Patient Dose & Precautions For Handling Of Radionuclides that used in NM

PATIENT DOSE

In nuclear medicine, investigations the dose to a patient is not related to how many images are taken or which part of the body is being imaged.

The source is internal.

The excretory organs and those of interest generally receive the highest doses

Absorbed dose depends on:

1. Activity administered to the patient (linearly proportional)

2. Additional dose from activity in surrounding tissues.

3. Fraction taken up by the organ (linearly proportional)

4. Fraction escapes from the organ & not contribute to the absorbed dose.

5. Effective half-life of the radionuclide (Non linearly proportional … decay is non-linear)

6. Renal excretion rate (inverse proportion)

7. Energy (MeV) of gamma radiation emitted in each disintegration

Effective dose:

• The distribution of a dose is non-uniform and specific to the examination
• After IV injection - most tissues may receive some dose, but the target organ and the organs of excretion generally receive the highest doses.

Most investigations deliver an ED of 1 mSv or less

Measures to minimize patient dose,

• Using isotopes with half-lives that are suitable for the investigation
• Patients should drink a good plenty of water and empty the bladder frequently to reduce the dose to the gonads and pelvic bone marrow
• Interruption of breast feeding is recommended after exam

Safety & Precautions For Handling Of Radionuclides

When handling radionuclides, there are hazards from:

• External radiation
• Internal radiation (accidental ingestion or inhalation of the radionuclide or wound contamination) … Greater risk

It is therefore important to avoid contamination of the environment, the workplace, and persons, and to control any spread of radioactive materials.

Segregation

A nuclear medicine facility must have separate areas for:

• Preparation & storage of material
• Injection of patients
• Patients to wait
• Imaging
• Temporary storage of radioactive waste

Personal protection

• Use should be made of distance "inverse square law", shielding, and time.
• Staff should only enter areas where there is radioactivity when it is strictly necessary
• All procedures must be carried out promptly and efficiently.
• Departmental local rules must be followed.
• Some general guidance:

1. Radionuclides are contained in shielded generators or bottles in lead pots.

2. Handling bottles and syringes with long‐handled forceps (tongs).

3. Manipulations, such as the labeling of pharmaceuticals and the loading of syringes, are carried out with the arms behind a lead barrier which protects the body and face, and over a tray, lined with absorbent paper, to catch any drips.

4. Syringes are protected by heavy metal or lead glass sleeves (reduce finger doses by 75%) & transported in special containers or on a kidney dish.

5. Before injection, syringes are vented into swabs or closed containers and not into the atmosphere.

6. Lead‐rubber aprons are ineffective against the high‐energy gamma rays of 99mTc.

7. To avoid accidental ingestion → waterproof (double‐latex) surgical gloves are worn when handing radionuclides.

8. Cuts and abrasions must be covered first.

9. There must be no eating, drinking or facial contact inside the room.

10. Staff hands and work surfaces are routinely monitored for radioactive contamination.

11. Air in Radiopharmacies may also be sampled and monitored.

12. Swabs are taken from the workstation to monitor for radioactive and bacterial contamination.

13. Hands should be washed regularly at special wash hands free designated basins.

14. After spills, decontamination should be carried out, involves the use of water, mild detergents, and swabs, which are then sealed in plastic bags and disposed of as radioactive waste in marked bins. Any use of a nail brush should be gentle; if contamination is obstinate, special detergent solutions may be necessary.

Patient protection

• Every radionuclide should be checked for activity before administration, using a radionuclide (well) calibrator.
• The patient's identity must he checked against the investigation to be made and the activity to be administered, and this must be recorded.
• Particular care should be taken to avoid contamination during oral administrations.
• Special circumstances apply for pregnant patients and those with babies they are breast-feeding.

Dealing with a radioactive spill

In the case of a radioactive spill, vomiting, incontinence, etc.:

• Clear the area of non-essential persons.
• Wearing gloves, aprons, and overshoes.
• Mop the floor with absorbent pads and seal the swabs in designated plastic bags.
• Continue until monitoring shows the activity to be at a satisfactorily low level.
• If necessary, cordon off the area or cover it with impervious sheeting until sufficient decay has occurred.
• Contaminated materials are treated as waste.

Disposal of radioactive waste:

• Follow the two principles of:

- Containment and decay

- Dilution by dispersal to the environment.

• Every hospital is subject to strict limitations on the amount which can be disposed of by each of the following routes.
• Gaseous waste can be vented to the atmosphere:
• In lung ventilation studies, 133Xe and 99mTc aerosols should be exhausted to the exterior of the building.
• Aqueous liquid waste → well diluted with water → disposed of via designated sinks with drains running directly to the foul drain
• Solid waste (swabs, syringes, bottles, etc.) → placed in designated sacks for disposal by incineration or, if suitably diluted with ordinary waste, to waste disposal sites.
• Old generators are kept in a secure shielded store until they are returned to the manufacturer.
• Contaminated clothing and bedding is appropriately bagged and stored in a secure protected area until sufficiently decayed for release to the laundry.
• Records must be kept for inspection of all deliveries, stocks, administration, stored waste, and disposals of waste.