Summary:
Cystourethrography studies contribute significantly to the diagnosis of
malformations or functional disorders of the urinary tract or other major
congenital abnormalities, such as posterior urethral valves in boys. Barium
meal studies are often performed in paediatric radiology order to assess
Gastroesophageal reflux, but also laryngopharyngeal reflux, malrotations and
vascular rings.
However, both studies use fluoroscopy and multiple radiographs all of which
result in high radiation doses to patients.
Children are a special group of patients with a higher probability to develop
delayed effects due to radiation, considering that they are 5-7 times more
sensitive to radiation than adults. According to European legislation directive
97/43/Euratom (EC, 1997) as well to Greek legislation, it is essential to
investigate children’s radiation exposures from X-rays examinations.
Additionally, special Diagnostic Reference Levels (DRLs) for children have been
proposed by the European Commission (European Guidelines on Quality Criteria
for Diagnostic Radiographic Images in Pediatrics) and by National Radiological
Protection Board, UK (Reference doses and patient size in pediatric radiology).
The purpose of this study is to estimate the organ doses, effective doses and
the corresponding conversion factors, to paediatric patients undergoing Barium
meal and Micturating Cystourethrography examinations, by clinical measurements
and Monte Carlo simulation. In clinical measurements, dose–area products (DAPs)
were assessed during examination of 50 patients undergoing barium meal and 90
patients undergoing cystourethrography examinations, separated equally within 3
age categories: namely newborn, 1-year and 5 years old. Monte Carlo simulation
of photon transport in male and female mathematical phantoms was applied, using
the MCNP5 code, in order to estimate the equivalent organ doses. Regarding the
micturating cystourethrography examinations the organs receiving considerable
amounts of radiation doses were: the urinary bladder (1.87, 2.43 and 4.7 mSv,
the first, second and third value in the brackets corresponds to neonatal, 1
and 5-year old patients respectively), the large intestines (1.54, 1.8, 3.1
mSv), the small intestines (1.34, 1.56, 2.78 mSv), the stomach (1.46, 1.02,
2.01 mSv) the gall bladder (1.46, 1.66, 2.18 mSv) depending upon the age of the
child. Organs receiving considerable amounts of radiation during Barium meal
examinations were: the stomach (9.81, 9.92, 11.5 mSv), the gall bladder (3.05,
5.74 7.15 mSv), the pancreas (5.8, 5.93, 6.65 mSv) and the spleen (6.9, 7.5,
4.7 mGy) depending upon the age of the child.
For all views of both examinations, the organ dose conversion factors (organ
doses per unit DAP) and effective doses conversion factors decrease with age of
the patient. The fluoroscopic projections during barium meal examinations
contribute the 93-96% of the total DAP value or of the total effective dose
value, depending on the age of the examinees. The corresponding percentage
concerning the micturating cystourethrography studies ranged from 85 to 87%.
The Risk of exposure-induced cancer death (REID) was calculated for both
examinations. The REID values for female patients were slightly higher than the
corresponding number for males for both age groups. The magnitude of the risk
of cancer in boys attributable to the radiation exposure during Barium Meal
examinations was found to be (4.7910-2, 3.010-2 and 2.010-2 %) for neonatal,
1-year old and 5 years old patients respectively. The corresponding values for
girl patients calculated (12.110-2, 5.510-2, and 3.410-2%). In case of
Micturating Cystourethrography examinations the corresponding values found to
be (5.910-3, 5.610-3 and 8.610-3 %) while for girls was (6.910-3, 6.410-3
and 9.910-3 %).
Keywords:
Dosimetry, Monte Carlo, Paediatric examinations, Cystourethrography, Barium meal
