ObjectiveTo study the CT values of certain phantoms scanned by various CT scanners with dissimilar parameters.Methods The CT values of tissue equivalent inserts was measured in the TM164 and CIRS-062 phantom scanned by TOSHIBA AQUILIONTM,SIEMENS SOMATOMTMSENSATIONTM 64 and SIEMENS SOMATOMTM SENSATIONTM OPEN with different voltages,currents and slice thicknesses and then the corresponding CT-to-density curves was compared. Results There are no significant differences of CT values with various currents and slice thicknesses and also for low atom number materials scanned by different scanners with various tube voltages.The CT values of high atom number materials have obvious differences scanned with tube voltage,the maximum is about 400 HU.There are also significant differences between CT-density curves of two phantoms in the range from soft tissues to dense bone,the maximum is up to 500 HU.ConclusionsCT-density curves were highly affected by materials of phantoms,scanners and tube voltages.It is necessary to measure the curve with a comfortable phantom and certain scanner to assure the accuracy for dose calculation for treatment planning system.

Bladder cancer is one of the most common malignant tumors of the urinary system, among which urothelial carcinoma is the main one. The traditional treatment methods are mainly surgical resection and chemotherapy, but the treatment effect of advanced patients is not good, and the prognosis is poor. In recent years, with the development of immune checkpoint inhibitors, there are many treatment options that are more effective than traditional therapies. Programmed cell death protein 1 (PD-1)and programmed cell death ligand 1(PD-L1)inhibitors stop the negative regulation of the immune system by blocking the binding of PD-1 and PD-L1, thereby enhancing the anti-tumor activity of the body's immune system. This article mainly reviews the efficacy and safety of PD-1/PD-L1 inhibitors commonly used in the clinical treatment of locally advanced or metastatic urinary tract carcinoma of the bladder.