Medical physics

Who is a medical physicist

Medical physicists play an important role in modern medicine, most often in diagnosis of diseases and cancer treatment. They are a part of an interdisciplinary team in radiation oncology, radiodiagnosis and nuclear medicine.

“A medical physicist is a healthcare professional who has specialized education and professional training in the concepts and methods of applying physics in medicine and who is competent to practice independently in one or more sub-fields of medical physics.

What does he do

There are three main areas in clinical medical physics:

• “Radiation therapy” (radiation oncology),
• "Radiodiagnosis",
• "Nuclear medicine".

In different areas, medical physicists have different basic functions.

Medical physicists at the UMIT Tomotherapy Center work in the field of radiation oncology.

Obligations of a medical physicist in our center are as follows:

1) Clinical dosimetry

The main task of clinical dosimetry consists in the selection and explanation of irradiation means that provide an optimal spatiotemporal distribution of the absorbed radiation energy in the body of the irradiated patient and a quantitative description of this distribution.

The tasks of clinical dosimetry are the following:

• measurement of radiation characteristics for therapeutic radiation beams;
• measurement of radiation fields and absorbed doses in phantoms;
• direct measurement of radiation fields and absorbed doses on patients;
• measurement of radiation fields of diffuse radiation in canyons with therapeutic equipment (for the purpose of radiation safety of patients and personnel);
• carrying out absolute calibration of detectors for clinical dosimetry;

2) Treatment planning

A virtual model of a patient is built based on various medical images (for example, from a CT, MRI and PET scanner), in which the body contours, the “target” and all organs of the patient in the area of the intended radiation are determined.

After that, the optimization of the dose delivery to the patient is carried out taking into account all the factors that affect it: the speed of the therapeutic table, the rotation speed of the accelerator that generates ionization radiation, as well as the degree of the radiation output intensity modulation, etc.

In accordance with the prescription of the radiation oncologist, the minimum dose values for a certain tumor volume and the maximum allowable values for organs and healthy tissues (in accordance with international recommendations) are calculated.

The main task of a medical physicist is to irradiate the “target” as much as possible, at the same time preserving healthy organs and tissues in the irradiation zone.

3) Verification of dosimetric plans

After the radiation oncologist approves the dosimetric plan, medical physicists begin to verify it.

In radiation therapy, verification is an independent comprehensive control that confirms that the dose distribution delivered to the target in the patient's body corresponds to the planned distribution.

Verification is carried out using special dosimetric equipment before starting the tomotherapy course for each patient.

4) Quality control of tomotherapy equipment

In our center, medical physicists have developed a quality control program for Tomotherapy machines based on the recommendations of international professional communities and the manufacturer.

Quality control is the evaluation of functional characteristics that ultimately affect the geometric and dosimetric accuracy of dose delivery, and is also a key element in the radiation protection of patients.

Performance features of equipment may change suddenly due to failure of any part or mechanical breakdown, or slowly due to wear and tear of parts.

In this regard, medical physicists regularly test all equipment, including the devices used for quality control.

The purpose of these procedures is to ensure the consistency of the specified characteristics and physical parameters set during the commissioning of the equipment.

Every morning, medical physicists perform daily checks, and only after making sure that the devices are in correct working order, they are handed over to X-ray laboratory technicians to perform tomotherapy for patients.

5) Radiation safety.

Medical physicists are responsible for the radiation safety of both patients undergoing tomotherapy and the staff of our Center.