Changes

[[file:Pet_CT.jpg|200px|thumb|'''Figure 3:''' Example of true positive metastatic lesions detected by 18F-FDG PET/CT restaging (Courtesy: Eur. J. Nucl. Med. Mol. Imaging, 45: 1742/CC By 4.0)]]

Diagnostic radiology, the imaging modalities using ionizing radiation, produces images of anatomical internal structures of human organs and physiological (functional) biological systems and helps significantly improve patient management and care in screening and diagnosis, assessing treatment response, predicting prognosis, and detecting disease recurrence. Modern diagnostic radiology assures faster, more precise diagnosis and enables monitoring of a large proportion of diseases. It has been estimated that in about one half of all cases, radiological procedures (conventional radiography, fluoroscopy, computed tomography) have a substantial impact on the speed of diagnosis and in a large fraction of cases they are of decisive importance in guiding patient management and therapy.

In diagnostic radiology, x rays, produced by machines, are transmitted through the patient’s body and detected by a receptor (or detection) system to generate the required image of the organs under investigation. The differential absorption of x rays in tissues and organs, owing to their atomic composition, is the basis for the various imaging methods used in diagnostic radiology. Modern diagnostic radiology uses a digital process for image acquisition, transfer, process and storage. Over the past years, with the tremendous technological progress and collaborative efforts in radiation protection, the radiation doses used in diagnostic radiology have been significantly reduced and continue to be reduced through technological innovations especially in CT ([[ICRP Publication 135]] Diagnostic Reference Levels in Medical Imaging; [[ICRP Publication 121]] Radiological Protection in Paediatric Diagnostic and Interventional Radiology; [[ICRP Publication 105]] Radiological Protection in Medicine; [[ICRP Publication 93]] Managing Patient Dose in Digital Radiology).

[[file:SPECT_CT_gamma.jpg|200px|thumb|'''Figure 7:''' Example of a SPECT/CT gamma camera (Source: © 2018 Siemens Healthcare GmbH. All Rights Reserved. Product photo provided courtesy of Siemens Healthcare GmbH) ]]

Nuclear medicine procedures for treatment are non-invasive and present no risk of direct complications to patients, but limited to several well-established situations where killing hyperfunctioning or malignant cells is important (for example hyperthyroidism, cancer of the thyroid, degenerative and inflammatory diseases of joints, palliative treatment of metastases to the skeleton). In addition, there are many studies showing significant potential for radio-labelled antibodies and receptor-avid peptides to be used in the treatment of several malignancies.

A patient undergoing nuclear medicine imaging or treatment becomes a radiation source and remains “radioactive” after the radiopharmaceutical has been administered. Radiation protection advice depends on the specific radioisotope and its radiopharmaceutical form administered and whether the procedure is diagnostic or therapeutic. However, the general principles of the ICRP system of radiological protection apply in nuclear medicine as they do for other medical imaging modalities using ionising radiation. In addition [[ICRP Publication 52]] Protection of the Patient in Nuclear Medicine (and Statement from the 1987 Como Meeting of ICRP) and [[ICRP Publication 94]] Release of Patients after Therapy with Unsealed Radionuclides provide recommendations and guidance on the protection and release of patients after therapy with unsealed radionuclides (e.g. post 131 Iodine therapy for thyroid cancer), and [[ICRP Publication 128]] Radiation Dose to Patients from Radiopharmaceuticals: A Compendium of Current Information Related to Frequently Used Substances provides dose coefficients to patients from radiopharmaceuticals.

Nuclear medicine techniques are used in veterinary care as well. Diagnostic nuclear medicine procedures provide more information on the functioning of organs and tissues than radiographies, but the morphological information provided is less detailed. For these reasons, diagnostic nuclear medicine is more and more being combined with CT-scanning. Such examinations are referred to as “mixed modality” or “hybrid imaging”, with SPECT-CT and PET-CT as typical representatives. A more recently developed combination of nuclear medicine with magnetic resonance imaging (MRI) is also possible and provides similar advantages.

[[file:Portable_PET_1.6.jpg|200px|thumb|'''Figure 9:''' A portable PET scanner being used for diagnosis of the left hind-leg of a horse (Photo courtesy of Dr. Spriet, UC Davis Veterinary Medicine, USA)]]