Careers: Nuclear Medicine Physics

What is Nuclear Medicine?

Nuclear Medicine is the use of liquid or gaseous radioactive substances to diagnose or treat human disorders. A nuclear medicine technique involves measuring the uptake or “tracing” the distribution of the radioactivity throughout the patient’s body. A major part of the department’s services provides scanning and metabolic studies using either ‘gamma camera’ or scanning type imaging equipment. The diagnostic studies provide a non-invasive method for assessing the physiological body functions as well as imaging the size and distribution of the labelled radioactivity in any part of the body. It’s an exceptionally useful, sensitive method that complements the other X-ray and magnetic resonance imaging techniques. Nuclear medicine continues to be an essential healthcare technology service.

Nuclear Medicine Physicist Skills

Nuclear Medicine Physicists are essential members of the multidisciplinary clinical team providing healthcare for diagnostic and therapeutic purposes. The Nuclear Medicine Physicists work in collaboration with the hospital’s Radiochemist Specialists. Combined, they provide the scientific basis of nuclear medicine procedures for patient care. They are trained experts in the production and processes of radiation interaction in the body.

Nuclear Medicine Physicists are qualified post-graduate professionals with extensive training in:

• mathematics;
• radiation physics; and
• the biological system.

The Nuclear Medicine Physicist oversees or provides:

• the department’s proper equipment operation;
• adequate radiation safety and protection of staff, patients and carers.
• teaching and training of junior scientists and medical staff;
• advanced IT and computing applications;
• troubleshooting of scan artefacts or abnormal appearances; and
• verifies results of clinical radiation studies by simulated measurements.

The Nuclear Medicine Physicist also works closely with the specialist physicians and technologists for the clinical delivery of the patient’s treatment procedure. He/she has clinical responsibilities to ensure that all radioactive materials and nuclear medicine equipment are accurately and safely used by the clinicians. The work often involves consulting with the clinicians and technologists, particularly when it requires:

• problem-solving of unusual clinical case presentations; or
• difficult patient results that may need further development; or
• there’s a need to improve organ function analysis; or
• there’s simply a continued need to better understand the patient’s abnormal biological processes.

Problem-solving is a major activity for the Nuclear Medicine Physicist.  Creative solving of problems or devising new imaging tests and analyses, are important skills. To be a respected integral participant in a highly specialised clinical group, the Nuclear Medicine Physicist should have a solid knowledge/understanding of the clinical basis of most common diseases and disorders that patients attending nuclear medicine have. The Nuclear Medicine Physicist should be able to effectively contribute expertise during the consultation processes with the multidisciplinary team managing the patient.

Nuclear Medicine Physicists may apply their physics expertise when involved in the following broad areas, as a member of the multidisciplinary team:

Clinical Role of the Nuclear Medicine Physicist

Clinical Nuclear Studies

The Nuclear Medicine Physicist is expected to have a scientific understanding of the patient’s measurement or imaging data. While the clinicians may recognise disease caused abnormalities in this data, the physicist should have sufficient expertise to understand the complete diagnostic or therapeutic chain processes – from the initial radioactive compound intake through to the final image or instrument measurement results.

Skills to competently analyse abnormal patient data is essential. When developing new clinical applications, the goal should be to optimise and refine the methodology of data collection and its analysis.

The Nuclear Medicine Physicist plays a major role in implementing new clinical procedures, including processing the work by manual confirmation of the quantitative measurements, before it is used for patient studies.

Instrumentation

Nuclear Medicine Physicists are responsible for ensuring the correct operation and calibration of all equipment, used in nuclear medicine facilities, such as:

• the radioactive source dose calibrator (which measures the amount of radioactivity in a container,  vial or patient injection);
• the accurate calibration of the nuclear imaging cameras and scanners;
• testing to ensure error-free software programs (used to compute the patient images).

The knowledge and skills the Nuclear Medicine Physicist obtains during their studies and training, equip them well to support the department to keep the sophisticated high technology equipment running. There are often staff calls to troubleshoot or resolve equipment malfunctions. This may entail deciding whether the nuclear scanning system may continue to be reliably used for patient tests.

Computing and image analysis

Nuclear Medicine is heavily reliant on computers, information technology and networks.  The imaging computer equipment uses sophisticated algorithms to:

• create three-dimensional image reconstructions;
• model the kinetic physiological system;
• determine rates of change over time during the “uptake” of the radioactive substance in tissues and organs; and
• predict cancer cell kill and tissue damage from the uptake of a radioactive substance.

Nuclear Medicine Physicists need one or more programming language skills for the development of new analytical techniques that can be used on the specialised image scanner workstations.

Modern nuclear medicine imaging equipment is described as a ‘hybrid multimodal device’. By combining data from separate image systems, the Nuclear Medicine Physicist must have sufficient expertise to use sophisticated integration tools that make exchangeable DICOM files compatible. The DICOM files need a method of detecting any source of error and a means of validating the measurement technique.

Radiation dosimetry and safety:

1. Radiology and Other X-ray Suites

The use of X-ray apparatus for diagnostic imaging of the patient, is well known. As well as the specialised use of X-ray equipment (planar X-ray imaging, fluoroscopic imaging and CT scan imaging), many other clinics (cardiology, gastroenterology, neurology) and operating theatres (for urology,  orthopaedics and general surgery) use a form of X-ray imaging for either diagnostic or surgical purposes.

Providing the X-ray exposure is kept to as-low-and-reasonably-achievable (the ALARA principle), these procedures are considered radiation safe for the patient. That is, there are no immediate or long-term radiation effects to the patient. Radiology Medical physicists or Nuclear Medicine Physicists can provide radiation support and advice to these hospital departments.

Radiation dosimetry and safety:

1 Radiology and Other X-ray Suites

The use of X-ray apparatus for diagnostic imaging of the patient, is well known. As well as the specialised use of X-ray equipment (planar X-ray imaging, fluoroscopic imaging and CT scan imaging), many other clinics (cardiology, gastroenterology, neurology) and operating theatres (for urology,  orthopaedics and general surgery) use a form of X-ray imaging for either diagnostic or surgical purposes.

2. Radiotherapy

But, for high X-ray exposures, there will be ‘ionising effects’ that can ‘kill’ living cells. Fortunately, cancer cells are slightly more sensitive to the X-rays than the normal tissue cells. Radiotherapy uses this radiation advantage to ‘kill’ cancer cells while protecting the normal cells from irreversible damage.

3 Nuclear Medicine

Virtually all nuclear medicine procedures involve liquid or gaseous (referred to as ‘unsealed’) radioactive substances. The unsealed radioactive substances may emit one or more forms of alpha, beta or gamma radiation. The absorption in tissue of these different radiations is very complex. It requires Nuclear Medicine Physics expertise to calculate the absorbed dose to the tissue cells.

(i) Diagnostic Nuclear Medicine Studies

A small amount of radioactive substance (mostly emitting gamma radiation) is injected into the patient for a radiation safe diagnostic study. The activity of the radioactive substance quickly decays so that any residual activity in the patient is not a danger to the general public after the procedure is finished. The Nuclear Medicine Physicists ensures that procedures for shielding and storing radioactive substances or measuring, injecting and imaging the patient are carried out safely with accurately calibrated equipment.

(ii) Therapy Nuclear Medicine

Similar to that described for the radiotherapy use of ionising radiation, nuclear medicine therapy can be provided using a liquid radioactive substance. Radioactive iodine has been used for many years to treat patients for thyrotoxicosis (the patient receives a relative low activity dose as an out-patient) or thyroid cancer (the patient receives a much higher activity and is kept as an in-patient under surveillance for a few days). The patient drinks the dose of radioactive iodine liquid. The radioactive iodine is naturally taken up into the patient’s thyroid and gives a high dose to it from the emitted gamma and beta-rays. The Nuclear Medicine Physicist oversees the radiation safe aspects of these procedures and provides instruction and patient care advice for ward care, discharge and general public safety.

A more recent therapeutic technique involves the injection of a radioactive isotope labelled to a cancer seeking drug. The Nuclear Medicine Physicist is involved in the prescribing of these cancer patient treatments. The method of calculating a suitable radioactive dose is highly complex because it requires an in-depth knowledge of tissue absorbed dose from the radiation, the uptake of the radioactive substance in the cancer cells and the radiation sensitivity of normal versus cancer cells.

Teaching and research

Nuclear Medicine Physicists are expected to approach clinical problems based on their knowledge and scientific training – that is, they should develop methods that can solve the problem and test it with an open mind, refining the research as necessary.

Nuclear medicine is heavily based on science. It has applied mathematics, radiation physics, biology, physiology and instrumentation. It requires solving inverse problems.

The Nuclear Medicine Physicist is often involved in research programs and the teaching of a broad range of health professionals.  It may be nurses from the hospital ward concerned about the patient receiving radioactive treatment, or the radiographers and technologists involved in performing the scans and other clinical patient measurements, or the medical specialists or other clinical colleagues involved in the patient’s management.

Finally, the hospital is staffed by a very large number of medical specialists and health professionals who regularly interact at joint or ad-hoc clinical meetings. The goal of these meetings is to review current techniques, compare patient treatment outcomes and discuss better methods of treatment. Many of the suggestions for new techniques and improved analyses are often initiated in interdisciplinary discussions. The Nuclear Medicine Physicist is a key contributor to better patient healthcare.

For Professor Bailey’s description for how he found his career progressed, click on this ABC Catalyst video