| Radionuclide cisternogram | |
|---|---|
| Medical diagnostics | |
| Purpose | determine if there is abnormal CSF flow within the brain |
A radionuclide cisternogram is a medical imaging study which involves injecting a radionuclide by lumbar puncture (spinal tap) into a patient's cerebral spinal fluid (CSF) to determine if there is abnormal CSF flow within the brain and spinal canal which can be altered by hydrocephalus, Arnold–Chiari malformation, syringomyelia, or an arachnoid cyst. [1] It may also evaluate a suspected leak (also known as a CSF fistula) from the CSF cavity into the nasal cavity. A leak can also be confirmed by the presence of beta-2 transferrin in fluid collected from the nose before this more invasive procedure is performed.
Medical imaging is the technique and process of creating visual representations of the interior of a body for clinical analysis and medical intervention, as well as visual representation of the function of some organs or tissues (physiology). Medical imaging seeks to reveal internal structures hidden by the skin and bones, as well as to diagnose and treat disease. Medical imaging also establishes a database of normal anatomy and physiology to make it possible to identify abnormalities. Although imaging of removed organs and tissues can be performed for medical reasons, such procedures are usually considered part of pathology instead of medical imaging.
A radionuclide is an atom that has excess nuclear energy, making it unstable. This excess energy can be used in one of three ways: emitted from the nucleus as gamma radiation; transferred to one of its electrons to release it as a conversion electron; or used to create and emit a new particle from the nucleus. During those processes, the radionuclide is said to undergo radioactive decay. These emissions are considered ionizing radiation because they are powerful enough to liberate an electron from another atom. The radioactive decay can produce a stable nuclide or will sometimes produce a new unstable radionuclide which may undergo further decay. Radioactive decay is a random process at the level of single atoms: it is impossible to predict when one particular atom will decay. However, for a collection of atoms of a single element the decay rate, and thus the half-life (t1/2) for that collection can be calculated from their measured decay constants. The range of the half-lives of radioactive atoms have no known limits and span a time range of over 55 orders of magnitude.
Lumbar puncture (LP), also known as a spinal tap, is a medical procedure in which a needle is inserted into the spinal canal, most commonly to collect cerebrospinal fluid (CSF) for diagnostic testing. The main reason for a lumbar puncture is to help diagnose diseases of the central nervous system, including the brain and spine. Examples of these conditions include meningitis and subarachnoid hemorrhage. It may also be used therapeutically in some conditions. Increased intracranial pressure is a contraindication, due to risk of brain matter being compressed and pushed toward the spine. Sometimes, lumbar puncture cannot be performed safely. It is regarded as a safe procedure, but post-dural-puncture headache is a common side effect.
The patient may be instructed to not eat or drink, or take medications such as aspirin or other blood thinners before the procedure. Pledgets can be inserted into the nasal cavity before the procedure when a CSF leak is suspected.
Aspirin, also known as acetylsalicylic acid (ASA), is a medication used to treat pain, fever, or inflammation. Specific inflammatory conditions which aspirin is used to treat include Kawasaki disease, pericarditis, and rheumatic fever. Aspirin given shortly after a heart attack decreases the risk of death. Aspirin is also used long-term to help prevent further heart attacks, ischaemic strokes, and blood clots in people at high risk. It may also decrease the risk of certain types of cancer, particularly colorectal cancer. For pain or fever, effects typically begin within 30 minutes. Aspirin is a nonsteroidal anti-inflammatory drug (NSAID) and works similarly to other NSAIDs but also suppresses the normal functioning of platelets.
The patient's spinal fluid is injected with a radiopharmaceutical tracer, such as DTPA tagged with indium 111, through a lumbar puncture (spinal tap). The tracer will diffuse up the spinal column and into the intracranial ventricles and the subarachnoid spaces around the brain. The progress of the tracer's diffusion through the CSF will be recorded by a nuclear medicine gamma camera. Images are usually taken immediately, at 6 hours, and at 24 hours. The patient may be asked to return for 48- and 72-hour follow-up scans.
Indium (49In) consists of two primordial nuclides, with the most common (~ 95.7%) nuclide (115In) being measurably though weakly radioactive. Its spin-forbidden decay has a half life of 4.41×1014 years.
Diffusion is the net movement of molecules or atoms from a region of higher concentration to a region of lower concentration. Diffusion is driven by a gradient in chemical potential of the diffusing species.
A gamma camera (γ-camera), also called a scintillation camera or Anger camera, is a device used to image gamma radiation emitting radioisotopes, a technique known as scintigraphy. The applications of scintigraphy include early drug development and nuclear medical imaging to view and analyse images of the human body or the distribution of medically injected, inhaled, or ingested radionuclides emitting gamma rays.
The pledgets will be removed and either imaged with a gamma camera or counted using a gamma counter. If the tracer has leaked onto the pledget through the skull, it will appear on the gamma camera image or register abnormal counts allowing the diagnostician to determine the location of the leak within the sinus cavity. The site of the CSF leak can be plugged with fat or muscle by endoscopic surgery.
A gamma counter is a machine to measure gamma radiation emitted by a radionuclide. Unlike survey meters, gamma counters are designed to measure small samples of radioactive material, typically with automated measurement and movement of multiple samples.
Headaches following the procedure are common, but should fade in 3–5 days. Drinking caffeinated liquids, as well as bed rest, is often recommended, though at least one scientific paper disputes the practice.
Bed rest, also referred to as the rest-cure, is a medical treatment in which a person lies in bed for most of the time to try to cure an illness. Bed rest refers to voluntarily lying in bed as a treatment and not being confined to bed because of a health impairment which physically prevents leaving bed. The practice is still used although a 1999 systematic review found no benefits for any of the 17 conditions studied and no proven benefit for any conditions at all, beyond that imposed by symptoms.
