What is the function of a scintillator?

Scintillators are materials that are able to convert high energy radiation such as X or gamma-rays to a near visible or visible light. They are widely used as detectors in medical diagnostics, high energy physics and geophysical exploration (ref. Knoll).

How do scintillator detectors work?

Scintillation detectors are usually water clear crystalline materials and work better if they contain heavy elements, which are more likely to intercept a gamma ray within the material and absorb its energy. After absorbing a gamma ray, a scintillation crystal emits a pulse of light, usually in the visible spectrum.

What are the parts of a gamma camera?

There are three major components in a gamma camera: collimator, scintillation crystal, and photomultiplier tube (PMT) array (Fig. 2).

What is gamma camera resolution?

Gamma cameras have a spatial resolution of 3 to 5 mm. Use of a scintillation crystal for acquisition of data for image formation has led to the labeling of this technique as scintigraphy.

Why do we need a scintillator detector?

Scintillation detectors are used for the determination of the high-energy part of the X-ray spectrum. In scintillation detectors the material of the detector is excited to luminescence (emission of visible or near-visible light photons) by the absorbed photons or particles.

Which device converts scintillation light into an electrical signal?

photomultiplier tube
There are two major types of devices used to form an electrical signal from scintillation or Cherenkov light: the photomultiplier tube and the photodiode. Photomultiplier tubes are vacuum tubes in which the first major component is a photocathode.

What can a gamma camera diagnose?

Gamma cameras or scintillation cameras are pieces of apparatus which allow radiologists to carry out ‘scintigraphy scans’, tests which provide detailed diagnoses about the functioning of the thyroid, the heart, the lungs and many other parts of the body.

How does the gamma camera work?

The gamma camera records the energy emissions from the radiotracer in your body and converts it into an image. The gamma camera itself does not emit any radiation. It has radiation detectors called gamma camera heads. A computer creates the images using the data from the gamma camera.

What does gamma camera look like?

The gamma camera itself does not emit any radiation. It is composed of radiation detectors, called gamma camera heads, which are encased in metal and plastic and most often shaped like a box, attached to a round circular donut shaped gantry.

What does the collimator do in a gamma camera?

N.B. The collimator acts as a lens to reject photons that have a path that means they do not hit the camera in a location that corresponds to their original location i.e. its purpose is for spatial mapping. It does not reject scatter.

How are gamma photons detected in a camera?

The figure below shows a schematic depiction of the parts of the camera. The gamma photon to be detected passes through a collimator first, then it generates scintillation (light) photons in the scintillaton crystal covered with a reflective coating.

How is energy discrimination done in a gamma camera?

This cannot be done by the collimator and is, therefore, done electronically by a process called energy discrimination. A gamma photon that scatters within the patient will never hit the scintillator with the full energy (i.e. it won’t lie within the peak).

How are gamma photons related to the scintillation crystal?

This converts the current produced at the anode of the PMT to a voltage pulse. The amplitude of the voltage pulse is directly proportional to the charge produced at the anode and, therefore, the amount of light received by the PMT, which is proportional to the number of gamma photons that hit the scintillation crystal.