Saint-Gobain Crystals has been a key supplier to the Medical Market for decades. For imaging applications, Single Photon Emission Computed Tomography (SPECT) and Positron Emission Tomography (PET) crystals and detectors have been provided by Saint-Gobain (including its predecessor companies Bicron and Harshaw) since the modalities were introduced. In addition, Saint-Gobain provides detectors for a variety of other Medical applications, including Bone Mineral Densitometry (BMD), Radioimmunoassay (RIA), surgical probes, blood analysis and whole body scanning. Saint-Gobain also provides radiotranslucent sapphire for use in Intraoperative CT and MRI Imaging without distortion or artifacts.
Pixellated arrays of high stopping power scintillation crystals are used in PET systems to image patients for cancer, Alzheimer’s Disease, cardiac issues and other health problems.
PET technique evolved in the mid-1970’s and uses positron emitting isotopes (e.g. C-11, O-15, F-18) to study chemical and biological processes in the body. PET detectors require that the detector material be of high enough Z to maximize the photoelectric cross sections for 511 keV, be fast enough to handle the count rates involved, and be able to distinguish coincident events.
LYSO and BGO are traditional materials used in this application. The introduction of LaBr3(Ce) has opened up unprecedented performance levels for Time of Flight systems. Monolithic crystals, in some cases mounted directly on light sensors such as PMTs or SiPMs, may also be used.
Nuclear imaging systems called gamma cameras determine the radiation distribution, transit time or uptake of a pharmaceutical labeled with a suitable, short-lived radioactive nuclide administered to the patient. The camera’s externally placed NaI(Tl) detector plates measure the radiation, and special imaging devices display the radioactivity distribution. The images yield information about the function of an organ or part of the body. SPECT and PET are two of the imaging techniques used.
Radiation detectors are used in a variety of Medical applications. These include well type detectors to analyze blood samples in test tubes for Radioimmunoassay (RIA), blood volume, red blood cell and other tests. Detectors are also used in surgical probes or whole body scanners. Optical fibers or light guides can also be used in medical imaging applications, particularly where positional information is required or to separate the photomultiplier tubes from high magnetic fields, such as in PET/MR systems. Pixellated arrays can be used for CT and other imaging applications.
Typical configurations include packaged detectors and fully integrated solutions including the photomultiplier tube (PMT) or silicon photomultiplier (SiPM) and electronics.
Detectors with NaI(Tl) crystals integrated with photomultiplier tubes provide an excellent mix of value and performance to measure X-Rays in Bone Mineral Densitometry (BMD) systems. Detectors are also available with special low energy entrance windows if required. Other crystals, such as PreLude 420 (LYSO), and light sensors, such as photodiodes and silicon photomultipliers, are also good options for BMD.
Image guided surgery, using CT and MRI, is an emerging application. Many traditional materials, such as steel, cannot be used in this application due to resulting distortion in the image or incompatability with magnetic fields. Sapphire is an excellent alternative as it is radiotranslucent, non-magnetic and features high strength and excellent optical transmission. It has been used both for mechanical applications such as skull pins and for optical applications including laser probes.