Multi-centre analysis of incidental findings on low-resolution CT attenuation correction images

Abstract

Objective: To review new incidental findings detected on low-resolution CT attenuation correction (CTAC) images acquired during single-photon emission CT (SPECT-CT) myocardial perfusion imaging (MPI) and to determine whether the CTAC images had diagnostic value and warrant reporting.

Methods: A multicentre study was performed in four UK nuclear medicine departments. CTAC images acquired as part of MPI performed using SPECT were evaluated to identify incidental findings. New findings considered to be clinically significant were evaluated further. Positive predictive value (PPV) was determined at the time of definitive diagnosis.

Results: Of 1819 patients studied, 497 (27.3%) had a positive CTAC finding. 51 (2.8%) patients had findings that were clinically significant at the time of the CTAC report and had not been previously diagnosed. Only four (0.2%) of these were potentially detrimental to patient outcome.

Conclusion: One centre had a PPV of 0%, and the study suggests that these CTAC images should not be reported. Two centres with more modern equipment had low PPVs of 0% and 6%, respectively, and further research is suggested prior to drawing a conclusion. The centre with best quality CT had a PPV of 67%, and the study suggests that CTAC images from this equipment should be reported.

Advances in knowledge: This study is unique compared with previous studies that have reported only the potential to identify incidental findings on low-resolution CT images. This study both identifies and evaluates new clinically significant incidental findings, and it demonstrates that the benefit of reporting the CTAC images depends on the type of equipment used.

Figure 1.

Patient from Centre 1. CT attenuation correction image acquired using GE Infinia™ Hawkeye™ (GE Healthcare, Buckinghamshire, UK) one-slice single-photon emission CT-CT system, which reveals a single pulmonary nodule in the left lower lobe. This was confirmed by diagnostic CT (Figure 2).

Figure 2.

The same patient as in Figure 1. Diagnostic multidetector CT confirming diagnosis of pulmonary lesion detected on the CT attenuation correction acquisition.

Figure 3.

The same patient as in Figures 1 and 2. Diagnostic multidetector CT demonstrating a further lesion in the left upper lobe.

Figure 4.

Patient from Centre 2. CT attenuation correction image (lung windows) from cardiac single-photon emission CT-CT study using GE Infinia™ Hawkeye™ (GE Healthcare, Buckinghamshire, UK) four-slice demonstrating mass in right lower lobe abutting the heart.

Figure 5.

The same patient as in Figure 4. Contrast-enhanced diagnostic multidetector CT image demonstrating lung mass with serpiginous vessels.

Figure 6.

Patient from Centre 3. CT attenuation correction images using GE Infinia™ Hawkeye™ (GE Healthcare, Buckinghamshire, UK) four-slice. Cross-hairs identify an approximately 6-mm nodule. A, anterior; I, inferior; L, left; P, posterior; R, right; S, superior.

Figure 7.

The same patient as in Figure 6. Diagnostic multidetector CT confirming the presence of a nodule (N3). This was considered stable on subsequent CT images over a period of 24 months. Avg, average; Eff Diam, effective diameter; Max, maximum; Min, minimum.

Figure 8.

Patient from Centre 4. CT attenuation correction image from Philips Precedence 16-slice multidetector CT (Philips Healthcare, Guildford, UK) demonstrating a right lower lobe nodule in a 77-year-old male patient, which was confirmed as T3 carcinoma at resection.

Figure 9.

Another patient from Centre 4. CT attenuation correction image from Philips Precedence 16-slice multidetector CT (Philips Healthcare, Guildford, UK) demonstrating single pulmonary nodule in a 77-year-old male patient, which was confirmed as T2a N0 M0.

Figure 10.

Illustrating a suspected pulmonary nodule on GE Infinia Hawkeye™ (GE Healthcare, Buckinghamshire, UK) one-slice CT attenuation correction image that was confirmed as pulmonary fibrosis on diagnostic multidetector CT. L, length; DFOV, display field of view; Im, image; W, width.