1. IAEA E-learning Program
Safety and Quality in Radiotherapy

2. Safety and Quality in Radiotherapy
MODULE 4: process maps, severity metrics, basic causes & safety barriers
Sections:
4.1 Process Maps
4.2 Severity Metrics
4.3 Basic Causes
4.4 Safety Barriers
In Module 3 we gained an overview of Incident Learning Systems and their key features. In this Module we’ll look in more detail at several of the key components of an ILS.

3. Safety and Quality in Radiotherapy
MODULE 4: process maps, severity metrics, basic causes & safety barriers
Sections:
4.1 Process Maps
4.2 Severity Metrics
4.3 Basic Causes
4.4 Safety Barriers
Safety barrier is the last topic in our overview of major components of an incident learning system.

4. Safety and Quality in Radiotherapy
MODULE 4: process maps, severity metrics, basic causes & safety barriers
Section 4: safety barriers
OBJECTIVES
To understand the value of incorporating safety barriers in an incident learning system.
To review 3 approaches to the identification of safety barriers.
The section objectives are to understand the value of incorporating safety barriers in an incident learning system and to review 3 approaches to the identification of safety barriers.

5. Safety and Quality in Radiotherapy
MODULE 4: process maps, severity metrics, basic causes & safety barriers
Section 4: safety barriers
OBJECTIVES
To understand the value of incorporating safety barriers in an incident learning system.
To review 3 approaches to the identification of safety barriers.
Firstly we will understand the value of incorporating safety barriers in an incident learning system.

6. Safety and Quality in Radiotherapy
MODULE 4: process maps, severity metrics, basic causes & safety barriers
Section 4: safety barriers
What is a Safety Barrier?
A safety barrier is a step in the process designed to intercept errors that may have entered during previous steps. Safety barriers complement preventive actions developed through an Incident learning system and process improvements implemented as a result of fault tree analysis.
A safety barrier is a step in the process designed to intercept errors that may have entered during the previous steps. Safety barriers complement and may actually be preventive actions developed through an incident learning system. The placement of safety barriers such as checklist can be guarded by fault tree analysis as discussed in module 9.

7. Safety and Quality in Radiotherapy
MODULE 4: process maps, severity metrics, basic causes & safety barriers
Section 4: safety barriers
What’s the purpose of a Safety Barrier?
Optimizing safety requires fundamentally safe procedures together with safety barriers to catch the inevitable errors which will occur along the treatment preparation/delivery pathway. Safety barriers are another way of enhancing the safety of a critical process. However safe we design the process to be, there will always be the possibility of an error slipping through.
What is the purpose of a safety barrier? Optimizing safety requires fundamentally safe procedures together with safety barriers to catch the inevitable errors which will occur along the treatment preparation and delivery pathway. Safety barriers are another way of enhancing the safety of a critical process. However safe we design the process to be, there will always be the possibility of an error slipping through.

8. Safety and Quality in Radiotherapy
MODULE 4: process maps, severity metrics, basic causes & safety barriers
Section 4: safety barriers
What’s the purpose of a Safety Barrier?
Dr. James Reason, a highly respected safety analyst, has illustrated what happens when all safety barriers fail with his Swiss Cheese model1.
Dr. James reason, a highly respected safety analyst has illustrated what happens when all safety barriers fail with his Swiss cheese model. If there are multiple pathways that lead to an incident and not just one as shown here, then safety barriers have to be designed and placed at appropriate points to intercept system failures along any pathway. We will explore this issue further when we discuss fault tree analysis in module 9.
Multiple sequential safety barriers along the process map constitute what is known as ‘Defence in death’. Clearly the more safety barriers along a particular failure pathway, the less likely it is that an error will not be intercepted and penetrate through the patients.
Multiple sequential safety barriers along the process map constitute “Defence in Depth”.

9. Safety and Quality in Radiotherapy
MODULE 4: process maps, severity metrics, basic causes & safety barriers
Section 4: safety barriers
Why include Safety Barriers in an incident learning system?
Safety barriers, like any other quality assurance measure, consume resources. Our understanding of the effectiveness of Safety Barriers which we commonly employ is limited. Capturing information on which barriers are effective and which not will lead to the more efficient use of scarce resources within the radiotherapy program. Ford and colleagues are one group that has explored the effectiveness of conventional safety barriers in 2 U.S. radiotherapy departments2. Results of such studies are likely to be dependent on the operating procedures and safety environment of individual departments.
Safety barriers like any other quality assurance measure, consume resources. Our understanding of the effectiveness of safety barriers which we commonly employ is limited. Capturing information on which barriers are effective and which are not will lead to the more efficient use of scarce resources within the radiotherapy program. However there is a practical limit to how many and how complex this safety barrier can be. Hence, we need to understand more about safety barriers and particularly their effectiveness.
Ford and colleagues are one group that has explored effectiveness of conventional safety barriers in 2 U.S. radiotherapy departments. In interpreting the results of such studies, however, it is important to recognize they are likely to be dependent on the operating procedures and safety environment of the individual departments.

10. Safety and Quality in Radiotherapy
MODULE 4: process maps, severity metrics, basic causes & safety barriers
Section 4: safety barriers
Why include Safety Barriers in an incident learning system2?
This is what Ford and colleagues found. The analysed the effectiveness of various safety barriers. This results to some extent to reflect local practice at the participating institutions. This chart also indicates the types of activities that can be classified as safety barriers.

11. Safety and Quality in Radiotherapy
MODULE 4: process maps, severity metrics, basic causes & safety barriers
Section 4: safety barriers
Why include Safety Barriers in an incident learning system2?
This graph also from the work of Ford and colleagues, demonstrates the point made earlier that the more safety barriers in place, the safer the system will be. Low severity incidents are shown in red and high severity incidents in black. However the more safety barriers we have, the more it will cost in terms of people's time.

12. Safety and Quality in Radiotherapy
MODULE 4: process maps, severity metrics, basic causes & safety barriers
Section 4: safety barriers
OBJECTIVES
To understand the value of incorporating safety barriers in an incident learning system.
To review 3 approaches to the identification of safety barriers.
Now we will review three approaches to the identification of safety barriers.

13. Safety and Quality in Radiotherapy
MODULE 4: process maps, severity metrics, basic causes & safety barriers
Section 4: safety barriers
AAPM Safety Barriers3
This is a reminder of the AAPM’s process map. 

14. Safety and Quality in Radiotherapy
MODULE 4: process maps, severity metrics, basic causes & safety barriers
Section 4: safety barriers
AAPM Safety Barriers3
6. On-treatment quality management
SB Initial physics check
SB Review of portal images
SB Review of localization images (including CBCT)
6.4 Adaptive replanning
SB 6.5 Weekly physics chart check
SB 6.6 Weekly physician management visit, social work, nutrition and nursing
SB 6.7 Weekly therapist chart check
6.8 Other
In the expanded tabular form of the process map, those activities which can be called safety barriers are identified as SB.

15. Safety and Quality in Radiotherapy
MODULE 4: process maps, severity metrics, basic causes & safety barriers
Section 4: safety barriers
Canadian System Safety Barriers4
A Canadian group is also developing an incident learning system for national use. The system should be released in This shows the draft safety barriers table. The intention is to find out more about which barriers are more effective and which less.

16. Safety and Quality in Radiotherapy
MODULE 4: process maps, severity metrics, basic causes & safety barriers
Section 4: safety barriers
SAFRON5
Here are the SAFRON safety barriers. The reporter is asked to identify those barriers which failed as well as those successfully intercepted the system failure. Again the information to be gleaned from reports, such as this, helps us identify those safety barriers which are effective and which are not. We will be using this example table in module 7.

17. Safety and Quality in Radiotherapy
MODULE 4: process maps, severity metrics, basic causes & safety barriers
Section 4: safety barriers
summary
We have:
Explored the value of incorporating Safety Barriers in an Incident Learning System.
Reviewed 3 approaches to the identification of Safety Barriers.
In summary, we have explored the value of incorporating safety barriers in an incident learning system and we have reviewed 3 approaches to the identification of safety barriers.

18. Safety and Quality in Radiotherapy
MODULE 4: process maps, severity metrics, basic causes & safety barriers
Section 4: safety barriers
References and additional resources
Reason, J. (1990) Human Error. Cambridge: University Press, Cambridge.
Ford EC, Terezakis S; Souranis A; et al. Quality control quantification (QCQ): A tool to measure the value of quality control checks in radiation oncology. Int J Radiat Oncol Biol Phys. 2012;84(3):e263-e269.
Ford E, Fong de los Santos L, Pawlicki T , et al. Consensus recommendations for incident learning database structures in radiation oncology. Medical Physics 39,
Canadian system.
SAFRON.