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

Incidental Extracardiac Findings of Technetium-99m Pyrophosphate Scintigraphy: A Pictorial Review

Technetium-99m pyrophosphate (Tc-99m PYP) cardiac imaging is a simple, widely available, noninvasive method to identify patients with transthyretin-type cardiac amyloidosis (ATTR), and it has remarkably high diagnostic accuracy with very high sensitivity and specificity. Visual scores of 0, 1, 2, and 3 indicate non-myocardial uptake, uptake less than rib, equal to rib, and greater than rib uptake, respectively. Semiquantitative assessment using the heart-to-contralateral lung ratio of more than 1.5 at 1 hour accurately distinguishes ATTR from the cardiac amyloid light chain subtype. However, there are several incidental non-cardiac findings that can be seen in planar images, rotating single-photon emission computed tomography (SPECT) images, maximum intensity projection images, or computed tomography images acquired for attenuation correction. These findings may lead to the early detection of a noncardiac condition that may require additional treatment. The intent of this review is to demonstrate several incidental noncardiac abnormalities that have an impact on patient management and follow-up.

Holistic AI analysis of hybrid cardiac perfusion images for mortality prediction

Background

While low-dose computed tomography scans are traditionally used for attenuation correction in hybrid myocardial perfusion imaging (MPI), they also contain additional anatomic and pathologic information not utilized in clinical assessment. We seek to uncover the full potential of these scans utilizing a holistic artificial intelligence (AI)-driven image framework for image assessment.

Methods

Patients with SPECT/CT MPI from 4 REFINE SPECT registry sites were studied. A multi-structure model segmented 33 structures and quantified 15 radiomics features for each on CT attenuation correction (CTAC) scans. Coronary artery calcium and epicardial adipose tissue scores were obtained from separate deep-learning models. Normal standard quantitative MPI features were derived by clinical software. Extreme Gradient Boosting derived all-cause mortality risk scores from SPECT, CT, stress test, and clinical features utilizing a 10-fold cross-validation regimen to separate training from testing data. The performance of the models for the prediction of all-cause mortality was evaluated using area under the receiver-operating characteristic curves (AUCs).

Results

Of 10,480 patients, 5,745 (54.8%) were male, and median age was 65 (interquartile range [IQR] 57-73) years. During the median follow-up of 2.9 years (1.6-4.0), 651 (6.2%) patients died. The AUC for mortality prediction of the model (combining CTAC, MPI, and clinical data) was 0.80 (95% confidence interval [0.74-0.87]), which was higher than that of an AI CTAC model (0.78 [0.71-0.85]), and AI hybrid model (0.79 [0.72-0.86]) incorporating CTAC and MPI data (p<0.001 for all).

Conclusion

In patients with normal perfusion, the comprehensive model (0.76 [0.65-0.86]) had significantly better performance than the AI CTAC (0.72 [0.61-0.83]) and AI hybrid (0.73 [0.62-0.84]) models (p<0.001, for all).CTAC significantly enhances AI risk stratification with MPI SPECT/CT beyond its primary role - attenuation correction. A comprehensive multimodality approach can significantly improve mortality prediction compared to MPI information alone in patients undergoing cardiac SPECT/CT.

Prevalence and clinical significance of incidental findings on CT attenuation correction for myocardial perfusion imaging

BACKGROUND

The appropriate clinical approach to incidentally detected lesions (IDLs) on CT attenuation correction (CTAC) images in myocardial perfusion imaging (MPI) remains uncertain. We sought to establish their prevalence and clinical significance in a large cohort and compared to previous studies to help provide further clarity and guide future clinical practice.

METHODS AND RESULTS

A total of 3758 MPI studies were reviewed retrospectively. IDLs of potential clinical significance-not known before MPI - were reported in 245 (6.5%) of these cases. Following appropriate further investigation/follow-up, these were of proven clinical significance in 30 (12.2%) cases with 14 patients (5.7%) harboring previously undiagnosed or progressive malignancies. The positive predictive value (PPV) for clinically significant incidental findings on CTAC images was 17.2% and the PPV value for incidental malignant findings was 8.0%.

CONCLUSION

Although incidental findings on CTAC images in MPI are common and often clearly insignificant at time of MPI reporting, many are clinically significant with a relatively high positive predictive value. This is especially so for malignancies. Our findings, therefore, in combination with previous studies as described here support routine reporting and appropriate further investigation of incidental CTAC findings in MPI.

Incidental findings on single-photon emission computed tomography/computed tomography (SPECT/CT) lymphoscintigraphy in breast cancer: the proposed Westmead SPECT/CT incidental findings classification

Background

The aim of this study is to determine the prevalence of incidental radiological findings detected on SPECT/CT performed as part of pre‐operative lymphoscintigraphy for sentinel lymph node biopsy (SLNB) in patients undergoing breast cancer surgery and development of a modified classification to workup these lesions.

Methods

A retrospective audit was performed of all SPECT/CT performed in combination with lymphoscintigrams in breast cancer patients presenting with clinically node negative axillae and operated on by breast surgeons at the Westmead Breast Cancer Institute over a 12‐month period.

Results

Four hundred and nineteen patients were included in the study. In 149 patients (35.6%), there was a total of 205 incidental findings. The most common findings were, pulmonary abnormalities (38.5%), abdominal findings (27.8%), thyroid nodules (14.6%), cardiac abnormalities (10.7%) and others (8.3%). Using our proposed Westmead SPECT/CT incidental findings (WSIF) classification, 7.8% were known, 17.6% were major findings, 48.3% were minor findings, 15.1% were minimal findings and 11.2% were equivocal findings. 17.6% (n = 36) underwent further workup and investigation and 3.4% of patients (n = 5) required therapeutic intervention, including chemotherapy for primary lung cancer(n = 1) and surgeries (thoracotomy, n = 1; thyroidectomy, n = 2; colonoscopy, n = 1). 93.8% (n = 393) had at least one SLN mapped, most commonly located in Level 1 of the axilla.

Conclusion

The incidental findings on SPECT/CT in combination with lymphoscintigraphy is within the range of previous studies (27.3–59.5%). A small proportion of patients required significant major interventions (3.4%). We propose that all incidental findings should be assessed according to our WSIF classification to aid in triaging need for further investigation and management.

Implementation of Ultrasound in Anatomy Education

The use of different ways to view the body has always been associated with anatomy. With advancing technology, the use of ultrasound has become more portable and accessible as a way for students to learn anatomy. Moreover, ultrasound's direct clinical context makes it an important skill that students need to acquire and be competent in, not only after graduation but on clinical placements as a student. There does appear to be a learned skill in being able to interpret ultrasound images and to be able to relate the anatomy seen to existing anatomical knowledge. In addition, there is a learned skill in being able to correctly hold the ultrasound probe and gain clear images. Because ultrasound use and interpretation is a skill it therefore needs to be taught as part of undergraduate medical and allied health care professional education. A key to successful training is regular teaching sessions distributed longitudinally throughout the curriculum with active, hands-on learning time being the focus of any teaching session.

Incidental Findings of Malignancy of the Chest by Single Photon Emission Computed Tomography Myocardial Perfusion Imaging (SPECT-CT MPI): One Year Follow-Up Report

Introduction

We recently reported six cases of pulmonary/hilar malignancies as the result of incidental findings (IF) on CT attenuation correction (CTAC) during Single Photon Emission Computed Tomography Myocardial Perfusion Imaging (SPECT-CT MPI). In this study, clinical features, diagnostic procedures, and clinical outcomes were examined on all patients who had malignancies or significant IF that required further follow-up.

Methods

Of 1,098 consecutive patients who underwent cardiac SPECT-CT MPI from September 1, 2017 to August 31, 2018, their MPI and CTAC were reviewed contemporaneously. Patients with known history of prior pulmonary or chest malignancy were excluded.

Results

A total of 79 (7.2%) patients were identified to have significant IF on CTAC. After diagnostic CT, 47 patients had significant findings that warranted further follow-up and included in this study. Eight of 1,098 patients (0.73%) and 8/79 patients (10.1%) were found to have malignancy of the chest because of IF on the CTAC. There were no statistically significant differences in baseline characteristics and cancer risk factors among patients who had cancer versus those without. At the time of diagnosis, four patients had cancer at an advanced stage, resulting in death within 12 months. Three others had early stage lung cancer and one had mantle cell lymphoma; they were alive at a mean follow-up of 17.5+/−2.1 months. Biopsy for tissue diagnosis was performed safely with needle biopsy. Major complication occurred in one patient (1/9 or 11.1%) with needle biopsy; none with surgical biopsy.

Conclusion

This study underscored the importance of reviewing CTAC images obtained during cardiac SPECT-CT MPI to detect clinically important IF.

Incidental Findings of Pulmonary and Hilar Malignancy by Low-Resolution Computed Tomography Used in Myocardial Perfusion Imaging

BACKGROUND

Low dose, low-resolution computed tomography (CT) is used for attenuation correction to improve the quality of single-photon emission computed tomography (SPECT) myocardial perfusion imaging (MPI). Because of its low resolution, these CT images are considered non-diagnostic and are not routinely or uniformly reviewed or interpreted by a cardiologist. On the other hand, low-dose CT has been used for lung cancer screening to reduce lung cancer mortality and is recommended for annual screening of high-risk patients by the US Preventive Services Task Force.

METHODS

Siemens Symbia Intevo Excel SPECT/CT scanners, used primarily for cardiac MPI, were used in the study. The study was intended to report incidental findings of pulmonary and hilar malignancy detected by these CT images during cardiac evaluation. It included 1,098 consecutive patients who had SPECT MPI from September 1, 2017 to August 31, 2018. When suspicious pulmonary nodules or abnormalities were identified, primary care providers were notified of the findings and recommendations for further evaluation.

RESULTS

Five patients were found to have lung cancer (all male with substantial smoking history, aged 64-75 years), 1 had mantle cell lymphoma. Six of 1,098 (0.55%) patients were found to have incidental pulmonary/hilar malignancy, which is comparable to the yield (0.65%/year) of detecting lung cancer using low-dose CT for screening in The National Lung Screening Trial.

CONCLUSIONS

Routine review and report of incidental findings on low-resolution CT during cardiac MPI by physicians skilled in CT interpretation is necessary to identify incidental but clinically important findings, including malignancies.

Prevalence and variability in reporting of clinically actionable incidental findings on attenuation-correction CT scans in a veteran population

BACKGROUND

Myocardial perfusion imaging (MPI) often employs attenuation-correction computed tomography (CTAC) to reduce attenuation artifacts and improve specificity. While there is no specific guideline on how they should be reported, incidental noncardiac findings identified on these scans may be clinically significant. The prevalence of these findings in veterans is not currently known. In addition, variability in reporting these findings may depend on the interpreting physician's specialty.

METHODS

To guide future decision-making, CTACs in veterans referred for MPI were prospectively evaluated in a quality-control project for a set of prespecified actionable incidental findings by cardiologists and a radiologist.

RESULTS

On the 771 scans performed over eight months, 285 incidental noncardiac findings were identified by the interpreting cardiologists and 378 were identified by the interpreting radiologist. Pulmonary nodules were the most common occurring in 20% of studies read by the radiologist. Interreader agreements between cardiologists and the radiologist were poor for pulmonary nodules ≥ 10 mm and hiatal hernias; fair for pulmonary nodules < 10 mm, extracardiac masses, and aortic aneurysms; and moderate for pleural plaques.

CONCLUSION

Incidental noncardiac findings on CTACs are common in our veteran population. Overall interobserver agreement in identifying these findings between cardiologists and radiologists is fair. Specific guidelines are needed on how CTACs should be read and reported.

The importance of appropriate reporting and investigation of incidental findings on computed tomography attenuation correction images during myocardial perfusion scintigraphy

We present a case of lung cancer incidentally detected as a pulmonary nodule on computed tomography attenuation correction (CTAC) images during myocardial perfusion scintigraphy (MPS). Unfortunately, the incidental lesion was not fully investigated following MPS report and had developed into metastatic lung carcinoma when diagnosed over 1 year later, with failure of subsequent emergent chemotherapy. The disease appeared to be localized when initially detected during MPS. This case highlights the importance and potential clinical value of routine review of CTAC images in MPS with appropriate reporting and further investigation of suspicious incidental findings. In addition, the importance of effective communication between nuclear medicine department and treating team is clear to ensure suspicious incidental findings are given sufficient credence and thoroughly investigated promptly to avoid adverse clinical outcomes.

Prognostic impact of myocardial perfusion single photon emission computed tomography in patients with major extracardiac findings by computed tomography for attenuation correction

BACKGROUND

Attenuation correction computed tomography (CT) contributes to an improvement in the diagnostic accuracy of myocardial perfusion imaging (MPI) by single photon emission tomography (SPECT). The aim of this study was to explore the prognosis of patients with major findings by CT according to the results of MPI.

METHODS AND RESULTS

1506 patients who underwent MPI by SPECT were retrospectively included. Attenuation correction CT images were systematically analyzed for major and minor abnormalities. 830 (55.1%) and 212 (14.1%) patients had minor and major extracardiac findings, respectively. Among patients with major extracardiac findings, the abnormality was previously unknown in 113 (53.3%) patients. 90 (41.9%) had abnormal MPI, 73 (34.4%) had a myocardial infarction scar, 55 (25.9%) had myocardial ischemia, and 38 (17.7%) patients had both myocardial infarction scar and myocardial ischemia. Among the 201 patients available for survival analysis, there were 67 (31.2%) deaths over a follow-up period of 3.2±1.3 years. There was no significant impact on survival arising from MPI, whatever the result. The results were the same among the 103 patients with previously unknown major extracardiac findings.

CONCLUSION

Extracardiac findings by CT during MPI are frequent. Patients with major extracardiac findings have a poor mid-term outcome, whatever the results of the myocardial perfusion imaging. Extracardiac findings should be systematically checked when attenuation correction CT is performed.

The Clinical Dilemma of Incidental Findings on the Low-Resolution CT Images from SPECT/CT MPI Studies

Incidental findings are common in medical imaging. There is a particularly high prevalence of incidental findings within the thorax, the most frequent being pulmonary nodules. Although pulmonary nodules have the potential to be malignant, most are benign, resulting in a high number of false-positive findings. Low-resolution CT images produced for attenuation correction of SPECT images are essentially a by-product of the imaging process. The high number of false-positive incidental findings detected on these attenuation-correction images causes a reporting dilemma. Early detection of cancer can be beneficial, but false-positive findings and overdiagnosis can be detrimental to the patient. Attenuation-correction CT images are not of diagnostic quality, and further diagnostic tests are usually necessary for a definitive diagnosis to be reached. Given the high number of false-positive findings, the psychologic effect on the patient should be considered. This review recommends caution when the findings on attenuation-correction CT images are routinely reported.

Multicentre analysis of incidental findings on low-resolution CT attenuation correction images: an extended study

OBJECTIVE

To review new incidental findings detected on low-resolution CT attenuation correction (CTAC) images acquired during single-photon emission CT-CT myocardial perfusion imaging as an extension to our initial study.

METHODS

CTAC images acquired as part of myocardial perfusion imaging performed using single-photon emission CT at four UK nuclear medicine centres were evaluated as part of a multicentre study. New incidental findings that were considered to be clinically significant were evaluated further. Positive-predictive value (PPV) was determined at the time of definitive diagnosis.

RESULTS

Out of 3485 patients, 962 (28%) patients had a positive finding on the CTAC image, of which 824 (24%) were new findings. 84 (2.4%) patients had findings that were considered clinically significant at the time of the CTAC report and which had not been previously diagnosed. However, only 10 (0.29%) of these had findings that were confirmed as clinically significant, with the potential to be detrimental to patient outcome, after follow-up and definitive diagnosis.

CONCLUSION

The overall PPV from all centres over the 2-year period was 12%. Each centre achieved what we considered to be low PPVs with no significant difference between the present and initial studies. The additional data from the combined studies show that, statistically, there is no significant difference between the PPVs from any of the centres. We conclude that routine reporting of CTAC images is not beneficial.

ADVANCES IN KNOWLEDGE

This study combined with the previous study offers a unique evaluation of new clinically significant incidental findings on low-resolution CT images in an attempt to determine the benefit of reporting the CTAC images.