Part 9: Medical Exposure Lesson 1: Overview - this lecture is complemented by parts 10 and 11 Learning objectives: On completion of the module the participant will understand the concept of “medical exposure” as set out by the BSS in the context of radiotherapy appreciate the importance of justification and optimization for medical exposures To understand strategies for optimization of dose to patients, relatives and volunteers Activity: lecture Duration: 2 hours References: BSS
The Safety Fundamentals provide the basis for the BSS - the hierarchy of IAEA documents is discussed in part 4 of the course.
BSS is really going to be quoted throughout Who is affected? Mainly Patients - however also volunteers and support persons
This is an opportunity to point out the central role of the concept of “Medical Exposure” for the objectives of the course. About 30% of the course is dedicated to this topic.
It may be useful to go through some of the requirements word by word - the lecturer will have the opportunity to point out why and how this is relevant for radiotherapy practice.
The following are quotes from the BSS - the lecturer should try to place them in perspective of current radiotherapy practice. Comments are also given in the notes section to some slides.
It is important to note that the medical practitioner is the start all and end-all of medical procedures. No medical exposure can be performed with out a prescription and she/he is ultimately responsible for the patient’s safety during the procedures. This central role of the medical practitioner should be pointed out (in particular if the course is given to a significant number of clinicians)
The last point is discussed in more detail in parts 10 and 11 for external beam and brachytherapy, respectively. This is done particularly in the context of ICRU reports 38, 50, 58 and 62.
This slide extends the concept to other professions - again a good opportunity to point out that this is indeed relevant for all professionals participating in the course.
This is directly taken form BSS - it makes also good sense in a radiotherapy environment. More details on the next two slides.
This slide graphically illustrates the magnitude of different groups of persons who are affected by medical exposures in radiotherapy. The lecturer can point out that this is also reflected in the structure of the present course with parts 10-12 largely dedicated to cancer patients. In the following more details will be provided
The lecturer should advise students that diagnostic exposures are covered in similar courses on diagnostic radiology and nuclear medicine. If possible a prospectus could be circulated. The last three points are expanded on in the following
The lecturer can point out that other exposures, in particular diagnostic ones for follow up, are possible and usually required for radiotherapy patients. However, the exposures discussed and shown here are specific for radiotherapy and as such subject of the present course.
This was discussed in more detail in part 4 of the present course.
The lecturer can also refer to the increasing body of clinical evidence which can guide the justification process. Radiotherapy is one of the more ‘scientific’ approaches where outcomes are relatively well documented and well conducted clinical trials have yielded good evidence for particular treatment approaches.
It is important for the lecturer to point out that secondary does not mean NO concern. On the contrary… leading to the next slide. This slide is designed to reflect the experience of many radiotherapy professionals. From there the need for consideration of radiation protection is made in the following slides. However, there may be audiences where this and the next two slides cause more confusion than they are helpful. The lecturer may in this circumstance decide to omit the slides.
The lecturer can point out that good practice aims to increase the window of opportunity and help to make rational decisions in terms of justification of medical exposures.
Optimization will be the main objective of parts 10 to 13. Here only a brief summary of the subject heading is given which leads to the next slide… Optimization in radiotherapy is conventionally linked to optimizing the dose to the target, often with the aim to increase the dose. Radiation protection on the other hand has the objective to ‘optimize protection’. The point can also be illustrated on the next slide. The objective is to separate tumor control and normal tissue complication probability by doing both: Maximizing the dose to the tumor AND Minimizing the dose to healthy structures It is interesting to note that modern inverse treatment planning has both types of objectives included in the approach: constraints for dose to the target and dose constraints for organs at risk. The platypus illustrates the concept of optimization (at least to some degree): The animal has features from a number of different species (bill, claws, fur, pouch, lays eggs) which make it optimally adapted for its environment.
…which emphasizes optimization as the main objective of safety in radiotherapy.
The lecturer may want to point out that in some circumstances it could be advantageous to include relatives explicitly in the care of brachytherapy patients. Given appropriate training, they can support the patient in his/her isolation. As the relative typically only care for one individual, they will overall be exposed to considerably less dose than staff who would look after many many patients in any one year. This practice is common in many centers - however, its ‘justification’ needs to be discussed very carefully.
The next two slides raise an issue which unfortunately does not arise too often in radiotherapy as most cancer patients are elderly - the lecturer can refer to ICRP report 77 for more information. International Commission on Radiological Protection. Radiological Protection and Safety and pregnancy, ICRP report 77. Oxford: Pergamon Press; 1999.
This slide provides a lot of information - the important message is that radiotherapy and pregnancy are in most circumstances incompatible. However, risks can be calculated (compare eg ICRP report 77) and the circumstances of the patient must be taken into consideration when making a decision. The lecturer can remind participants also of the fact that many people accept the risks of smoking during pregnancy - despite the fact that also smoking has been shown to have a negative affect on the development of the fetus.
The lecturer could discuss with participants the need for children to visit their parents while they undergo brachytherapy. In practice this should be avoided - however, one needs to carefully evaluate each individual case
The lecturer can explain the points made above: Participation in clinical trials is always voluntary. There must be no pressure on patients and they must be able to withdraw form the trial at any time without any negative consequences for them There are situations when side effects in patients (usually palliative treatments) are scored for radiobiological research. Examples are skin reactions. Often new radiotherapy techniques are used on palliative patients first - in this case a larger variation of dose is acceptable without the dramatic effect on treatment outcome which might occur in radical treatments
In the case of volunteers for radiotherapy research, justification is the most important issue.
The three professions have the most important tasks in assuring that medical exposure in radiotherapy is optimized. The lecturer could point out that also other professionals such as nurses have a role to play - however, their impact on treatment justification and optimization is typically via one of the above professionals. The list may be altered by the lecturer if a significant number of participants for the course are from one of the other professions - in this case the relevant profession should be dealt with explicitly. Please note also that the question at the end of part 9 is specifically aimed at discussing the role of other medical staff. To maintain an element of surprise, they should not be mentioned here.
Lecture notes: ( about 100 words) Instructions for the lecturer/trainer
Two important concepts here are discussed in the next slides
Clinical evidence is one of the key concepts in medicine. It has obvious implications for best practice and maximum benefit for the patient. However, it is also of great importance for resource allocation and planning of expenditures for medical procedures. As such health insurers and pedicel professional organizations both are very interested in clinical evidence which can prove that a particular treatment approach meets its objectives.
Prescription is part of the responsibilities of the medical practitioner.
The lecturer can point out that the term ‘clinical dosimetry’ used in accordance to BSS included treatment planning. To quote BSS: Clinical dosimetry II.20. Registrants and licensees shall ensure that the following items be determined and documented: (a) in radiological examinations, representative values for typical sized adult patients of entrance surface doses, dose-area products, dose rates and exposure times, or organ doses; (b) for each patient treated with external beam radiotherapy equipment, the maximum and minimum absorbed doses to the planning target volume together with the absorbed dose to a relevant point such as the centre of the planning target volume, plus the dose to other relevant points selected by the medical practitioner prescribing the treatment; (c) in brachytherapeutic treatments performed with sealed sources, the absorbed doses at selected relevant points in each patient; (d) in diagnosis or treatment with unsealed sources, representative absorbed doses to patients; and (e) in all radiotherapeutic treatments, the absorbed doses to relevant organs.
The last statement is a good point to turn to other professionals in radiotherapy (next slide). The focus is on team.
This slide introduces the professionals who typically are in closest contact with the patient during their treatment from day to day. The profession of radiation therapy technologists is defined differently in different countries. In some countries they are responsible for parts of clinical dosimetry (treatment planning) and have a degree, while in other counties they have a diploma of technology and their main responsibility is to set-up patients for treatment. The lecturer may modify the slide depending on the situation of the country where the course is held.
More details on radiation protection officers is given in part 18 of the course.
The lecturer can point out that optimized treatment outcome in practice is identical to optimized ‘medical exposure’ in radiotherapy as discussed in the BSS.
This question is of particular relevance to hospital administrators and all medical practitioners participating in the course. It illustrates the network of professions which are responsible for the treatment and for its optimization, including the radiation protection aspects subject of the present course.