Ok both fluoroscope and CT are forms of XRays I was using the terms interchangeably. That actually makes a lot of sense it's fluoroscope cause you want to take a bunch of XRays as the fluid moves down.
I misread the above post about the bone scan being similar to PET scan but it is not actually a PET scan. I know pet looks nothing like radiography if done alone, but it looks like a ct when it it a pet/ct
Good explanations so far but there still seems some confusion so I'll break it down more.
Fluoroscopy and CT are not forms of X-rays, but modalities of imaging that use X-rays. Radiography is another modality of imaging that uses X-rays. The imaging studies that people colloquially call chest X-rays are chest radiographs. Radiography looks at static images of anatomy, while fluoroscopy involves essentially a series of radiographs to image anatomy in dynamic motion, with differences being in timing and energy of X-rays used and their detection. A fluoroscope is the machine used in fluoroscopy.
An upper GI series involves fluoroscopy or series of radiographs of the upper GI system following oral contrast administration. The contrast material can be barium-based, although one can also use water-soluble iodinated contrast. A subset of upper GI series using barium contrast that are focused on the pharynx or esophagus can be known as a modified barium swallow or barium swallow, respectively. A modified barium swallow can also be known as a video fluoroscopic swallow study. A barium swallow can also be known as a barium esophagram. A full upper GI series will follow the contrast into the stomach and duodenum. An upper GI series with small bowel follow-through will follow the contrast through the rest of the small intestine. Between these variations, your choice of order depends on the level of anatomy you're interested in.
In CT/fluoroscopy/radiography, a machine makes X-rays that pass through the patient. Nuclear medicine exams are different in that the source of the rays/photons comes from within the patient. These rays/photons are called gamma rays. Gamma rays are pretty much the same as X-rays (eg, in range of energy) but with a different source. X-rays come from electrons such as those excited in an X-ray machine's cathode-anode apparatus. Gamma rays come directly or indirectly from a nuclear decay event. Nuclear medicine exams image gamma rays produced by radionuclides (radioactive isotopes of atoms, ie, radioisotopes). These radionuclides are administered to the patient as part of a radiopharmaceutical (a drug bound to a radionuclide).
The radionuclides used in nuclear medicine imaging undergo nuclear decay and generate either gamma rays (gamma decay) or positrons (beta plus decay). For example, the radionuclide technetium-99m emits gamma rays, and the radionuclide fluorine-18 emits positrons. Gamma decay emits gamma rays one by one, ie, single photons. In comparison, after beta plus decay, the emitted positrons interact with nearby electrons and in an event called electron-positron annihilation create a pair of gamma rays going in opposite directions, ie, photon pairs.
Single photon nuclear medicine exams involve detecting single gamma rays (emitted from radionuclides that undergo gamma decay) in either a planar (2D) fashion, analogous to radiographs, or a tomographic (3D) fashion, analogous to CT. The former is referred to as scintigraphy, which uses devices called gamma cameras (alternatively scintillation camera or Anger camera). The latter is referred to as single photon emission computed tomography (SPECT). Positron emission tomography (PET) involves detecting pairs of gamma rays (emitted from annihilation events shortly following positron emission) and imaging that in a tomographic fashion.
SPECT and PET are often performed sequentially with CT, which allows for attenuation correction and anatomic correlation. These combination exams are abbreviated SPECT/CT and PET/CT. Attenuation correction means controlling for how much energy is lost in the gamma rays emitted from the center of the body versus the periphery. Anatomic correlation means figuring out where exactly in the body the gamma rays are coming from. Nuclear medicine provides the functional/physiologic information, whereas CT provides the anatomic information. The CT done for attenuation correction and anatomic correlation is typically low radiation dose. A higher dose CT, and perhaps with contrast media administration, can also be performed if less noise and greater anatomic detail is desired for diagnostic purposes, which is called a diagnostic CT. In either case, the SPECT or PET images can be registered (aligned) with the CT images and then fused, so you see both types of information on one image. In the fused images, the CT portion is typically depicted on the grey scale while the SPECT or PET images are depicted on a color scale. When you open up a PET/CT study, you'll typically see a series of PET images in greyscale, a series of CT images in greyscale, and a series of PET/CT fused images in combined grey and color scales.
Bone scan is also known as bone scintigraphy, a planar (2D) single photon nuclear medicine technique that most commonly uses the radiopharmaceutical technetium-99m methylene diphosphonate (MDP). Alternatively, you could get SPECT imaging with Tc99m-MDP if you wanted 3D detail, such as in the spine, and this may still be colloquially referred to as a bone scan. MDP is a bisphosphonate. Technetium-99m is the radionuclide attached to MDP that undergoes gamma decay. Tc99m-MDP binds to bone particularly at areas of active bone formation. Bone scans therefore detect areas of osteoblastic tumors, fractures, and infection.
PET scans can be performed with a number of radiopharmaceuticals for different reasons. The most common type of PET scan is FDG PET, which is fluorine-18 fluorodeoxyglucose. FDG is a glucose molecule labeled with radioactive fluorine-18, which undergoes nuclear decay and emits positrons. FDG PET detects areas of high glucose uptake, ie, metabolically active tissues like malignancies.
Skeletal surveys are series of bone radiographs of the body. Whereas bone scans look for bone formation as indicated by bisphosphonate binding, skeletal surveys look for bone loss as indicated by areas of thinned or broken bones. Pure osteolytic lesions like multiple myeloma may show up on skeletal survey but not bone scan. Nuclear medicine studies involve more radiation exposure, acquisition time, and expense than radiographic studies. Therefore, to look for nonaccidental trauma in infants and children, skeletal surveys are the imaging test of choice to evaluate for fractures.
tldr: Bone scan nuclear, skeletal survey x-ray. Bone scan osteoblastic, skeletal survey osteolytic. Barium swallow down to esophagus, upper GI down to duodenum. Barium swallow pharyngeal and esophageal lesions, upper GI gastric and duodenal lesions.
