Intracranial calcification can be detected by CT, MRI, and cranial plain film, among which CT is the most sensitive method to detect intracranial calcification and shows the best result of intracranial calcification. In MRI T1WI and T2WI, intracranial calcifications can show four types of signals: high, equal, low and very low signals, with equal and low signals in T1WI and low and very low signals in T2WI. In addition, the sensitivity of MRI is closely related to the size of calcification. Intracranial calcification is divided into two types: pathological and physiological calcification. Physiologic calcifications are mostly seen in pineal and rein joint calcifications, choroid plexus calcifications, dural calcifications, basal ganglia and dentate nucleus calcifications. Physiologic calcification has a high incidence in the population, up to 74.6%. More than 2 sites of calcification are present at the same time in up to 35.4%. 1. Calcification of the pineal gland and reins: It is common in adults and is usually 3-5 mm in diameter. If the calcification of the pineal gland exceeds 12 mm * 12 mm, the possibility of a tumor in the pineal region should be considered. The hallux union is located posterior to the third ventricle and anterior to the pineal gland. 15% of individuals over 30 years of age have cranial CT suggestive of hallux union calcification. Typical calcification foci are C-shaped. 2. Choroid plexus calcification: It is the most common intracranial physiological calcification, and the appearance rate increases gradually with age, about 75% have calcification at the age of 50 years, with calcification of the choroid plexus in the lateral ventricle being the most common, and calcification of the choroid plexus in the third and fourth ventricles is rare. The manifestations are varied, ranging from limited dots to masses of up to 1 cm in diameter, mostly bilateral and symmetrical. Calcifications in the dura mater are more common in middle-aged and elderly people. Calcifications in the falx cerebri and cerebellar curtain are easy to recognize and are distributed along the falx cerebri and cerebellar curtain on imaging. 4. Basal ganglia calcification: It is divided into physiological and pathological. Physiologic calcifications are most often seen in people over 40 years of age and are usually small. If the calcification foci are large and combined with cerebellar dentate nucleus calcification, the possibility of pathological calcification should be considered. Calcification in the basal ganglia is often dominated by the pale bulb, mostly symmetrical on both sides, and the calcification is ovoid, forming a figure-of-eight shape on both sides. If the shell nucleus, caudate nucleus and thalamus are calcified at the same time, the outline of the internal capsule can be outlined. Pathological calcification (a) Tumors: Many brain tumors will show calcification. Glioma: The most common brain tumor, calcification is seen in 5% of cranial radiographs. Gliomas are usually slow-growing, less malignant gliomas are easily calcified, and highly malignant ones are rarely calcified. About 50% of oligodendrogliomas have calcification, which may appear as limited dotted sheets, curved cords, irregular masses, or cortical gyrus. 2. Craniopharyngioma: It is more common in children, and calcification can be seen in more than 75% of cases. It is characterized by calcification centered on the saddle, crustal calcification of the cystic wall and circumferential enhancement. The diagnosis of craniopharyngioma in adults is difficult because calcification is not common, but the saddle septum can be seen to bulge forward due to tumor compression. Meningioma: The calcification is spherical, mainly located in the parsagittal sinus or in the typical dural location. If the tumor invades the fornix or pterygoid crest, thickened bone can be seen, and meningeal vascular signs can also be seen. Some scholars have studied that calcified meningiomas do not recur, and they suggested that calcification may be an important factor suggesting that meningiomas do not recur. 4. Epidermoid cyst: It is a common tumor of the posterior cranial fossa and skull base, and multiple arcuate calcifications are seen. 5. Teratoma: It is commonly found in the pineal region and suprasellar region of children, and calcifications are common. In addition to teratoma, pineal cell tumor can also be seen as calcification. CT scan often shows round isointense or slightly hyperintense shadow with clear boundary in the pineal region, and uniform enhancement can be seen after contrast injection. 6. Ventricular meningioma: Mostly seen in the posterior cranial fossa in children, but also seen in the supratentorial space in adults, calcification is not common, but high density foci of calcification can be seen. 7. papilloma of the choroid plexus: mainly seen in children, with about 1/4 calcifications. Calcifications are located in the lateral ventricle or the fourth ventricle. Calcifications can help distinguish them from adult neural tube cell tumors, which are largely noncalcified. Lipomas and chordomas: Lipomas are often located in the corpus callosum and may present with a highly specific bracket sign. Chordoma has irregular calcification in only a few cases. 9. Metastases: CT scan metastases tend to appear as variable size, multiple, hypodense nodules, with a few being isointense or dense. Calcification of metastases is very rare. （Aneurysms: When aneurysms are present for a long time, they show typical curved or rounded marginal calcifications. Most of them are located around the ring of Willis. Although intracranial aneurysms are common, calcification is uncommon, and most of them leading to subarachnoid hemorrhage are not calcified. 2. Myxoid vascular malformations: Intra-aneurysmal calcifications appear as scattered punctate flakes or fine gravel, and appear as irregular high-density images on CT with central calcification and low density. MRI, on the other hand, is a more accurate diagnosis, showing irregular mixed-signal mass shadows containing different stages of hemorrhagic signals. Subcortical lesions not seen on CT can be seen using gradient-echo and spin-echo sequences. 3. Arteriovenous malformations: thread-like calcifications are seen. 4. chronic epidural hematoma, intracranial hematoma: longer epidural hematoma can calcify, but calcification of the hematoma envelope is more common. 5. Atherosclerosis: linear speckle shadow, especially common in the carotid siphon. It may lead to atherosclerotic plaque rupture and thrombosis. 6. Sturge-Weber syndrome: craniofacial angiomatosis, a specific type of cerebrovascular malformation with facial angiomas and epileptic seizures as its clinical features. Foci of cortical calcification are usually located below the soft meningeal hemangioma and may extend to the white matter below. The site of calcification is usually located in the parietal and occipital lobes ipsilateral to the facial hemangioma, in a double-tracked or gyral shape. (iii) Infectious diseases 1. Tuberculosis: Imaging features of tuberculous meningitis: basal meningeal enhancement, cerebral edema, and infarcts in the brainstem and parenchymal curtain. Long-term tuberculous meningitis causes calcification and localized atrophy of the meninges, and characteristic calcified nodules may be seen at the base of the skull in the exudate. 2. Congenital toxoplasmosis: calcification is very specific, with multiple scattered punctate shadows in the cerebral cortex and linear streaks in the basal ganglia area. 3. Cytomegalovirus infection: often severe intrauterine intracranial infection with microcephaly and characteristic periventricular calcifications outlining dilated ventricles. The calcifications are speckled, bilaterally symmetrical and distributed along the periventricular area. 4. cerebral cysticercosis: characteristic scattered calcified nodules, round or oval, 2-3 mm in diameter. no edema around the calcification, no enhancement on enhancement scan. (D) Metabolic diseases 1. Hypoparathyroidism: Decreased blood calcium not only leads to hand and foot twitching, epileptiform generalized convulsions, and sometimes chorea or Parkinson’s syndrome, but also produces signs and symptoms of cerebellum in some patients. In addition, patients may have multiple cranial nerve palsy, optic nerve atrophy, neuromotor disorders, learning disabilities, and other symptoms. About half of the patients with hypoparathyroidism develop calcification of the basal ganglia, which is often symmetrical, with symmetrical figure-of-eight and round calcification of the pallidum; calcification of the cisternal nucleus is figure-of-eight or pointed-down triangle; calcification of the caudate nucleus head is inverted figure-of-eight; calcification of the thalamus is bilaterally round-like, and all calcifications are pointed-up triangle; calcification of the cerebellar dentate nucleus is symmetrical irregular, and in obvious cases, kidney-shaped; deep lobes are mostly The calcifications in the deep lobes of the brain are mostly irregular or striped. Calcifications in the brain occur in the following order: basal ganglia, dentate nucleus, cerebral gray-white matter junction and cerebellar gray matter, and also in the thalamus, brainstem and around the lateral ventricles. 2. Basal ganglia calcification: conical or long symmetrical calcification in the pale bulb, inverted octagonal or lamellar calcification in the head of the caudate nucleus, band-like calcification in the body of the caudate nucleus, and punctate, lamellar or irregular calcification in the shell nucleus. 3. Neurofibromatosis: Some patients may have calcification of the choroid plexus in the third ventricle and lateral ventricles. 4. Tuberous sclerosis: It is a disease with abnormal cell differentiation and reproduction. Facial sebaceous adenoma, epilepsy, and mental retardation are the three typical clinical features, and can involve the brain, skin, kidney, heart, eye, bone and other organs of the body. Subventricular calcified nodules are the characteristic CT manifestations, mainly located in the lateral wall of the lateral ventricular body and near the interventricular foramen, and protrude into the ventricles, and appear as nodules of different sizes on CT or MRI, called brain stones. 6. The calcification of the lateral ventricular wall is curvilinear. Calcification in the occipital cortex is characteristic because calcium is deposited in the atrophic cortex and is seen as a parallel linear high-density shadow traveling along the cerebral sulcus, known as rail lines. 7. Other: The characteristic manifestation of anencephaly is the presence of small foci of calcification approximately 3 mm in diameter posterior to the hyaloid septum and interventricular foramen. The imaging manifestations of intracranial calcifications are diverse and require comprehensive analysis of CT and MRI. We mainly analyze them comprehensively in terms of their CT values, size, morphology and clinical symptoms, and sometimes need to differentiate them from hemorrhagic foci and determine the cause of calcification by combining them with the patient’s medical history. Those who still cannot be distinguished from CT performance and clinical symptoms should be identified by dynamic observation. Regarding the pathophysiological factors of intracranial calcification, there are few reports in the literature, and more research is needed.