Intravenous Injection Of Gd-DTPA Research Articles

A role for dynamic contrast-enhanced magnetic resonance imaging in predicting tumour radiation response.

Background:Dynamic contrast-enhanced (DCE) MRI may provide prognostic insights into tumour radiation response. This study examined quantitative DCE MRI parameters in rat tumours, as potential biomarkers of tumour growth delay following single high-dose irradiation.Methods:Dunning R3327-AT1 prostate tumours were evaluated by DCE MRI following intravenous injection of Gd-DTPA. The next day tumours were irradiated (single dose of 30 Gy), while animals breathed air (n=4) or oxygen (n=4); two animals were non-irradiated controls. Growth was followed and tumour volume-quadrupling time (T4) was compared with pre-irradiation DCE assessments.Results:Irradiation caused significant tumour growth delay (T4 ranged from 28 to 48 days for air-breathing rats, and 40 to 75 days for oxygen-breathing rats) compared with the controls (T4=7 to 9 days). A strong correlation was observed between T4 and extravascular-extracellular volume fraction (ve) irrespective of the gas inhaled during irradiation. There was also a correlation between T4 and volume transfer constant (Ktrans) for the air-breathing group alone.Conclusions:The data provide rationale for expanded studies of other tumour sites, types and progressively patients, and are potentially significant, as many patients undergo contrast-enhanced MRI as part of treatment planning.

Detection of liver metastases in patients with adenocarcinomas of the gastrointestinal tract: comparison of 18F-FDG PET/CT and MR imaging

Aim of our study was to compare the diagnostic performance of (18)F-FDG PET/CT and MR imaging (MRI) in the detection of liver metastases in patients with adenocarcinomas of the gastrointestinal tract. A total of 49 patients with adenocarcinomas of the gastrointestinal tract who had undergone (18)F-FDG PET/CT and MRI of the liver were included in this study. The MRI protocol included diffusion-weighted imaging and dynamic contrast-enhanced MR imaging after intravenous injection of Gd-DTPA. PET and MR images were analyzed by two experienced radiologists. Imaging results were correlated with histopathological findings or imaging follow-up as available. Sensitivities of both modalities were compared using McNemar Test. Receiver operating characteristic (ROC) curves were calculated to determine the diagnostic performance in correctly identifying liver metastases. A total of 151 metastases were confirmed. For lesion detection, MRI was significantly superior to (18)F-FDG PET/CT. Sensitivity of MRI in detecting metastases was 86.8% for Reader 1 (R1) and 87.4% for Reader 2 (R2), of PET/CT 66.2% for R1 and 68.2% for R2. Regarding only metastases with diameters of 10 mm or less, sensitivities of MRI were 66.7% for R1 and 75.0% for R2, and were significantly higher than those of PET/CT (17.9% for R1 and 20.5% for R2). ROC analysis showed superiority for lesion classification of MRI as compared to (18)F-FDG PET/CT. MRI is significantly superior to (18)F-FDG PET/CT in the detection and classification of liver metastases in patients with adenocarcinomas of the gastrointestinal tract, especially in the detection of small metastases.

The magnetic susceptibility effect of gadolinium-based contrast agents on PRFS-based MR thermometry during thermal interventions.

BackgroundProton resonance frequency shift (PRFS) magnetic resonance (MR) thermometry exploits the local magnetic field changes induced by the temperature dependence of the electron screening constant of water protons. Any other local magnetic field changes will therefore translate into incorrect temperature readings and need to be considered accordingly. Here, we investigated the susceptibility changes induced by the inflow and presence of a paramagnetic MR contrast agent and their implications on PRFS thermometry.MethodsPhantom measurements were performed to demonstrate the effect of sudden gadopentetate dimeglumine (Gd-DTPA) inflow on the phase shift measured using a PRFS thermometry sequence on a clinical 3 T magnetic resonance-guided high-intensity focused ultrasound (MR-HIFU) system. By proton nuclear magnetic resonance spectroscopy, the temperature dependence of the Gd-DTPA susceptibility was measured, as well as the effect of liposomal encapsulation and release on the bulk magnetic susceptibility of Gd-DTPA. In vivo studies were carried out to measure the temperature error induced in a rat hind leg muscle upon intravenous Gd-DTPA injection.ResultsThe phantom study showed a significant phase shift inside the phantom of 0.6 ± 0.2 radians (mean ± standard deviation) upon Gd-DTPA injection (1.0 mM, clinically relevant amount). A Gd-DTPA-induced magnetic susceptibility shift of ΔχGd-DTPA = 0.109 ppm/mM was measured in a cylinder parallel to the main magnetic field at 37°C. The temperature dependence of the susceptibility shift showed dΔχGd-DTPA/dT = -0.00038 ± 0.00008 ppm/mM/°C. No additional susceptibility effect was measured upon Gd release from paramagnetic liposomes. In vivo, intravenous Gd-DTPA injection resulted in a perceived temperature change of 2.0°C ± 0.1°C at the center of the hind leg muscle.ConclusionsThe use of a paramagnetic MR contrast agent prior to MR-HIFU treatment may influence the accuracy of the PRFS MR thermometry. Depending on the treatment workflow, Gd-induced temperature errors ranging between -4°C and +3°C can be expected. Longer waiting time between contrast agent injection and treatment, as well as shortening the ablation duration by increasing the sonication power, will minimize the Gd influence. Compensation for the phase changes induced by the changing Gd presence is difficult as the magnetic field changes are arising nonlocally in the surroundings of the susceptibility change.

Blood-Brain Barrier Permeability of Normal Appearing White Matter in Relapsing-Remitting Multiple Sclerosis

BackgroundMultiple sclerosis (MS) affects the integrity of the blood-brain barrier (BBB). Contrast-enhanced T1 weighted magnetic resonance imaging (MRI) is widely used to characterize location and extent of BBB disruptions in focal MS lesions. We employed quantitative T1 measurements before and after the intravenous injection of a paramagnetic contrast agent to assess BBB permeability in the normal appearing white matter (NAWM) in patients with relapsing-remitting MS (RR-MS).Methodology/Principal FindingsFifty-nine patients (38 females) with RR-MS undergoing immunomodulatory treatment and nine healthy controls (4 females) underwent quantitative T1 measurements at 3 tesla before and after injection of a paramagnetic contrast agent (0.2 mmol/kg Gd-DTPA). Mean T1 values were calculated for NAWM in patients and total cerebral white matter in healthy subjects for the T1 measurements before and after injection of Gd-DTPA. The pre-injection baseline T1 of NAWM (945±55 [SD] ms) was prolonged in RR-MS relative to healthy controls (903±23 ms, p = 0.028). Gd-DTPA injection shortened T1 to a similar extent in both groups. Mean T1 of NAWM was 866±47 ms in the NAWM of RR-MS patients and 824±13 ms in the white matter of healthy controls. The regional variability of T1 values expressed as the coefficient of variation (CV) was comparable between the two groups at baseline, but not after injection of the contrast agent. After intravenous Gd-DTPA injection, T1 values in NAWM were more variable in RR-MS patients (CV = 0.198±0.046) compared to cerebral white matter of healthy controls (CV = 0.166±0.018, p = 0.046).Conclusions/SignificanceWe found no evidence of a global BBB disruption within the NAWM of RR-MS patients undergoing immunomodulatory treatment. However, the increased variation of T1 values in NAWM after intravenous Gd-DTPA injection points to an increased regional inhomogeneity of BBB function in NAWM in relapsing-remitting MS.

Dynamic contrast-enhanced magnetic resonance imaging of the wrist in early arthritis

MRI has been proposed as the imaging method of choice to evaluate the long-term outcome in patients with early arthritis. The role of dynamic MRI, performed at presentation, in predicting the outcome of patients with early arthritis has been addressed in the present study. 39 patients with early arthritis, involving at least one wrist, were studied with clinical visits and laboratory investigations, every 3 months. Dynamic MRI was performed with a low-field (0.2T), extremity-dedicated machine (Artoscan, Esaote, Genova, Italy) equipped with a permanent magnet and with a dedicated hand and wrist coil. During the intravenous injection of Gd-DTPA, twenty consecutive fast images of 3 slices of the wrist were acquired. The synovial contrast enhancement ratio was calculated both as rate of early enhancement (REE) per second during the first 55" and as relative enhancement (RE) at t seconds. In our cohort of patients, REE and RE were significantly lower than those observed in a historical cohort of 36 patients with active rheumatoid arthritis. In univariate analysis, low RE predicted complete remission of arthritis. In multivariate analysis, fulfillment of RA criteria during follow-up was predicted by high RE. The need for immunosoppressive treatment at the end of follow-up was predicted by both low RE and high REE. Dynamic MRI may be used to predict several outcomes of early arthritis involving the wrist.

Abstract 4189: Characterization of tumor progression and chemoresponse in a novel transgenic mouse model of neuroblastoma (TH-MYCN) using magnetic resonance imaging

Abstract Neuroblastoma is the most common extracranial childhood solid tumour, accounting for between 7-10% of paediatric cancers, and originates in peripheral nerve tissues. The proto-oncogene MYCN is amplified in 25% of high-risk neuroblastoma and is associated with an aggressive tumour phenotype, enhanced tumour angiogenesis and poor clinical prognosis. The Mycn oncoprotein is highly expressed in tumour but not in normal tissues, making it an attractive candidate for targeted therapeutics. To assess the relevance of MYCN overexpression in neuroblastoma, and to test Mycn-targeted therapeutics, a murine transgenic model that faithfully replicates the disease biology of high-risk neuroblastoma by targeting overexpression of MYCN to the neural crest was constructed. As a prelude to the assessment of novel therapeutics for the treatment of neuroblastoma, and given the retroperitoneal localisation of these tumours, the TH-MYCN model has been characterised in vivo by non-invasive MRI. Mice with abdominal tumours identified by palpation were imaged on a 7T Bruker MicroImaging system (n=7). Anatomical T2-weighted coronal images revealed that all TH-MYCN mice developed large peri-renal retroperitoneal tumours, likely originating from the adrenal glands, that displaced major abdominal organs (kidney, liver, stomach). Major vessels were characteristically distorted, with enlargement of the abdominal aorta and vena cava. Forty-eight hours after treatment with cyclophosphamide (100mg/kg x 2 doses, over 48 hours), tumours were difficult to identify or were undetectable, consistent with previous studies showing remission in TH-MYCN and with the clinical sensitivity of childhood neuroblastoma to CP. Further screening of these mice by MRI is ongoing to interrogate tumour relapse. Additionally, quantitation of tumour MRI relaxation rates revealed a very heterogeneous spatial distribution of T1 (1748 ± 14ms), T2 (55 ± 1ms) and R2* (115 ± 3s−1). The relatively fast baseline R2* is indicative of a large tumour blood volume, confirmed by the intense red coloration of these tumours at excision, and the presence of a large proportion of blood lakes observed histologically. The high degree of tumour perfusion was corroborated by dynamic contrast-enhanced MRI following intravenous injection of Gd-DTPA, and which revealed parenchymal enhancement typically across the whole tumour (IAUGC60 = 0.13 ± 0.01ms). This study reinforces the TH-MYCN murine model as a faithful representation of human neuroblastoma in its anatomical and radiological appearance, and in its high sensitivity to CP. It also demonstrates that the implementation of MRI screening is an asset in the development of novel therapeutics for neuroblastoma and could accelerate their clinical development by allowing simultaneous evaluation of MRI biomarkers of treatment response. Note: This abstract was not presented at the AACR 101st Annual Meeting 2010 because the presenter was unable to attend. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 4189.

Longitudinal quantitative MR imaging of cartilage morphology in the presence of gadopentetate dimeglumine (Gd‐DTPA)

MRI-based cartilage morphometry can monitor cartilage loss in osteoarthritis. Intravenous Gd-DTPA injection is needed for compositional (proteoglycan) cartilage imaging with delayed gadolinium enhanced MRI (dGEMRIC). However, longitudinal changes of cartilage morphology have not been compared in the presence and absence of Gd-DTPA. Baseline and 2-year follow-up images were acquired in 41 female participants with definite medial radiographic osteoarthritis, both before and 2 h after Gd-DTPA injection, and cartilage thickness was measured. In the absence of Gd-DTPA, a 2.6% reduction in cartilage thickness was observed between baseline and follow-up in the central subregion of the medial femorotibial compartment (standardized response mean [SRM]= -0.33; P<0.05), but only a 0.7% reduction (SRM= -0.10; P=0.51) in the presence of Gd-DTPA. The findings suggest that morphometric cartilage measurement in the presence of Gd-DTPA needs to undergo further validation, before one can recommend longitudinal dGEMRIC and morphological cartilage imaging to be performed in a single session.

Correlation Between Left Ventricular Diastolic Function and Ejection Fraction in Dilated Cardiomyopathy Using Magnetic Resonance Imaging With Late Gadolinium Enhancement

The distribution of left ventricular (LV) fibrosis and the percent fibrosis in patients with dilated cardiomyopathy (DCM) were evaluated using late gadolinium enhanced (LGE) MRI. Then the relation with the LV ejection fraction (EF) and deceleration time (DT), an index of diastolic function obtained using echocardiography, was investigated. LGEMRI at 20 min after intravenous injection of Gd-DTPA (0.15 +/-0.03 mmol/kg) was performed in 17 patients with DCM. The distribution of the LV enhanced area and LGE rate (%) were calculated. EF, as well as E/A ratio and DT were obtained using echocardiography. LGE was observed in 15 out of 17 patients (88%) and the enhanced region appeared to represent myocardial fibrosis. The LV fibrosis was often found in the intraventricular septum (IVS), but there were no differences in its distribution. The LGE rate (%) had a correlation between cardiac magnetic resonance ejection fraction (CMREF) (Y = 51.7 - 2.1X [R(2) = 0.23, P<0.001]) and DT (Y = 162.2 +12.0X [R(2) = 0.35, P<0.001]). The LV fibrosis is often found in the IVS with DCM. A correlation exists between LGE rate (%) to EF on CMR and DT on echocardiography in patients with DCM.

Quantitative imaging of cartilage morphology at 3.0 Tesla in the presence of gadopentate dimeglumine (Gd‐DTPA)

MRI-based cartilage morphometry was previously validated in the absence of gadopentate dimeglumine (Gd-DTPA). However, Gd-DTPA is required for compositional (proteoglycan) imaging using delayed gadolinium-enhanced MRI of cartilage (dGEMRIC). Therefore, the effect of Gd-DTPA on cartilage morphometry was studied. A total of 165 female participants (67 with and 98 without osteoarthritis [OA]) were imaged at 3.0 Tesla before and 2 hr after intravenous Gd-DTPA injection. Flip angles in post-Gd-DTPA scans varied between 12 degrees and 35 degrees . Cartilage volume and thickness of post- vs. pre-Gd-DTPA scans showed intraclass correlation coefficients (ICCs) of 0.85 > or = r > or = 0.95, mean differences between -2.1% and +1.1%, and standard deviations (SDs) of differences between 4.7% and 9.2%. Mixed-effect models found no consistent impact of flip angle and OA status on post- vs. pre-Gd-DTPA differences. Accurate morphological measurements of cartilage can be obtained after Gd-DTPA injection, allowing compositional and morphological imaging to be combined into one session.

Magnetic Resonance Imaging of Acute Reperfused Myocardial Infarction: Intraindividual Comparison of ECIII-60 and Gd-DTPA in a Swine Model

To compare a necrosis-avid contrast agent (NACA) bis-Gd-DTPA-pamoic acid derivative (ECIII-60) after intracoronary delivery with an extracellular agent Gd-DTPA after intravenous injection on magnetic resonance imaging (MRI) in a swine model of acute reperfused myocardial infarction (MI). Eight pigs underwent 90 min of transcatheter coronary balloon occlusion and 60 min of reperfusion. After intravenous injection of Gd-DTPA at a dose of 0.2 mmol/kg, all pigs were scanned with T1-weighted MRI until the delayed enhancement of MI disappeared. Then they were intracoronarily infused with ECIII-60 at 0.0025 mmol/kg and imaged for 5 hr. Signal intensity, infarct-over-normal contrast ratio and relative infarct size were quantified, compared, and correlated with the results of postmortem MRI and triphenyltetrazolium chloride (TTC) histochemical staining. A contrast ratio over 3.0 was induced by both Gd-DTPA and ECIII-60. However, while the delayed enhancement with Gd-DTPA virtually vanished in 1 hr, ECIII-60 at an 80x smaller dose depicted the MI accurately over 5 hr as proven by ex vivo MRI and TTC staining. Both Gd-DTPA and ECIII-60 strongly enhanced acute MI. Comparing with fading contrast in a narrow time window with intravenous Gd-DTPA, intracoronary ECIII-60 persistently demarcated the acute MI, indicating a potential method for postprocedural assessment of myocardial viability after coronary interventions.

Retinoblastoma—MR appearance using a surface coil in comparison with histopathological results

The purpose of this work was to evaluate the characteristic appearance of untreated retinoblastoma on a large sample in comparison to the histological findings after therapeutical enucleation. In a prospective clinical trial 46 children with retinoblastoma in 63 affected untreated eyes were examined under general anesthesia on MRI using a 1.5-T system. The examinations were performed with a special surface coil applying an examination protocol including fast T2- and T1-weighted spin echo sequences and additional fast T1-WI after intravenous injection of Gd-DTPA in different planes. The imaging results were compared to the histopathological findings in 29 patients with 30 affected eyes. Comparing MRI findings and histopathological results, optic nerve infiltration was detected with a sensitivity of 53.8% and a specificity of 82.3% on MRI, infiltration of the choroid with a sensitivity of 75.0% and a specificity of 100.0%, and the degree of tumor calcification with a sensitivity of 91.7% and a specificity of 88.9%. In this study the characteristic MR appearance of untreated retinoblastoma was evaluated. MRI was helpful in relevant aspects of pretherapeutical retinoblastoma staging, deficits remain regarding optic nerve infiltration.

MRI diagnosis of benign sacrococcygeal teratomas of the infants

To investigate the value of MR imaging in the diagnosis of benign sacrococcygeal teratomas of the infants. MR imaging of benign sacrococcygeal teratomas in 6 cases proved by surgery and pathology was retrospectively reviewed. In all patients, a fast imaging sequence, fast spin echo sequence was employed, together with short time inversion recovery sequence and contrast enhancement scanning by intravenous injection of Gd-DTPA. There were 6 benign sacrococcygeal teratomas, which were heterogeneous masses and arose from the distal sacrococcygeal region in the pelvis. The MR imaging appearances of the benign sacrococcygeal teratomas were characteristic, T1- and T2-weighted images demonstrated a large mass containing round, well-defined areas of varying signal intensity representing its cystic, solid, and sometimes fat, calcification within the lesions. MR imaging provides definitive information of benign sacrococcygeal teratomas and clearly shows both extra-and intra-pelvic components, and even better anatomic details, which facilitates the surgical planning adequately.

Cartilage glycosaminoglycan loss in the acute phase after an anterior cruciate ligament injury: Delayed gadolinium‐enhanced magnetic resonance imaging of cartilage and synovial fluid analysis

To examine the glycosaminoglycan (GAG) content in cartilage and that in synovial fluid and determine whether they are associated, in patients with an acute anterior cruciate ligament (ACL) injury. Twenty-four patients (14 of whom were male) with a mean age of 27 years (range 17-40 years) were assessed with delayed gadolinium-enhanced magnetic resonance imaging (MRI) of cartilage an average of 3 weeks after an ACL rupture and compared with 24 healthy volunteers. Two hours after an intravenous injection of Gd-DTPA(2-) (0.3 mmoles/kg body weight), quantitative measurements of the T1 relaxation time (T1(Gd) [T1 relaxation time in the presence of Gd-DTPA]) were made in lateral and medial femoral weight-bearing cartilage. In the patients, synovial fluid was aspirated immediately before the MRI, and GAG was analyzed using dye precipitation with Alcian blue. Fifteen of the 24 patients had an isolated bone bruise in the lateral femoral condyle, where the cartilage T1(Gd) was shorter than that in the controls (mean +/- SD 385 +/- 83 msec and 445 +/- 41 msec, respectively; P = 0.004), consistent with decreased GAG content. However, the T1(Gd) was also decreased in the medial femoral cartilage, where bone bruises were rare (376 +/- 76 msec in patients versus 428 +/- 38 msec in controls; P = 0.006). The mean +/- SD synovial fluid GAG concentration in patients was 157 +/- 86 mug/ml and showed a positive correlation with the T1(Gd) (r = 0.49, P = 0.02). This study indicates that an ACL injury causes posttraumatic edema of the lateral femoral cartilage but initializes a generalized biochemical change within the knee that leads to GAG loss from both lateral and medial femoral cartilage. In cartilage with a high GAG content (long T1(Gd)), more GAG is released into the synovial fluid, suggesting that cartilage quality is a factor to consider when interpreting cartilage biomarkers of metabolism.

Functional evaluation of normothermic ischemia and reperfusion injury in dog kidney by using MR perfusion-weighted imaging

目的 结合病理对照研究MR灌注成像评价犬肾缺血再灌注损伤后肾功能的变化.方法雄性家犬12只随机分成4组,分别结扎左侧肾动脉30、60、90和120 min,开放后再灌注损伤1 h.MR检查选择5个时间段,即动脉结扎前、动脉结扎后即刻、动脉开放前、动脉开放后即刻和再灌注损伤后,分别进行常规T2WI和(或)重T2WI(T2*WI)[包括:真实稳态进动快速成像(true-FISP),快速自旋回波(TSE),平面回波成像(EPI)]和T1WI,最后进行灌注加权成像(PWI)[采用反转恢复快速小角度激发(IR-turbo-FLASH)序列]检查.测量肾皮层(C)、外髓层(OM)和内髓层(IM)的信号强度值(SI),比较不同时间段肾脏各层之间的信号变化,并绘制信号强度与时间关系曲线(SI-T曲线).选择曲线峰值(P)、达峰时间(Tp)和曲线下面积(A)作半定量分析.结果动脉结扎后,在T2WI、T2*WI上左肾各层信号明显下降;动脉开放后,EPI各组中左肾OM和IM信号仍明显低于右肾.右肾各层SI-T曲线清晰显示三期增强方式,而左肾OM和IM均表现为单期增强,无明显的增强峰出现,且曲线下面积较右肾明显减低.结论PWI能较准确地评价缺血再灌注损伤后肾功能的变化。

MRS of hyperpolarized 129BXe in the chest of mouse—effect of contrast agents on the MRS

Use of hyperpolarized noble gases with MRI/magnetic resonance spectroscopy (MRS) has been expected as a new technique for functional imaging. The noble gases ( 3He and 129Xe) polarized by optical pumping have enabled visualization of the lung gas space. We report the spectroscopy of the gas or dissolved phase of 129Xe in the lungs of mice. The effect of an intravenous injection of MRI contrast agent was examined in relation to the signal assignment, which was essential for the analysis of lung functions. After inhalation of hyperpolarized xenon gas, gas and dissolved phase signals of 129Xe were observed at 0–10 and 190–200 ppm, respectively, in the chests of mice. The dissolved phase signals decreased in intensity immediately after intravenous injection of Gd-DTPA. These signals were assigned to originate from plasma or interstitial space in the lung, considering the distribution of the contrast agent. Such a study would be useful for the diagnosis of lung function.

Parametric and quantitative analysis of MR renographic curves for assessing the functional behaviour of the kidney

The aim of this study was to refine the description of the renal function based on MR images and through transit-time curve analysis on a normal population and on a population with renal failure, using the quantitative model of the up-slope. Thirty patients referred for a kidney MR exam were divided in a first population with well-functioning kidneys and in a second population with renal failure from ischaemic kidney disease. The perfusion sequence consisted of an intravenous injection of Gd-DTPA and of a fast GRE sequence T1-TFE with 90° magnetisation preparation (Intera 1.5 T MR System, Philips Medical System). To convert the signal intensity into 1/T1, which is proportional to the contrast media concentration, a flow-corrected calibration procedure was used. Following segmentation of regions of interest in the cortex and medulla of the kidney and in the abdominal aorta, outflow curves were obtained and filtered to remove the high frequency fluctuations. The model of the up-slope method was then applied. Significant reduction of the cortical perfusion ( Q c=0.057±0.030 ml/(s 100 g) to Q c=0.030±0.017 ml/(s 100 g), P<0.013), of the medullary perfusion ( Q m=0.023±0.018 ml/(s 100 g) to Q m=0.011±0.006 ml/(s 100 g), P<0.046) and of the accumulation of contrast media in the medulla ( Q a=0.005±0.003 ml/(s 100 g) to Q a=0.0009±0.0008 ml/(s 100 g), P<0.001) were found in presence of renal failure. High correlations were found between the creatinine level and the accumulation Q a in the medulla ( r 2=0.72, P<0.05), and between the perfusion ratio Q c/ Q m and the accumulation Q a in the medulla ( r 2=0.81, P<0.05). No significant difference was found in times to peak between both populations despite a trend showing T a the time to the end of the increasing contrast accumulation period in the medulla, arriving later for renal failure. Advances in MR signal calibration with the building of quantitative model such as the up-slope allow to assess kinetic and haemodynamic and functional parameters of the diseased kidney.

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-DTPA(2-). 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-DTPA(2-) 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.

MR to assess renal function in children.

Renal function evaluation in the pediatric patient is generally based on scintigraphic examinations where a baseline gamma-camera renography is used to determine single kidney function, and diuresis renography is obtained to assess urinary drainage from the pelvicalyceal system. Magnetic resonance imaging also permits the evaluation of renal functional processes using fast dynamic sequences. Principally, an agent cleared by renal excretion is intravenously injected and its cortical uptake, parenchymal transport, and eventually its urinary excretion are followed with serial images. Different approaches have been presented most of which are based on T1-weighted gradient-recalled echo sequences with short TR and TE and a low flip angle obtained after intravenous injection of Gd-DTPA or Gd-DOTA. These techniques permit renal functional assessment using different qualitative and quantitative parameters; however, most of these methods are not suitable for the evaluation of urinary tract dilatation in infants and children. For the diagnostic work-up of children with congenital urinary tract obstruction and malformation a technique was developed which permits quantitative determination of single kidney function, in addition to evaluating urinary excretion disturbances analogous to that possible with scintigraphy.

Inflammatory change in the upper joint space in temporomandibular joint with internal derangement on Gadolinium-enhanced MR imaging

Abstract.The object of this study was to clarify the relationship between gadopentetate dimeglumine (Gd-DTPA) contrast enhancement of the upper joint space and the severity of internal derangement of the temporomandibular joint (TMJ). Fifty patients with 63 painful TMJs underwent 1.5T MR imaging with T1-weighted images before and after an intravenous injection of Gd-DTPA with or without fat suppression. The relationship was investigated between the contrast enhancement at the upper joint space and disc position, disc morphology or bone morphology. Of the 63 joints, a significant contrast enhancement in the upper joint space was detected in 32 joints. There was a significant high incidence of anterior disc displacement without reduction in the contrast-enhancement positive group compared to the negative group (P=0.021), but there was no significant difference for disc morphology (P=0.094) and bone morphology (P=0.384). Gd-DTPA enhanced MR imaging may potentially have diagnostic value for internal derangements of TMJs.

Value of Subtraction Technique in Gd-DTPA-enhanced Magnetic Resonance Angiography of the Thoracic Aorta

AIM: To assess routine image subtraction in 3D gadopentate dimeglumine (Gd-DTPA)-enhanced magnetic resonance (MR) angiography of the thoracic aorta. MATERIALS AND METHODS: This was a prospective study of 22 consecutive patients referred for magnetic resonance imaging (MRI) of the thoracic aorta. All patients had 3D MR aortography (TR/TE/FA; 5/2 ms/25°) performed before and after bolus intravenous injection of Gd-DTPA. The Gd-DTPA enhanced and unenhanced data sets were subtracted and maximum intensity projections (MIP) projections of the thoracic aorta were performed. The standard unsubtracted MIP images were initially evaluated. These were then reviewed together with the subtracted images to assess for additional diagnostic information. Signal to noise ratios (SNR) and contrast to noise ratios (CNR) were measured. RESULTS: In four cases there was mild image degradation due to patient movement. In no case did subtraction alter the diagnosis. The mean SNR in the unsubtracted MIP images was 10.8±4.0 (median 11.1) and on the subtracted images was 21.2±9.9 (median 20.7;P<0.0001). The mean aorta-to-mediastinal fat CNR was 3.9±2.8 (median 3.9) on the unsubtracted images and 15.0±10.6 (median 13) on the subtracted images (P<0.0001). The mean aorta-to-vertebral body CNR was 5.2±3.1 (median 4.4) on the unsubtracted images and 15.1±9.3 on the subtracted images (P<0.0001). CONCLUSION: Image subtraction significantly improved both the SNR and CNR, but did not alter the final diagnosis, and does not appear warranted in routine practice. O’Connell, M.J. and Murray, J.G.(2001). Clinical Radiology56, 545–549