Medical X-Ray Tube Spectra
for Mammography and Radiology

Design Objective

This detector system was designed with the objective of simultaneously measuring the X-Ray tube peak potential (kVp), and to characterize the mammographic X-Ray tube spectrum.

Significance of the Measurement

• Both the tube spectrum and the peak potential (kVp) are important parameters affecting the image quality in film-screen and digital mammography.
• Automatic selection of proper target/filter combination in modern mammography systems maybe affected by improper kVp.
• In conventional devices, the user depends on central laboratory calibration and has no easy way to calibrate the instrument during use.

Complete System Includes: Detector - "XR-100T-CZT/TJ Box" Power Supply/Amplifier - "PX2T-CZT" Collimator Kit - "Collimator Kit" MCA8000A Multichannel Analyzer - "MCA8000A"

XR-100T-CZT system shown with Amptek MCA8000A Multichannel Analyzer and a notebook computer

System Description

The XR-100T-CZT is a high performance X-Ray and Gamma Ray detector mounted on a thermo-electric cooler (Peltier type) together with the input FET to the preamplifier. Monitored by an integrated circuit, these components are kept at -30° C and are enclosed in a hermetic package with a vacuum tight, light tight Beryllium window. Power and signal processing to the detector is provided by the PX2T-CZT in order to ensure quick, stable operation in less than one minute from power turn-on. The output pulse produced by the PX2T-CZT connects directly to the input of the Multichannel Analyzer MCA8000A "Pocket MCA."

Collimator Kit

Amptek has developed a Collimator Kit to collimate the primary X-ray beam. This system is comprised of a special Detector/Preamp box (TJ BOX) which slides inside a Collimator Housing. The Collimator Housing can accommodate up to two Tungsten collimator disks that are placed inside a bayonet holder in front of the detector. By selecting the appropriate Tungsten collimator disks, the user can reduce the incoming X-ray flux and allow the detector and electronics to process the X-ray spectrum. Seven different Tungsten collimator disks are provided with different size holes (ranging from 25 µm to 2,000 µm hole) in order to allow for a wide range of applications. The Collimator Housing is made out of brass in order to shield the detector and electronics from the primary X-ray source. Additionally, the bottom of the Collimator Housing incorporates a screw type fitting to allow for a standard tripod mount.

References

1. Matsumoto, Massao, et al. Direct measurement of mammographic x-ray spectra using CdZnTe detector, Medical Physics 27 (7), July 2000. p. 1490.
2. Vedantham, Srinivasan, et al. Mammographic imaging with a small CCD-based digital casette: Physical characteristics of a clinical system, Medical Physics 27 (8), August 2000.
3. Vedantham, Srinivasan, et al. Full breast digital mammography with an amorphous silicon-based flat panel detector: Physical characteristics of a clinical prototype, Medical Physics 27 (3), March 2000.

Medical X-Ray Detector Specifications and description in PDF format (418k)

Revised February 7, 2001