For Healthcare Professionals

Technical Specifications

Intended Use
DVS® is intended for use in radiation therapy to verify treatment planning and radiation dose to tissue and organs in or near the irradiated areas of the patient.

System Operation
The implantable dosimeter measures in vivo dose from photon beam therapy. The dosimeter uses two semiconductor devices called MOSFETs (metal oxide semiconductor field effect transistor) to measure radiation. The values from the two MOSFETs are averaged for improved accuracy. Radiation within the human therapeutic dose range causes a shift in the threshold voltage of the MOSFET. By measuring the threshold voltage before and after radiation therapy, the dose fraction can be calculated. Cumulative dose can be calculated by tabulating the radiation dose measured at each fraction.

The dosimeter is powered by the Reader Wand utilizing electromagnetic energy and does not contain a battery. The dosimeter derives all power from the Reader-generated electromagnetic field. The dosimeter modulates the electromagnetic field to send the digitized threshold voltage readings back to the Reader.

Radiation Dosimeter
Two MOSFET detectors: Sensitive
volume 0.3mm x 0.05mm

Calibration
Factory calibrated using Co⁶⁰; no additional
calibration required; ADCL accuracy verification
performed on each lot

Implant Depth
3-12 cm maximum from any one skin surface

Implant Distance
At least 1 cm distance between each dosimeter

Energy Range
6 to 18 MV Photon

Dose Range
80 Gy maximum

Dose Per Fraction
150 to 250 cGy

Time to read dosimeter
Up to 10 minutes following radiation therapy. Optimal read time is 2 to 3 minutes following irradiation.

Operating Conditions:

Dosimeter
Dosimeter is optimized for use in vivo at temperatures ranging from 34^oC to 40^oC. Dosimeter performance
at room temperature has not been characterized.

Reader
Temperature: 10^oC-40^oC (50^oF-104^oF)
Humidity at 10% to 95%, non-condensing

Storage Conditions
Temperature: -18^oC to 55^oC
Humidity at 10% to 95%, non-condensing

*Accuracy
< 5.5% (2 sigma) up to 20Gy
< 6.5% (2 sigma) up to 74Gy*

Actual lot accuracy is specified in Lot Calibration Certificate.
*Accuracy decreases slightly above 74Gy.

Figure 1A
^{(a) Relative response of dosimeters to delivered dose}

Figure 1B
^{(b) Average readings of two DVS dosimeters. The dashed lines encompass data
within ± 2% of dose delivered (200cGy).1}

The average data from the two different dosimeters is indicative of the performance expected using a single dosimeter with two MOSFETs.

¹A.S. Beddar, M. Salehpour, T.M. Briere, H. Hamidian, and M.T. Gillin. Preliminary evaluation of implantable MOSFET radiation dosimeters. Phys. Med. Biol., 2005. Vol. 50, pp 141-149.

For complete technical specifications refer the DVS Instructions for Use Rev.05 (PDF 775kb)