Urinary PSA	Fluorescence Imaging	Ultrasound Imaging
Steps (time required)	Anesthetize mice. Collect 110 μL urine. (~ 1 h) Perform PSA ELISA (total incubation time: 2 h 30 min) Creatinine assay (incubation time: 5 min)	Anesthetize mice. Shave fur on abdominal region. Perform imaging.	Anesthetize mice. Shave fur on abdominal region. Catheterize and instill 100 μL of saline into the bladder. Apply conductive gel to lower abdomen and obtain ultrasound images.
Specialized equipment	ELISA plate reader (at wavelength of 450 nm and 510 nm)	Imaging System	Ultrasound Imaging System
Modification of tumor cells	Required (expressing PSA)	Required (fluorescence)	Not required
Advantages	Reliable	Simple and quick	Can detect large tumors
Limitations	May not get enough urine A negative value does not mean absence of tumor (PSA gene expression analysis increases sensitivity but is limited to end-point analysis)	Careful selection of fluorescence dye is needed to prevent high background.	Cannot detect small tumors. One mouse at a time.