Evaluation of canine prostate volume in calculated tomographic images-comparison of two assessment methods

Background Since most prostatic diseases are associated with the organ's enlargement, evaluation of prostatic size is a main criterion in the diagnosis of prostatic state of health. While enlargement is a non-uniform process, volumetric measurements are believed to be advantageous to any single dimensional parameter for the diagnosis of prostatomegaly. In a previous study, volume was analysed with a slice addition technique (SAT), which was validated as highly accurate. Irrespective of high accuracy, SAT represents a complex and time-consuming procedure, which limits its clinical use. Thus, demand exists for more practical volume assessment methods. In this study, the prostatic volume of 95 canine patients (58 intact males, 37 neutered males) were analysed retrospectively by using the ellipsoid formula (Formula) and an imaging "wrap" function tool (Wrap) to help assess accuracy and applicability. Accuracy was checked against phantom measurements and results were compared to SAT measurements of the same patient pool obtained from a previously published paper. Patients were grouped according to prostatic structure (H = homogeneous, I = inhomogeneous, C = cystic) and volume using the SAT (volume group = vg: 1, 2 and 3). Results High correlation between the Formula or Wrap volume and the phantom volume was found, the values being higher for the Formula. Mean Formula volumes (vg 1: 2.2 cm(3), vg 2: 14.5 cm(3), vg 3: 109.4 cm(3), respectively) were significantly underestimated, while mean Wrap volumes (vg 1: 3.8 cm(3), vg 2: 19.5 cm(3), vg 3: 159.2 cm(3)) were statistically equivalent to SAT measurements (vg 1: 3.1 cm(3), vg 2: 18.6 cm(3), vg 3: 157.2 cm(3), respectively). Differences between Formula and SAT volumes ranged from 22.4-31.1%, while differences between Wrap and SAT volumes were highest in small prostates (vg 1: 22.1%) and fell with increasing prostatic size (vg 3: 1.3%). Conclusion The Wrap function is highly accurate, less time-consuming and complex compared to SAT and could serve as beneficial tool for measuring prostatic volume in clinical routine after further validation in future studies. The Formula method cannot be recommended as an alternative for volumetric measurements of the prostate gland due to its underestimation of volumes compared to SAT results.