Foto: argus/ Maik Schröder mit freundlicher Genehmigung des Instituts für Mikrotechnik Mainz GmbH Quelle: DLR Göttingen Quelle: DLR Göttingen
Physik im Kontext
What are X-Rays
Röntgen's Discovery
History of Radiology
X-Ray Production
X-rays & Matter
Detection Issues
Detection Methods
Background: Fluorescence

Physics & the Detection of Medical X-Rays
Electronic (Digital) Detection

The most recent advances in medical imaging involve converting the x-ray information directly or indirectly into digital information. Two advantages of digital images are storage and the ability to manipulate the information on the image.

Just as with an digital information the digital medical image can be stored on any type of computer device. These images can also be sent electronically too other health care providers. One does need to ship a film if a specialist far away from the patient needs to be part of a diagnostic team.

Manipulation of the image can be a process as simple as changing the contrast in order to see some aspect more clear. It can also be used to remove uninteresting aspects of the image or the watch change over time. For example, digital subtraction angiography is a rather fancy name for removing the unwanted information. An image of a region of the body is taken before and after a procedure such as injecting a compound which highlights certain organs. The tow images are subtracted bit-for-bit. The result is an image which shows only the parts of the body in which the physician is interested.

Digital images can be created in five basic ways.

  1. Directly from a digital process such as computed tomography.
  2. Digitizing fluoroscopic images
  3. Using a solid state x-ray detection system instead of film (computed radiography)
  4. Using an array of solid state detectors (direct radiography)
  5. Scanning film.

Processes 3-5 involve applications of contemporary physics in the effort to convert the information in the x-ray beam to digital.

A common detector consists of an array of charge coupled devices (CCD). These solid state devices involve the photoelectric effect and electron-hole production. The system is frequently set up as a chip that is divided into a large number of bins (pixels). The bins create a 2-dimensional array. Incoming x-ray photons eject electrons. Thus, charge builds up depending on number of photons which strike each bin. A computer-type device reads the charge on each bin (pixel). This charge is then directly related to the number of photons and thus the brightness of the image at that pixel.

We have had some difficulty finding appropriate links for this section.  Much of the technology is still emerging.  Thus, many sites are devoted to telling the readers about how the company's devices are superior to all others while less screen space is used for basic education on how the devices work.

Charge Coupled Devices
Some basic physics of these devices

Direct Detection of X-Rays Using ... CCD Technology
A rather detailed technical report which has a description of CCD physics at the beginning.

pn-CCD Detektoren für Röntgenstrahlung
A qualitative description of pn CCDs that are used for x-ray detection.

An Introduction to Scientific Imaging Charge Coupled Devices
This PDF page provides an introduction for someone who has some has some basic knowledge of condensed matter physics.

Detektoren für Röntgenstrahlung
A set of PowerPoint slides a various types for x-ray detection.  The site has several slides on solid state detectors.

This page is primarily an advertisement for a detector, but it contains a few nice images.

The role of technology in future medical imaging
This PDF file on the Philips web site discusses a variety of imaging techniques and Philips solutions.  The first part includes a qualitative introduction to CCD technology in medical imaging.

Medical Image Acquisition Systems
This PDF file contains 71 slides related to medical imaging.  The emphasis is one digital processes.  It includes other forms of imaging such as MRI as well as x-rays.

Hightech, Digitales Röntgen in der Zahnheilkunde
This text article is written for dentists and describes the basics of digital x-ray detection.

We have not found any simple set of words that provides a reasonable result on a Web search engine.

    Flags indicate the language of the Web site.
In cooperation with
Modern Miracle Medical Machines
Physics Education Research Group
Kansas State University