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Radiation Protection in Pediatric Radiology

Introduction:

The past decade has seen a phenomenal increase in the Medical X-ray equipment in the country. Along with this there has also been an increasing and at times excess use of high radiation dose modalities such as Computed Tomography and interventional radiology. It has thus become imperative to spread the knowledge of radiation safety amongst the medical community. Although there is no conclusive evidence that radiation causes cancer or heredity effects, large population studies have shown a slight increase in cancer even from small amounts of radiation.

Children are biologically more vulnerable and this vulnerability (Ref: IAEA 71) is owing to their radio-sensitivity, their life expectancy and the amount of radiation exposures received over a time period. Thus the lifetime risks are expected to be higher in a child than in an adult. The increased radio-sensitivity in children is because of proliferation during growth periods, at cellular and sub-cellular levels. As most malignant tumors become manifest many years after exposure, children, because of their longer life expectancy, have a higher chance of being alive at the time of tumour presentation.

The fundamental principles of radiation protection are Justification, Optimization and Dose Limits.

In medicine, use of ionizing radiation is a well-justified practice, as it has proved to be life saving, both with respect to diagnosis and therapy. However, examples (Ref: ICRP-121) such as these come under unjustified radiation exposures.

• Skull radiograph in an infant or child with epilepsy;
• skull radiograph in an infant or child with headaches;
• sinus radiograph in an infant or child under 6 years of age suspected of having sinusitis;
• cervical spine radiograph in an infant or child with torticollis without trauma;
• radiographs of the opposite side for comparison in limb injury;
• scaphoid radiographs in children under 6 years of age;
• nasal bone radiographs in children under 3 years of age;
• routine daily chest examination in intensive care units;
• Radiological examinations requested purely for medico-legal purposes

The second stage is the optimization of exposures. Most of the times, though x-ray exposures are required, it is far from being optimized. With just a little conscious application, it is possible to optimize (also called ALARA; As Low as Reasonably Achievable) the exposures very effectively. The various optimization techniques to be followed in each modality are described in this article.

Medical exposures (usually patient) have no “dose limits”. The dose limits, prescribed by competent authority are applicable for the radiation workers and public. For patients, as a good practice there exist what are called “Diagnostic Reference levels (DRLs), explained in this article.

How can exposures be optimized for children?

• By being wary of “unfavorable conditions”;
• Through proper choice of equipment;
• Through proper operational procedures for different modalities.

• Using unsuitable Automatic Exposure systems; in imported equipment, which are not customized to Indian demography before use;
• Following adult exposure protocols for children;
• Using sub-standard equipment, which has not been design approved (AERB Type Approved) and not subjecting the equipment to periodic quality control tests;
• Not using all dose-minimizing features that the machine provides;
• Radiographs taken by unqualified personnel, who do not fully appreciate the implication of their actions;
• Not considering alternate means of diagnosis (MRI, USG etc);
• Not asking for previous x-ray records, for same ailment; Expecting best quality images, even if there is no additional gain in terms of diagnosis; Unnecessary referrals.

• Do not buy refurbished equipment from un-authorized suppliers:
• Such equipments are not design approved by AERB.

• The equipment shall be AERB Type approved
• High frequency and high power (kW) equipment, i.e. higher mA (> 300 mA) stations should be preferred (facilitates to use shorter exposure times and reduced retakes)
• small focal spot of about 0.5 mm - 0.8 mm
• removable anti scatter grid
• AEC (Automatic Exposure Control) provision with proper calibration of paediatric protocols carbon fiber couch
• patient dose recording option is recommended for continual monitoring and optimization

When second-hand equipment is considered, it needs to maintain the original manufacturer’s specifications and meet the local minimum criteria for acceptability and proof obtained.

During regulatory inspections, AERB officers have advised users on many occasions. In particular, AERB officers have observed that infants are exposed as shown below.

• AVOID “Babygrams”. Expose only areas of interest
• Replace faulty collimator bulb immediately. Not having a light beam as a guide could result in the complete opening of collimator an infant and cause whole body exposure. (see below a representation)

• Use shielding and immobilization devices: These devices help towards correct collimation, and proper positioning of shielding devices, to protect radiosensitive organs such as gonads, breast, eye lens and thyroid.
• Judiciously use Anti-scatter grid:Anti-scatter grid is used for reducing scatter radiation, thereby improving the image quality. The flipside of using these grids is the need for higher exposure parameters. For children doseis increased 3-5 times without any concomitant improvement in image quality.

Radiation Oncologist is the radiological medical practitioner in Radiotherapy. The radiation oncologist shall have the sole responsibility for the overall care of the patient. He/She shall ensure that the provisions of the Atomic Energy (Radiation Protection) Rules, 2004, or modified thereafter, are implemented.

The responsibilities shall include:

1. Consultations with the patient, clinical evaluation of the disease and the justification for the proposed line of treatment;
2. Establishment of treatment plan, including dose prescription;
3. Executions of treatment and participation in it on a regular basis;
4. On-treatment evaluations and patient monitoring;
5. Preparation of treatment summary at the end of the treatment procedure; and
6. Evaluation of the treatment and follow-up.

Nuclear Medicine Physician is the radiological medical practitioner in Nuclear Medicine.

The nuclear medicine physician shall

1. have the responsibility of dosage administration and maintenance of records providing name of the patient, nature of procedure, radiopharmaceutical prescribed, quantity prescribed, name of the nuclear medicine physician with signature and date, and name of the person administering the radiopharmaceutical with signature and date;
2. prevent any possibility of misadministration and promptly report to the licensee and the competent authority in the event of any misadministration, adverse reaction or death of a patient administered with radioactivity;
3. consider factors such as proper choice of radiopharmaceuticals, monitoring of procedure and immobilisation of the patient in order to minimise absorbed dose to the patient;
4. consider justification of diagnosis/therapy on pregnant patients/lactating mothers in order to limit the exposure to the foetus/infant not exceeding an absorbed dose of 1 mGy;
5. consider appropriate measures for dose fractionisation, in order to minimise non-stochastic effects following radionuclide therapy;
6. adopt specific dosimetric consideration in pediatric patients to ascertain the risk-benefit ratio;
7. inform patient on safety measures to be observed to avoid radiation exposure to the family members and others;
8. ensure that where the quantity of radioactivity administered to a patient is in excess of the limits specified in AERB Safety Code for Nuclear Medicine facilities (AERB/RF-MED/SC-2 (Rev. 2)) for radiopharmaceuticals
   • patient is hospitalised and kept isolated,
   • spread of contamination prevented and
   • exposure of staff, other patients and public minimised;
9. instruct nursing and ancillary staff on radiation safety and precautions in nursing/management of therapy patients;
10. obtain an informed consent from the relatives of the patient, prior to administration of therapeutic dose; and
11. instruct on the time duration for avoidance of pregnancy following radionuclide therapy such that the absorbed dose to the conceptus shall not exceed 1 mGy.