Hubertus Pietsch

What Evidence Is There That Gadobutrol Causes Increasing Signal Intensity within the Dentate Nucleus and Globus Pallidus on Unenhanced T1W MRI in Patients with RRMS

ᅟKey Points• The study by Stojanov et al does not convincingly support the conclusion that gadobutrol causes higher T1 enhancement in brain on unenhanced MRI • The study by Stojanov et al does not rule out confounding factors • The study by Stojanov et al has limitations in study design

Perfusion MRI for Monitoring the Effect of Sorafenib on Experimental Prostate Carcinoma: A Validation Study

OBJECTIVE The purpose of this study was to investigate with immunohistochemical validation whether dynamic contrast-enhanced MRI with small-molecule contrast medium is useful for monitoring the effects of the multikinase inhibitor sorafenib on prostate carcinomas in rats. MATERIALS AND METHODS Copenhagen rats (n = 20) into which prostate carcinoma (MAT-Ly-Lu-B2) had been implanted subcutaneously were imaged on the day of implantation and 7 days later with 3-T dynamic gadobutrol-enhanced MRI. The therapy group (n = 10) received daily administration of 10 mg/kg body weight sorafenib. Quantitative measurements of tumor perfusion, tumor vascularity, and permeability-surface area product were calculated with a two-compartment model. Dynamic contrast-enhanced MRI values were correlated with immunohistochemical results for validation. RESULTS Tumor perfusion in sorafenib-treated prostate carcinoma declined significantly from day 0 to day 7 (47.9 ± 36.8 mL/100 mL/min to 24.4 ± 18.6 mL/100 mL/min; p < 0.05). No significant effect on permeability-surface area product was observed in either the therapy or the control group (p > 0.05). Tumor vascularity decreased significantly (p < 0.05) from day 0 to day 7 under sorafenib treatment (15.6% ± 11.4% to 5.4% ± 2.1%). Immunohistochemical analysis revealed significantly lower tumor vascularity in the therapy than in the control group (rat endothelial cell antigen 1, 74.4 ± 16.9 cells vs 197 ± 75.4 cells; p < 0.05). In sorafenib-treated tumors, significantly more apoptotic cells (terminal deoxynucleotidyl transferase-mediated nick end labeling, 6923 ± 3761 vs 3167 ± 1500; p < 0.05) and significantly fewer proliferating cells (Ki-67, 10,198 ± 3064 vs 15,003 ± 3674; p < 0.05) were observed than in the control group. Modest but significant correlations were observed between tumor perfusion and immunohistochemical tumor cell apoptosis (r = -0.56; p < 0.05) and between tumor perfusion and immunohistochemical tumor vascularity (r = 0.56; p < 0.05). CONCLUSION Tumor perfusion quantified with gadobutrol-enhanced dynamic contrast-enhanced MRI can be used as a noninvasive surrogate parameter for monitoring the antiangiogenic, antiproliferative, and proapoptotic effects of sorafenib on prostate carcinoma allografts as validated with immunohistochemical analysis.

Impact of iodine delivery rate with varying flow rates on image quality in dual-energy CT of patients with suspected pulmonary embolism.

RATIONALE AND OBJECTIVES To prospectively compare four contrast material injection protocols for dual-energy computed tomography (CT) pulmonary angiography (DE-CTPA) in patients with suspected pulmonary embolism (PE). MATERIALS AND METHODS One hundred twenty consecutive patients were randomized to contrast material injection protocols defined by different iodine concentrations and iodine delivery rates (IDRs): (A) 80 mL iopromide 370/4 mL/sec = IDR 1.4 gI/sec; (B) 80 mL iopromide 370 at 3 mL/sec = IDR 1.1 gI/sec; (C) 98 mL iopromide 300 at 4.9 mL/sec = IDR 1.4 gI/sec; and (D) 98 mL iopromide 300 at 3.7 mL/sec = IDR 1.1 gI/sec. Attenuation values were measured in the inflow tract (subclavian vein-superior vena cava-right atrium), target tract (right ventricle-pulmonary trunk-pulmonary arteries), and outflow tract (left atrium-left ventricle-ascending aorta). Two readers assessed subjective image quality of CTPA images and iodine perfusion maps. The number of artifacts due to hyperdense contrast material on iodine perfusion maps was recorded. RESULTS Target tract attenuation was highest for protocol A with 374 ± 98 Hounsfield units (HU) (highly concentrated contrast material/high IDR). This was significant compared to protocols B and D (P = .0118, P = .0427) but not compared to protocol C (P = .3395). No significant difference in target tract attenuation was found between protocols B (309 ± 80 HU), protocol C (352 ± 119 HU), and D (325 ± 74 HU). CTPA and iodine perfusion map image quality for protocol A was rated significantly higher compared to all other protocols (median score = 5/4; P < .0001 for both) with moderate interreader agreement (κ = 0.58/0.47). Protocols A and B displayed increased artifacts on iodine perfusion maps compared to protocols C and D (3 versus 2). CONCLUSION Despite increased artifacts on iodine perfusion maps, highly concentrated iodinated contrast material combined with high flow rates provides improved diagnostic image quality and has the highest target-tract attenuation for DE-CTPA protocols.

PET/CT in lung cancer: Influence of contrast medium on quantitative and clinical assessment.

AbstractObjectivesTo evaluate the influence of intravenous contrast medium and different contrast medium phases on attenuation correction, PET image quality and clinical staging in combined PET/CT in patients with a suspicion of lung cancer.MethodsSixty patients with a suspicion of lung cancer were prospectively enrolled for combined 18F-FDG-PET/CT examination. PET images were reconstructed with non-enhanced and arterial and venous phase contrast CT. Maximum and mean standardised uptake values (SUVmax and SUVmean) and contrast enhancement (HU) were determined in the subclavian vein, ascending aorta, abdominal aorta, inferior vena cava, portal vein, liver and kidney and lung tumour. PET data were evaluated visually for clinical staging and image quality.ResultsSUVmax was significantly increased between contrast and non-contrast PET/CT at all anatomic sites (all P < 0.001). SUVmax was significantly increased for arterial PET/CT compared to venous PET/CT in the arteries (all P < 0.001). Venous PET/CT resulted in significantly higher SUVmax values compared to arterial PET/CT in the parenchymatous organs (all P < 0.05). Visual clinical evaluation of malignant lesions showed no differences between contrast and non-contrast PET/CT (P = 1.0).ConclusionsContrast enhanced CT is suitable for attenuation correction in combined PET/CT in lung cancer; it affects neither the clinical assessment nor image quality of the PET images.Key Points• Positron emission tomography combined with computed tomography is now a mainstream investigation • There has been debate about whether CT contrast agents affect PET results • Contrast-enhanced CT is satisfactory for attenuation correction in lung cancer PET/CT • Multiphase CT does not affect PET; additional unenhanced CT is unnecessary • For quantitative follow-up PET analysis, an identical PET/CT protocol is required

Monte Carlo simulation of contrast-enhanced whole brain radiotherapy on a CT scanner

PURPOSE To perform a feasibility study of contrast-enhanced whole brain radiotherapy for treating patients with multiple brain metastasis using a conventional computed tomography (CT) scanner. METHODS The treatment dose was optimized to be applied in a single run using a maximum tube power of 5200 kWs at 140 kV. CT scans of a large and a small head were used as reference. Irradiation geometry, shielding, axial beam collimation, radial beam collimation, gantry tilt, and tube current for beam modulation were optimized using a Monte Carlo simulation and a contrast agent concentration of 5 mg/ml iodine in the tumor. The statistical uncertainty of the Monte Carlo simulation was corrected using back convolution. RESULTS Using a CT tube with a beam collimation of 28.8 mm, a mean tumor dose of 1.76 +/- 0.13 Gy was achieved, while the head bone dose was 2.61 +/- 0.18 Gy with a normal brain dose of 0.98 +/- 0.06 Gy, eye dose of 0.19 +/- 0.05 Gy, and lens dose of 0.15 +/- 0.03 Gy, respectively. Using a CT tube with dose modulation and a beam collimation of 40.0 mm, the mean tumor dose was 2.00 +/- 0.11 Gy with a head bone dose of 1.96 +/- 0.14 Gy, normal brain dose of 1.13 +/- 0.08 Gy, eye dose of 0.21 +/- 0.05 Gy, and lens dose of 0.16 +/- 0.02 Gy, respectively. Thus a standard CT scanner enables an effective tumor dose of 37.0 Gy to be administered in 13 fractions, while exposing healthy brain to an effective dose of 17.2 Gy and head bone to 69.3 Gy. Additional radial collimation implemented in the hardware improves the therapeutic tumor dose by 25.2% in relation to the bone dose. CONCLUSIONS Contrast-enhanced total brain radiotherapy is feasible using a conventional CT tube with optimized dose application.

Contrast medium injection protocol adjusted for body surface area in combined PET/CT

AbstractObjectivesTo evaluate the effect of contrast medium dose adjustment for body surface area (BSA) compared with a fixed-dose protocol in combined positron emission tomography (PET) and computed tomography (CT) (PET/CT).MethodsOne hundred and twenty patients were prospectively included for 18F-2-deoxy-fluor-glucose (18F-FDG)-PET/CT consisting of a non-enhanced and a venous contrast-enhanced CT, both used for PET attenuation correction. The first 60 consecutive patients received a fixed 148-ml contrast medium dose. The second 60 patients received a dose that was based on their calculated BSA. Mean and maximum standardised FDG uptake (SUVmean and SUVmax) and contrast enhancement (HU) were measured at multiple anatomical sites and PET reconstructions were evaluated visually for image quality.ResultsA decrease in the variance of contrast enhancement in the BSA group compared with the fixed-dose group was seen at all anatomical sites. Comparison of tracer uptake SUVmean and SUVmax between the fixed and the BSA group revealed no significant differences at all anatomical sites (all P > 0.05). Comparison of the overall image quality scores between the fixed and the BSA group showed no significant difference (P = 0.753).ConclusionsBSA adjustment results in increased interpatient homogeneity of contrast enhancement without affecting PET values. In combined PET/CT, a BSA adjusted contrast medium protocol should be used preferably.Key Points• Intravenous contrast medium is essential for many applications of PET/CT • Body surface area adjustment of contrast medium helps standardise contrast enhancement • Underdosing or overdosing of contrast medium will be reduced • PET image quality is not influenced • BSA adjusted contrast medium protocol should be used preferably in combined PET/CT

Lymph node staging using dedicated magnetic resonance contrast agents—the accumulation mechanism revisited

When diagnosing cancer, assessing the nodal stage is tremendously important in determining the patients prognosis. Computed tomography (CT) and magnetic resonance (MR) imaging (MRI) assessments of the regional lymph node (LN) size and shape are currently used for the initial nodal staging in clinical settings, although this approach has a rather low sensitivity, and biopsy often leads to restaging of the LNs. Acknowledging the great medical need to accurately stage LNs, scientists and clinicians have been working since the late 1980s on MR contrast agents that provide more reliable staging results. Different types of molecules (i.e., iron oxide nanoparticles and Gd-based contrast agent) have shown promising LN accumulation and imaging results, but no clinically approved, dedicated LN staging contrast agent is currently available. The literature describes a mechanism of contrast agent accumulation in the LNs that considers some but not all published experimental evidence. However, confidence in the mechanism of LN accumulation is a prerequisite for the directed synthesis of compounds for accurate and sensitive LN staging. To improve our understanding of the LN contrast agent accumulation mechanism, we reviewed the published data on the enrichment of colloidal MR contrast agent candidates in LNs, and we suggest an extended mechanism for contrast agent enrichment in LNs. For further clarification, physiology and results from drug targeting studies are considered where applicable.

Revival of monophasic contrast injection protocols: superiority of a monophasic injection protocol compared to a biphasic injection protocol in high-pitch CT angiography.

Background Biphasic injection protocols are frequently used because they yield homogenous contrast enhancement. We hypothesize that with faster scanners and shorter scan times, biphasic injection protocols are no longer necessary. Purpose To evaluate whether a monophasic injection protocol is equivalent to a biphasic protocol in terms of contrast enhancement and homogeneity. Material and Methods Repeated high-pitch CTA (pitch 3) and conventional standard-pitch computed tomography angiography (CTA) (pitch 1.2) from the cervical region to the symphysis was performed in seven beagles (11.2 ± 2.5 kg) in a cross-over study design. Arterial contrast enhancement was measured along the z-axis in the ascending, descending, and abdominal aorta and the iliac arteries. The z-axis is the longitudinal axis of the human body and at the same time the direction in which the CT table is moving. The data were analyzed using repeated measures ANOVA with a post-hoc t-test and visual assessment of the scans. Results In high-pitch CTA, monophasic injection protocols were superior to biphasic injection protocols in enhancement levels (P < 0.05) and enhancement homogeneity along the z-axis (P < 0.05). In conventional CTA, enhancement levels did not differ. Contrast homogeneity was better for biphasic protocols. Conclusion High-pitch CTA monophasic injection protocols are superior to biphasic injection protocols, due to a higher and more homogeneous contrast enhancement with the same amount of contrast medium used.