The severity of a ground glass nodular image seen on IM18 in the apical posterior segment of the upper lobe of the left lung should be determined by the size and nature of the nodule. It is not serious when the nodule is small and benign, and it is more serious when the nodule is large or malignant. If the diameter of the IM18 ground-glass nodule in the apical posterior segment of the upper lobe of the left lung is less than 8mm, the boundary of the nodule is clear, and there is no sign of blood vessels, the possibility of malignant transformation is small, and observation and follow-up is usually adopted; since ground-glass nodules can be caused by bacterial, tuberculosis and other infections, levofloxacin, isoniazid, and other medications can be taken to eliminate local inflammation and thus eliminate the shadow of the ground-glass nodule as instructed by the doctor. When the diameter of IM18 ground-glass nodule in the apical posterior segment of the left upper lobe of the lung is larger than 8mm, the edges of the nodule are uneven, and there are blood vessels passing through the nodule, etc., there is a higher possibility of malignant transformation; the patient needs to take further pathological puncture examination to clarify the nature of the nodule; malignant nodules in the lungs are tumors, which will affect the patient’s lung function, metastasize, and shorten the patient’s life span, etc.; therefore, malignant nodules are more serious. The examination found that the left lung upper lobe apical posterior segment IM18 see grinding glass nodule shadow should go to the hospital in a timely manner, under the guidance of the doctor for regular follow-up and treatment.