I. Head and neck
Ocular ring thickness 2-4mm.
Optic nerve thickness 3-6mm.
The third ventricle is 3-8mm wide.
The width of the apical cerebral sulcus should not exceed 5 mm.
The anterior-posterior diameter of the opening of the internal auditory canal is normally 3-5mm, and greater than 5mm is enlarged.
The pituitary height is 1.4-5.9mm (average 3.5mm) in men and 2.7-6.7mm (average 4.8mm) in women, and the height of young women, especially during pregnancy, can be 9-10mm (some people reported 12mm), and the transverse diameter is about 8mm. Xiao Hui, Department of Neurology, Lianyungang City Hospital of Traditional Chinese Medicine
Algorithm of blood volume of cerebral hemorrhage: length × width × height × π/6 (unit: ml).
It enters the phagocytosis phase at 2-3w of cerebral infarction, and often the blurring effect can be seen.
The size of lacunar cerebral infarction is generally less than 15mm, those less than 5mm are not easily detected by CT, and those larger than 15mm are giant lacunae with a maximum diameter of 35mm.
Cranial suture separation: it is generally believed that the cranial suture differs bilaterally by more than 1mm, and the unilateral suture spacing is greater than 1-2mm; in adults, a cranial suture greater than 1.5mm unilaterally can be diagnosed; in children, some cranial sutures are wider, but they should not exceed 2mm.
The CT value of intracranial hematoma is more than 60Hu, between 60-90Hu, and the maximum should not exceed 94Hu (the CT value when the red blood cell pressure volume is 100%).
The CT value of adipose tissue is -80 to -130Hu.
Subdural hematoma staging: acute <3d, subacute 4d-3w, chronic >3w.
Hyaline septal cyst: its transverse diameter is >3mm, bilateral wall is bulging outward, oval or subspherical, and cerebrospinal fluid density.
Ocular protrusion: On a well-posed transaxial image, a line is made between the zygomatic processes on both sides, and in normal individuals approximately 1/3 of the eye lies behind this line, indicating a meaningful ocular protrusion if less than 1/3 of the eye area lies behind this line.
The bony external auditory canal is approximately 1.5 cm long and occupies 2/3 of the inner part of the external auditory canal and the outer 1/3 is the cartilaginous part.
The cervical esophagus is flattened posteriorly above the inferior border of the 6th cervical vertebra, anteriorly above the cricoid cartilage, which meets the pharynx, and inferiorly below the oblique plane of the jugular vein cut to the superior border of the 1st thoracic vertebra.
The upper end of the cervical trachea is located at the level of the lower edge of the 6th cervical vertebra, connected with the cricoid cartilage, the anterior edge of the lower border is flat at the level of the lower edge of the 7th cervical vertebra, and the posterior edge is located at the level of the lower edge of the 7th cervical vertebra, moving downward to the thoracic trachea, the adult cervical trachea is about 6.5 cm long, the transverse diameter is about 1.94 cm, the sagittal diameter is about 1.87 cm, there are 6-8 tracheal cartilages, the trachea moves up and down about 1.5 cm when the head is tilted up or down, and its upper segment is superficially located The upper segment is superficial, while the lower segment is deeper, about 4 cm from the skin.
The cervical spinal canal approximates a triangle with the tip backward, C1-C3 gradually becomes smaller, C4-C7 is the same size, the anterior and posterior diameters are 16-27 mm in C1 and 12-21 mm in the lower cervical cervical spinal canal.
The thyroid gland is located in the middle of the neck on both sides of the trachea, consisting of the left and right lobes and the isthmus connecting the two lobes in a butterfly shape, the left and right lobes are located in the lower part of the larynx and the upper part of the trachea, starting from the thyroid cartilage and going down to the 6th tracheal ring, which is equivalent to the level of the 2nd-4th tracheal cartilage. The normal thyroid gland weighs 10-60g, usually 25-30g.
There are two pairs of parathyroid glands, the upper pair is located in the upper 1/3 behind the left and right lobes of the thyroid gland, often buried in the thyroid gland, and the lower pair is located in the lower pole of the left and right thyroid glands, each parathyroid gland is about 5×3×1.5mm3 in size and weighs about 30-50mg, which is not visible on normal CT.
The thyroid notch is located on both sides of the thyroid cartilage combined with the upper front notch, about flat neck 5 plane. on CT, the prevailing standard for enlarged lymph nodes in the neck is more than 1.5cm.
II. Thorax
The ascending aorta is always larger than the descending aorta, with a ratio of 2.2-1.1:1 between the two.
The normal diameter of the lymph nodes in the odd vein can be up to 10 mm.
The normal measurement of the intrapericardial portion of the right pulmonary artery is 12-15 mm, and the normal diameter of the main pulmonary artery should not exceed 29 mm.
The intrathoracic trachea is about 6-9 cm long and is located in the midline or slightly to the right. The normal human trachea diameter is about 10-27 mm averaging 19.5 mm in men and 17.5 mm in women.
The thickness of the esophageal wall depends on the degree of expansion, usually not more than 3mm, and any diameter of the lymph nodes in the mediastinum greater than 1cm is considered abnormal. The sternotomy is the cut enclosed between the sternoclavicular joint and the sternum on both sides, about flat chest 2 plane. Pulmonary nodules are round-like lesions in the lungs less than 4 cm in diameter, while those 4 cm and above are called masses, and corn nodules are punctate nodules less than 4 mm in diameter.
The vacuolar sign is a dotted translucent shadow 1-2 mm (or <5 mm) within the lesion.
Lobulation of intrapulmonary nodules or masses: arc chord distance/chord length ≥0.4 for deep lobulation; =0.3 for intermediate lobulation; ≤0.2 for superficial lobulation.
Intrapulmonary lesions less than 2 cm were 80% benign; those greater than 4 cm were overwhelmingly malignant. Thick-walled cavities have a wall thickness greater than 3 mm.
Small intrapulmonary nodules or corn nodules are about 1-2mm in size.
The posterior end of the left oblique fissure is located at the level of the 3rd-4th thoracic vertebrae and travels forward and downward against the anterior rib diaphragm angle; the posterior end of the right oblique fissure is located at the level of the 5th thoracic vertebrae, obliquely downward and ends at about 3-5 cm from the anterior chest wall; the inner end of the transverse fissure at the level of the 4th rib points to the pulmonary hilar angle, the posterior end corresponds to the midpoint of the oblique fissure and the outer end ends at the lateral chest wall. The upper boundary of normal pericardial thickness is 4 mm, and if it is greater than 4 mm, it is abnormal.
A small amount of effusion in supine position is usually located below the posterior wall of the left ventricle with a small width, and there is only a small or no liquid dark area in the lateral and precordial regions of the heart, and the amount of effusion is usually below 100ml; a medium amount of effusion is evenly distributed in the posterior part of the left ventricle, before the apical, lateral and anterior wall of the right ventricle, and the most at the atrioventricular sulcus, and the amount of effusion is between 100 and 500ml; a large amount of effusion is easily detected by CT scan. 500ml; large amount of effusion, the dark area of effusion is wider, all around the heart, the most after the heart, after the posterior wall of the left atrium can also be seen, sometimes the heart is suspended in the effusion, the volume of its effusion is more than 500ml.
Pneumothorax: If the width of the pneumothorax is equal to 1/4 of the width of the affected thorax, the compressed lung is about 25%; when it is 1/3, the compressed lung is about 50%; when it is 1/2, the compressed lung is about 65%. The walls of the alveoli rupture and fuse to form an air-containing cavity, which is called a large alveolus with no walls when it is larger than 10 mm. Staging of lobar pneumonia: congestive edema phase (12-24h); red hepatomegaly phase (2-3d); gray hepatomegaly phase (4-6d); dissipation phase (7-10d).
III. Abdomen
The liver is the largest organ in the body, and the adult liver weighs about 1300g, which is about 2% of body weight. The liver is surrounded by peritoneum, but there are 3 areas without peritoneum: inferior vena cava fossa, gallbladder fossa, and diaphragmatic surface bare area.
The division between the left and right lobes of the liver on CT is the line connecting the gallbladder fossa and the inferior vena cava fossa, known as the Cantlie’s line (Cantlie).
There are three sets of intrahepatic vascular system: hepatic vein, hepatic artery, and portal vein. The hepatic blood supply is dual, 20-25% to the hepatic artery; 75-80% to the portal vein.
Because of the high glycogen content in the liver, the density of liver parenchyma is slightly higher than that of pancreas, kidney and spleen in plain scan, and liver is on average 7-8 Hu higher than spleen. normal values of portal vein: trunk length is 4.8-8.8 cm average 7.3 cm, transverse diameter 0.7-1.6 cm average 1.09 cm.
Total hepatic duct diameter is 3-5mm, which usually cannot be shown, total hepatic duct and gallbladder duct and and form common bile duct, common bile duct diameter <6mm is normal, 6-10mm is suspicious dilatation, >10mm is dilatation.
The thickness of the gallbladder wall is uniform, with a normal thickness of 1-2mm (not visible on CT), more than 3.5mm is considered abnormal, and more than 5mm is definitely thickened.
The long diameter of the gallbladder is 4-5 cm, and the enlarged gallbladder shows CT as a long diameter greater than 5 cm, and its wall is blurred or has a hypodense ring with the gallbladder fossa and surrounding liver due to inflammatory edema of the gallbladder wall, congestion or secondary edema of the liver tissue. The diameter of the intrahepatic bile ducts is usually 1-3 mm.
The dilatation of intrahepatic bile ducts can be divided into 3 levels according to the scope: only the bile ducts near the hepatic hilum are mildly dilated; both the hepatic hilum and the peripheral bile ducts are moderately dilated; both the hepatic hilum and the periphery are significantly dilated as severe dilatation, and the degree of dilatation of intrahepatic bile ducts is divided into 0.5cm in diameter as mild; 0.6-0.8cm as moderate; and 0.9cm or more as severe.
The pancreas is about 15 cm long, located in the pararenal space in front of the retroperitoneal cavity, and is a convex forward bow-shaped soft tissue shadow spanning between the 1st and 2nd lumbar vertebrae. The normal internal diameter of the pancreatic duct is about 2-4 mm, and 1-2 segments of the pancreatic duct are occasionally visible on high-resolution CT images, and only the dilated pancreatic duct can be displayed throughout the entire pancreas.
In general, the size of the head of the pancreas does not exceed the transverse diameter of the 2nd lumbar vertebra; the caudal part of the body does not exceed 2/3 of the transverse diameter of the 2nd lumbar vertebra, and the maximum diameter of the head of the pancreas (anterior-posterior diameter) is 29.3 mm; the maximum diameter of the body is 25.6 mm; the maximum diameter of the caudal part is 21.2 mm, and the bulging changes that suddenly exceed the adjacent pancreas by more than 3 mm should be given great attention.
Increased serum amylase in acute pancreatitis can be measured within 24 hours after the onset of the disease, with a significant increase in serum amylase >500 U/dl, (normal value 40-80 U/dl, Somogyi method), followed by a gradual decrease to normal within 7 days.
Urinary amylase measurement is also a sensitive indicator for the diagnosis of acute pancreatitis, urinary amylase is slightly elevated but lasts longer than serum amylase, urinary amylase is significantly elevated with diagnostic value (normal value 80-300U/dl, Somogui method) The higher the value of amylase, the greater the rate of correct diagnosis, but not proportional to the severity of the disease.
In adults, the spleen weighs 100-250g, is 12cm long, 7cm wide, and 3-4cm thick. The normal spleen length does not exceed 15cm, the lower edge of the spleen does not exceed the lowermost edge of the right lobe of the liver, and the anterior edge of the spleen does not exceed the mid-axillary line.
CT cross-sectional view with 5 rib units was used as the normal standard for the spleen.
There are two areas where the thickness of the stomach wall can exceed 1 cm, one is the gastroesophageal junction, the thickness of which is between 0.6-1.8 cm, forming the so-called “pseudotumor”; the other is the small curved side of the gastric sinus.
Generally, the thickness of gastric wall >10mm is considered abnormal, but if limited thickening is found, even <10mm is considered abnormal.
The small intestine and jejunum are located in the left upper abdomen and may show feathery or circular mucosal type; the ileum is located in the right lower abdomen and pelvis and has no characteristic mucosal type.
Usually, the lumen of small intestine is not less than 3 cm, the thickness of normal small intestine wall is less than 3-4 mm, the thickness of small intestine wrinkled wall is about 2-3 mm, mesenteric lymph nodes are not visible when normal, or show linear or nodular soft tissue density shadow with diameter less than 5 mm.
The wall thickness of normal colon does not exceed 3mm in case of expansion, and does not exceed 5mm when it is empty, and its wall thickness exceeds 5mm, which is suspicious thickening, and more than 10mm is definitely abnormal.
The rectum is about 12-15 cm long. the thickness of the normal adrenal gland does not exceed the thickest part of the ipsilateral foot of the diaphragm on the same scan level.
In adults, the adrenal glands are approximately 1-4 cm long, 1-3.3 cm wide, and 0.2-0.8 cm thick.
The kidney is about 3-4 lumbar vertebrae long, i.e. 12-14 cm, and 5-7 cm wide. the right kidney is 1-2 cm lower than the left kidney, and the difference in size between the two kidneys should not exceed 1 cm.
Prostate under 30 years old male, the upper and lower diameter of 3cm, anterior and posterior diameter of 2-3cm, left and right diameter of 3.1cm; 60-70 years old upper and lower diameter of 5cm, anterior and posterior diameter of 3.4cm, left and right diameter of 4.8cm.
In adults, the testes are 3-4 cm long, 1-2 cm thick and 2-3 cm wide.
Adult ovaries are on average 2-3.5 cm long, 1-1.9 cm wide and 0.5-1 cm thick, and gradually shrink at the age of 35-40, and can shrink by more than half after menopause.
The uterus is 5.5-8.0 cm long, 3.5 cm wide, and 2.5 cm thick during the fertile period; 7.0-9.0 cm long, 4.5-6.0 cm wide, and 2.5-3.5 cm thick during menstruation.
The uterine cavity was a narrow suture-like fissure averaging 6 cm in length, and the myometrial wall was 1.5-2.5 cm thick.
The glabellar process was approximately flat in the 10th plane of the chest. The umbilical foramen was approximately flat in the lumbar 3-4 plane. The pubic symphysis is approximately flat in the plane of sacrococcygeal vertebra.
IV. Spine
CT cross-sectional view clearly shows 7 accessory protrusions of each vertebral arch, i.e. 1 spinous process, 2 transverse processes and 4 articular processes, with a normal joint space of 2-4 mm.
The normal anterior-posterior diameter of the spinal canal is 15-25 mm, the transverse diameter is 20-30 mm, the anterior-posterior diameter of the lateral saphenous fossa (the distance from the posterior edge of the vertebral body to the anterior edge of the superior articular eminence) is normally greater than 5 mm, and the thickness of the ligamentum flavum is 3-5 mm.
CT can provide a variety of measurement information about the morphology of the spinal canal, for clinical purposes, the most important of which is the measurement of the central anterior-posterior diameter of the spinal canal, the cervical segment <10mm for spinal stenosis, the lumbar segment 12mm should be considered relatively narrow, if reduced to 10mm for absolute stenosis, the literature reported that the average anterior-posterior diameter of the lumbar spine body is 16-17mm, the lower limit is 11.5mm, the average value of the intervertebral arch diameter 20-21mm (24 mm for lumbar 5), with a lower limit of 16 mm. The anteroposterior diameter of the lateral saphenous fossa ≤ 3 mm suggests lateral saphenous stenosis, and ≤ 2 mm is definitely stenosis.
The main physical signs of the spine: the longest spine of the 7th cervical vertebra; the spine of the 3rd thoracic vertebra is flat at the medial end of the scapular gonad; the spine of the 7th thoracic vertebra is flat at the inferior angle of the scapula; the spine of the 4th lumbar vertebra is flat at the highest point of the iliac spine on both sides and the umbilicus; the dural sac is finally at the level of the 2nd sacral vertebra, and the lower end becomes thin and attached to the coccyx.