Solid-state gamma detectors save weight and cost
Since the late 1960s, gamma cameras have been used in nuclear medicine for static and functional imaging applications. To image the human body using gamma cameras, patients are first fed or injected doses of radioactive isotopes that concentrate in certain regions or organs. These radioactive isotopes emit gamma rays that strike a sodium iodide crystal in the gamma camera. The scintillation of the sodium iodide that occurs is magnified using a photomultiplier tube (PMT). By digitizing the signal from the PMT, computers can then reconstruct images of the human body.
Because such gamma cameras use PMTs, they can weigh up to 5000 lbs, are cumbersome to operate, and incur high maintenance costs. Now, a proprietary, solid-state imaging detector invented by Digirad (San Diego, CA) promises to revolutionize nuclear medicine. Using cadmium zinc telluride (CdZnTe) modules, the company has developed a solid-state detector array that converts gamma rays directly to electrical signals. By digitizing the signals directly from the sensor, no PMTs are required, greatly reducing the cost of the detector and the weight of the imaging head. At present, each detector array is fabricated with 1-in.2 modules that are assembled into a large 64-in.2 imaging head.
To market the camera, Digirad is offering the detector in its 2020 TC Imager, a system that has been evaluated by Dr. Iraj Khalkali, director of breast imaging and outpatient radiology at the Harbor UCLA Medical Center (Los Angeles, CA). "Using the camera, we can detect regions of the breast where cancers may be missed with currently available gamma cameras," he reports. Karen Klause, president and chief executive officer of Digirad, says that the Federal Drug Administration has cleared the camera technology for marketing this year. The company is planning to capture a large percentage of the gamma-camera market over the next five years and expects to generate revenues in excess of $200 million.