Patient Safety

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TU_27_3072 - Risk Assessment in HDR Brachytherapy using AAPM TG 100 Methodology

Tuesday, October 23
1:00 PM - 2:30 PM
Location: Innovation Hub, Exhibit Hall 3

Risk Assessment in HDR Brachytherapy using AAPM TG 100 Methodology
W. Gao; Overton Brooks VA Medical Center, Shreveport, LA

Purpose/Objective(s): to analyze major risks associated with HDR brachytherapy based on reported medical events and to provide a reasonable estimate of O (Occurrence), S (Severity) and D (lack of detectability) factors for major failure modes (FM) in HDR brachytherapy procedures.

Materials/Methods: Between January 1999 and December 2017, two hundred and nineteen (226) patients received HDR Brachytherapy treatments that were reported to NRC as medical events. The present study focuses on 150 of those events, as sufficient details were supplied in the event reports. Events related to equipment or device failures are excluded from the current study. For each FM, the Occurrence (O) factor is determined as the frequency of occurrence relative to the most common failure mode(O=10). The Severity (S) factor of each event, on a scale of 1-10, was given mainly based on the magnitude of dose deviation from the prescribed dose or source displacement relative to the planned position. The Severity of each FM is then taken as the average of the severity factors of all medical events in the very category. The Lack of Detectability (D), also on a scale of 1-10, is assigned to each FM based on the nature of the failure, number of patients involved in the same error and author’s experience. The Risk Priority Number or RPN is calculated as RPN=OxSxD. Process mapping is performed to illustrate different steps in HDR procedures. Faulty tree analysis (FTA) is carried out to reveal possible causes to the failures.

Results: Thirty-three (33) major failure modes (FM) are identified in the study. The RPN values range from 47 to 856. The 10 riskiest FMs are: 1. New catheter or transfer tube used for treatment but lengths of old catheters are used for planning; 2. Wrong step size entered for treatment delivery (for manual afterloaders); 3. Treatment length entered wrongly in planning; 4. Incorrect measurement of catheter length; 5. Use of standard or default length instead of measured lengths in planning; 6. Catheter or applicator moves during treatment 7. Catheter/applicator insertion too close or too far; 8. Wrong set of transfer tube or catheter used for treatment; 9. Applicator insertion to the wrong site; and 10. Catheter pulled out by patients during treatment. The majority of high risk failures occur in treatment planning or treatment delivery. Faulty tree analysis (FTA) shows that organizational factors could also pose significant risks to safety.

Conclusion: Reported medical events can be used to estimate RPN values for errors in HDR brachytherapy. AAPM TG 100 provides an effective tool for developing a QM program by prioritizing the use of QA resources with priorities given to the most hazardous failures or conditions. Nevertheless, the effectiveness of any QM program will ultimately be determined by individuals’ quality as well as operation and safety environment.

Author Disclosure: W. Gao: Independent Contractor; SAMP. Honoraria; ACR.

Wanbao Gao, PhD

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