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Advances in Radiotherapy
& Nuclear Medicine Optimal tube voltage for dental CBCT

2. Materials and methods The RaySafe Xi multimeter has a built-in sensor
(internal silicon detector) for measurements of a wide range
2.1. DAP meter of parameters such as tube current (mA, mAs, waveform),
This prospective research used a DAP meter to achieve exposure time, pulses, pulse rate, and tube voltage (kVp).
direct comparability and to prevent patient radiation in an Besides, it can also be used as a dosimeter to measure the
experimental setting. The scan was done using the Planmeca dose, dose rate, dose-area product (DAP), and half-value
ProMax 3D Mid CBCT unit (Planmeca, Helsinki, Finland) layer all at the same time with a single exposure setting. 22
at Advanced Medical and Dental Institute, Universiti Sains The instrument is controlled by two buttons: the On/Off
Malaysia. The device provides a manual selection of scan buttons and the arrow button for scrolling the measured
parameters for every scan. data. The carefully built liquid crystal display (LCD) clearly
The DAP meter was attached to the X-ray detector to displays both the measured values and their units.
cover the entire irradiated area at a distance of 120 cm The RaySafe Xi multimeter consists of a flat plane
from the source. Since the back of the X-ray detector ionization chamber for easy adaptability over the detector
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is shielded, backscatter from the imaging device was not of the CBCT unit. This device, which is a multiparameter
included in the measured doses when using this solid-state X-ray meter, has an internal silicon detector that can
detector, i.e., to ensure that there was no backscattering of measure kVp, dose rate, and time with a maximum
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radiation upon reaching the detector, and the DAP meter inaccuracy of 0.5% and 2% for all other measurements.
was connected to a Raysafe electrometer (UNFORS).
The UNFORS detector has an active width of about
2.2. UNFORS RaySafe multimeter 2 mm, permitting it to be situated inside the X-ray beam for
the entire exposure, even with the narrow X-ray beam used
In this study, the UNFORS RaySafe Xi multimeter (UNFORS by some models that utilize a scanning narrow X-ray beam.
Raysafe, AB, Sweden) is a device used for radiation dose
measurement, covering various performance parameters After positioning the DAP meter behind the gantry, it
for quality assurance testing of the digital dental CBCT unit. was scanned using a varying tube current ranging from 5 to
This meter was used for the measurement and evaluation of 16 mA at a constant 70 kV as the scan parameter for every
CBCT performance testing (Figure 1). scan. For each scan, the exposure time was set at 10.51 s,
which represents the standard mode for a 360° rotation,
The UNFORS RaySafe Xi multimeter was connected to and the radiation output was acquired during the 360°
the base unit by a long electric cable. The base unit displays rotation of the detector and the X-ray source (Figure 2).
all the measurement values that were pre-set by the users.
The long electrical cable allows the measurements to be A total of five imaging protocols were chosen, and
taken and recorded from the base unit at the control room, all tests were carried out without the DAP meter being
which is outside the scanning room, offering radiation moved between scans. The DAP, half-value layer, and
protection to the staff during the phantom scanning. measured dose were provided by the device for each scan
parameter and recorded for each scan. The values of these
parameters were different and unique for each test, due to
the permutations of kV and mAs values.
Similarly, the protocols for the scanning were repeated
with constant milliampere-seconds of 105.1 mAs and a

Figure 1. UNFORS RaySafe Xi meter used in this study with base unit for
measurement of tube output Figure 2. The positioning of the dose area product meter

Volume 2 Issue 2 (2024) 3 doi: 10.36922/arnm.2972