Jean-Paul Esquerré

Acupuncture meridians and radiotracers

&NA; Acupuncture is frequently used and in particular for the treatment of pain. One of the cornerstones of its use, at least in Western countries, is the concept of the acupuncture meridian. Yet, their existence has never actually been proven. Recently, a report was published stating that injection of a radiotracer at an acupuncture point allows the visualization of the corresponding meridian in the shape of a radioactive path which is apparent on scintiscans. The present work confirms the appearance of radioactive paths after the injection of a radiotracer at acupuncture points. However, the cross‐checks made with the method used (counting the radioactivity of the venous blood, studying radioactivity of the organs which normally take up the tracer, scintiscan study of the complete meridian paths as they are described in traditional Chinese medicine and studying the effect of venous blockade on the observed radioactive paths) show that the radioactive paths in fact correspond to vascular drainage of the radiotracer.

Iterative three-dimensional expectation maximization restoration of single photon emission computed tomography images: application in striatal imaging.

Single photon emission computed tomography imaging suffers from poor spatial resolution and high statistical noise. Consequently, the contrast of small structures is reduced, the visual detection of defects is limited and precise quantification is difficult. To improve the contrast, it is possible to include the spatially variant point spread function of the detection system into the iterative reconstruction algorithm. This kind of method is well known to be effective, but time consuming. We have developed a faster method to account for the spatial resolution loss in three dimensions, based on a postreconstruction restoration method. The method uses two steps. First, a noncorrected iterative ordered subsets expectation maximization (OSEM) reconstruction is performed and, in the second step, a three-dimensional (3D) iterative maximum likelihood expectation maximization (ML-EM) a posteriori spatial restoration of the reconstructed volume is done. In this paper, we compare to the standard OSEM-3D method, in three studies (two in simulation and one from experimental data). In the two first studies, contrast, noise, and visual detection of defects are studied. In the third study, a quantitative analysis is performed from data obtained with an anthropomorphic striatal phantom filled with 123-I. From the simulations, we demonstrate that contrast as a function of noise and lesion detectability are very similar for both OSEM-3D and OSEM-R methods. In the experimental study, we obtained very similar values of activity-quantification ratios for different regions in the brain. The advantage of OSEM-R compared to OSEM-3D is a substantial gain of processing time. This gain depends on several factors. In a typical situation, for a 128 x 128 acquisition of 120 projections, OSEM-R is 13 or 25 times faster than OSEM-3D, depending on the calculation method used in the iterative restoration. In this paper, the OSEM-R method is tested with the approximation of depth independent resolution. For the striatum this approximation is appropriate, but for other clinical situations we will need to include a spatially varying response. Such a response is already included in OSEM-3D.