The 16th Annual Meeting of the Chinese Society of Radiology was held in Hangzhou from October 15-18, 2009, and I noticed that the cardiothoracic group was full every day! It seems that radiology colleagues all over China are still interested in diagnostic imaging of chest diseases. The root of this is that the diagnosis and differential diagnosis of thoracic diseases is a real challenge. In particular, the differential diagnosis of isolated pulmonary nodules (SPN) is even more difficult with CT! Misdiagnosis often occurs in various hospitals, but most of the misdiagnosis is reasonable. Why is this? According to research, about 70% of SPN cases are indistinguishable from benign to malignant on CT images. In order to treat patients with malignant lesions in a timely manner and to relieve the psychological pressure of patients with unknown diagnosis, the share of benign and malignant manifestations in the imaging diagnosis is equal, i.e., half of the patients have benign SPN manifestations and half have malignant SPN manifestations, and some of them are recommended for short-term follow-up and continued observation, or other tests such as PET-CT are recommended. In most cases, the doctor recommends surgery. Finally, the diagnosis is made through postoperative pathology. Each hospital has its own process, so we all have our own experiences, but these experiences are shared in the spirit of academic discussions, yet we cannot directly apply the experience gained from different machine models, different scanning procedures, and different technical parameters to our own work environment, and this is where the difficulty lies! But the exchange will get some insight. That’s why this year’s annual meeting of the cardiothoracic group was overcrowded. To be realistic, many people have been fooled in their daily diagnostic work and want to learn what else is worth learning. The chest has the best natural contrast in the human body, so X-rays have been used in clinical practice since it was known to be the most used method of examination in clinical work, and medical professionals seem to be able to “read” chest films! Please remember that all the items that seem to be possible are actually not studied in detail, and there are still few people who specialize in them. So these are another reason why people are interested in diagnostic imaging of chest diseases. Has anyone wondered why some of the experiences of others in chest diagnosis cannot be directly replicated? So far I have not seen anyone working on this substantive issue. Personally, after nearly 30 years of consultation, especially in the past 15 years, I believe that this is a quality control issue in diagnostic imaging, the most important of which is the standardized quality control of image generation. At present, there are various kinds of imaging equipment used in the radiology departments of hospitals across the country, that is, the same model of equipment, the examination method is also different, each family has its own processing and scanning methods. Therefore, the same patient in different hospitals with different scanners, or the same model of scanner with different methods of examination will yield different image results. This makes it difficult for doctors to diagnose chest diseases. The idea of sharing medical resources has recently been proposed, which is to share all the hospitals’ auxiliary patient examination data through computer networking in an attempt to save medical costs! This is a great idea, but the original designer, the person who came up with the idea, had no idea how all this shared information was generated in each unit? Among the shared resources were the images! If the information from the labs passed a rigorous quality control demonstration, it was clearly accessible to networking with mutual recognition between units under the same quality control conditions. Does the immediate image QC really achieve standardized control at every step of the way? Of course, this is extremely difficult work, is to pass the standard quality control, but the morphological changes of the disease encountered is diverse, is a microcosm of the tangible world of nature in the human body, diagnostic imaging is to rely on the morphology to recognize and diagnose! Therefore, to dig out the real form of the lesion in the patient’s body, first of all, we need good equipment or “hardware”, which is like the painting tools in the hands of a painter; secondly, the examination technique designed according to the specific situation of each patient, which is the specific technical parameters of the scan for CT, which is equivalent to the artistic skills of a painter, and in the current fashionable language, “software”. In today’s fashionable language, it is “software”. Both hardware and software are in the best ideal state, the more realistic the morphology of the lesion is reflected. As a responsible physician, we strive to be realistic and to reflect the pathology of the lesion in modern imaging, so that our diagnostic accuracy can be improved. The differential diagnosis about SPN has always been a difficult point, and it is even more difficult to diagnose SPN with a maximum diameter of 3 cm or less than 3 cm without examination methods in place. In the face of such cases, HRCT scan must be performed on the basis of conventional scan, and most medical institutions now use multi-row spiral CT, so the chance of missing the scan is almost non-existent. In addition, the post-processing of images after multi-row spiral scans is abundant, so we should make full use of the volume scan data to display certain cases with diagnostic difficulties from different angles in a multi-axis manner and conduct comprehensive studies. Every time I give a lecture or write an article I will especially emphasize the techniques I mentioned above repeatedly, and only on the basis of the techniques in place can we discuss the imaging performance of this SPN. I think the patient’s imaging data is carefully scanned in the mind first, together with the medical history and laboratory data, huh, this is when I am in the specialist clinic, I constantly have to ask the patient many relevant questions since the onset of the disease, and then, on the HRCT images of SPN signs one by one, this process will take brain power, and of course time! What are we thinking about at this time? The focus is on what is the pathological essence of these signs? Are the images shown on the film realistic? Is it possible to scientifically and rationally explain the clinical symptoms and laboratory findings with the pathology reflected in the images? And so on, this is a complex thinking process! In this process, the reader will often be encountered in the past, the confirmed, deposited in the brain of the case out of the comparison, this is the so-called clinical experience! Of course, the so-called main line of decoding the information on the images! During the diagnosis and differential diagnosis of SPN, there are several signs that are very helpful in the diagnosis of benign and malignant SPN. They are lesion morphology/density/alteration of adjacent pleura, etc. The most valuable of them is still the alteration of SPN adjacent pleura. Patients in the Internet a check, it seems that PET-CT is the most capable, some field comrades chest X-ray found lung problems, the first PET-CT, in fact, the sensitivity of PET is very high, the specificity is actually very limited, but also further in-depth study. In our daily medical work is currently mainly morphological research, this morphology on the one hand is the imaging performance of the SPN itself; on the other hand is the SPN around some performance, these signs can assist in the diagnosis.