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 light readout Thermoluminescence (read-out) photomultiplier OSL 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 life a range of photon energies a range of activities have an activity accuracy within ±5% e.g. 57 Co, 133 Ba, 137 Cs, 60 Co 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 3 H or 14 C (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).