El Paso Patient Dosimetry Services Patient Dosimetry Services El Paso Texas

About Dosimetry

Computed Tomography (CT) Studies
It is important to remember that CTDIvol taken from CT scanners is not patient dose; it is a measure of the CT unit's x-ray output for specific scan parameters on a test device. Using in vivo OSL dosimeters, an individual's dose can be determined using algorithms to compute patient dose from skin dose measurements. In vivo patient doses in CT are similar to the Multiple Scan Average Dose (MSAD) value mentioned in AAPM Report # 96 and similar to the equilibrium dose (Deq) in the AAPM TG-111 Report.

It is possible to assess additional cancer risk utilizing the data published by the U.S. National Academy of Sciences, Biological Effects of Ionizing Radiation (Revision VII) with measured dose, gender and age. The risk values as a function of age are averaged aggregate expectations. The greater risk of pediatric age patients is clearly shown. The specific risk for a particular patient for a given dose can only be determined as a "risk probability". Individual patient risk calculations can be useful in patient consultations showing that the increased cancer risk from a single CT study can be small whereas the increased cancer risk gets greater with multiple studies.

Using in vivo OSL dosimetry is a good, cost effective way to supplement CT protocol management now required in some states.

Fluoroscopically Guided Interventional (FGI) Studies
Fluoroscopically guided interventional studies have the potential for inducing deterministic injuries in some patients. Using in vivo dosimetry, the skin dose can be measured and compared to published dose ranges for tissue reactions from single-delivery radiation dose. With this information, the patient can be advised whether or not additional skin care will be necessary. Only procedures with long fluoroscopy times need to be measured.

Patient Data
Individual patient dose data is archived in the PDS secure database and is used to help individual facilities better understand what radiation doses they are actually giving to patients at higher risk for radiation injuries. Patient dose data can be imported into an institution's radiology information management system (RIS) to monitor individual patient dose if available or used by other software programs such as spreadsheets.