Life and health

Radiochemotherapy

Radiochemotherapy (chemoradiotherapy, CRT) is the combination of chemotherapy with radiotherapy, given concurrently or sequentially, and standard of care in cervical, rectal, anal, and nasopharyngeal cancer.

Radiocontrast agent

Radiocontrast agent (contrast medium): iodinated compounds for X-ray/CT, gadolinium chelates for MRI, barium sulfate for GI imaging, and microbubbles for ultrasound; classes differ in osmolality, safety, and kidney and thyroid risks.

Radiodynamic therapy

Radiodynamic therapy is a cancer treatment in which X-rays activate a sensitizing agent that generates reactive oxygen species to kill tumor cells, reaching deep tumors that visible or near-infrared light cannot.

Radioembolization

Therapeutic radioembolization (SIRT, TARE, Y-90 radioembolization): catheter-based liver cancer therapy injecting yttrium-90 glass or resin microspheres into hepatic arteries; used for unresectable HCC and metastases, with FDA-approved TheraSphere and SIR-Spheres devices.

Radiofrequency ablation

Radiofrequency ablation (RFA): catheter-based cardiac procedure using RF-heated tips to destroy arrhythmic tissue; standard for AF pulmonary vein isolation since Haissaguerre's 1998 work, with ~4.5% major complication rate.

Radiofrequency neurotomy

Radiofrequency neurotomy is a pain procedure that heats small spinal nerves, such as the facet joint's medial branch nerves, to interrupt chronic back or neck pain for months.

Radiofrequency Therapy

Radiofrequency therapy is the use of radio waves to heat, stimulate, or ablate tissue, encompassing radiofrequency ablation, pulsed radiofrequency, and non-invasive techniques used for pain, arrhythmias, and tumors.

Radiofrequency thermocoagulation

Radiofrequency thermocoagulation is a minimally invasive pain procedure that heats and destroys nerve tissue with an electrode, most often for trigeminal neuralgia and facet joint pain.

Radiographer

Radiographer (radiologic technologist): allied health professional producing diagnostic images (X-ray, CT, MRI, PET) or delivering radiotherapy. Distinct from the radiologist, a physician who interprets images; UK titles protected by HCPC registration.

Radiographic Image Enhancement

Radiographic image enhancement is the digital processing of X-ray and other radiation images after acquisition, adjusting contrast and frequency properties so clinically important features stand out.

Radiographic Magnification

Radiographic magnification: enlargement of an X-ray image, factor M = SID/SOD. Used in magnification mammography for microcalcifications; geometric magnification outperforms electronic zoom; must be corrected in hip templating.

Radiographics : a review publication of the Radiological Society of North America, Inc

RadioGraphics (ISSN 0271-5333 print, 1527-1323 online) is RSNA's peer-reviewed education journal in diagnostic radiology, launched 1981, edited by Christine Cooky Menias, publishing solicited RSNA meeting exhibits; 2025 impact factor 6.2.

Radiography

Radiography (projection X-ray imaging) records a static image after an X-ray beam passes through the body, distinct from fluoroscopy and CT. Discovered via Röntgen's 1895 X-rays; lower dose than CT; now digital and AI-assisted.

Radioguided surgery

Radioguided surgery is a technique in which a radioactive tracer, detected with a handheld gamma probe, guides surgeons in removing tissue, notably for sentinel lymph node biopsy.

Radioimmunoassay

Radioimmunoassay (RIA), developed by Rosalyn Yalow and Solomon Berson at the Bronx VA hospital, is a competitive antibody-based technique using radioactive labels such as iodine-125 to measure hormones like insulin at nanogram or picogram levels; it won Yalow the 1977 Nobel Prize.

Radioimmunodetection

Radioimmunodetection (RAID), also called radioimmunoscintigraphy, is a nuclear medicine technique using radiolabeled monoclonal antibodies to image tumors; it evolved into immunoPET after FDG-PET displaced it for staging.

Radioimmunoprecipitation Assay

Radioimmunoprecipitation assay (RIPA, Farr assay): sensitive immunoassay using radiolabeled antigens to detect and quantify specific antibodies in serum or CSF; gold standard for AChR antibodies in myasthenia gravis, limited by radioisotope handling.

Radioimmunotherapy

Radioimmunotherapy is a cancer treatment in which a monoclonal antibody linked to a radioactive isotope is given intravenously, carrying radiation to tumor cells; FDA-approved agents treat non-Hodgkin lymphoma.

Radioiodine therapy

Radioiodine therapy is a nuclear medicine treatment using orally taken radioactive iodine-131 to destroy thyroid tissue, treating hyperthyroidism and differentiated thyroid cancer such as papillary and follicular types.

Radioisotope Diagnostic Techniques

Radioisotope diagnostic techniques, the basis of nuclear medicine, use radiotracers imaged by SPECT and PET to show organ function; Tc-99m, F-18 FDG, and I-123 are the workhorse isotopes.

Radioisotope Dilution Technique

Radioisotope dilution technique: MeSH-defined method of injecting a known radionuclide quantity into a system and monitoring downstream concentration over time; used for blood volume (51Cr, 131I), cardiac output, and industrial flow measurement.

Radioisotope Teletherapy

Radioisotope teletherapy, also called teleradioisotope therapy, is external beam radiotherapy using gamma rays from a sealed radioisotope source, chiefly cobalt-60 units introduced in Canada in 1951 after radium teletherapy, now largely replaced by linacs in high-income countries.

Radiolabeling

Radiolabeling is a technique that covalently attaches a radioactive isotope to a biomolecule, cell, or material so the decay signal can detect, quantify, and track it.

Radiolaria

Radiolaria: marine planktonic protists with axopodia and a central capsule, once classified by Haeckel into four legions; modern molecular work recognizes six orders, silica or strontium sulfate skeletons, and a fossil record used in biostratigraphy.

Radiolarian fossil record and radiolarian ooze

The radiolarian fossil record runs from early Cambrian rocks to modern seafloor sediments, and radiolarian ooze slowly converts to chert, making radiolarians valuable for dating oceanic strata.

Radiole

Radiole: the ciliated, feather-like feeding filament forming the radiolar crown of fan worms (Sabellida: Sabellidae, Serpulidae, Fabriciidae); each bears pinnules, filters particles and oil droplets, aids respiration, and may carry eyes or form the serpulid operculum.

Radioligand Assay

A radioligand assay is an analytical technique that quantitatively determines receptors or binding proteins in body fluids or tissue using a radioactively labeled binding reagent, including the radioimmunoassay.

Radiolites

Radiolites is an extinct genus of rudist bivalves, marine mollusks with cone-shaped, reef-dwelling shells, established by Lamarck in 1801; its fossils occur in Cretaceous shallow-water carbonates from the early Aptian to the Maastrichtian.

Radiologic technology

Radiologic technology: allied health profession of radiologic technologists (radiographers) performing X-ray, CT, MRI, nuclear medicine, and ultrasound imaging and radiation therapy; rooted in Roentgen's 1895 X-ray discovery, credentialed by ARRT, organized by ASRT.