Coronary Artery and Aortic Valve Calcification Quantification in CT Chest Studies of Lung Cancer Screening

Rapid Communication

Austin J Radiol. 2024; 11(1): 1224.

Coronary Artery and Aortic Valve Calcification Quantification in CT Chest Studies of Lung Cancer Screening

Girgis M*; Gutierrez M; McCreavy D; Radike M; Fairbairn T

Liverpool Heart & Chest Hospital, Liverpool, United Kingdom

*Corresponding author: Mina Girgis Liverpool Heart & Chest Hospital, Liverpool, United Kingdom. Email: minamaher195@gmail.com

Received: December 26, 2023 Accepted: January 20, 2024 Published: January 27, 2024

Abstract

Reporting Coronary Artery Calcification (CAC) and Aortic Valve Calcification (AVC) on non-gated, non-contrast CT scans is recommended in the guidelines. This study aimed to assess the adherence guidelines in reporting incidental CAC and AVC present in the scans. It also aimed to assess the agreement between visual assessment and Agatston Score (AS) evaluating the severity of CAC and AVC in lung cancer screening chest CTs scans. This retrospective study included 100 patients’ low dose, non-gated, non-contrast CT scans. The scans were retrieved from the targeted lung health check program. The visual assessment of CAC and AVC was done by multiple reporters participating in the screening program. It was interpreted as none, mild, moderate or severe. The Agatston score, a reliable precursor of CAC and AVC was calculated using Siemens SyngoVia and interpreted as none, mild (<100), moderate (101-300) or severe (>300). The two scoring systems were compared to each other. CAC was present in 81 % of the cases and there was a comment on it in every report. There was a moderate agreement between the visual assessment of CAC and AS. Weighted kappa score was 0.516. AVC was reported in 4 cases of the 100 cases. It was present in only one case of them after reviewing the Agatston score of all the cases. AVC was present in 6 cases. It was reported in one case and missed in five cases. The reported case was with moderate AVC, and the missed cases were all with mild AVC.

Keywords: Chest CT; Cardiovascular disease; Coronary artery calcium

Introduction

Atherosclerotic cardiovascular disease is the leading cause of death in the UK. Coronary heart disease causes almost 66000 deaths each year, roughly 180 people each day, or one death every eight minutes [1]. Approximately one in eight men and one in fourteen women die from coronary heart disease, which makes primary prevention crucial to prevent events leading to death or long-term disability. In the UK, primary prevention with lifestyle modification is indicated in all patients with any cardiovascular risk factor [2]. When the 10-year risk of future cardiovascular events is 10 % or more, preventive therapy with statins is indicated. The individual cardiovascular risk is assessed using models that consider demographics, clinical and biochemical factors [3-5]. However, coronary calcium score has proven in multiple studies to outperform the prediction power of traditional risk prediction models [6]. In a recent multicentric study including more than 60.000 patients higher coronary calcium increased cardiovascular, and all-cause mortality regardless of risk factors burden [7].

The gold standard for assessment of Coronary Artery Calcification (CAC) is the Agatston score, which is based on an ECG-gated, non-contrast enhanced CT covering the heart. 3mm thick slices without overlap are acquired in end-diastole. Coronary calcification is defined as areas with >130 Hounsfield Units (HU) and at least 1mm2 (=3 consecutive pixels) [8]. The score is then calculated by adding the weighted sum of lesions (higher density lesions score higher) and classified in categories linked to the risk of future cardiovascular events. Similar, but slightly different classifications exist. In this paper we followed the one endorsed by the Society of Cardiovascular Computer Tomography and the Society of Thoracic Radiology in 2016: Agatston score 0 = no CAC (very low risk), 1-99, mild CAC (mildly increased risk), 100-299= moderate CAC (moderately increased risk), =300= moderate to severe CAD (moderately to severely increased risk) [9].

Despite the absence of ECG gating, chest CTs are a perfect chance to provide opportunistic risk stratification to patients being scanned for multiple reasons. With this in mind, a joint statement by the BSCI/ BSCCT and BSTI has recommended reporting the degree of coronary calcium in all thoracic scans. They recommend the heart to be reviewed on all CT scans where it is covered, and the presence of coronary artery and aortic valve calcification identified and quantified using simple visual quantifications (none, mild, moderate severe).

So far, various studies have evaluated the agreement between visual analysis and CAC scoring on non-ECG gated CTs in comparison with CAC scoring using ECG-gated CTs. Their results show good agreement in the identification of CAC between ECG-gated Agatson score, non-ECG gated Agatson score and visual assessment [10]. All these studies used a limited number of reviewers and/or a semiquantitative scale when visual evaluation was used.

In this descriptive study, we aim to assess agreement between calcium score and visual assessment on low dose lung cancer screening chest CTs. Studies have been reported by multiple readers, as part of their daily clinical practice, without guidance on how to quantify coronary calcification. All reports within the UK Targeted Lung Health Check program are structured, which guarantees adherence to the recommendation of reporting coronary artery calcification. Additionally, we have assessed the adherence to the recommendation of identifying and quantifying aortic valve calcification.

Methods

Institutional Review Board approval was waived by our Research and Innovation Department, which classified the study as Service Evaluation. A retrospective, single centre study was performed. One hundred low dose chest CTs from the lung cancer screening program acquired between March 2022 and June 2023 were filtered on PACS and reviewed. The only inclusion criteria were belonging to the Targeted Lung Health project. Patients from across the UK aged from 55-74 who have a positive smoking history receive an invitation by post to have a low dose CT scan. Patients without significant findings are receive a follow up invitation in 2years. Shorter term follow ups or referral for further investigations can be done when appropriate. Two exclusion criteria were applied: patients with previous coronary intervention and follow up scans.

All studies were acquired following NHS England recommended protocol for lung cancer screening [11]. All patients lay supine with the arms above their head and thorax centred on the table. Images were obtained in maximal inspiration following a low dose volumetric protocol. Automatic dose modulation was implemented to adapt the kilovoltage (Kv) and milliamperage (mAs) to body habitus with the objective of keeping total dose below 2mSv. Thin axial slices were reconstructed using lung and soft tissue windows. Additionally, a sagittal reconstruction was obtained for assessment of the spine (e.g., incidental compression fractures).

Images were interpreted and reported by multiple thoracic radiologists participating in the reginal lung cancer screening program, without particular guidance on how to report coronary or aortic valve calcification. A single operator retrospectively assessed the radiological reports and quantified coronary artery calcification (Agatston score) using Siemens SyngoVia. Visual analysis identified four degrees of coronary calcification: none, mild, moderate and severe. In consequence, the Agatston score levels were reclassified to 0=none, 1-99= mild, 100-299=moderate and =300=severe.

Apart from the coronary artery evaluation, it was also assessed if the there was a comment on aortic valve calcification. As with coronary calcification the visual scoring system was none, mild, moderate or severe. The aortic valve calcium score was calculated on SyngoVia.