Peter Leander

Delayed gadolinium-enhanced MRI of cartilage (dGEMRIC) in early knee osteoarthritis.

Delayed contrast‐enhanced MRI of cartilage (dGEMRIC) is a noninvasive technique to study cartilage glycosaminoglycan (GAG) content in vivo. This study evaluates dGEMRIC in patients with preradiographic degenerative cartilage changes. Seventeen knees in 15 patients (age 35–70) with arthroscopically verified cartilage changes (softening and fibrillations) in the medial or lateral femoral compartment, knee pain, and normal weight‐bearing radiography were included. MRI (1.5 T) was performed precontrast and at 1.5 and 3 hr after an intravenous injection of Gd‐DTPA2− at 0.3 mmol/kg body weight. T1 measurements were made in regions of interest in medial and lateral femoral cartilage using sets of five turbo inversion recovery images. Precontrast, R1 (R1 = 1/T1, 1/s) was slightly lower in diseased compared to reference compartment, indicating increased hydration (P = 0.01). Postcontrast, R1 was higher in diseased than in reference compartment at 1.5 hr, 3.45 ± 0.90 and 2.64 ± 0.58 (mean ± SD), respectively (P < 0.01), as well as at 3 hr, 2.94 ± 0.60 and 2.50 ± 0.37, respectively (P = 0.01). The washout of the contrast medium was faster in diseased cartilage as shown by a higher R1 at 1.5 than at 3 hr in the diseased but not in the reference compartment. In conclusion, dGEMRIC can identify GAG loss in early stage cartilage disease with a higher sensitivity at 1.5 than 3 hr. Magn Reson Med 49:488–492, 2003.

dGEMRIC (delayed gadolinium-enhanced MRI of cartilage) indicates adaptive capacity of human knee cartilage.

Delayed gadolinium‐enhanced MRI of cartilage (dGEMRIC) is a new imaging technique to estimate joint cartilage glycosaminoglycan content by T1‐relaxation time measurements after penetration of the hydrophilic contrast agent Gd‐DTPA2‐. This study compares dGEMRIC in age‐matched healthy volunteers with different levels of physical activity: Group 1 (n = 12): nonexercising individuals; Group 2 (n = 16): individuals with physical exercise averaging twice weekly; Group 3 (n = 9): male elite runners. dGEMRIC was performed 2 hr after an intravenous injection of Gd‐DTPA2‐ at 0.3 mmol/kg body weight. T1 differed significantly between the three different levels of physical exercise. T1 values (mean of medial and lateral femoral cartilage) for Groups 1, 2, and 3 were: 382 ± 33, 424 ± 22 and 476 ± 36, respectively (ms, mean ± SD) (P = 0.0004, 1 vs. 2 and 0.0002, 2 vs. 3). Irrespective of the exercise level, T1 was longer in lateral compared to medial femoral cartilage (P = 0.00005; n = 37). In conclusion, this cross‐sectional study indicates that human knee cartilage adapts to exercise by increasing the glycosaminoglycan content. Furthermore, results suggest a compartmental difference within the knee with a higher glycosaminoglycan content in lateral compared to medial femoral cartilage. A higher proportion of extracellular water, i.e., larger distribution volume, may to some extent explain the high T1 in the elite runners. Magn Reson Med 51:286–290, 2004.

Gd-DTPA2)-enhanced MRI of femoral knee cartilage: a dose-response study in healthy volunteers

The negatively charged contrast agent Gd‐DTPA2– distributes inversely to the cartilage fixed charged density. This enables structural cartilage examinations by contrast‐enhanced MRI. In line with the development of a clinically applicable protocol for such examinations, this study describes the temporal pattern of Gd‐DTPA2– distribution in femoral knee cartilage at three different doses in healthy volunteers. Nineteen volunteers (ages 21–28 years) were examined with a 1.5T MRI system. Quantitative relaxation rate measurements were made in weight‐bearing central parts of femoral cartilage using sets of five turbo inversion recovery images with different inversion times. The cartilage was analyzed before and four times (1–4 h) after an intravenous injection of Gd‐DTPA2– at single, double, and triple doses: 0.1, 0.2, and 0.3 mmol/kg body weight, respectively. The increase in R1 postcontrast was linearly dose‐related at all times. The highest R1 values were registered at 2 and 3 h postcontrast, suggesting 2 h to be optimal in the clinical situation. The triple dose indicated a subtle compartmental difference in men, with higher contrast distribution medially than laterally. Results suggest that the triple dose is needed to detect minor cartilage matrix differences. Magn Reson Med 46:1067–1071, 2001.

Radiology of the spleen

Abstract The spleen is generally not considered a challenge to the radiologist. Most often it poses a problem by anomalies or an irregular but normal contrast enhancement; however, a variety of inflammatory, infectious and neoplastic diseases may involve the spleen. CT and ultrasonography are screening modalities for the spleen. For problem solving, MR imaging can be helpful, especially due to its free choice of the imaging plane and because of the high resolution in contrast MR imaging. Splenic angiography as a diagnostic tool has generally been replaced by CT, ultrasound, or MR and is now used as an interventional method, e. g., in non-surgical management of patients with chronic idiopathic thrombocytopenia or in patients with splenic trauma. This article reviews the radiology of the spleen, including anatomy, embryology, splenomegaly, splenic injury, infarction, cysts, tumors, abscesses, sarcoidosis, and AIDS. Knowledge about the use of different imaging modalities and underlying gross and microscopic pathologic features leads to a better understanding of the radiologic findings.

Delayed gadolinium-enhanced MRI of cartilage (dGEMRIC): intra- and interobserver variability in standardized drawing of regions of interest.

Purpose: To establish the reproducibility of a standardized region of interest (ROI) drawing procedure in delayed gadolinium‐enhanced magnetic resonance imaging (MRI) of cartilage (dGEMRIC). Material and Methods: A large ROI in lateral and medial femoral weight‐bearing cartilage was drawn in images of 12 healthy male volunteers by 6 investigators with different skills in MRI. The procedure was done twice, with a 1‐week interval. Calculated T1‐values were evaluated for intra‐ and interobserver variability. Results: The mean interobserver variability for both compartments ranged between 1.3% and 2.3% for the 6 different investigators without correlation to their experience in MRI. Post‐contrast intra‐observer variability was low in both the lateral and the medial femoral cartilage, 2.6% and 1.5%, respectively. The larger variability in lateral than in medial cartilage was related to slightly longer and thinner ROIs. Conclusion: Intra‐observer variability and interobserver variability are both low when a large standardized ROI is used in dGEMRIC. The experience of the investigator does not affect the variability, which further supports a clinical applicability of the method.

Hyperpolarized (3)He apparent diffusion coefficient MRI of the lung: Reproducibility and volume dependency in healthy volunteers and patients with emphysema.

To measure the apparent diffusion coefficient (ADC) of hyperpolarized (HP) 3He gas using diffusion weighted MRI in healthy volunteers and patients with emphysema and examine the reproducibility and volume dependency.

Is administration of gadolinium-based contrast media to pregnant women and small children justified?

The use of gadolinium‐based contrast media in pregnant or lactating women has been discouraged at many radiology departments due to the lack of knowledge of the risks for the fetus and the unwillingness to expose neonates to unnecessary drugs. In the present review the current literature and present guidelines regarding the use of gadolinium‐based contrast media have been reviewed to validate the justification for their administration to pregnant or lactating women and small children. J. Magn. Reson. Imaging 2011;.

Validity of apparent diffusion coefficient hyperpolarized 3He-MRI using MSCT and pulmonary function tests as references.

PURPOSE To compare apparent diffusion coefficient (ADC) measurements from hyperpolarized (HP) helium ((3)He)-magnetic resonance imaging (MRI) with quantitative data from multislice Computed Tomography (CT) (MSCT) of the whole lungs and pulmonary function tests (PFT). MATERIALS AND METHODS Twenty-seven subjects, 22 with established emphysema and 5 with preclinical emphysema defined by PFT criteria, were examined with HP (3)He-MRI and MSCT. Mean age was 55 (+/-12) years, 18 female and 9 male. Mean ADC from (3)He-MRI was compared with emphysema index (EI), 15th percentile and mean lung density (MLD) values from MSCT. Both mean ADC and MSCT data were compared to PFT, especially percent of predicted diffusing capacity of carbon monoxide (%predicted DLCO), using Pearsons correlation test. RESULTS Mean ADC and standard deviation values were 0.392+/-0.119 cm(2)/s for the established emphysema group and 0.216+/-0.046 for the pre-clinical emphysema group. MSCT values for the established emphysema group and pre-clinical emphysema group were: EI (%) 11+/-12 and 0.4+/-0.6, respectively; 15th percentile (Hounsfield Units (HU)), -956+/-25 and -933+/-13, respectively and MLD (HU) -877+/-20 and -863+/-15, respectively. Correlations between mean ADC and EI and 15th percentile were both r=0.90 and for MLD r=0.59. There was higher correlation between mean ADC and %predicted DLCO (r=0.90) than between EI and %predicted DLCO (r=0.76). CONCLUSION HP (3)He-MRI correlates well with density measurements from MSCT and agrees better than MSCT with %predicted DLCO which is the PFT most related to emphysema.

Image artifacts due to a time-varying contrast medium concentration in 3D contrast-enhanced MRA.

The purpose of this work was to study image effects due to time‐varying contrast medium concentration in contrast‐enhanced three dimensional (3D) magnetic resonance angiography (MRA) images. Two different simulation models (1D and 3D) and two different contrast medium variation schemes were used. Phantom measurements were also performed. Experiments were performed for several different bolus timings. Similar sequence and image object parameters were used in both simulations and measurements (TE/TR 2.1/7.8 mses, flip angle 30°, T1/T2 1200‐80/150‐40 msec, flow velocity 100 cm/sec). A small variation in bolus timing yielded large variations in the appearance of the image effects, especially if the center of k‐space was sampled in the vicinity of rapid contrast medium concentration variation. For a typical bolus injection in a patient, a severe signal loss but only minor ringing and edge artifacts appeared if the bolus injection was poorly timed. Effects of pulsatile flow were minor. The 3D model proved to be a useful tool in these studies. J. Magn. Reson. Imaging 1999;10:919–928.

MR imaging in clinically suspected acute cholecystitis: A comparison with ultrasonography

Purpose: The diagnostic value of fast pulse sequences in MR imaging was compared with US in patients with clinically suspected acute cholecystitis. Material and Methods: In a prospective study of 94 patients, 35 were examined with both MR and US within 24 h. Results: MR diagnoses were acute cholecystitis in 23, gallbladder and common bile duct stones in 3, other pathologic conditions of the abdomen in 7 and normal in 2 patients. US diagnoses were acute cholecystitis in 17, gallbladder stones in 8, other pathologic conditions of the abdomen in 2, normal in 5 and non-conclusive in 3 patients. Conclusion: MR has a higher sensitivity than US for diagnosing acute cholecystitis and, with increased accessibility, may be the first imaging method.