@article{oai:repo.qst.go.jp:00047403,
 author = {Yagahara, A. and Sato, H. and 横岡, 由姫 and Tsuji, S. and Kurowarabi, K. and Ogasawara, K. and 横岡 由姫},
 issue = {7},
 journal = {Journal of Medical Imaging and Health Informatics},
 month = {Dec},
 note = {Background: We introduce a new hierarchical task analysis (HTA), called bottom-up hierarchical task analysis (B-HTA), which is an extension of the HTA method. HTA is a task analysis method that uses the probability of failure (P) multiplied by the cost of failure (C) rule (P × C rule) to describe a hierarchical structure of tasks and subtasks by decomposing each task into subtasks. In contrast, B-HTA describes a hierarchical structure of clustered individual tasks without using the P × C rule. This study applies our proposed B-HTA to the mammography examination process.
Methods: First, we employed HTA to analyze the mammography examination process, focusing on mediolateral oblique (MLO) positioning. Second, we employed B-HTA to analyze the examination process. The process flow was as follows: An affinity diagram was constructed to cluster and connect the tasks extracted by brainstorming. Finally, a hierarchical structure was constructed based on the clusters and relationships in the affinity diagram. We compared the number of tasks in HTA with that in B-HTA to describe the MLO positioning process, and interviewed five radiologic technologists regarding the validation and impression of the results from HTA and B-HTA.
Results: In HTA, there were 50 tasks. In B-HTA, 167 labels were extracted and classified into eight larger groups and 16 relations in the affinity diagram. In addition, a hierarchical structure was constructed with 164 tasks, nine top levels, and a maximum of five ranks. It was revealed that it was important for radiologic technologists to allow patients to relax before positioning. The result of the interview revealed that all technologists considered that B-HTA described the flow of the mammography examination process and the tasks in detail 
Conclusion: Our proposed B-HTA (without the P × C rule) clarified the hierarchical structure of a mammography process comprising 164 tasks. B-HTA was able to describe the process in detail.},
 pages = {1429--1434},
 title = {Proposal for Bottom-up Hierarchical Task Analysis: Application to the Mammography Examination Process},
 volume = {5},
 year = {2015}
}