A CT-based radiomics integrated model for discriminating pulmonary cryptococcosis granuloma from lung adenocarcinoma-a diagnostic test

Abstract

Background: Chest computed tomography (CT) is a critical tool in the diagnosis of pulmonary cryptococcosis as approximately 30% of normal immunity individuals may not exhibit any significant symptoms or laboratory findings. Pulmonary cryptococcosis granuloma and lung adenocarcinoma can appear similar on noncontrast chest CT. This study evaluates the use of an integrated model that was developed based on radiomic features combined with demographic and radiological features to differentiate pulmonary cryptococcosis nodules from lung adenocarcinomas.

Methods: Preoperative chest CT images for 215 patients with solid pulmonary nodules with histopathologically confirmed lung adenocarcinoma and cryptococcosis infection were collected from two clinical centers (108 cases in the training set and 107 cases in the test set divided by the different hospitals). Radiomics models were constructed based on nodular lesion volume (LV), 5-mm extended lesion volume (ELV), and perilesion volume (PLV). A demoradiological model was constructed using logistic regression based on demographic information (age, sex) and 12 radiological features (location, number, shape and specific imaging signs). Both models were used to build an integrated model, the performance of which was assessed using the test set. A junior and a senior radiologist evaluated the nodules. Receiver operating characteristic (ROC) curve analysis was conducted, and areas under the curve (AUCs), sensitivity (SEN), and specificity (SPE) of the models were calculated and compared.

Results: Among the radiomics models, AUCs of the LV, ELV, and PLV were 0.558, 0.757, and 0.470, respectively. Age, lesion number, and lobular sign were identified as independent discriminative features providing an AUC of 0.77 in the demoradiological model (SEN 0.815, SPE 0.642). The integrated model achieved the highest AUC of 0.801 (SEN 0.759, SPE 0.755), which was significantly higher than that obtained by a junior radiologist (AUC =0.689, P=0.024) but showed no significant difference from that of the senior radiologist (AUC =0.784, P=0.388).

Conclusions: An integrated model with radiomics and demoradiological features improves discrimination of cryptococcosis granulomas from solid adenocarcinomas on noncontrast CT. This model may be an effective strategy for machine complementation to discrimination by radiologists, and whole-lung automated recognition methods might dominate in the future.

Keywords: Radiomics; computed tomography (CT); lung adenocarcinoma; pulmonary cryptococcosis granuloma.

Figure 1

Flowchart of the case selection. GGO, ground-glass opacity; GGN, ground-glass nodule.

Figure 2

Illustration of three types of the VOI. (A) An irregular nodule appears on the CT image (lung window). (B) LV (green region) was obtained by manually drawing the whole lesion. The boundary of the LV was increased by 5 mm, and the ELV (red and green regions) was generated after excluding the regions outside the lung (yellow line). (C) PLV (red region) was obtained by subtracting LV (green region) from ELV. VOI, volume of interest; LV, lesion volume; ELV, extended lesion volume; PLV, perilesion volume.

Figure 3

ROC curves of models and radiologists. (A) M_{demoradiological}, (B) M_integrated, (C) Radiologist 1, (D) Radiologist 2. ROC, receiver operating characteristic; AUC, area under the ROC curve.

Figure 4

Representative easy-mimicking pulmonary nodules on CT images. (A) A 59-year-old male patient with pulmonary cryptococcosis was misdiagnosed with a malignant mass by both radiologists but was correctly identified by the classifier model. (B) A 60-year-old male patient with lung cancer was misdiagnosed with a benign nodule by both radiologists but was correctly recognized by the classifier model. (C) A 64-year-old male patient misdiagnosed with pulmonary carcinoma by both radiologists and the integrated model was pathologically confirmed to have cryptococcal granuloma. (D) Histopathological examination (hematoxylin erythrosine staining) of lung tissue reveals granulomatous inflammation. The fungal cells are round, lightly basophilic, fill the alveolar space and are surrounded by a clear space that represents the capsular material (see arrows, ×200). (E) Positive periodic acid-Schiff staining of the yeast wall, suggesting pulmonary cryptococcosis (see arrows, ×200).