# Surgical Phase Recognition: From Public Datasets to Real-World Data
## 3 Results
### Comparative Analysis of Chole80 and Our Dataset  
Surgeries in our dataset were much longer than surgeries in Chole80. Our surgeries had a median duration of 54 minutes (min: 13, max: 374) against 34 minutes (min: 12, max: 99) for the Chole80 videos (see Supplementary Figure S1 online for a more detailed distribution of the video lengths). Attentively inspecting each video in our dataset, we found some surgical phases which were not present in our guidelines (see Supplementary Table S1 online for the complete set of our annotation guidelines) and in the public Chole80 dataset. In collaboration with a board certified surgeon, we identified these phases as _gallbladder drainage_, _iver biopsy_, and _intraoperative cholangography_:  
* _Gallbladder drainage_: a metal needle is used to puncture the gallbladder before the dissection of [PERSON]'s triangle. The aim is to reduce the inflamed gallbladder volume to avoid the spread of the gall into the abdomen;
* _Liver biopsy_: tissue samples are collected from the liver, i.e., generally towards the end of the procedures;
* _Intraoperative cholangography_: The cystic duct is cut and a plastic tube is inserted to apply a contrast medium for cholangiography. This is an X-ray imaging of the biliary tract to check whether gallstones block the common bile duct and/or the biliary tract is dilated. Qualitative examples of video frames associated with these surgical phases are displayed in Figure 1(a)-c. These three phases appeared in relatively fewer videos compared to other phases: _gallbladder drainage_ in 26 videos, _liver biopsy_ in 18 videos, and _intraoperative cholangography_ in 47 of all 384 videos (see Supplementary Figure S2 for more details). Moreover, we observed less visual variability in the surgical instruments used across interventions associated with the _gallbladder drainage, liver biopsy_, and _intraoperative cholangiocarcinoma_ _giography_ phases in our dataset. In addition to these phases, we observed the presence of non-cholesterectomy-related surgical procedures. These included procedures such as intraoperative ultrasonography and liver or pancreas resection (see Figure 2d-f for qualitative examples). To avoid mixing these miscellaneous procedures with cholecyst-specific phases, we explicitly labeled these procedures as _other procedure_. We observed these non-cholesterotomy related procedures in 68 of the 384 videos we gathered. With a median duration of 82 minutes (min: 1.2, max: 263), this phase was one of the longest in our dataset (Figure 3). Due to the variability of the tasks involved, the surgical instruments used during this _other procedure_ phase varied across the interventions. Videos in the Cholec80 dataset did not include any of the _gallbladder drainage, liver biopsy_, _other procedure_ and _intraoperative cholangiocarcinoma_ phases. Consequently, Cholec80 did not include any definition for these phases. Carefully looking at the clipping and cutting scenes, we observed that the surgical flow between these phases was not necessarily linear. We found many cases where _clipping_ and _cutting_ were performed multiple times; the surgeons came back and forth between the two. To enable our annotation to capture this non-linear workflow, we chose to define _clipping_ and _cutting_ as two separate phases. Cholec80 had a unified _clipping and cutting_ phase instead. Surgical phase duration was strongly imbalanced in both datasets (Figure 3). Besides non-cholecystectomy procedures (_other procedure_), _calot triangle dissection_ was the longest phase in both datasets. In accordance with the full-video length, Cholec80 had shorter phase durations across videos and shorter video durations compared to our dataset (see Supplementary Figures S1 and S3 online).