A solitary pulmonary nodule (SPN) is defined as a focal, round or oval area of increased opacity in the lung with its maximum diameter no larger than 3.0 cm.1, 2, 3 It is also one of the most common chest radiography (CR) or computed tomography (CT) abnormalities that are often identified incidentally in clinical practice with 150,000 SPNs incidentally detected in the United States on CR or CT every year.1 It is estimated that the prevalence of SPNs in the general population is about 2.0% to 24.0%. Among those with more risk factors of lung malignancies (
The etiology of SPNs includes neoplasms (
Compared with CR, magnetic resonance imaging (MRI), and positron emission tomography (PET), a CT plays an important role in the diagnosis and management of SPNs.1, 2, 3,5,6 For conventional CT (non-contrast enhanced CT, NECT), it is usually used to evaluate the size, margins, contour, and internal characteristics of a SPN. For contrast enhanced CT (CECT), it helps evaluate the vascularity of a SPN. With the development of CT technologies, CT perfusion imaging (CTPI) and dual-energy CT (DECT) are increasingly used in clinical practice.7-10 For example, in a study by Wen
We hypothesized that multimodality CT imaging may contribute to improving the diagnostic accuracy of SPNs. However, to the authors’ knowledge, there are no publications in the literature in which NECT, CECT, CTPI and DECT were comprehensively used to differentiate benign or malignant SPNs. Thus, the aim of this study was to investigate the value of NECT, CECT, CTPI, and DECT in the differentiation of benign or malignant SPNs with a multi-institutional and prospective study.
This study was conducted at our three teaching hospitals and approved by the institutional review committee of Suining Central Hospital (Suining, China; approval no. LLSNCH20200004). All patients were included after providing informed consent.
Patients with SPNs were admitted and treated at one of the three hospitals from January 2019 to June 2021 and were consecutively enrolled into our study. The inclusion criteria were: (1) SPNs were detected with NECT in the lung window; (2) each SPN size is 1.5 cm–3.0 cm; (3) benign or malignant SPNs were confirmed by CT-guided percutaneous biopsy or pathology after surgery; (4) CTPI and DECT were performed within one week prior to CT-guided percutaneous biopsy or surgery; (5) SPNs were not treated by any antitumor therapies (
All patients were scanned with the same DECT system (Revolution CT, GE Healthcare, Milwaukee, WI, USA), and all the scanning parameters were set at the same level. The multimodality CT imaging protocol included three steps,
For NECT, the patients were asked to hold their breath at the end of inspiration, and the scanning ranges were taken from the thoracic inlet to the bilateral costophrenic angle. The tube voltage was 100 kVp; the tube current was modulated by a SmartmA technology, which provides reasonable tube current to decrease the radiation dose; and the preset noise index was adjusted for patient circumference.
For CTPI, the patients were asked to take relaxed and slow respiration. After the position of an SPN was determined by the NECT, a GSI Chest Perfusion protocol was used with a scanning range of 3.0 cm above and below the central level of a SPN. A non-ionic iodine contrast agent of 400 mg/ml (Iomeron®, Shanghai Braccosine Pharmaceutical Co., Ltd.) was injected into an antecubital vein with a binocular power injector (Stellant D-CE, MEDRAD, Bayer Healthcare Co., Ltd.), at a flow rate of 5.0 ml/s (40.0 ml). After that, 20.0 ml of normal saline at a speed of 5.0 ml/s was used to flush the tube. The CTPI was performed after injection of the contrast medium with a delay time of 4.0 s. The tube voltage and tube current were 70 kVp and 250 mA respectively. There were 18 scanning phases with an interval of 2.5 s, and the total acquisition time was about 43.0 s.
For DECT, the patients were asked to hold their breath at the end of inspiration, and the scanning ranges were the same as the NECT. Another 50.0 ml contrast agent was injected into the antecubital vein with the binocular power injector, at a flow rate of 2.5 ml/s. After that, 20.0 ml of normal saline at a speed of 2.5 ml/s was used to flush the tube. A ROI was placed in the thoracic aorta at the level of bronchial bifurcation, and the threshold was set to 120 HU. After reaching the threshold, the arterial phase was scanned with a delay time of 7.0 s, and the venous phase delay time was 30.0 s. The tube voltage, tube current, and noise index were the same as the NECT.
The same scanning parameters for NECT, CTPI, and DECT were: detector coverage = 80 mm; pitch = 0.992: 1; coverage speed = 158.75 mm/s; rotation time = 0.5 s; preset adaptive statistical iterative reconstruction-V (ASIR-V) = 50%; postset ASIR-V = 60%; slice thickness = 5.0 mm; slice interval = 5.0 mm; reconstructed slice thickness = 1.25 mm; reconstructed slice interval = 1.25 mm.
After the multimodality CT imaging protocol, the volume CT dose index (CTDIvol, mGy) and dose-length product (DLP, mGy.cm) were recorded. The estimated effective dose (ED, mSv) was calculated with the formula: ED = DLP ×
For NECT, the lung window images were further processed with the post-processing workstation AW 4.7 (GE Healthcare, Milwaukee, WI, USA) to obtain multiplanar reconstruction (MPR) coronal and sagittal images (1.25 mm).
For CTPI, the images were transferred to the post-processing workstation AW 4.7 (GE Healthcare, Milwaukee, WI, USA), CTPI parameters of the blood volume (BV, ml/100 g), blood flow (BF, ml/100 g/min), mean transit time (MTT, s), and permeability surface (PS, ml/100 g/min) with their perfusion artificial color maps were automatically generated by the CT perfusion 4D software. The ROI should be placed in the soft tissue area of a SPN at its maximum plane, and the thoracic aorta at the same level plane was selected as the reference vessel for calculating the arterial input function and a time density curve (TDC). When placing a ROI, the calcification, bleeding, liquefaction necrosis area, blood vessels, and anomalies by heart beats or other artifacts should be avoided as much as possible.
For DECT, the arterial and venous phase mediastinal window images were respectively processed with the GSI volume viewer software (AW 4.7, GE Healthcare, Milwaukee, WI, USA), to obtain the arterial and venous phase iodine-based images. The following principles should be followed in outlining the ROI: (1) ROI should be placed in the solid area of a SPN with uniform enhancement, and the outlined area should be as large as possible; (2) the calcification, bleeding, liquefaction necrosis area, blood vessels, and anomalies by heart beats or others artifacts should be avoided as much as possible; (3) the position and size of ROI measurement in each phase should be consistent.
The para meter measurements for CTPI, DECT, and the CT enhancement amplitude value were independently measured by two senior radiologists with more than 15 years of experience in chest CT. All indices were measured two times, and the average values were taken as the final results. Disagreements were resolved through consensus. Parameter measurements for CTPI included BV, BF, MTT, and PS. Parameter measurements for DECT included iodine overlay (OL), iodine concentration (IC), and normalized iodine concentration (NIC) at the arterial and venous phases (
First, another two senior radiologists with more than 15 years of experience in chest CT randomly and independently interpreted the conventional NECT images of each SPN. Any disagreements were solved through consensus. The SPNs were then classified into five categories,
Measurement data were expressed as the mean ± standard deviation or median and interquartile range (P25, P75). The comparisons were performed with the two independent samples
In using the pathological diagnosis as the gold standard, the sensitivities, specificities, accuracies, positive predictive values (PPVs) and negative predictive values (NPVs) of the three diagnostic methods separately used (Method A, B, and C) and in combination (Method A + B, Method A + C, Method B + C, and Method A + B + C) for the diagnosis of benign and malignant SPNs were calculated, and the McNemar’s test was used to compare the sensitivity, specificity, and accuracy of the various diagnostic methods.
All statistical analyses were performed by using the software of GraphPad Prism 8.0.0 and MedCalc 19.5.3. Significant differences were set at a
Patient characteristics in 285 patients with solitary pulmonary nodules
Characteristics | Pathology |
||
---|---|---|---|
Benign SPNs (n = 118) | Malignant SPNs (n = 167) | ||
Male | 56 (47.46%) | 96 (57.49%) | |
Female | 62 (52.54%) | 71 (42.51%) | 0.1170 |
50.84 ± 19.60 | 52.93 ± 20.30 | 0.3952 | |
Yes | 52 (44.07%) | 81 (48.50%) | |
No | 66 (55.93%) | 86 (51.50%) | 0.4721 |
Yes | 17 (14.41%) | 28 (16.77%) | |
No | 101 (85.59%) | 139 (83.23%) | 0.6245 |
Normal | 103 (87.29%) | 139 (83.23%) | 0.4026 |
Abnormal | 15 (12.71%) | 28 (16.77%) |
SPNs = solitary pulmonary nodules; *compared with the Fisher’s exact test; #compared with the two independent samples t-test
Pathological results of the 285 solitary pulmonary nodules (SPNs) included in this study
SPNs | Pathology | Datum (%) |
---|---|---|
Tuberculosis | 46 (29.0%) | |
Acute and chronic inflammation | 32 (27.1%) | |
Inflammatory pseudotumor | 14 (11.9%) | |
Hamartoma | 9 (7.6%) | |
Pulmonary sclerosing hemangioma | 6 (5.1%) | |
Sequestration | 4 (3.4%) | |
Bronchogenic cyst | 3 (2.5%) | |
Rheumatoid arthritis | 2 (1.7%) | |
Granulomatosis with polyangiitis | 2 (1.7%) | |
Primary pulmonary carcinoma | 116 (69.5%) | |
Solitary metastasis | 23 (13.8%) | |
Primary lung neuroendocrine tumor | 21 (12.6%) | |
Primary pulmonary lymphoma | 7 (4.2%) |
Ultimately, 285 SPNs were included in this study. Of these, 178 (62.46%, 178/285) SPNs were confirmed by CT-guided percutaneous biopsy, and 107 (37.54%, 107/285) SPNs were confirmed by pathology after surgery. The patients’ characteristics are shown in Table 1. There were no significant differences between the malignant and benign SPNs relative to gender, age, smoking status, history of tumors, or tumor biomarkers (all
Of the 285 SPNs, 118 were benign SPNs (41.4%, 118/285) and 167 were malignant SPNs (58.6%, 167/285). Of the 118 benign SPNs, 46 were tuberculosis (29.0%, 46/118), 32 were acute and chronic inflammation (27.1%, 32/118), and 14 were inflammatory pseudotumors (11.9%, 14/118). Of the 167 malignant SPNs, 116 (69.5%, 116/167) were primary pulmonary carcinomas (including adenocarcinomas in 52, squamous cell carcinomas in 35, and small cell lung cancer in 17,
After the multimodality CT imaging protocol, the CTDIvol, DLP, and ED in the SPNs were 66.88 ± 4.36 mGy, 768.29 ± 91.65 mGy.cm, and 10.76 ± 1.28 mSv, respectively.
In the malignant SPNs (n = 167), 49 (29.34%, 49/167), 115 (68.86%, 115/167), 108 (78.81%, 108/167), 38 (22.75%, 38/167), 89 (53.29%, 89/167), and 84 (50.30%, 84/167) cases were seen with smooth margins, lobulated sign, spiculated sign, vacuole sign, pleural indentation, and vessel convergence, respectively. In the benign SPNs (n = 118), the same CT findings were seen in 84 (71.19%, 84/118), 29 (24.58%, 29/167), 25 (21.19%, 25/118), 13 (11.02%, 13/118), 25 (21.19%, 25/118), and 33 (27.97%, 33/118) cases (Table 3), respectively. There were significant differences between the malignant and benign SPNs in above mentioned findings on NECT (all
For the classification of SPNs (Table 4), among the 118 benign SPNs, there were 39, 9, 48, 22, and 0 SPNs that were classified as the Category I, II, III, IV, and V nodules, respectively. Among the 167 malignant SPNs, there were 0, 5, 54, 19, and 89 SPNs that were classified as the Category I, II, III, IV, and V nodules, respectively.
For CECT, among the 167 malignant SPNs, 118 cases (70.66%, 118/167) were noted with a CT enhancement amplitude value of 20–60 HU; and among the 118 benign SPNs, 75 cases (63.56%, 75/118) were noted with a CT enhancement amplitude value of less than 20 HU or more than 60 HU (Figure 3).
The parameters of BF, BV, MTT, and PS of CTPI in malignant SPNs were higher than those of benign SPNs (Figure 4, Table 5). However, there was only significant difference in the PS parameter (
For DECT in evaluating SPNs (Figure 6), parameters of aOL, vOL, aIC, vIC, aNIC, and vNIC in malignant SPNs were significantly higher than those of benign SPNs (all
For methods A, B, C, A+B, A+C, B+C, and A+B+C, the sensitivities, specificities, accuracies, PPVs, and NPVs were 83.23% to 97.60%, 63.56% to 88.14%, 75.09% to 93.68%, 76.37% to 92.09%, and 72.82% to 96.30%, respectively (Table 9).
Solitary pulmonary nodules evaluated with non-contrast enhanced CT
CT findings* | Benign SPNs (n = 118) | Malignant SPNs (n = 167) | |
---|---|---|---|
Yes | 84 (71.19%) | 49 (29.34%) | < 0.0001 |
No | 34 (28.81%) | 118 (70.66%) | |
Yes | 29 (24.58%) | 115 (68.86%) | |
No | 89 (75.42%) | 52 (31.14%) | < 0.0001 |
Yes | 25 (21.19%) | 108 (78.81%) | |
No | 93 (64.67%) | 59 (35.33%) | < 0.0001 |
Yes | 13 (11.02%) | 38 (22.75%) | 0.0120 |
No | 105 (88.98%) | 129 (77.25%) | |
Yes | 9 (7.63%) | 16 (9.58%) | |
No | 109 (92.37%) | 151 (90.42%) | 0.6727 |
Yes | 33 (27.97%) | 56 (33.53%) | 0.3643 |
No | 85 (72.03%) | 111 (66.47%) | |
Yes | 10 (8.47%) | 6 (3.59%) | |
No | 108 (91.53%) | 161 (96.41%) | 0.1149 |
Yes | 6 (5.08%) | 4 (2.40%) | 0.3277 |
No | 112 (94.92%) | 163 (97.60%) | |
Yes | 25 (21.19%) | 89 (53.29%) | < 0.0001 |
No | 93 (78.81%) | 78 (46.71%) | |
Yes | 33 (27.97%) | 84 (50.30%) | 0.0002 |
No | 85 (72.03%) | 83 (49.70%) | |
Yes | 26 (22.03%) | 43 (25.75%) | 0.4867 |
No | 92 (77.97%) | 124 (74.25%) | |
Upper and middle lobes | 53 (44.92%) | 79 (47.31%) | 0.7186 |
Inferior lobe | 65 (55.08%) | 88 (52.69%) | |
15–20 | 29 (24.58%) | 46 (27.54%) | 0.5883 |
20–30 | 89 (75.42%) | 121 (72.46%) |
SPNs = solitary pulmonary nodules; *compared with the Fisher’s exact test
There were no significant differences between the methods A, B, and C in sensitivities, specificities, and accuracies, and so did the methods A+B, A+C, B+C, and A+B+C (all
As low-dose CT scanning is more and more widely used in the early screening of lung cancers, to some extent, NECT scanning has become one of the most commonly used examination modalities for SPNs.12 In addition to confirming the location, NECT is also used to perform a morphologic evaluation of SPNs. Generally speaking, the smaller the SPN, the more likely it is to be a benign lesion. In terms of the margins and contours of an SPN, it can be classified as smooth, lobulated, irregular, or spiculated.1,5,6 Studies have reported that about 80% of benign SPNs are not larger than 2.0 cm in diameter.1,5,6,13 However, some studies showed that about 15% of malignant SPNs are not larger than 1.0 cm in diameter, and 42% of malignant SPNs are not larger than 2.0 cm in diameter.1,14 Most benign SPNs have smooth and well-defined margins. However, about 21% of malignant SPNs have well-defined margins.15 A lobulated, irregular, or spiculated contour is usually associated with a malignant SPN. However, lobulation also occurs in up to 25% of benign SPNs.16 Therefore, there are considerable overlaps in the size, margins, and contours of benign and malignant SPNs. Internal characteristics (
In our study, there were significant differences between the malignant and benign SPNs only in smooth margins (29.34%
Non-enhanced computed tomography (NECT) in evaluating solitary pulmonary nodules (SPNs) with various categories in 285 patients
Items | Category I | Category II | Category III | Category IV | Category V |
---|---|---|---|---|---|
Benign SPNs (n = 118) | 39 | 9 | 48 | 22 | 0 |
Malignant SPNs (n = 167) | 0 | 5 | 54 | 19 | 89 |
Category I = most likely benign; Category II = possibly benign; Category III = uncertain benign or malignant; Category IV = possibly malignant; Category IV = most likely malignant
For CECT, it is helpful to improve the accuracy of differential diagnosis between benign and malignant SPNs. The degree of enhancement is directly associated with the possibility of malignancy and the vascularity of the SPNs. Swensen
Solitary pulmonary nodules evaluated with CT perfusion imaging
Parameters* | Benign SPNs (n = 118) | Malignant SPNs (n = 167) | |
---|---|---|---|
BF (ml/100 g/min) | 49.34 (27.78, 72.81) | 58.44 (24.91, 80.47) | 0.1022 |
BV (ml/100 g) | 4.79 (2.87, 7.66) | 4.84 (2.90, 7.74) | 0.1829 |
MTT (s) | 6.71 (3.05, 9.58) | 7.66 (3.83, 10.54) | 0.2034 |
PS (ml/100 g/min) | 8.89 (4.94, 12.45) | 14.37 (11.50, 16.29) | < 0.0001 |
BF = blood flow; BV = blood volume; CT = computed tomography; MTT = mean transit time; PS = permeability surface; SPNs = solitary pulmonary nodules; *compared with the Mann Whitney rank sum test
Solitary pulmonary nodules (SPNs) evaluated with dual-energy CT
Parameters* | Benign SPNs (n = 118) | Malignant SPNs (n = 167) | |
---|---|---|---|
aOL (HU) | 13.24 (10.97, 21.58) | 19.58 (13.29, 26.07) | < 0.0001 |
vOL (HU) | 11.09 (10.09, 14.86) | 14.99 (10.59, 23.98) | < 0.0001 |
aIC (mg/ml) | 0.69 (0.47, 0.985) | 1.13 (0.70, 1.56) | < 0.0001 |
vIC (mg/ml) | 0.55 (0.44, 1.00) | 0.97 (0.50, 1.46) | < 0.0001 |
aNIC | 0.10 (0.06, 0.13) | 0.18 (0.11, 0.25) | < 0.0001 |
vNIC | 0.23 (0.13, 0.32) | 0.54 (0.43, 0.65) | < 0.0001 |
aIC = Iodine concentration at the arterial phase; aNIC = normalized iodine concentration at the arterial phase; aOL = Iodine overlay at the arterial phase; CT = computed tomography; HU = Hounsfield unit; SPNs = solitary pulmonary nodules; vIC = Iodine concentration at the venous phase; vNIC = normalized iodine concentration at the venous phase; vOL = Iodine overlay at the venous phase; *compared with the Mann Whitney rank sum test
CTPI allows the derivation of several physiologic parameters, including BV, BF, MTT, and PS. BV is defined as the integral under a corrected attenuation curve for enhancement values from a contrast material bolus. It is a relative measure of the blood volume within small vessels in a region of specific tissue. BV is related to the number and diameter of open vessels,
Solitary pulmonary nodules evaluated with dual-energy CT
Parameters | AUC | Threshold | Sensitivity | Specificity | 95% CI | |
---|---|---|---|---|---|---|
aOL (HU) | 0.636 | 13.89 | 70.66 | 61.02 | 0.577–0.692 | < 0.001 |
vOL (HU) | 0.638 | 12.79 | 59.88 | 72.03 | 0.580–0.694 | < 0.001 |
aIC (mg/ml) | 0.657 | 0.65 | 67.66 | 69.49 | 0.599–0.712 | < 0.001 |
vIC (mg/ml) | 0.703 | 0.85 | 68.86 | 71.19 | 0.646–0.755 | < 0.001 |
aNIC | 0.728 | 0.12 | 67.66 | 74.58 | 0.672–0.778 | < 0.001 |
vNIC | 0.790 | 0.35 | 75.45 | 80.51 | 0.738–0.836 | 0.0001 |
aIC = Iodine concentration at the arterial phase; aNIC = normalized iodine concentration at the arterial phase; aOL = Iodine overlay at the arterial phase; AUC = area under the curve; CT = computed tomography; HU = Hounsfield unit; vIC = Iodine concentration at the venous phase; vOL = Iodine overlay at the venous phase; vNIC = normalized iodine concentration at the venous phase
95 % CI = 95 % confidence interval
Pairwise comparison of AUC of dual energy CT parameters in 285 patients with solitary pulmonary nodules
Parameters* | ||
---|---|---|
aOL |
0.0995 | 0.9207 |
aOL |
0.813 | 0.4162 |
aOL |
2.485 | 0.0129 |
aOL |
3.171 | 0.0015 |
aOL |
5.170 | < 0.0001 |
vOL |
0.702 | 0.4829 |
vOL |
2.567 | 0.0103 |
vOL |
3.280 | 0.0010 |
vOL |
5.345 | < 0.0001 |
aIC |
2.034 | 0.0420 |
aIC |
2.755 | 0.0059 |
aIC |
4.728 | < 0.0001 |
vIC |
1.036 | 0.3001 |
vIC |
3.227 | 0.0013 |
aNIC |
2.708 | 0.0068 |
aIC = Iodine concentration at the arterial phase; aOL = Iodine overlay at the arterial phase; aNIC = normalized iodine concentration at the arterial phase; AUC = area under the curve; CT = computed tomography; vIC = Iodine concentration at the venous phase; vNIC = normalized iodine concentration at the venous phase; vOL = Iodine overlay at the venous phase; *compared with the DeLong test
CTPI can be used to evaluate the perfusion and vascularity of lesions in the lung and many other organs.21-28 Wang
In our study, only the PS parameter of CTPI was found to be significant difference between the malignant and benign SPNs (
Solitary pulmonary nodules evaluated with multimodality CT imaging
Methods* | Sensitivity (%) | Specificity (%) | Accuracy (%) | PPV (%) | NPV (%) |
---|---|---|---|---|---|
Method A | 83.23 | 63.56 | 75.09 | 76.37 | 72.82 % |
Method B | 85.63 | 67.80 | 78.25 | 79.01 | 76.92 % |
Method C | 84.43 | 66.10 | 76.84 | 77.90 | 75.00 % |
Method A+B | 94.61 | 74.58 | 86.32 | 84.04 | 90.72 % |
Method A+C | 92.81 | 77.97 | 86.67 | 85.64 | 88.46 % |
Method B+C | 95.81 | 81.36 | 89.82 | 87.91 | 93.20 % |
Method A+B+C | 97.60 | 88.14 | 93.68 | 92.09 | 96.30 % |
CT = computed tomography; Method A = non-contrast enhanced CT combined with contrast enhanced CT; Method B = non-contrast enhanced CT combined with dual energy CT; Method C = non-contrast enhanced CT combined with CT perfusion imaging; Method A + B = non-contrast enhanced CT combined with contrast enhanced CT and dual energy CT; Method A + C = non-contrast enhanced CT combined with contrast enhanced CT and CT perfusion imaging; Method B + C = non-contrast enhanced CT combined with dual energy CT and CT perfusion imaging; Method A + B + C = non-contrast enhanced CT combined with contrast enhanced CT, dual-energy CT, and CT perfusion imaging; NPV = Negative predictive value; PPV = Positive predictive value; *compared with the McNemar’s test
There are mainly three techniques commercially available for DECT scanning. These techniques include: (a) fast voltage switching DECT, (b) layer detector DECT, and (c) dual-source DECT.30 In this study, we used a fast voltage switching DECT system. It has the ability to obtain virtual nonen-hanced images, arterial phase and venous phase contrast enhanced images, and iodine maps in one examination.30
An iodine map is the decomposition of material components realized by dual DECT according to the different attenuation characteristics of substances under high and low energy. It is the imaging of iodine material density extracted from enhanced iodine components. Iodine maps can effectively inhibit the background CT value and match with artificial color maps which can directly reflect the difference in iodine concentration in the lesion. The iodine concentration in the lesions can be measured quantitatively, and the lesions with slight enhancement can be displayed more sensitively. The CT value of the lesions measured on the iodine maps is the net enhancement value of the lesions. By measuring the enhancement value of lesions in iodine maps, we can evaluate the hemodynamic changes of tumors and the curative effects after tumor treatments.
In our results, parameters of DECT, which included aOL, vOL, aIC, vIC, aNIC, and vNIC, in malignant SPNs, were significantly higher than those of benign SPNs (all
Zhou
In this study, the diagnostic performances of the three diagnostic methods were separately used or in combination for differentiating benign and malignant SPNs were calculated, and the results showed that multimodality CT imaging had higher performances than single modality CT imaging in differentiating between benign and malignant SPNs in sensitivity, specificity, and accuracy (all
Step-wise approach of multimodality CT imaging for evaluating solitary pulmonary nodules14647
1. Solid | ||
Density | 2. Subsolid | |
3. Round or oval | ||
Shape | 4. Triangular or polygonal | |
5. Smooth | ||
Margins | 6. Lobulated | |
7. Spiculated | ||
Non-contrast enhanced CT | 8. Fat | |
Internal characteristics | 9. Calcification | |
10. Cavitation | ||
11. Pleural retraction | ||
12. Air bronchogram | ||
Some complex findings | 13. Bubble like lucencies (pseudocavitation) | |
14. Cystic airspace | ||
15. Vascular convergence | ||
Contrast enhanced CT | Parameter (s) | 16. Degree of enhancement |
CT perfusion imaging | Parameter (s) | 17. Permeability surface |
Dual-energy CT | Parameter (s) | 18. Normalized iodine concentration at the venous phase |
Radiation is an important consideration when using a multimodality CT imaging protocol. Previous studies have reported that the radiation dose of CTPI is the key factor hindering its application.9,36 In our study, the CTDIvol, DLP, and ED in the SPNs were 66.88 ± 4.36 mGy, 768.29 ± 91.65 mGy.cm, and 10.76 ± 1.18 mSv, respectively. We have tried to make the radiation dose in our study at an acceptable level by using low tube voltage, SmartmA, and iterative reconstruction.37-39 Tube voltage and tube current are positively correlated with the radiation dose.40-42 In addition, it is recommended that postset ASIR-V% (60% in this study) should be higher than or equal to preset ASIR-V% (50% in this study).43-45 All these radiation reduction techniques have been shown to decrease the radiation dose while maintaining the image quality.40-45
Some limitations of this study are: (a) only a fast voltage switching DECT was used in our study, and we did not compare our results with parameters from a layer detector DECT or dual-source DECT; (b) we did not compare our results with parameters from a magnetic resonance imaging (MRI) or positron emission tomography computed tomography (PET/CT); (c) some parameters of CTPI and DECT were not included into our study for evaluating; (d) radiation dose of our multimodality CT imaging protocol is still at a relatively high level; and (e) we did not include some advanced medical image analysis methods, such as artificial intelligence (AI), deep learning, or radiomics in our study. As a result, further investigations are needed to strengthen our findings in the future.
In conclusion, SPNs evaluated with multimodality CT imaging contributes to improving the diagnostic accuracy of benign and malignant SPNs (Table 10). NECT helps to locate and evaluate the morphological characteristics of SPNs. CECT helps to evaluate the vascularity of SPNs. CTPI using parameter of PS and DECT using parameter of vNIC both are helpful for improving the diagnostic performance.