Évaluation des doses d’irradiation aux organes en scanographie pédiatrique

Radiation dose evaluation of pediatric patients in CT brain examination: multi-center study

There is currently no Pediatric Regulatory Diagnostic Reference Level (DRL) in Cameroon to standardize protocols in hospitals. France, a European country, has DRL allowing them to optimize their examination protocol. For the sake of radiation protection, we have proposed to evaluate the dose and acquisition parameters delivered to our pediatric patients to optimize the protocols used. We also compared the 75th percentile values of dose parameters by acquisition between the three hospitals to Diagnostic Reference Level (DRL) of France. In this retrospective and evaluative multicenter study, a total of 320 patients who had at least one cranial CT scan were enrolled from three medical centers. The CT acquisition parameters including tube potential (kV), tube current (mA), slice Thickness (T), spiral or sequential scanning techniques, volume CT dose index (CTDIvol), and dose length product (DLP) were analyzed. CTDIvol values in our centers were found up to 17.42%, 46.01%, 21.56% respectively for children aged 1-4 higher than values of France's DRL. For those aged 5-9, we obtained 44.58%, 43.15%, 42.21% respectively. In addition, for children aged 10-14 there are also up to 47.73%, 44.11%, 46.39% respectively higher than values of France's DRL. It is similary for DLP values. The study showed a significant dosimetric overshoot compared to the France's DRL and prompted us to make corrections to the protocols used and to a more rigorous monitoring of the principles of radiation protection and optimization rules in pediatric computed tomography in our hospitals. Our results have led us to make changes to our protocols which are the subject of a new dosimetric evaluation. The development of DRL for improving the pediatric CT scan in our country is necessary to optimize our protocols. Our results have led us to make changes to our protocols which are the subject of a new dosimetric evaluation. It would be necessary to set up a quality control structure in Cameroon and their applications in current practice.

Radiation exposure from CT in early childhood: a French large-scale multicentre study

OBJECTIVES

The increasing use of CT scans in the paediatric population raises the question of a possible health impact of ionising radiation exposure associated with CT scans. The aim of this study was to describe the pattern of CT use in early childhood.

METHODS

In 14 major French paediatric radiology departments, children undergoing at least 1 CT scan before age 5, between 2000 and 2006, were included. For each examination, absorbed organ doses were calculated.

RESULTS

43% of the 27 362 children in the cohort were aged less than 1 year during their first exposure, with 9% being aged less than 1 month. The mean number of examinations per child was 1.6 (range 1-43). The examinations included: head in 63% of the cases, chest in 21%, abdomen and pelvis in 8% and others in 8%. Brain and eye lenses received the highest cumulative doses from head examinations, with mean organ dose values of 22 mGy (maximum 1107 mGy) and 26 mGy (maximum 1392 mGy), respectively. The mean cumulative effective dose was 3.2 mSv (range 0.1-189 mSv).

CONCLUSION

CT scan exposure in childhood is responsible for relatively high doses to radiosensitive organs. The rather large dose range according to the protocols used requires their optimisation. The cohort follow-up will study the risk of long-term radiation-induced cancer.

Assessment of organ absorbed doses and estimation of effective doses from pediatric anthropomorphic phantom measurements for multi-detector row CT with and without automatic exposure control

This study was designed to measure organ absorbed doses from multi-detector row computed tomography (MDCT) on pediatric anthropomorphic phantoms, calculate the corresponding effective doses, and assess the influence of automatic exposure control (AEC) in terms of organ dose variations. Four anthropomorphic phantoms (phantoms represent the equivalent of a newborn, 1-, 5-, and 10-y-old child) were scanned with a four-channel MDCT coupled with a z-axis-based AEC system. Two CT torso protocols were compared: a first protocol without AEC and constant tube current-time product and a second protocol with AEC using age-adjusted noise indices. Organ absorbed doses were monitored by thermoluminescent dosimeters (LiF: Mg, Cu, P). Effective doses were calculated according to the tissue weighting factors of the International Commission on Radiological Protection (). For fixed mA acquisitions, organ doses normalized to the volume CT dose index in a 16-cm head phantom (CTDIvol16) ranged from 0.6 to 1.5 and effective doses ranged from 8.4 to 13.5 mSv. For the newborn-equivalent phantom, the AEC-modulated scan showed almost no significant dose variation compared to the fixed mA scan. For the 1-, 5- and 10-y equivalent phantoms, the use of AEC induced a significant dose decrease on chest organs (ranging from 61 to 31% for thyroid, 37 to 21% for lung, 34 to 17% for esophagus, and 39 to 10% for breast). However, AEC also induced a significant dose increase (ranging from 28 to 48% for salivary glands, 22 to 51% for bladder, and 24 to 70% for ovaries) related to the high density of skull base and pelvic bones. These dose increases should be considered before using AEC as a dose optimization tool in children.

Reliability of 3D reconstruction of the spine of mild scoliotic patients

STUDY DESIGN

A reliability study was conducted in quantitative 3-dimensional (3D) measurements for mild scoliosis.

OBJECTIVE

To evaluate the intrarater and interrater reliability of a computer tool used for 3D reconstruction of the spine.

SUMMARY OF BACKGROUND DATA

No reliability study of spinal in vivo 3D medical imaging measurements has been performed in the literature.

METHODS

This study included 30 patients (mean age 13 years) with mild idiopathic scoliosis. Spinal 3D reconstruction was performed using a new technique called semiautomatic 3D reconstruction, which requires only the location of the corners of each vertebral body on 2 orthogonal views. Three raters performed the 3D reconstruction procedure on the 30 pairs of radiographs in random order. One of the raters repeated the procedure for the 30 patients 15 days later. Inter-reliability and intra-reliability were estimated for different parameters: thoracic kyphosis, lumbar lordosis, Cobb's angle, pelvic morphologic and positional parameters, and axial rotation.

RESULTS

Intraclass correlation coefficient showed good or very good agreement for most of the measurements. The 95% prediction limits are approximately 4 degrees for the measurements of spinal curves, 2 degrees for pelvic parameters, and axial vertebral rotation.

CONCLUSIONS

The reliability of 3D reconstruction of the spine is acceptable, and this technique can be used for clinical studies.