The performance of the Rigiscan in the measurement of penile tumescence and rigidity.

The validity of the Rigiscan as a measure of both penile circumference and rigidity was assessed. In the first study, the Rigiscan was used simultaneously with a mercury-in-rubber strain gauge to monitor nocturnal penile tumescence. The Rigiscan was found to underestimate the circumference proportional to the degree of erection. In a second study a calibration system was developed which allowed independent variation of circumference and rigidity. Assessment of the Rigiscan with this system confirmed that circumference was underestimated, particularly at lower levels of rigidity, and also that different devices consistently recorded different degrees of rigidity. The use of this type of system for regular calibration is recommended, and other potential improvements in the device for research purposes are discussed.