Abstract
Lower urinary tract symptoms in men with prostatic enlargement may or may not be associated with bladder outlet obstruction (BOO). Also, BOO suggestive benign prostatic hyperplasia (BPH) is a common disease in elder men. The present golden standard diagnostics, however, is an invasive method, named pressure-flow studies. The purposes of the thesis are to develop non-invasive procedures for diagnosing obstruction. Prostate volume is a frequently used, non-invasive variable, but the present methods are not able to be accurately measured. Thus, one of the aims of the study was to propose an eccentricity parameter (EP index) based correction to the ellipsoid formula to improve the evaluation of the prostate volume defined by transabdominal ultrasonography (TAUS) at different stages of benign prostatic hyperplasia. By applying the correction formula, the mean prostate volume differences of TAUS with computed tomography (CT) were improved from 27.0%, -23.9%, and 0.8% to 6.2%, -3.2%, and 0.8% for EP < 0.055, 0.055 < EP < 0.14, and EP > 0.14, respectively. Hence, for EP > 0.14, representing the advanced stage of BPH, TAUS with the ellipsoid formula can be regarded as an effective tool for computing volume; while for EP < 0.14, the correction formula is recommended to improve the volume estimation based on TAUS. The study was also to investigate how apex-localizing methods and the slice-thickness affected the CT based prostate volume estimation. Interobserver variations to locate the bottom of ischial tuberosities (ITs) and the bulb of the penis were, on average, 0.10 cm (range: 0.03 to 0.38 cm) and 0.30 cm (range: 0.00 to 0.98 cm), respectively. The range of slice-thickness varied from 0.08 to 0.48 cm was adopted to examine the influence of the variation on volume estimation. The volume deviation from the reference case (0.08 cm), which increases in tandem with the slice thickness, was within ±3 cm3, regardless of the adopted apex-locating reference positions. In addition, the maximum error of apex identification was 1.5 times of slice thickness. These results will help to identify factors that affect prostate volume calculation and to contribute to the improved estimation of the prostate volume based on the CT images. After correcting prostate volume estimations, the study investigates the development of an index, named PVQ, which combines prostate volume and maximum free uroflow rate as a reliable predictor of obstruction. The formula of PVQ index was, (15/ Q)×(PV/30), where the values of 15 (mL/sec) and 30 (cm3) are the threshold values for Q and PV, respectively. A PVQ value of 1 was an accurate metric for the determination of BOO that corresponded to a BOO index of 20 to the following extent: accuracy 93%, sensitivity 96%, specificity 80%, PPV 96%, NPV 80% and kappa 0.76. The PVQ parameter outlined in this article can differentiate obstruction in the majority of men with LUTS and it is in nearly complete agreement with the BOO Index. Therefore, this metric is suggested as an early predictor of obstruction. If an individual's measurements correspond to a PVQ > 1, we suggest that he undergoes further intensive testing. Finally, the study also develops a non-invasive procedure, which combines computational fluid dynamics and the medical imaging techniques, as a novel approach for diagnosing BOO. Based on the computed tomography images, the lower urinary tract system is reconstructed. The flow resistance within the urinary tract is predicted using the computational fluid dynamics. It is shown that this quantity displayed a high correlation (r: 0.86) with the golden standard parameter, BOO index, i.e., clinically measured data for patients with BOO. This indicates that the present method may be potentially valid substitute for invasive BOO index.