When a lung or pleural lesion ruptures the dirty pleura and causes air to enter the pleural cavity, forming a pneumothorax, it is called a pneumothorax. When a small amount of air enters the pleural cavity, a translucent band is formed in the apical part of the lung and the outer band, and the edge of the dirty pleura is clearly visible, which is called pleural line. There is no lung texture in the pneumothorax. On the orthopantomogram, the degree of lung tissue compression can be roughly determined in percentage as follows: on the pneumothorax side, the reference range is from the outer edge of the transverse process to the inner edge of the chest wall (for the entire side of the lung field), when the lung field side is compressed to 1/4 of the above range, the lung tissue is approximately 35% compressed; when it is compressed to 1/3, the lung tissue is 50% compressed; when it is compressed to 1/2, the lung tissue is 65% compressed; When the pressure is up to 2/3, the lung tissue is compressed by 80%; and when all the lung tissue is compressed to the hilum, which is soft tissue density, the lung tissue is compressed by about 95%. If a small amount of pneumothorax is limited to the upper lung field, the lung field will be divided into three equal parts from top to bottom, and then divided equally with 35% of the above method when the compression is 1/4, which is about 10%-15%. The rest of the cases can be determined according to the above method. If the width of pneumothorax accounts for 1/4 of the total width, the compression is 35%, if the width of pneumothorax accounts for 1/3 of the total width, the compression is 50%, if the width of pneumothorax accounts for 1/2 of the total width, the compression is 65%, if the width of pneumothorax accounts for 2/3 of the total width, the compression is 80G. This method may not be very accurate, but it is more commonly used by clinicians and is relatively simple.