagnosis was based on fast spin-echo axial T2-weighted images with and without frequency selective fat-suppression and fast spin-echo coronal T2-weighted images. Thirty-one consecutive patients (mean age 61 years, range 49 to 71 years) underwent pelvic MRI before radical prostatectomy. Correlation with whole-mount step-sections of the surgical specimens showed that the tumours were correctly localized in all but one prostate gland in which the tumour could not be seen on pelvic MRI. The transverse diameter of the visible tumour at pelvic MRI appeared to represent an approximate estimate of the true tumour dimension. Based on histopathologic whole-mount step-sections of the surgical specimens, 22 of 31 patients (71%) had tumours extending beyond the confines of the prostatic capsule. The specificity for MRI to predict capsular penetration and seminal vesicle invasion was relatively high (0.80 and 0.86, respectively). The sensitivity was acceptable for capsular penetration (0.62) but poor for seminal vesicle invasion (0.30).

Discrimination between fluid, synovium, and cartilage in patients with rheumatoid arthritis: Contrast enhanced spin echo versus non-contrast-enhanced fat-suppressed gradient echo MR imaging

PURPOSE: The aim of this study was to compare fat-suppressed T1-weighted 3D-Gradient Echo (GE)-images and conventional T1-weighted contrast-enhanced SE images in the assessment of patients with rheumatoid arthritis in an attempt to improve discrimination of inflamed synovium, joint fluid, and cartilage. PATIENTS AND METHODS: 28 knee joints in 20 patients with rheumatoid arthritis were examined with a 3 D-GE-T1 weighted sequence with frequency-selective fat suppression (Flash 3D fat sat) and T1-weighted SE-sequences after intravenous gadolinium-containing contrast agent administration using a 1.5T system. Differentiation of cartilage, synovium, and joint effusion was assessed on both sequences qualitatively by two observers and quantitatively by signal intensity measurements. RESULTS: Qualititative analysis revealed higher grading rates for cartilage/fluid differentiation with fat-suppressed T1-weighted GE images than contrast enhanced T1-SE images. Quantitative analysis by measurements of contrast-to-noise ratios revealed significantly higher rates for the Flash 3D fat sat with regard to cartilage/fluid discrimination, significantly higher rates for T1-SE post-contrast for cartilage/synovium discrimination, and significantly higher rates for T1-SE post-contrast for synovium/fluid discrimination. CONCLUSION: 3D-GE-imaging with fat-suppressed T1 weighted sequences allows sufficient differentiation of cartilage and joint fluid in patients with rheumatoid arthritis without application of contrast agents and may assist in monitoring disease progression and response to therapy. The higher contrast to noise ratios of cartilage/synovium and synovium/fluid on T1-SE images following administration of gadolinium-containing contrast agents may improve detection of disease activity.

Detection of extracapsular extension of prostate cancer: role of fat suppression endorectal MRI.

The purpose of this work was to compare the efficacy of fat-suppressed and non-fat-suppressed fast spin echo (FSE) endorectal MRI in the detection of extracapsular extension (ECE) of prostate cancer by experienced and inexperienced readers. Seventy-nine patients with biopsy-proven prostate cancer underwent axial FSE T2-weighted endorectal MRI of the prostate prior to radical prostatectomy. Twenty-one patients were imaged with frequency-selective fat suppression, and 58 were imaged without fat suppression. All images were retrospectively and independently reviewed by two readers of different experience levels who were blinded to clinical and pathological findings. Readers assessed the presence or absence of ECE on a 5 point scale for each side of the prostate, and step-section pathology was used as the standard of reference in all patients. Receiver operating characteristics analysis was used to compare the performance of fat-suppressed and non-fat-suppressed images by both readers. ECE was present in 33 of 79 (42%) patients. The more experienced reader demonstrated better diagnostic performance (p < 0.05) than the less experienced reader in terms of sensitivity and area under the ROC curve (Az) for MRI without fat suppression. Use of frequency-selective fat suppression did not result in any significant improvement in diagnosis of ECE compared with MRI without fat suppression for either the experienced (Az 0.81 vs. 0.79) or the inexperienced (Az 0.76 vs. 0.68) reader. Even when reader experience is considered, use of frequency-selective fat suppression did not significantly improve the diagnosis of ECE by MRI. The decision to use fat suppression and the selection of a fat suppression technique can be left to the discretion of the individual reader.

Examination of the hand and wrist joints with a dedicated low-field MRI device

Purpose of this study was to evaluate the diagnostic value of a low field dedicated MRI system in hand and wrist imaging. All 308 exams of the hand and wrist, that were performed on a low-field dedicated MRI system (Artoscan, Esaote Biomedica, Italy) in our institution in 1996, and high-field MRI exams performed in addition as part of the diagnostic work-up, were evaluated and correlated to final operative (n = 64) and histologic (n = 12) reports. 90% of all low-field MRI scans stated a diagnosis according to clinical suspicion. In 62% the clinical question was answered, and in 26% additional pathologies were identified. An MR-diagnosis completely different from the clinical suspicion was stated in 2%. High field exams contributed additional information in 6 of 36 patients. In 3 patients a tumor was not shown completely in the limited field-of-view of the dedicated low-field MRI-system. Frequency-selective fat-suppression pulse sequences and a better spatial resolution were the reasons for the additional information obtained in the other three patients. Low-field dedicated MR-imaging is a valuable method in the extensive work-up of the hand and wrist. Osseous, ligamentous and tendinous pathologies are well depicted. Large or infiltrative tumors should be referred to a high-field system.

Presurgical Identification of Extradural Nerve Root Anomalies by Coronal Fat-Suppressed Magnetic Resonance Imaging

In an attempt to depict the anatomy of the nerve roots, we obtained magnetic resonance (MR) images of the lumbar spine in the coronal plane with the frequency-selective fat-suppression technique. With this technique, extradural anomalies were identified in 20 (6.7%) of 300 patients. We report the appearance on coronal MR images of six surgically confirmed extradural anomalous nerve roots together with the myelography findings. These include type Ia, type Ib, and type 3 anomalies. These are readily recognized and allow detailed evaluation of the type of nerve root anomaly.