# Dual-Energy CT Applications in Urological Diseases
## 5 Limitations
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Authors** & **Pathologies** & **N° pz** & **Acquisition Phase in DECT** & **Main Results** \\ \hline \multirow{5}{*}{[PERSON] et al. [77]} & & & & \textless{}ensitivity, specificity and accuracy were 98.7\%, 98.9\%, and 98.8\%, respectively, for the one-step approach to malignant mass detection and 98.7\%, 97.9\%, and 98.3\% for the dual-phase approach (\(p\) \(>\) 0.05 for all comparisons). \\  & Hematuria & 171 & Late-venous phase & \textless{}Onfitting the methanol around reduced the mean \\  & & & & \textless{}In comparison to venous-phase CT, attenuation, and signal-to-noise-ratio in exciver-phase VMI 40 keV \\  & & & & \textless{}R-Regarding image noise, no significant difference was found between venous-phase CT and excretory-phase VMI 40 keV (\(p\)-range.08-1.00). \\  & & & & \textless{}Contrast-to-noise ratio of urothelial carcinoma to circumvent bladder wall was significantly higher in excretory-phase VMI40 keV compared to venous-phase CT. \\  & & & & \textless{}Subjective vessel contrast and delineation of primary tumor and distant metastases received equivalent or higher Likert scores in excretory-phase VMI40 keV than in venous phase. \\ \hline \multirow{5}{*}{[PERSON] et al. [86]} & & & \textless{}The mean difference in CT number between the cancer and bladder wall value at 40 keV was significantly higher than that of vitral 120 keV \\  & Bladder cancer & 52 & Nephrogenic phases & (80.5 \(\pm\) 54 vs. 11.4 \(\pm\) 125 HU, \(p\) \(<\) 0.01). \\  & & & & \textless{}Average scores of subjective evaluations in the virtual-120 keV and 40 keV images were 1.7 \(\pm\) 1.2 and 2.1 \(\pm\) 1.2, respectively (\(p\) \(<\) 0.001). \\ \hline \multirow{5}{*}{[PERSON] et al. [87]} & & & \textless{}Urobchial tumors were identified on 35 s series, 8 min series, and both series combined, with sensitivity of 91.9\%, 83.4\%, and 97.3\%, respectively. \\  & hematuria and known & & & \textless{}Urobchial tumors showed stronger virtual enhancement (\(p\) = 0.02) and higher iodine concentration (\(p\) = 0.03) than lesions of other origin. \\  & neoplastic disease & & & \textless{}Distinction between urothelial tumors and nontumoral lesions was possible with sensitivity of 91.9\%. \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Characteristics and results of the studies dealing with urothelial and bladder cancer characterization with dual-energy CT. Image quality of VNC images can be decreased by a rough texture and poor spatial resolution or shows a smooth appearance not appreciated by radiologists [58; 92; 93]. Another issue with VNC images is the incomplete iodine removal in cases of very high iodine concentration, and loss of tiny and not highly attenuated calcite areas during the VNC reconstruction process, as well as higher image noise and reduced conspicuity of calcification in renal masses that can affect kidney lesion interpretation [4]. The use of DECT can be contraindicated in obese patients, as larger bodies may result in greater image noise and reduced image quality (related to the limited number of photons reaching the detectors), affecting material decomposition and limiting tissue characterization [94]; moreover, beam hardening artifacts are more evident in obese subjects because of the longer path where the X-ray beam is attenuated [95]. Therefore, patient selection for DECT acquisition should be established after assessing the patients' size on the scout radiograph [96]. Another limitation of DECT is represented by the equipment cost, as a DECT scanner can be a costly acquisition for healthcare systems: whereas 16-slice CT scanners average USD 402,000 and 64- and 80-slice scanners average USD 549,000, a DECT scanner can average USD 1.29 million and possibly even more [97].