Radio Iodine Therapy In Cancer Thyroid Prof. Dr. Hosna Moustafa Professor of NM depart. Cairo University, Egypt

Diagnosis Tc99m- thyroid scan may show autonomous hot nodule which is rarely malignant, or cold nodule which may be malignant in 10 – 15% . Fine needle aspiration biopsy is needed for final diagnosis guided by ultrasound .

Picture for solitary cold nodule

Treatment lines Surgery. Radio-iodine. Hormonal

Technical consideration of whole body 131I scanning Patient preparation: Physician to instruct patient to be in low iodine diet. Thyroid medication should be stopped for 4 weeks. Radiopharmaceutical: Dose 1 – 2mCi 131I given to fasting patient with no further eating for 2 hours. Equipment: High energy parallel whole collimator, with 20% window in 364 kev of 131I.

Procedure It is performed after surgery or radio iodine therapy after 6 months. Whole body scanning at 48 or 72 hours 10cm/min. Spot view on thyroid for 5 minutes. SPECT/CT for neck and chest is a viable Image interpretation: Normal uptake in salivary glands, stomach, colon and urinary bladder. Any radiotracer accumulation in neck or metastatic sites in lung, bones or brain should be considered abnormal.

I-131 Whole body scans Neck residue + Lung mets Normal Neck residue

Metastatic lesions to bone with SPECT CT localization

Metastatic lesions to lungs with SPECT CT localization

131I therapy: radiopharmaceutical iodine-131 (131I) as sodium iodide physical half life: 8.1 d principle γ-ray: 364 KeV principle β-particle: max. E 0.61 MeV, average E 0.192 MeV mean range in tissue 0.8 mm (max. 2.4 mm) Administered dose: remnant thyroid tissue: 70 - 80 mCi local metastases: 100 -125 mCi pulmonary metastases: 80 – 100 mCi bone metastases: 150 – 200 mCi

Before ablation After ablation

Metastatic lung case, with good response to therapy

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