## 4 Discussion
### Sources of Error and Precautionary Steps
Even though this technique has several limitations, it has the advantages of minimising subject movement, limiting the post-dofling effect, and preventing the distortion of the residual limb's shape because there is no contact with the residual limb while measuring. The digitalisation of this laser scanning technology has also resulted in improved error reduction because researchers can collect and analyse data in the CAD software (TT Design 5.0, 2010; Geomagic Studio 2012.1.1, 2012; VXelements 6.1, 2017; Canfit(tm) 15, 2019; Artee Studio Software 16, 2020) after scanning. Researchers can use the CAD software to compare the images obtained from various types of scanners, which allows them to determine which scanner is the best to use. [PERSON] et al. [30], [PERSON] et al. [45], and [PERSON] et al. [40] conducted studies to compare the performance of various types of scanners and discovered that the majority of scanners (Artec Eva scanner [45], TT Design, Omega Scanner, BioSculptor Bioscanner, Radio4D Scanner [40], and CAPOD [30]) are reliable in determining the residual limb volume. Aside from that, optical scanning techniques (both silhouetting and fringe projection) also demonstrate the ability to capture images of residual limbs very quickly. The ability of this technique to capture the image in less than 1.5 s was proven by studies conducted by [PERSON] et al. [58] (0.75 s), [PERSON] and [PERSON] (1.1 s) [36], and [PERSON] and [PERSON] (1.5 s) [38]. Even the optical technique can capture the image of the residual limb very quickly, but it still has a significant chance of error since the silhouetting technique cannot capture the concavities of the residual limb. The subject's position during capture is also considered a potential source of error for the fringe technique since the subject must be placed so that the residual limb may be viewed from all angles. The researchers will have some difficulty capturing the image and will also come up with a wrong interpretation of the residual limb volume if the individuals have certain constraints in positioning their bodies in a proper position, particularly for transfemoral amputation and elderly subjects. The authors of the review also found that bioimpedance techniques appear to have fewer sources of error; however, this technique cannot be demonstrated to be 100% accurate because it only evaluates the residual limb volume change and cannot be compared to other techniques. As was previously mentioned, the bioimpedance and SXCT techniques both only assess the volume change in the residual limb, but it is difficult to compare the two techniques because the SXCT technique can only measure the residual limb in stationary positions. More research on the reliability and validity of the bioimpedance and SXCT techniques is required to demonstrate that they are the most accurate and have the fewest potential errors because the authors were unable to locate any studies relating to these topics, and most of the studies that were conducted only concentrate on the transtibial amputation level. Other techniques such as the anthropometric measurement technique also show their weaknesses since they have a high chance of error. The placement of the measurement device while measuring the residual limb circumference can be viewed as a potential source of error since the researchers need to position the measurement tape at the same place and, at the same time, apply the same amount of tension during the measurement to avoid any error. In the study conducted by [PERSON] et al. [33], it was also discovered that the circumference measurement was not related to the residual limb volume, which, at the same time, will give the wrong interpretation of the residual limb volume measurement. Finally, because the post-dofling effect directly affects the residual limb volume, the lengthy duration of measuring techniques may potentially contribute to inaccuracies in the interpretation of the residual limb volume.