Akademik Veri Yönetim Sistemi
TURKISH PHYSICAL SOCIETY 40TH INTERNATIONAL PHYSICS CONGRESS, Muğla, Türkiye, 2 - 06 Eylül 2024, ss.73
Recently, there has been a significant increase in the number of diagnostic x-ray applications.
Computed tomography (CT) and interventional procedures are associated with relatively higher
patient doses and studies aiming to achieve adequate image quality and low patient doses continue
to be the focus of research. All x-ray examinations using ionizing radiation need to be justified and
optimized in terms of benefits and risks. Effective dose (ED) is a risk-related dosimetric quantity for
use in radiation protection against stochastic effects and recommended by the International
Commission on Radiological Protection (ICRP). Determination of the effective dose for radiological
procedures is quite difficult and several indirect methods based on the use of tabulated data obtained
by Monte Carlo simulations have been recommended to enable easy determination of effective dose.
Conversion coefficients to calculate effective dose from patient dose quantities for all common
radiological procedures have been provided by the National Radiological Protection Board (NRPB),
ICRP and the American Association of Physicists in Medicine (AAPM). The dosimetric quantity
Dose Area Product (DAP) is used for radiography and interventional procedures. For projection
radiography Entrance Surface Dose (ESD) is used in addition to DAP to represent the radiation dose
at the entrance of the patient. Cumulative Air Kerma (CAK) at the patient entrance reference point
is also reported as a second dosimetric quantity in interventional radiology systems. For Computed
Tomography (CT), the Dose Length Product (DLP) and the Volume CT dose index (CTDIvol) are
used. The Size-Specific Dose Estimate (SSDE) can also be used for CT and considered to be more
accurate for dose estimation dependent on patient size. On the other hand, breast glandular tissue
radiation dose is the best indicator of the potential risk from mammography. The number and
complexity of interventional radiology (IR) procedures continue to increase, and these procedures
can produce high doses of radiation for both patients and staff. Patient and staff doses are measured
simultaneously for these procedures and staff dose normalized to patient dose quantity are reported
for dose comparisons and for estimation of staff dose from the patient dose. Staff doses per procedure
are also reported to check whether personnel have reached the annual dose limits reported by ICRP.
After detailed review of epidemiological studies for radiation-associated cataracts, the threshold
absorbed dose value for the lens of the eye set to 0.5 Gy for both acute and chronic exposures in
ICRP report 118. Based on this, ICRP decreased previous annual dose limit for the lens of the eye
from 150 mSv to 20 mSv per year, averaged over defined periods of 5 years, with no annual dose in
a single year exceeding 50 mSv. Dose monitoring of staff is performed by measuring the personal
dose equivalent Hp(d) at a reference depth (d, mm). The measured personal dose equivalent at a
reference depth of 3 mm (Hp(3)) is used to assess eye lens doses, whereas the personal dose
equivalent at 10 mm depth is used for estimation of effective dose. The Hp(0.07) personal dose
equivalent at 0.07 mm is an operational quantity for estimation of extremity dose.
In this talk, patient dose measurement methods for different radiological procedures and staff dose
measurement methods for IR procedures will be explained and the importance of employing medical
physicist in radiology departments will be emphasized. In addition, data compiled from the literature
for patient and staff doses will be presented and basic protection measures that can be applied to
reduce staff radiation doses will be briefly mentioned.