CLAUDIO COSTA – ORTO 2012
Technique
Effective
Dose in uSv 1990 ICRP
tissue weights
Dose as
multiple of
single
Panoramic
Dose (ICRP1990)
Dose in days
of per capita
background
dose
Dose in terms
of % medical
CT equivalent
Dose in terms
of % annual
per capita
background
dose
NewTom3G - Full (12”) FOV*
45
7
4
2.1%
1.2%
NewTom3G - chin tilt & Thyroid Shield*
28
4
3
1.3%
0.8%
CB Mercuray - F (12”) FOV 10 mA-100 kV*
477
74
48
22.7%
13.2%
CB Mercuray - P (9”) FOV*
289
45
29
13.8%
8.0%
CB Mercuray - I (6”) FOV (maxillary)*
169
26
17
12.0%
4.7%
CB Mercuray - I (6”) FOV w/ chin tilt*
125
19
12
5.9%
3.5%
i-CAT - Full (12”) FOV*
135
21
13
6.4%
3.7%
i-CAT - chin tilt & thyroid shield*
57
9
6
2.7%
1.6%
Panoramic (OrthoPhos Plus DS)†
6
1
1
0.3%
0.2%
CT Maxillo-Mandibular‡
2100
385
243
100.0%
58.3%
CT Maxillary‡
1400
164
103
100.0%
38.9%
*Ludlow JB, Davies-Ludlow LE, Brooks, SL, Howerton B. Dosimetry of 3 CBCT Units for Oral and Maxillofacial Radiology. Abstract
accepted for 15th International Congress of the International Association of Dento-Maxillo-Facial Radiology, Cape Town, South Africa June
2005.
†Ludlow JB, Davies-Ludlow LE, Brooks, SL. Dosimetry of two extraoral direct digital imaging devices: NewTom cone beam CT and
Orthophos Plus DS panoramic unit. Dentomaxillofacial Radiology 2003;32:229-34
‡ Ngan DC, Kharbanda OP, Geenty JP, Darendeliler MA. Comparison of radiation levels from computed tomography and conventional
dental radiographs. Aust Orthod J. 2003;19:67-75
RADIOPROTEÇÃO EM CBCT
Artigo mais recente – Julho 2012
Dentomaxillofac Radiol. 2012 Jul;41(5):373-8.
Dose reduction of cone beam CT scanning for the entire oral and maxillofacial regions with thyroid collars.
Qu XM, Li G, Sanderink GC, Zhang ZY, Ma XC.
Source
Department of Oral and Maxillofacial Radiology, Peking University School, Beijing, China.
Abstract
OBJECTIVE:
The aim of this study was to evaluate the influence of thyroid collars on radiation dose during cone beam CT (CBCT)
scanning.
METHODS:
Average tissue-absorbed dose for a NewTom 9000 CBCT scanner (Quantitative Radiology, Verona, Italy) was
measured using thermoluminescent dosemeter chips in a phantom. The scans were carried out with and without
thyroid collars. Effective organ dose and total effective dose were derived using International Commission on
Radiological Protection 2007 recommendations.
RESULTS:
The effective organ doses for the thyroid gland and oesophagus were 31.0 µSv and 2.4 µSv, respectively, during
CBCT scanning without a collar around the neck. When the thyroid collars were used loosely around the neck, no
effective organ dose reduction was observed. When one thyroid collar was used tightly on the front of the neck, the
effective organ dose for the thyroid gland and oesophagus were reduced to 15.9 µSv (48.7% reduction) and 1.4 µSv
(41.7% reduction), respectively. Similar organ dose reduction (46.5% and 41.7%) was achieved when CBCT scanning
was performed with two collars tightly on the front and back of the neck. However, the differences to the total
effective dose were not significant among the scans with and without collars around the neck (p = 0.775).
CONCLUSIONS:
Thyroid collars can effectively reduce the radiation dose to the thyroid and oesophagus if used appropriately.
J Am Dent Assoc. 2008 Sep;139(9):1237-43.
Patient risk related to common dental radiographic examinations: the impact of 2007 International
Commission on Radiological Protection recommendations regarding dose calculation.
Ludlow JB, Davies-Ludlow LE, White SC.
Source
Department of Diagnostic Sciences, University of North Carolina School of Dentistry, Chapel Hill, NC 275997450, USA. [email protected]
Abstract
BACKGROUND:
In 2007, the International Commission on Radiological Protection (ICRP) revised estimates of the radiosensitivity
of tissues including those in the maxillofacial region. The authors conducted a study to reassess patients' risk
related to common dental radiographic exposures using the 2007 ICRP recommendations.
METHODS:
The authors used a tissue-equivalent head phantom to measure dose. They calculated effective doses by using
both 1990 and revised 2007 ICRP recommendations. Effective dose is a calculation that takes into consideration
the different sensitivities of organs to long-term effects from ionizing radiation. It is the preferred method for
comparing doses between different types of exposures.
RESULTS:
Effective doses (per the 2007 ICRP) in microsieverts were as follows: full-mouth radiographs (FMX) with photostimulable phosphor (PSP) storage or F-speed film with rectangular collimation, 34.9 microSv; four-image
posterior bitewings with PSP or F-speed film with rectangular collimation, 5.0 microSv; FMX using PSP or Fspeed film with round collimation, 170.7 microSv; FMX with D-speed film and round collimation, 388 microSv;
panoramic Orthophos XG (Sirona Group, Bensheim, Germany) with charge-coupled device (CCD), 14.2
microSv; panoramic ProMax (Planmeca, Helsinki, Finland) with CCD, 24.3 microSv; posteroanterior
cephalogram with PSP, 5.1 microSv; and lateral cephalogram with PSP, 5.6 microSv. These values are 32 to 422
percent higher than those determined according to the 1990 ICRP guidelines.
CONCLUSIONS:
Although radiographs are an indispensable diagnostic tool, the increased effective doses of common intraoral
and extraoral imaging techniques are high enough to warrant reconsideration of means to reduce patients'
exposure.
CLINICAL IMPLICATIONS:
Clinicians can reduce patients' dose substantively by using digital receptors or F-speed film instead of D-speed
film, rectangular collimation instead of round collimation and radiographic selection criteria.
RADIOPROTEÇÃO EM CBCT
Conclusões
As doses de radiação em CBCT são menores do que as utilizadas
em TC médicas single e multislice
Não existe necessidade de proteção adicional ao avental de chumbo
O protetor de tireóide ajuda a reduzir a dose, porem interfere na
observação do exame, sendo essa redução estatisticamente não
significante (5%)
Os óculos de proteção para o cristalino não são citados na literatura,
além de interferir na observação das imagens da região.