T2*-Correction in Dynamic Contrast-Enhanced Magnetic Resonance Imaging of Glioblastoma From a Half Dose of High-Relaxivity Contrast Agent.

OBJECTIVE: The aim of this study was to evaluate the arterial input function (AIF) and tissue enhancement time curve (tissue function [TF]) obtained after the administration of a half-dose gadobenate dimeglumine (0.05-mmol/kg body weight [bw]) compared with a full dose (0.1-mmol/kg bw) of a standard-relaxivity contrast agent. METHODS: We enrolled 40 adult patients with glioblastoma in an interindividual comparative study. Patients were randomized to 1 of the 2 study arms: 20 patients received 0.1-mmol/kg bw of gadoterate; the other 20 patients received 0.05-mmol/kg bw of gadobenate. The patients underwent dynamic contrast-enhanced magnetic resonance imaging examinations. Arterial input function, tissue enhancement time curve (TF), tumor transfer rate (K), and tumor extracellular-extravascular volume fraction (Ve) were calculated for each patients. Averaged AIF, TF, K, and Ve of both groups were compared. RESULTS: A significant difference (P = 0.001) between the peak AIF values obtained with the 2 different gadolinium-based contrast agents was observed. No difference was found between TFs (P = 0.35). Comparison on kinetic parameters revealed a significant difference for K (P = 0.047) but no difference for Ve (P = 0.74). CONCLUSIONS: The administration of half dose of the high-relaxivity contrast agent gadobenate is effective in improving AIF by reducing T2*-shortening effects on dynamic contrast-enhanced magnetic resonance imaging and ensuring at the same time an adequate signal enhancement in tumor tissue. The use of 0.05-mmol/kg bw of gadobenate not only is feasible but also can lead to a better estimation of K based on a more accurate AIF assessment.

Effectiveness of a high relaxivity contrast agent administered at half dose in dynamic susceptibility contrast MRI of brain gliomas.

PURPOSE: To determine whether half of the approved dose of gadobenate dimeglumine (MultiHance) is as effective as a full dose of gadoterate meglumine (Dotarem) for qualitative and quantitative cerebral blood volume (CBV) perfusion evaluation at 3T in patients with brain gliomas. MATERIALS AND METHODS: We enrolled 65 adult patients in an interindividual comparative study. Patients were randomized to one of two study arms: 33 patients received 0.1 mmol/kg body weight (bw) of gadoterate, 32 patients received 0.05 mmol/kg bw of gadobenate. The patients underwent identical examinations at 3T. Arterial input function (AIF), tissue function (TF), and the maximum tumor CBV (CBV_T) were obtained from each patient. The quality of the CBV maps were independently reviewed by two neuroradiologists blinded to the administered contrast agent. RESULTS: The administration of a half dose of gadobenate led to a roughly 40% reduction in signal drop compared to that achieved with a full dose of gadoterate (P values for AIF and TF maximum and integral were <0.01); quantitative and qualitative assessment of CBV maps revealed no difference between contrast agents (P values for CBV_T of high- and low-grade gliomas, image quality evaluation were 0.87, 0.48, >0.65, respectively) CONCLUSION: The CBV maps obtained with a half dose gadobenate (0.05 mmol/kg bw) are of comparable diagnostic quality as the corresponding images acquired with a full dose of gadoterate (0.1 mmol/kg bw). LEVEL OF EVIDENCE: 2 J. Magn. Reson. Imaging 2017;45:500-506.

Multiphase contrast-enhanced CT with highly concentrated contrast agent can be used for PET attenuation correction in integrated PET/CT imaging.

PURPOSE: State-of-the-art positron emission tomography/computed tomography (PET/CT) systems incorporate multislice CT technology, thus facilitating the acquisition of multiphase, contrast-enhanced CT data as part of integrated PET/CT imaging protocols. We assess the influence of a highly concentrated iodinated contrast medium (CM) on quantification and image quality following CT-based attenuation correction (CT-AC) in PET/CT. METHODS: Twenty-eight patients with suspected malignant liver lesions were enrolled prospectively. PET/CT was performed 60 min after injection of 400 MBq of (18)F-fluorodeoxyglucose (FDG) and following the biphasic administration of an intravenous CM (400 mg iodine/ml, Iomeron 400). PET images were reconstructed with CT-AC using any of four acquired CT image sets: non-enhanced, pre-contrast (n-PET), arterial phase (art-PET), portal venous phase (pv-PET) and late phase (late-PET). Normal tissue activity and liver lesions were assessed visually and quantitatively on each PET/CT image set. RESULTS: Visual assessment of PET following CT-AC revealed no noticeable difference in image appearance or quality when using any of the four CT data sets for CT-AC. A total of 44 PET-positive liver lesions was identified in 21 of 28 patients. There were no false-negative or false-positive lesions on PET. Mean standardized uptake values (SUV) in 36 evaluable lesions were: 5.5 (n-PET), 5.8 (art-PET), 5.8 (pv-PET) and 5.8 (late-PET), with the highest mean increase in mean SUV of 6%. Mean SUV changes in liver background increased by up to 10% from n-PET to pv-PET. CONCLUSION: Multiphase CT data acquired with the use of highly concentrated CM can be used for qualitative assessment of liver lesions in torso FDG PET/CT. The influence on quantification of FDG uptake is small and negligible for most clinical applications.

Brain volume perfusion CT performed with 128-detector row CT system in patients with cerebral gliomas: a feasibility study.

OBJECTIVES: Validation of the feasibility and efficacy of volume perfusion computed tomography (VPCT) in the preoperative assessment of cerebral gliomas by applying a 128-slice CT covering the entire tumour. METHODS: Forty-six patients (25 men, 21 women; mean age 52.8 years) with cerebral gliomas were evaluated with VPCT. Two readers independently evaluated VPCT data, drawing volumes of interest (VOIs) around the tumour according to maximum intensity projection volumes, which were mapped automatically onto the cerebral blood volume (CBV), flow (CBF) and permeability (Ktrans) perfusion datasets. As control, a second VOI was placed in the contralateral healthy cortex. Correlation among perfusion parameters, tumour grade, hemisphere and VOIs was assessed. The diagnostic power of perfusion parameters was analysed by receiver operating characteristics curve analyses. RESULTS: VPCT was feasible in the assessment of the entire tumour extent. Mean values of Ktrans, CBV, CBF in high-grade gliomas were significantly higher compared with low-grade (p < 0.01). Ktrans demonstrated the highest diagnostic (97% sensitivity), positive (100%) and negative (94%) prognostic values. CONCLUSIONS: VPCT was feasible in all subjects. All areas of different perfusion characteristics are depicted and quantified in colour-coded 3D maps. The derived parameters correlate well with tumour histopathology, differentiating low- from high-grade gliomas.

Where contrast agent concentration really matters - a comparison of CT and MRI.

OBJECTIVES: First pass contrast-enhanced magnetic resonance imaging (MRI) and computed tomography (CT) are influenced by parameters that characterize the injected bolus. The aim of this study was to assess the role of contrast agent concentration and the differences between MRI and CT. MATERIAL AND METHODS: We systematically evaluated the published literature to define the differences between MRI and CT with regards to the influence of contrast agent concentration and flow rate on signal enhancement and image quality. Subsequently, we used a simulation model to simulate bolus dispersion in the human body for contrast agents with different concentration. We performed this simulation for different injection times (3-25 seconds) as well as for single and double contrast agent dose, and calculated the effect of contrast agent concentration and dose on the increase of local contrast agent concentration. RESULTS: Although CT studies have shown that even a moderate increase in contrast agent concentration leads to higher peak concentration in the tissue or artery of interest, MRI studies have failed to show a marked benefit of higher concentration. The simulation demonstrated that the use of high concentrated contrast agent leads to an increase in local contrast agent concentration within the tissue or artery of interest, only if injection time is long (in CT commonly >10 seconds) compared with the time constant of bolus dispersion (about 5 seconds in humans). If the injection time is shorter (in MRI commonly 1-4 seconds), the local contrast agent concentration is mainly affected by the injected dose. CONCLUSION: Contrast agent concentration is a key parameter for the optimization of dynamic imaging techniques such as angiography or perfusion in CT, whereas in dynamic MRI, contrast agent dose and relaxivities are the leading parameters.

How does the injection protocol influence the attenuation-time curve in CT perfusion measurements: comparison of measured and simulated data.

In this study the authors compared a computer simulation that models bolus dispersion during the first pass to patient PCT data acquired with three different types of injection protocols. PCT was performed in 27 patients with one of the three injection protocols: (1) Monophasic bolus injection with saline flush, (2) monophasic bolus injection without saline flush, and (3) biphasic bolus injection with saline flush. They performed computer simulation to model bolus dispersion in the three injection protocols. Finally, they compared the simulated attenuation-time curves to the measured ones. The simulated attenuation-time curves corresponded well to the measured data for protocol 1. With protocol 2 they found that simulation predicts bolus kinetics correctly but overestimates the concentration by about 31%. They attributed this to the missing saline flush. By comparing the simulated and measured data, they could show that without saline flush about 1/3 of the contrast agent does not contribute to the first pass. For the biphasic injection (protocol 3), they found that the first part of the attenuation-time curve can be modeled by simulating the bolus dispersion of only the high-flow portion of the injected bolus. Although the simulation model does only take into account of the first pass of the bolus, it is a useful tool to analyze and predict effects of modified injection protocols.

Intra-individual crossover comparison of gadobenate dimeglumine and gadopentetate dimeglumine for contrast-enhanced magnetic resonance angiography of the supraaortic vessels at 3 Tesla.

OBJECTIVE: To compare gadobenate dimeglumine (Gd-BOPTA) and gadopentetate dimeglumine (Gd-DTPA) for contrast-enhanced magnetic resonance (MR) angiography of the supraaortic vessels at 3 Tesla. MATERIALS AND METHODS: Twelve healthy volunteers each underwent two contrast-enhanced magnetic resonance angiography examinations, one with Gd-BOPTA and one with Gd-DTPA each at a dose of 0.1 mmol/kg bodyweight. The 2 examinations were performed in randomized order and were separated by at least 72 hours. Imaging was performed in the coronal plane at 3T (Magnetom TIM Trio Siemens) using a 12-channel neurovascular array coil. The MR sequence parameters were identical for all examinations. Maximum intensity projection reconstructions were evaluated separately and in matched-pairs by a single independent blinded reviewer in terms of qualitative (5-point scales for technical quality and vessel delineation) and quantitative (relative contrast-to-noise ratio) contrast enhancement across 19 arteries/arterial segments comprising the internal carotid arteries; anterior, middle, and posterior cerebral arteries; vertebral arteries; and basilar artery. Findings were compared using the Wilcoxon signed rank test. RESULTS: The mean technical quality across all examinations was significantly (P = 0.031) greater after Gd-BOPTA. The overall median score for vessel delineation was also significantly higher for Gd-BOPTA than for Gd-DTPA (4.3 vs. 3.7; P = 0.005). Matched-pairs assessment revealed significant (P

Relaxivity of Gadopentetate Dimeglumine (Magnevist), Gadobutrol (Gadovist), and Gadobenate Dimeglumine (MultiHance) in human blood plasma at 0.2, 1.5, and 3 Tesla.

OBJECTIVES: We sought to determine the relaxivity and accurate relaxation rates of Gd-DTPA, Gd-BT-DO3A, and Gd-BOPTA at 0.2, 1.5, and 3 T in human blood plasma. MATERIALS AND METHODS: Contrast media concentrations between 0.01 and 16 mM in human plasma were used for relaxation measurements. The R1 and R2 relaxation rates and r1 and r2 relaxivities were determined. RESULTS: Gd-BOPTA produced the highest relaxation rates and relaxivities at all field strengths. The r1 and r2 values for Gd-BOPTA were 107-131% and 91-244% higher than for Gd-DTPA, respectively, and 72-98% and 82-166% higher than for Gd-BT-DO3A. Higher field strengths resulted in lower values of R1, R2, and r1 for all contrast agents tested and of r2 for Gd-DTPA and Gd-BT-DO3A. A linear dependence of R1 and R2 on concentration was found for Gd-DTPA and Gd-BT-DO3A and a nonlinear dependence for Gd-BOPTA for concentrations larger than 1 mM. The r1 and r2 relaxivity of Gd-BOPTA increased with decreasing concentration. CONCLUSIONS: Gd-BOPTA demonstrates the highest longitudinal r1 at all field strengths, which is ascribable to weak protein interaction. The R2/R1 ratio increases at higher field strength only for Gd-BOPTA, hence very short echo times are required for Gd-BOPTA to benefit from the higher longitudinal relaxivity.