The Thyroid Gland & Iodine-131 Ablation Treatments Faradally A OLLITE 30th November 2001 The Thyroid Gland ( A General Introduction) RIGHT LOBE LEFT LOBE WINDPIPE Location: At the base of the neck, just below the Adam’s Apple. Each lobe of the thyroid lies on either side of the windpipe. Function: To make, store and release thyroid hormones into your blood. Thyroid Hormones The Thyroid gland produces the two main hormones ¾ Thyroxine (T3) ¾ Triodothyronine(T4) The thyroid hormones regulate ¾ ¾ ¾ ¾ ¾ heart rate, blood pressure, body temperature, the rate at which food is converted into energy (metabolism), and affects the nervous system, muscles, and other organs. Thyroid Hormones Thyroid Hormones Hypothalamic-pituitary-thyroid feedback system The amount of thyroid hormone in the body is adjusted by the hypothalamic-pituitary-thyroid feedback system ¾ The Thyroid Gland (Thyroid Hormone ) ¾ The Pituitary Gland (Thyroid-Stimulating Hormone, TSH) TRH Hypothalamus Pituitary TSH Thyroid ¾ The Hypothalamus (Thyroid-Releasing Hormone, TRH) Thyroid Hormones Thyroid Diseases (Hypothyroidism) Hypothyroidism Thyroid gland producing too little thyroid hormones Causes: Hashimoto’s thyroiditis or Iodine deficiency Signs & Symptoms: slow heartbeat, weight gain, tiredness amongst other symptoms Treatment: Thyroid hormone replacement therapy (Levothyroxine sodium) Mild Thyroid Failure A mild form of hypothyroidism (thyroid hormones level normal, but a high TSH level) Thyroid Diseases (Hyperthyroidism) Hyperthyroidism Thyroid gland producing too much thyroid hormones Causes: Grave’s disease or thyroid nodules Signs & Symptoms: fast heartbeat, nervousness, weight loss, among other symptoms Treatment: Anti-thyroid drugs, surgery, or radioactive iodine treatment Mild (Subclinical) Hyperthyroidism A mild form of hyperthyroidism (thyroid hormones level normal, but a low TSH level) Thyroid Diseases (Thyroid Nodules) Thyroid nodules A thyroid nodule is a lump, growth or swelling located in the thyroid gland. Signs & Symptoms: palpable neck mass,neck pain, swallowing and breathing difficulty Treatment: Treatment of thyroid nodules depends on the type of the nodules present Thyroid Cancer Test for thyroid nodules ¾ Physical examination of the thyroid ¾ Blood tests (thyroid hormone and TSH levels) ¾ Thyroid imaging tests (thyroid scan) ¾ Thyroid biopsy Thyroid nodules can be either benign or malignant. Thyroid Cancer is when the nodules are found to be malignant Thyroid Cancer (Treatment) The treatment of thyroid cancer depends on the type and stage of the cancer. The main types of treatment used are: ¾ ¾ ¾ ¾ Surgery Radiation therapy Hormone therapy Chemotherapy ¾ The most effective form of initial cancer therapy is surgery. ¾ Also in most cases there is total thyroidectomy. (i.e complete removal of the thyroid glands). I-131 Ablation Treatment Difficult to remove all the thyroid tissue when performing thyroidectomy. Thus after total thyroidectomy we usually have the radioactive iodine ablation treatment to destroy any residual thyroid tissues. Usually a large dose of I-131 administered in the patient (~100-200 mCi) and the patient has to be hospitalised. Iodine – 131 (Physical Data) Emission Energy Intensity Gamma 364 KeV 82% Beta 606 KeV (Maximum) 192 KeV (Average) 89% Physical Half Life: 8.05 days Biological Half Life: 138 days Effective Half Life: 7.60 days γ β Thyroid Iodine Uptake Large thyroid uptake 10 – 25 % for a typical thyroid 2–3% for residual thyroid tissue after a thyroidectomy Elimination of I-131 I-131 leaves body through bodily fluids (saliva, sweat, blood, urine, faeces) In most patient the majority of the administered radioactive iodine has been extracted after 48 hours. A recent study estimates a median effective half life of the administered radioactive iodine to be 14 hours, with substantial variation. I-131 Ablation treatment (Exposure and Contamination Risk) The thyroid dose is principally due to the I-131's short range beta radiation. The accompanying high energy penetrating gamma ray radiation mostly escapes the patient producing unwanted radiation fields. Exposure risk: to anyone in close proximity to the patient Contamination risk: to anything in contact with bodily fluids of patient Radiation Safety (Precautions & Practices) Special radiation safety precautions must be taken (i) to minimize exposure risk to ¾ other patients ¾ hospital workers ¾ family & friends (ii) to minimize the contamination risk All the radiation safety precautions associated with the management of I-131 patient before, during and after therapy are in accordance with the ALARA principle. ALARA As Low As Reasonably Achievable economic and social factors taken into account. Minimizing Exposure Without compromising patient care, all personnel should follow the following basic principles to minimize the radiation exposure: (i) Minimize time spent with patients by planning ahead and working efficiently (ii) Maximize distance by working as far from patient as possible Patient Accommodation Patient is assigned to a private room with a private bathroom and the patient is isolated to the room. Preferably a room in an outside corner of the building with the bed close to the outside wall. Flooring should be an impermeable material which is washable and easily decontaminated. All necessary equipment, housekeeping supplies and amenities for the duration of radioactive isolation should be placed in the room prior to the therapy. Room Preparation To minimize the risk of contaminating objects or areas, the room and furniture is protected using plastic and absorbent materials before the treatment is given in areas likely to be contaminated. Also the room is arrange in a manner to minimize the exposure to the visitors and to other patients, Information to Patient A verbal and written explanation of the therapy help the patient understand the nature of the treatment and its radiation risks both to the patient and to other persons. MUHC patient information sheet which gives information regarding the I-131 ablation treatment. Administration of Treatment Preplanning to minimize occupational exposure The pill container is opened under the fume hood. The I-131 is usually administered orally in form of capsule. Radiation warning sign clearly visible on the door of the room Information to Visitors Specific restrictions relating to visitors should also be posted outside the patient’s room 9 9 9 9 9 No pregnant women or children No eating or drinking in the room Do not use the patient’s bathroom Keep a reasonable distance from patient (~1-2 m) Keep visit short (< 1 h) Daily Procedures (Contamination Survey) Contamination survey of items (e.g. food trays, wastes, linen, etc.) prior to release from room, by Radiation Protection Services Wastes are surveyed, sorted and cleared from the room. 9 Contaminated waste are kept for decay in storage (radioactive label, activity, isotope, date) 9 Non-contaminated waste are treated as normal waste Always wear impermeable protective gloves and slip-off shoe covers during contamination survey Radioactive Spill Spillage of radioiodine or body fluids (via vomitus, incontinence, excessive sweating) will result in contamination of the area. In this case – The Radiation Safety office should be informed of the spill immediately. – No attempt to clean up the spill should be made by the patient or by the nursing staff. – All persons not involved in the spill should vacate the area immediately and access to the area should be restricted. – Those involved in the spill should be monitored for contamination before leaving. – Ensure that impermeable gloves and slip-off shoe covers are worn all the time during spill clean-up operation and decontamination. Daily Procedures (Exposure Level Measurements) 9 9 9 9 9 The exposure level measurements are taken at the neck the shoulder 1 metre from patient 2 metres from patient the entrance of the room This procedure is done just after the dose has been administered and on a daily basis during the period of hospitalization. MUHC Radiation Protection Follow Up Sheet Criteria for Patient Release Decision concerning the possible release of the patient is based on the results of a radiation survey in the proximity of the patient. Approximate Approximate Residual Radiation Dose Level Without restrictions @ 1 metre (NCRP 37, 1970) @ 2 metres (GMA 4, 1993) 8 mCi (296 MBq) 1.8 mR/hr With restrictions 30 mCi (1110 MBq) 6.75 mR/hr Without restrictions 8.11 mCi (300 MBq) 0.4 mR/hr With restrictions 29.7 mCi (1100 MBq) 1.6 mR/hr Restrictions (for released patients) Patients released with restrictions are strongly recommended to – – – – Avoid close contact with other persons Flush toilet 2 or 3 times after use and wash hands thoroughly Use separate linen, bath towels, etc. Wash clothes separately Also patients released without restrictions are also advised to follow these restrictions. Decommissioning Process Protective covering is removed and treated as radioactive waste All wastes, linen is surveyed and disposed of accordingly Floor and furniture are surveyed for contamination Contaminated areas are decontaminated according to CNSC regulations and internal standards. CNSC Regulations & Internal Standards (for decontamination level) From CNSC therapeutic nuclear medicine license for the room decommissioning Prior to decommissioning of the room the non-fixed contamination for I-131 must not exceed 3 Bq/cm2 MUHC Decommissioning Policy Wipe test results are less than 0.5 Bq/cm2 Decommissioning Process Wipe tests are taken to monitor the contamination level Process is repeated until the room is decontaminated according to regulations Head nurse is informed, warning signs removed when the room can be reopened to normal use Acknowledgements ¾ Dr Robert Corns ¾ Maureen McQueen ¾ Marylene Clavet ¾ Daniel Alu ¾ Jodi Powers Thank you !!!
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