CT (X-ray computed tomography) is a painless, non-invasive, non-hazardous, fast, convenient, suitable for any age and highly accurate auxiliary examination tool. The main changes found in patients with epilepsy are cerebral atrophy, cerebral neoplasia, cerebral infarction, abnormal brain development, hydrocephalus, calcifications, and arteriovenous malformations.
The CT film has clear images, high resolution, clear anatomical relationships, and clear pathology.
The purpose of CT brain examination: many causes can trigger epilepsy, such as cerebral atrophy, cerebral hypoplasia or retardation, brain tumor, cerebrovascular malformation, cerebral infarction, hydrocephalus, cerebral malformation, cerebral softening, cerebral calcification foci, high-density changes of unknown cause or nature, low-density changes and so on. If any of these lesions are present in the brain, CT examination can detect them. If CT films show normal, the presence of these lesions can generally be excluded.
Compared with MRI, the advantages of CT mainly include better display of bone, calcification, and early brain hemorrhage than MRI, as well as faster imaging and smaller motion artifacts of organs. Also, CT is more affordable.
Magnetic resonance imaging (MRI) is a new examination technique based on the principle that a magnetically distant nucleus can produce inter-level energy jumps under the action of a magnetic field. MRI helps to examine the energy state and cerebral blood flow in the brain of epilepsy patients, and is of great value in the diagnosis of degenerative diseases. MRI is realized by the action of high-frequency magnetic fields outside the body, and the signal is generated by the co-projection of energy from substances in the body to the surrounding environment, and the imaging process is similar to The imaging process is similar to that of image reconstruction and CT, except that MRI does not rely on external co-radiation, absorption and reflection, nor does it rely on the gamma co-radiation of radioactive materials in the body, but uses the interaction between the external magnetic field and the object to image, and the high-energy magnetic field is harmless to the human body. Therefore, MRI examinations are safe.
MRI is commonly used clinically to detect structural brain changes secondary to epilepsy. if the clinical classification of epilepsy syndrome is unknown, MRI can clarify whether the patient is caused by structural brain changes. intracranial tumors often cause epilepsy, and MRI has an extremely high confirmation rate for the diagnosis of low-grade astrocytomas, ganglia, gliomas, arteriovenous malformations and hematomas in the brain. MRI can clearly show brain atrophy in patients with epilepsy. The display of brain parenchyma and cerebrospinal fluid is excellent.
The main advantages of MRI compared to CT are.
1, Ionized radiation has no radiological damage to the brain tissue and no biological damage.
2.It can directly make cross-sectional, sagittal, coronal and various oblique images of the body layers.
3.No artifacts such as ray hardening in CT images.
4.It is not disturbed by bone image, and can satisfactorily display small lesions at the base of posterior cranial recess and brain stem, and has high diagnostic value for the top of skull and parsagittal sinus, lateral fissure structure and widely metastasized tumor.
5.Showing the pathological process of the disease more extensively and the structure more clearly than CT. It can detect isointense lesions that are completely normal on CT, especially demyelinating diseases, encephalitis, infectious demyelination, ischemic lesions and low-grade glioma.
6. The soft tissue components such as nerves, blood vessels and muscles are significantly better than CT.
Its main disadvantages are.
1, like CT, MRI is also an imaging diagnosis, and many lesions are still difficult to be diagnosed by MRI alone, unlike endoscopy which can obtain both imaging and pathological diagnosis;
2, the examination of the lungs is not superior to X-ray or CT, and the examination of the liver, pancreas, adrenal glands and prostate is not superior to CT, but the cost is much higher;
3.The lesions of the gastrointestinal tract are not as good as endoscopy;
4. MRI is not recommended for those who have metal objects in their bodies.
5. MRI is not recommended for critically ill patients, patients within 3 months of pregnancy, and patients with pacemakers.
Positron emission tomography (PET) is a newly developed nuclear medicine examination method. A radioactive agent labeled with certain positrons is injected into the patient before the scan, and the metabolic changes in brain tissue are measured from the metabolic processes in which they are involved. PET can be used to detect the exact site of abnormal brain metabolism based on the rate of glucose metabolism, and can measure abnormalities in brain metabolism and blood flow limitations in epilepsy patients in three dimensions.
Brain lesion areas in epileptic patients often have enhanced metabolism during seizures, and lesion areas during interictal periods show reduced metabolism, thus helping to identify the lesion. It is the only new imaging technique that can display biomolecular metabolism, receptor and neuromediator activity in vivo, and is now widely used in the diagnosis and differential diagnosis of many diseases, condition determination, efficacy evaluation, organ function research and new drug development.
The imaging principles are fundamentally different from those of the first three.
Compared with CT and MRI, its main features are.
1. High sensitivity: PET is a kind of imaging reflecting molecular metabolism, when the disease is in the early stage of molecular level changes, the morphology and structure of the lesion area has not yet shown abnormalities, MRI and CT examination can not be clearly diagnosed, PET examination can find the location of the lesion, and can obtain three-dimensional images, and can also carry out quantitative analysis to achieve early diagnosis, which is unparalleled by other imaging examinations.
2.High specificity: When MRI and CT examinations find tumors in organs, it is difficult to judge whether they are benign or malignant, but PET examination can make a diagnosis based on the characteristics of high metabolism of malignant tumors.
PET is a one-time whole-body imaging test that can be used to obtain images of all areas of the body.
PET examination requires a certain amount of radionuclide, but the amount of radionuclide used is very small, and the half-life is very short (12 minutes for the shortest and 120 minutes for the longest), and after physical decay and biological metabolism, the retention time in the body is very short. The radiation dose of a PET whole-body examination is much smaller than that of a conventional CT examination at one site, which makes it safe and reliable.