Inclusion Criteria:  Patients receiving MRT (177Lu-Peptide for Neuroendocrine Tumours and 131I for Thyroid Cancer and Benign Hyperthyroidism). Women of childbearing potential must use a reliable method of contraception and have a documented negative pregnancy test immediately prior to MRT administration in accordance with routine clinical practice. Able to comply with treatment plans, scheduled visits, all study whole body, SPECT/CT & PET/CT imaging and follow-up. Able to use a personalised dosimetry handheld device and record daily readings for 28 days post MRT. Willing and able to give informed consent.  Exclusion Criteria:  Pregnant or breastfeeding women. Any other considerations that may make the patient unable to tolerate whole body, PET or SPECT scans. Inability to use a personalised dosimetry handheld device and record the daily reading for 28 days post MRT. Participants who are involved in current research or have recently been involved in any research prior to recruitment.