Rationale and Objectives
Pulmonary nodules can be missed on the non-breath hold computed tomography (CT) portion of 18F-fluorodeoxyglucose positron emission tomography/computed tomography (FDG PET/CT), and for this reason prior studies have advocated for routinely performing dedicated breath hold CT of the chest in addition to PET/CT for routine staging of malignancy. We evaluated the rate of pulmonary nodule detection on standard CT images from whole body PET/CT studies (WB-PET/CT), high-resolution lung reconstruction CT images from PET/CT studies (HR-PET/CT), and diagnostic breath hold chest CT (BH-CT).
Materials and Methods
A cohort of 25 patients was identified who had a history of lung cancer as well as a PET/CT staging or restaging scan and BH-CT within 30 days of each other. All PET/CTs included a set of CT images using a soft tissue algorithm filter and 3.75- to 5-mm slice thickness, as well as high-resolution reformats with a sharp reconstruction filter and 2-mm slice thickness. The CT images from WB-PET/CT, HR-PET/CT, and BH-CT were reviewed by three radiologists. Significance was analyzed by two-way repeated measures analysis of variance.
Results
There were 2.84 nodules found per patient with WB-PET/CT, 3.85 nodules with HR-PET/CT, and 3.91 nodules with BH-CT. When only nodules less than or equal to 8 mm in size were considered, WB-PET/CT also demonstrated significantly fewer nodules (1.98) compared to the HR-PET/CT (2.94) or a BH-CT (2.86) ( P < 0.001). No difference in detection rate was noted between the two higher resolution modalities.
Conclusions
More pulmonary nodules are detected on the CT portion of PET/CT studies when high-resolution reformatted images are created and reviewed. The ability to detect nodules with the reformatted images was indistinguishable from dedicated BH-CT. Overall, high-resolution reformats of PET/CT images of the lungs can increase the sensitivity for pulmonary nodule detection, approaching that of dedicated BH-CT. These data suggest that if HR-PET/CT reformats are used, additional dedicated BH-CT is unnecessary for routine staging of lung cancer.
Introduction
8F-Fluorodeoxyglucose (FDG) positron emission tomography combined with whole body computed tomography (PET/CT) has become the standard of care imaging test for staging of patients with non-small cell lung cancer (NSCLC) . Staging of NSCLC is performed using the tumor, node, metastasis (TNM) classification system . Multiple prior studies have demonstrated that PET/CT is superior to CT alone for staging the primary mass (T stage) , associated nodal disease (N stage) , and distant metastasis (M stage) . For these reasons, PET/CT has become widely used for this application.
The presence or absence of pulmonary nodules, distinct from the primary mass, is an important contributor to the overall stage of NSCLC . Specifically, the presence of other nodules in the same lobe as the primary tumor confers the T3 stage, and the presence of nodules in the same side, different lobe, results in a T4 tumor. Metastatic pulmonary nodules in the contralateral lung confer M1a disease. An accurateassessment for nodules suggestive of metastatic disease can only be accomplished via imaging; therefore, it is critical to accurately assess the presence of even small pulmonary nodules.
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Methods
Patient Selection
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Scan Technique
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Imaging and Chart Review
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Statistical Analysis
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Results
Patient Demographics
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TABLE 1
Patient Demographics
Age 70.3 ± 7.2 years Sex Male 14/25 (56%) Female 11/25 (44%) Average time between PET and CT scan 17.8 ± 8.0 days Indication for CT Restaging/treatment response/surveillance 19/25(76%) Initial staging 4/25(16%) Suspected pulmonary embolism 2/25(8%) Indication for PET/CT Restaging/treatment response/surveillance 21/25(86%) Initial staging 4/25(16%)
PET/CT, positron emission tomography/computed tomography.
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Scan Interpretation
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![Figure 1, Examples of pulmonary nodules detected using various methods. ( a ) A 67-year-old man with history of non-small cell lung cancer (NSCLC) post-resection with a 4-mm nodule found along the suture line. The nodule was detected on whole body positron emission tomography/computed tomography (WB-PET/CT) by one out of three radiologists, on high-resolution PET/CT (HR-PET/CT) by three out of three radiologists, and on breath hold chest CT (BH-CT) by three out of three radiologists. ( b ) A 67-year-old man with history of NSCLC post-resection (same patient as [ a ] with a 4-mm left lower lobe pulmonary nodule). The nodule was detected on WB-PET/CT by one of three radiologists, on HR-PET/CT by three out of three radiologists, and on BH-CT by three out of three radiologists. ( c ) A 78-year-old woman with history of NSCLC with recurrence. Images demonstrate a 3-mm subpleural right upper lobe nodule, detected on WB-PET/CT by none of three radiologists, on HR-PET/CT by two out of three radiologists, and on BH-CT by two out of three radiologists.](https://storage.googleapis.com/dl.dentistrykey.com/clinical/DetectingPulmonaryNodulesinLungCancerPatientsUsingWholeBodyFDGPETCTHighresolutionLungReformatofFDGPETCTorDiagnosticBreathHoldChestCT/0_1s20S1076633216300769.jpg)
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Statistical Analysis
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Discussion
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