Introduction to nuclear medicine technology NMT 231

Aya Ahmed Saeed

Introduction to nuclear medicine equipment

Objective

To become familiar with counting and detection equipment, and imaging systems.

Contents

• Basic principals of detection

• Monitoring equipment

• Dose calibrators (activity meters)

• Sample counters and probes

• Scanners

• Gamma cameras (including SPECT and coincidence systems)

• Positron Emission Tomography

Principle of operation of a scintillation detector:

Basic Principles of Detection

If the gamma ray is absorbed, the scintillation detector converts the energy of the photon into a flash of light.

A radionuclide emits discrete energy photons which can either be totally absorbed, partially absorbed, or completely missed by a scintillation detector.

Principle of operation of a scintillation detector (cont):

Basic Principles of Detection (cont)

The flash of light is converted into an electrical pulse which is amplified and subsequently analyzed.

• a crystal• photomultiplier tube• high voltage supply• preamplifier• amplifier• pulse height analyzer• display device

scaler rate meter

A scintillation detector comprises:

• a cylindrically shaped, gas filled sealed chamber with a well;

Gas Filled Detectors

A dose calibrator (activity meter) comprises:

• high voltage supply applied to electrodes.

• specific energy settings for different

radionuclides;an activity readout (e.g. in

MBq, GBq, etc).

• Turn on the main power and wait for any self checks or warm-up up to complete.

Using a Dose Calibrator (Activity Meter)

• place the syringe or vial holder in the detector well;

• select appropriate (nuclide, energy) settings;

• zero the dose calibrator;

• measure the activity of the radionuclide in the syringe or vial;

• read the activity from the display console and record.

For any worker who is normally employed in a controlled area

Personal Monitoring

• Thermoluminescent (TLD) dosimeter

gamma, X and beta radiation

• Film dosimeter

gamma, X and beta radiation

Personal Monitoring (cont)

Doses from External Radiation

Personal Monitoring (cont)

Doses from External Radiation (cont)

Electronic dosimeter, with or without alarm

Film badge, electronic dosimeter, ring badge, TLD

Personal Monitoring (cont)

Thermoluminescence (exposure)

TLD being irradiated

Personal Monitoring (cont)

Filament heats TLD emitted lightreadout

Thermoluminescence (read-out)

photomultiplierOSL dosimeters use different material to TLDs emit light following stimulation by a laser.

Personal Monitoring (cont)

TLDs

• Urinalysis

• Whole body monitor

gamma emitting radioisotopes

• Thyroid monitoring

iodine radioisotopes

Personal Monitoring (cont)

Assessing Doses from Internal Radiation

• detect low activity contamination;

Counting and Survey Equipment

Geiger-Mueller (G-M) survey meters are used to:-

• perform surveys of rooms,

• monitor personnel and to determine when a patient who has received

a therapeutic treatment with radioactive substances can be released

from the hospital;

• survey incoming packages of radioactive material.

Monitoring (counting and survey) Equipment

have a long half lifea range of photon energiesa range of activitieshave an activity accuracy within ±5%

e.g. 57Co, 133Ba, 137Cs, 60Co

Calibration sources for Dose Calibrators

Calibration sources for dose calibrators typically:-

Mainly used for counting during thyroid uptake studies.

Non-imaging Counting Devices

• mainly to count blood and urine samples.

• to count wipe test samples to identify if radioactive contamination exists in the area surveyed.

Non-imaging Counting Devices (cont)

Scintillation Well Counters are used:-

• to count samples of low activity and low energy β particles such as 3H or 14C (but are not routinely found in Nuclear Medicine departments).

Non-imaging Counting Devices (cont)

Liquid Scintillation Detectors are used:-

• to show how the radiopharmaceutical distributes itself throughout the body or is taken up by specifically targeted organs.

Gamma Cameras

Gamma cameras are used:-

Gamma Cameras (cont)

•In most cases, gamma cameras are interfaced with a computer which controls data acquisition, processing and image display.

Gamma Cameras (cont)

Dynamic

Static

Tomographic

Still and dynamic images can be acquired

Gamma Cameras (cont)

• SPECT cameras looks at a patient from many different angles and is able to demonstrate very precise detail within the patient.

Single Photon Emission Computed Tomography

SPECT Imaging

Information is presented as a series of planes that correspond to certain depths within the body.

The planes presented may be a series of coronal, sagittal, transverse and/or oblique slices.

SPECT Imaging (cont)

Rollo 1977

Early scintillation imaging devices

Rectilinear Scanners

• Processes studied include blood flow, oxygen, glucose and fatty acid metabolism, amino acid transport, pH and neuroreceptor densities.

Positron Emission Tomography (PET) is used to study physiologic and biochemical processes within the body

PET Scanners

An on-site cyclotron is required to produce the very short half life PET radiopharmaceuticals.

PET Scanners (cont)

Mobile PET Scanner

(d) unsealed sources for nuclear medicine procedures (will) be calibrated in terms of activity of the radiopharmaceutical to be administered, and the activity shall be determined and recorded at the time of administration, and…...

Calibration of Equipment and Sources

[BSS II.19] Registrants and licensees shall ensure that:

(e) the calibrations (will) be carried out at the time of commissioning a unit, after any maintenance procedure that may have an effect on the dosimetry and at intervals approved by the Regulatory Authority

• The proper calibration of instruments should be maintained through a regular quality control program and performed by an organization recognized by the Regulatory Authority.

Calibration of Equipment and Sources (cont)

Equipment used in Nuclear Medicine requires routine calibration and a significant number of quality control measures (see 3.12 for more detail).