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Author: Dr. Zhang, ZhangyeReproductive Medicine Research Institute,

Zhangye Reproductive Medicine SpecialHospital

Overview

Pulmonarynodules are a very common manifestation of chest imaging. Pulmonary nodules aresmall, local and round with an increased shadow density on the imaging. Theycan be single or multiple, without atelectasis, hilar enlargement or pleuraleffusion. Single pulmonary nodules do not have typical symptoms. They areusually shadows that cannot be penetrated by X-rays, single, clearly defined,denser, ≤30 mm in diameter and surrounded by air-permeable lung tissue. Locallesions > 30 mm in diameter are called lung masses.

Inrecent years, with the popularization of DR and CT equipment, especially thewidespread clinical use of dynamic DR, the number of pulmonary nodules foundduring chest examinations has increased significantly. The precise diagnosis ofsolitary pulmonary nodules has always been difficult in imaging diagnostics.This article focuses on the clinical application experiences of dynamic DR inthe diagnosis and diagnostics of pulmonary nodules in our hospital.

Key points of pulmonarynodule imaging analysis

Pulmonary nodules can be divided as multiple nodules and singlesolitary nodules. The clinical symptoms of most solitary nodules are notobvious, and they are often found during chest fluoroscopy in a physicalexamination. There is a good natural contrast in the chest, and X-ray examinationis an important means of finding and diagnosing pulmonary nodules. In thedifferential diagnosis of benign and malignant pulmonary nodules, combined withvarious signs of pulmonary nodule imaging and clinical data of patients, a moreaccurate diagnosis can often be made.

The discovery of pulmonary nodules should be comprehensivelyanalyzed from the location of nodules, the size of the nodules, the shape ofthe lesion, the density, cavities, and pleural changes, as well as hilar andmediastinal lymphadenopathy.

Location of pulmonarynodules

Tuberculomas mostly occur in the posterior segment of the upperlobe and the dorsal segment of the lower lobe, while tumors and inflammationare more common in the anterior segment of the upper lobe and the basement ofthe lower lobe. Lung cancer mostly occurs in the upper lobe of the right lung.Adenocarcinoma and metastatic cancer tend to be distributed in the periphery.Squamous carcinoma is more common near the hilar.

Size of pulmonarynodules

Diameter of ≤7 mm is defined as micronodules, diameter of 10 mmis defined as small nodules, diameter of 10-30 mm is defined as large nodulesand masses with a diameter of> 30 mm. The concept of nodules and massesshould be distinguished. Nodules and masses can be different developmentprocesses of the same disease. It has been reported in the literature that thesize of solitary pulmonary nodules has a certain qualitative significance,which is helpful to the identification of benign and malignant. Single pulmonarynodules with a diameter of less than 30 mm are mostly benign. The larger thediameter, the greater the probability of malignancy. Whether it is a benignnodule or a malignant nodule, the growth process is from small to large, so itis necessary to observe the dynamic changes of the lesion. Benign nodules are aslow-growing process, while malignant nodules mostly show progressive growth,mostly without calcification, and patients are mostly over 40 years old.Pulmonary nodules with a doubling time of 5-18 weeks are more malignant.

Shape ofLesion

Usually benign nodules are clear, smooth, sharp, oval or round,and grow slowly, such as leiomyoma, papilloma, and tuberculosis; malignantnodules have blurred edges, irregular shapes, lobular signs, and burrs, showingprogressive growth. Deep lobes reflect the uneven growth of nodules in alldirections; deep lobes are common in lung cancer, and burr signs are common atthe edges, which are the proliferation of surrounding connective tissue and theformation of fibrous cords for tumor cells spreading in all directions or tumorstimulation. The edges of some metastatic tumors may be blurred with glitches. Shallowlobes may be seen.

Density of Lesion

Generally, the density of malignant nodules is uneven and low orappears as ground glass, such as early stage of adenocarcinoma. Histologically,it reflects the alternative growth mode of tumor. Tumor cells grow along thealveolar wall and replace the alveolar epithelium. The alveolar cavity is notfilled with tumor, the alveolar cavity is still inflated, and the alveolarstent and blood vessel background are still visible. In addition, focal groundglass shadow is also seen in thin inflammation and small pieces of bleeding orhemorrhage in the alveoli. In some cases, solid nodules can be seen in theground glass shadow, and the ground glass density around the nodule is alsocalled "halo sign", which is more common in undifferentiated cancer,followed by squamous cell carcinoma and adenocarcinoma. "Halo signs"are also seen in Aspergillus and Cryptococcus infections. The density of benignnodules is mostly uniform and high, such as inflammatory pseudotumor.

The key to calcification in nodules depends on the shape anddistribution of calcification. Centrality, stratified, popcorn-likecalcification, or ring-shaped calcification are the characteristics of benigncalcification. For example, hamartomas can have popcorn-like calcifications,and tuberculous bulbs often have annular envelope calcifications; eccentric,amorphous calcifications, or sand Granular calcification is often malignantnodular calcification, and calcification can be seen in lung metastases ofdigestive tract tumors and osteosarcoma.

Cavitation signs and bronchial air signs are mainly found inlung cancer, more commonly in highly differentiated adenocarcinoma, and theirappearance or existence is of great value in the diagnosis of lung cancer.Benign tumors and inflammatory pseudotumor do not show this sign. This signshould be distinguished from fissure holes in the tuberculosis bulb.

Cavities can be seen invarious nodules. The cavities of lung cancer are characteristic: thick-walledeccentric (distal eccentric) cavities, and nodules are seen on the inner wall.The cavity of the tuberculosis bulb is mostly near the drainage bronchus, whichis an eccentric cavity at the proximal end. The cavity wall is thin and smooth.Tuberculosis lesions (satellite stoves) are common around the cavity. The cavitywall of the inflammatory pseudotumor is thick and the inner wall is smooth.Pulmonary metastases can have cavities. The inner walls of the cavities are smooth,and the walls can be uneven. Most of the cavity walls of Wegener’sgranulomatosis are thinner, and a few of them are thicker, but the edges of theouter wall are usually clearer, and there are no changes in leaves and burrs.The cavity can be reduced or disappeared after treatment.

Pleural Change

Tuberculosis can be accompanied by pleural thickening,adhesions, and calcification. Pleural metastasis from lung cancer can causepleural effusion. Pleural depression can occur in inflammatory pseudotumor andlung cancer.

The imaging manifestations of pulmonary nodules are diverse. Allimaging signs may occur at a certain stage of the pulmonary nodule growthprocess. Therefore, the qualitative diagnosis of pulmonary nodules should becombined with clinical data, laboratory tests, and other Comprehensive analysisof inspection methods and imaging performance, regular follow-up. Dynamic DRplays an important role in the discovery of lung nodules and clinicaldiagnosis. It can clearly display the lung tissue of the subject. It has theadvantages of high resolution, clear images, convenient and fast, affordable,and easy to accept, Is the preferred method of imaging chest examination.

Application Advantagesof Dynamic DR

Dynamic digital medical X-ray Radiographic system (Dynamic DR)has high image quality and powerful post-processing functions. The imaging sizeis 17 × 17 inches square view, which has great advantages in clinicalapplications. One exposure can include the entire thorax. And the image isclear. The core advantage is that it can locate the target area under visualimage capture, observe the lesion activity and morphological changes duringdeep breathing, and freely rotate the patient's position according to the needsof the diagnosis. Missed diagnosis or misdiagnosis caused by shadows and hilarmajor vessels overlap or cover can be avoided. Especially the intrapulmonarylesions located on the lateral grooves on both sides of the spine of the chestand back. When the chest is projected in the right position, the lesions arelikely to overlap or cover with the mediastinum shadow and heart shadow. Due tothe lower and lower position, some lesions are in the posterior costal cornerregion. When the lesions are orthotopically projected, the lesions are coveredby the shadows or the lesions are projected under the diaphragm, which leads tomissed diagnosis or misdiagnosis of the lesions in the diaphragm. The dynamic DR has thevisual image capture function, which can dynamically observe the chest, ribs,mediastinum, heart shadow, diaphragm muscle, as well as thoracic, lung, andmediastinal lesions in the state of respiratory movement when the patient'sposition is rotated arbitrarily. This can effectively avoid missed diagnosisand misdiagnosis caused by incomplete and meticulous observation.

Multifunctional digital dynamic DR (dynamic DR) has been widelyused in clinical imaging diagnosis. Its multi-function, high-definitionimaging, real-time spot film, real-time playback, continuous spot film, wholebody stitching and other functions have been widely recognized for itsimportant role in clinical applications.

Case

Female, 52 years old, without symptoms. One month ago, a chestPA image was taken on a static flat panel DR in a hospital. The diagnosisreport indicated the right sub-condylar nodule shadow. Considering intrahepaticnodular disease, a liver ultrasound was recommended. Liver ultrasound showed noabnormalities. Recently, a chest fluoroscopy examination was performed in ourhospital, and a round high-density nodule with a diameter of about 17 × 15 mmwas found on the right side of the diaphragm, with clear edges. Immediatelyafter the patient's fluoroscopy, a dynamic rotation and multiple body positionobservation was performed, and it was clear that the basal segment nodularlesion of the right lower lobe was not a liver nodule (as indicated by the redarrow), and CT examination was recommended. Three days later, a CT scan of thechest confirmed a circular nodule in the posterior basal segment of the rightlower lobe, with calcification seen. CT diagnosis of the right basal segmentinduration in the right lower lung.

This case is special because the right lower lobe nodular lesionis in the posterior Costco sacral region and is positioned lower back. Duringthe static DR chest PA examination, the nodular lesion is projected below thediaphragm, and the static DR cannot have visual image capture and rotatingfluoroscopy. No chest LAT were taken, plus the inexperience of the examiningdoctor, which led to misdiagnosis.

This case is enough to prove the importance of dynamic DR visualimage capture and the rotating multi-angle observation function in clinicalapplication, which can effectively avoid and reduce missed diagnosis andmisdiagnosis.

PA: The shadow of the right lungnodule is projected below the diaphragm（←）。

LAT： The nodular shadowis located in the posterior basal segment of the right lower lobe and theposterior costal corner（→）。

FluoroscopyFrame 1：Shadow position of right lung nodule during deep inspiration（←）

Fluoroscopy Frame 2：Shadowposition of right lung nodule during deep exhalation（←）

Fluoroscopy Frame 3： Lateral perspective observation of the rightlower inferior lobe nodule shadow located in the posterior costal corner region（→）

Clinical Application Advantages of Dynamic DR in Diagnosis of Pulmonary Nodules

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