*3.1.1. PET-CT*

The first machine was created by University of Pittsburgh physicist David Townsend and engineer Ronald Nutt; the PET-CT machine was called the "Medical Science Invention of the Year" by *Time* magazine in 2000. After giving entire satisfactory at the research tests level and their importance in oncology and cardiology were well demonstrated, many international companies were interested in the fabrication of such kind of hybrid imaging machine. Actually, the market is shared mainly between General Electric (GE), Philips and Siemens (Figure 9).

<sup>2</sup> MRI: MagneticResonance Imaging.

GE offers a variation in its range of PET-CT "Discovery ST" machine to meet the specific clinical needs. After the Discovery ST oriented oncology and cardiology, the GE Discovery VCT sells dedicated cardiology is associated with a 64-slice scanner. The latest version offers a higher spatial resolution responding to neurological applications. GE ST machines are available in versions scanner 4, 8 or 16 cups. The 2D acquisition abandoned by other manufacturers is optional and defended by GE to obtain less noisy images (useful for some advanced applica‐ tions or for overweight patients) and for new applications mostly outside the scope FDG. GE believes that the increase of activity of PET-CT will be around 50% in the next three years and examines the association of PET and MRI modalities. The contribution of MRI compared to CT is questionable, except perhaps in functional imaging.

PHILIPS GEMINI PET/CT scanners combine the Brilliance CT technology, that is well-suited to cardiac imaging with its wide-coverage submillimeter imaging, ultra fast acquisition times and Rate Responsive image acquisition technology that adapts to the patient's heart rate and rhythm during acquisition. GEMINI PET/CT scanners deliver high spatial resolution and high sensitivity PET imaging resulting in improved image quality when imaging the short-lived radiopharmaceuticals used with cardiac PET. Philips PET-CT hybrid machines ALLEGRO maintain in the range GEMINI.

SIEMENS works to upgrade the install PET-CT around the world. The range of PET-CT, BIOGRAPH marketed since 2000 continues to benefit from developments. After improving the sensitivity BGO crystals by replacing the LSO crystals, SIEMENS in 2004 increased the detection speed by introducing a new channel detection (PICO 3D) with the coincidence window is only 4.5 ns and improved spatial resolution due to detector Hi-Rez (block 13 x 13 x 8 against 8 elements far). Note that BIOGRAPH have a tunnel of 70 cm diameter field used in whole to acquire PET scanner. This criterion is important for obese patients.

**Figure 9.** Example of commercially PET-CT scanners.
