Abstract: A device and methods for the real-time monitoring of stem cells in a stem cell transplant. The device comprises a linear member and particle detection device configured to occupy the lumen of a catheter while the catheter is in place to administer a stem cell transplant to a delivery site in the body of a patient. Monitoring of the stem cells permits the device to provide signals to a computer processor for the determination of one or more characteristics of stem cells in the stem cell transplant.