Intraoperative Structured Light Scanning creates Precise and Reliable Digital and 3D-printed Penile Models
Alen Huang, Undergraduate1, Victoria Lee, BS1, Akash Chauhan, Undergraduate1, Astha Sahoo, Undergraduate1, Joshua Li, BS2, George Aninwene, PhD1, Felix Yiu, BS1, Steven Lerman, MD1, Nicholas Jackson, PhD MPH2, Renea Sturm, MD1.
1Department of Urology, David Geffen School of Medicine at UCLA, Los Angeles, CA, USA, 2Department of Medicine Statistics Core, UCLA, Los Angeles, CA, USA.
BACKGROUND: Penile measurements are currently obtained manually by surgeons using a ruler or goniometer to measure dimensions and angles, respectively. However, these methods lack precision and accuracy across raters and cannot be reevaluated retrospectively following a surgical repair. The project aim was to evaluate the precision and reliability of penile dimensions obtained from digital and three dimensional (3D) printed models created from intraoperative (OR) structured light scans as compared to standard surgical measurements.
Methods: Boys aged 1 month to 6 years undergoing a primary/first stage penile surgery at a single institution were eligible for enrollment in this prospective study (IRB #20-000143). Procedures performed for subsequent stages or repair of complications were excluded. Standardized methods of retraction and manual intraoperative measurement of multiple measures including glans width, glans height, and penile length (with retraction suture stabilized, prior to incision without artificial erection after foreskin retraction) were defined for all participating surgeons. A digital model was created prior to penile repositioning using a structured light scanner (Artec Space Spider) and Artec Studio 13 software. Two different raters completed 10 digital measurements of each generated model in Autodesk Fusion 360. These digital models were subsequently 3D printed using a Formlabs Form 3 printer and Grey v4 resin. Two raters completed 10 manual measurements of dimensions of each 3D printed model using a ruler. A one-way random effects intraclass correlation coefficient (ICC) evaluated measures of agreement between and within raters, respectively. Analyses were conducted in R version 4.2.
Results: Six scans were obtained (hypospadias: 4, normal: 2). For both digital and 3D printed measurements, glans width showed excellent agreement with the OR measures (ICC 0.75 to 0.97). There was less consistent agreement between both digital and 3D printed methods in comparison with OR measurements (glans height: 0 to 0.92, penile length: 0.17 to 0.42). Intra-rater assessments showed excellent reliability across repeated digital measurements (0.99 to 1.0); manual measurements of 3D printed models had excellent reliability for glans width and penile length (0.93 to 0.97) but not glans height (0.34 to 0.84). Comparing digital to 3D printed measurements, inter-rater reliability was good to excellent for glans width (0.77 to 0.95) and penile length (0.71 to 0.88). However, there was substantial between rater variability for glans height (0 to 0.14).
Conclusions: The results of the study show that digital and 3D printed measurements had high consistency between each other, although digital measurements were more reliable versus manual evaluation of the 3D printed model. Glans width by digital or 3D printed measurements compared favorably with the OR assessment by surgeons, while glans height and penile length were less consistent with surgeon measurements. Structured light scanning is promising as a novel modality to digitally generate 3D models prior to complex reconstructive surgery, thereby informing personalized surgical planning and database creation. Further development of digital measurement methods to ensure consistency between raters for quantitative assessment of penile dimensions is needed.
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