New experimental apparatus for multimodal resonance imaging: initial EPRI and NMRI experimental results.

Electron paramagnetic resonance imaging (EPRI) is a recently developed imaging technique employed in the study of free radicals in living systems. A full understanding of many physiological and pathological processes involving free radicals has not yet been attempted. The reason for this is that whilst nuclear magnetic resonance imaging (NMRI) is able to generate very accurate images of soft tissues and organs, EPRI does not have this capability because of its sensitivity limitations and the large linewidths of paramagnetic probes. This work describes the development and optimization of a multimodal apparatus capable of performing both pulsed EPRI and NMRI experiments on the same sample. The instrument combines the possibilities offered by both techniques: the functional and biochemical information achieved with EPRI, and the high-resolution anatomical images generated by NMRI. At present, these experiments are performed by moving the sample from an EPRI spectrometer to an NMRI apparatus. Consequently, the acquisition times are very long and several problems arise in image reconstruction. On the other hand, a unique apparatus operating in the two modalities greatly reduces the acquisition times and makes it possible to relate accurately the observed distribution of electron spin density with the anatomical description of individual organs. The experiments are performed at 357 Gauss, corresponding to a resonance frequency of 1.52 MHz for NMR and 1 GHz for EPR. In the present work, a detailed description of the apparatus is reported, including the main magnet, the gradient assembly, the multimodal cavity and the transmitter and receiver systems. The preliminary experimental results obtained by this apparatus are presented.

EPR imaging from projections: errors due to misalignment of projection centres and their rectification by a novel acquisition modality.

Continuous wave and pulsed wave electron paramagnetic resonance imaging (EPRI) makes use of classical methods of acquisition of projections. Acquisition/reconstruction techniques, such as spin-echo, gradient-echo, etc, cannot be applied to EPRI because they would require very short switching times for the gradient coils. Due to the use of the polar acquisition technique, it is necessary to define a centre of rotation about which the measured projections are rotated during the reconstruction process. This centre represents the point at which the field gradient coils must produce zero magnetic field. Due to the presence of a magnetic field control system that serves to compensate for field variations, principally due to heating, some interference can occur in the control system between the main magnetic field and the magnetic field produced by the gradient coils. The effect changes as the orientation changes. This results in a shift of the centres of the projections as a function of the variation of magnetic field produced by the gradient coils on the control Hall probe. If this condition is present, some artefacts can appear on the reconstructed image. This effect is irrelevant when EPR is used for imaging of paramagnetic probes whose linewidths are of the order of 10(-4) T, while it can be significant in the case of linewidths of the order of 10(-5) T or lower or when EPR is used in microimaging applications (i.e. for high values of magnetic field gradient). We describe the effects that misalignments of the projections have on the reconstructed images. We present a useful method for estimating the real position of the centre and correcting the measured projections before the application of the reconstruction algorithm. Moreover, we demonstrate the functioning of our technique by presenting some examples of EPR reconstruction collected by an X-band EPR imaging apparatus.

Compliance with gluten-free diet in adolescents with screening-detected celiac disease: a 5-year follow-up study.

After 5 years of treatment, 22 patients with celiac disease, diagnosed by means of serologic mass screening (mean age, 17.9 years), showed a lower compliance with a gluten-free diet and frequent positivity of serum anti-endomysium antibodies (32%) in comparison with a group of 22 age-matched patients diagnosed because of "typical" symptoms during childhood.

Pulsed EPR imaging: image reconstruction using selective acquisition sequences.

Pulsed nuclear magnetic resonance imaging (NMRI) apparatus has developed very quickly. On the other hand, the development of apparatus for pulsed electron paramagnetic resonance imaging (EPRI) has been very slow. This fact is due to the extremely reduced relaxation times of the paramagnetic probes. EPR linewidths are larger than typical NMR linewidths. These large linewidths are also responsible for a substantial worsening of spatial resolution. Due to the brevity of the electronic relaxation times, not all the acquisition/reconstruction techniques currently used in NMRI (such as spin-echo, gradient-echo, etc) can be applied in pulsed EPRI. In fact, the usable sequences in pulsed EPRI are only acquisitions from projections, where it is possible to use stationary magnetic field gradients. Moreover, the use of high fixed magnetic field gradients induces a short decay time constant T2*. The low T2* value can make it impossible for the analogue to digital conversion system (ADC) to reproduce signal variations during the whole acquisition interval and the resolution can worsen. A new pulsed EPRI acquisition sequence from projections, based on selective reception, is presented that is particularly useful in solving the problems of worsening of spatial resolution associated with the use of an ADC. In order to demonstrate the capabilities of our acquisition method, simulated numerical tests will also be reported.

Association between insulin dependent diabetes mellitus and coeliac disease. A study on 175 diabetes patients.

BACKGROUND: The association between diabetes mellitus and coeliac disease has been known for many years. In a random group of 175 insulin dependent diabetes mellitus patients of varying ages the following tests have been carried out: serum antigliadin antibodies (AGA) of IgA and IgG class, antireticulin antibodies (ARA) and antiendomisyum antibodies (AEA), both of IgA class. MATERIALS AND METHODS: The patients, 85 males and 90 females, had ages ranging from 1 yr to 30 yrs (102 in paediatric age--mainly between 6 and 14 years--and 73 adults). Patients with pathological values for AEA and/or ARA underwent an intestinal biopsy. RESULTS: Out of 175 patients studied, 21 had pathological values for AEA with or without pathological values for ARA and AGA, and 2 patients had only pathological values for ARA. 23 patients (21 with pathological values for AEA with or without ARA and AGA, 2 only for ARA ) underwent intestinal biopsy, all patients with pathological values for AEA had villous atrophy. The prevalence of coeliac disease among IDDM patients was 8.8% (95% CI 3.3 to 14.3) for the children and 16.4% (95% CI 7.9 to 24.9) for the adults. In patients with mucous atrophy, ARA, AGA IgA and IgG were pathological in 85%, 71% and 61% respectively. Symptoms and insulin requirements in all patients affected by coeliac disease before and after one year on a gluten free diet were also evaluated. The patients had clinical features with prevalently one or only few atypical symptoms which disappeared on a gluten free diet. Insulin requirements after one year on a gluten free diet appeared unchanged in coeliac patients. CONCLUSIONS: The need to screen all diabetic patients for coeliac disease is underlined.