Detection of coronary artery disease by magnetic resonance myocardial perfusion imaging with various contrast medium doses: first european multi-centre experience

Aims Magnetic resonance (MR) first-pass myocardial perfusion imaging during hyperaemia detects coronary artery stenoses in humans with test sensitivity depending on contrast medium (CM)-induced signal change in myocardium. In this prospective multi-centre study, the effect of CM dose on myocardial signal change and on diagnostic performance was evaluated using a stress-only approach. Methods and results Ninety-four patients with known or suspected coronary artery disease (CAD) were randomised to 0.05,0.10, or 0.15 mmol/kg body weight of an extravascular CM (Gd-DTPA) and X-ray coronary angiography was performed within 30 days prior/after the MR examination. A multi-slice MR technique with identical hardware and software in all centres was used during hyperaemia (adenosine 0.14 mg/kg/min) to monitor myocardial CM wash-in kinetics and data were analysed semi-automatically in a core laboratory. Protocol violations resulted in 80 complete studies with CAD (defined as ⩾1 vessel with diameter stenosis ⩾50% on quantitative coronary angiography) present in 19/29, 13/24, and 20/27 patients for doses 1, 2, and 3, respectively. In normal myocardium, the upslope increased with CM dose (overall-p<0.0001, ANOVA). For CAD detection the area under the receiver operator characteristics curve for subendocardial data (3 slices with quality score<4 representing 86% of cases) was 0.91±0.07 and 0.86±0.08 for doses 2 and 3, respectively, and was lower for dose 1 (0.53±0.13, p<0.01 and p<0.02 vs. doses 2 and 3, respectively). Corresponding sensitivities/specificities (95% confidence intervals) for pooled doses 2/3 were 93% (77-99%; ns vs. dose 1) and 75% (48-92%;p<0.05 vs. dose 1), respectively. Conclusions With increasing doses of CM, a higher signal response in the myocardium was achieved and consequently this stress-only protocol, with CM doses of 0.10-0.15 mmol/kg combined with a semi-automatic analysis, yielded a high diagnostic performance for the detection of CA

Radioimmuno positron emission tomography with monoclonal antibodies: a new approach to quantifying in vivo tumour concentration and biodistribution for radioimmunotherapy.

Radioimmunodetection of tumours with monoclonal antibodies is becoming an established procedure. Positron emission tomography (PET) shows better resolution than normal gamma camera single photon emission tomography and can provide more precise quantitative data. Thus, in the present study, these powerful methods have been combined to perform radioimmuno PET (RI-PET). Monoclonal antibodies directed against carcinoembryonic antigen (CEA) an IgG, its F(ab')2 and a mouse-human chimeric IgG derived from it were labelled with 124I, a positron-emitting radionuclide with a convenient physical half-life of four days. Mice, xenografted with a CEA-producing human colon carcinoma, were injected with the 124I-MAb and the tumours were visualized using PET. The concentrations of 124I in tumour and normal tissue were determined by both PET and direct radioactivity counting of the dissected animals, with very good agreement. To allow PET quantification, a procedure was established to account for the presence of radioactivity during the absorption correction measurement (transmission scan). Comparison of PET and tissue counting indicates that this novel combination of radioimmunolocalization and PET (RI-PET) will provide, in addition to more precise diagnosis, more accurate radiation dosimetry for radioimmunotherapy

NCBHR communiqué

International audienceThe combination of functional and anatomical imaging technologies such as Positron Emission Tomography (PET) and Computed Tomography (CT) has shown its value in the preclinical and clinical fields. In PET/CT hybrid acquisition systems, CT-derived attenuation maps enable a more accurate PET reconstruction. However, CT provides only very limited soft-tissue contrast and exposes the patient to an additional radiation dose. In comparison, Magnetic Resonance Imaging (MRI) provides good soft-tissue contrast and the ability to study functional activation and tissue microstructures, but does not directly provide patient-specific electron density maps for PET reconstruction.The aim of the proposed work is to improve PET/MR reconstruction by generating synthetic CTs and attenuation-maps. The synthetic images are generated through a multi-atlas information propagation scheme, locally matching the MRI-derived patient’s morphology to a database of pre-acquired MRI/CT pairs. Results show improvements in CT synthesis and PET reconstruction accuracy when compared to a segmentation method using an Ultrashort-Echo-Time MRI sequence

Isotopic tools for IBD : PET and PET-CT.

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