## 4 Discussion  
Analysis of the 22 studies included in this review reveals several key findings, the first being that 3 DPLMs can enhance surgical planning and intraoperative guidance of LCR by providing a more cognisable representation of patient liver anatomy and pathology. The improved comprehension of patient liver anatomy granted by 3 DPLMs enhances surgical decision making and facilitates more targeted and accurate resections. 3 DPLMs may, therefore, provide an overall benefit to LCR patient outcomes; however, further experimental research and clinical trials are necessary to confirm and quantify this relationship definitively. Traditionally, LCR surgical planning is based on a patient's CT and/or MRI imaging. The surgeon uses 2D axial/multiplanar images and 3 DVRs to determine appropriate resection planes and vascular/biliary reconstruction approaches. This requires using images on a 2D screen to construct a 3D mental visualisation of sophisticated patient liver structures. 3 DPLMs can facilitate this task by providing a transparent [13; 14; 15; 16; 22; 31], colour-coded [12; 15; 16; 19; 22; 32; 34; 35; 36; 40], tactile [11; 14; 15; 16; 40], manipulable [11; 14; 16; 19; 29; 31; 40] and highly cognisable [14; 15; 16; 17; 19; 29; 31] representation of individualised patient liver anatomy, which improves comprehension of the complex and highly variable 3D spatial relationships between intrahepatic structures [14; 16; 19; 22; 29; 31; 33; 40] and enhances cognitive localisation of liver tumours [15; 16; 17; 29], as demonstrated in Figure 2. The improved anatomical perception assists surgeons in selecting the most appropriate surgical strategies [11; 14; 16; 17; 19; 29; 33; 40], resection planes [13; 16; 17; 33; 40], and vascular reconstruction approaches [13; 40]. The above description of 3 DPLMs' preoperative value is drawn primarily from qualitative, case-report evidence, limiting its generalisability. In a prospective observational study, however, [PERSON] et al. [17] reported that using 3 DPLMs in surgical planning of laparoscopic LCR resulted in preoperative changes to surgical strategy for four patients (21% of study sample) due to the models improving cognitive localisation of intrahepatic lesions. [PERSON] et al. [31] performed a descriptive survey of HPB consultants, which indicated unanimously that 3 DPLMs could improve preoperative understanding of intrahepatic spatial relationships and assist in defining the most appropriate LCR surgical strategies. These studies were limited by small sample sizes and were not truly experimental; however, they indicate 3 DPLMs' baseline utility in LCR surgical planning. Further original research supporting 3 DPLMs' surgical planning value is limited to resident/intern populations. In a randomised controlled study, [PERSON] et al. [29] showed statistically significant improvement in interns' surgical planning test scores when using 3 DPLMs (vs. CT and 3 DVRs). [PERSON] et al. [16], in a prospective comparative study involving surgical residents, demonstrated that 3 DPLMs (vs. CT and 3 DVRs) resulted in statistically significant improvements in tumour localisation and surgical plan design. These studies were more methodologically rigorous than those by [PERSON] et al. and  
Figure 2: Three-dimensional spatial location and relationship of liver tumour (T) with intrahepatic anatomy can be better appreciated using 3 DPLM (**right**) compared to CT (**left**). Reprinted with permission under the open access from [PERSON] et al. [29]. [PERSON] et al. ; however, they only demonstrated 3 DPLMs' surgical planning value for _tratnee_ liver surgeons. This raises the question: Do qualified liver surgeons, who are capable of planning/performing LCR using medical images, actually receive significant benefit from 3 DPLMs? In a quasi-experimental study, [PERSON] et al. [15] found no significant difference in the surgical planning abilities of HPB consultants and fellows when presented with either 3 DPLMs or 3D-PDF liver models (equivalent to 3 DVRs).