Photon-Counting Computed Tomography, Subsegmental Pulmonary Embolism
Conditions
Brief summary
Pulmonary embolism (PE) is a serious and potentially life-threatening condition caused by blood clots in the lungs. A particular type, subsegmental pulmonary embolism (SSPE), involves very small branches of the pulmonary arteries. Although these clots occur in smaller vessels, their risk of recurrence and complications may be similar to larger clots. Conventional CT pulmonary angiography (CTPA) is the standard imaging test for suspected PE, but image quality can sometimes be limited by motion artifacts, poor contrast filling, or body habitus, making the detection of SSPE challenging. Photon-counting computed tomography (PCCT) is a new CT technology that provides higher image resolution, lower radiation dose, and improved visualization of small blood vessels. Early studies suggest PCCT may reduce motion artifacts and increase the accuracy of detecting SSPE compared with conventional CT. This prospective cohort study will compare PCCT with dual-source CT in patients with suspected acute PE. The study aims to determine whether PCCT improves the detection rate and image quality for SSPE, and whether it can provide more reliable diagnostic information to guide clinical care.
Detailed description
Pulmonary embolism (PE) is a leading cause of morbidity and mortality worldwide. Subsegmental pulmonary embolism (SSPE), defined as thrombi confined to subsegmental pulmonary arteries, may account for up to 20% of acute PE cases detected by multidetector CT. While distal in location, SSPE carries a risk of recurrent venous thromboembolism and mortality that is comparable to more proximal PE, suggesting that SSPE is not a benign entity. Accurate diagnosis is therefore clinically important, but remains challenging due to motion artifacts, poor contrast opacification, and the large number of small subsegmental vessels that must be evaluated. Photon-counting computed tomography (PCCT) is a recently developed imaging technology that offers significant improvements over conventional energy-integrating detector CT (EID-CT). PCCT provides higher spatial resolution, direct spectral information, and the ability to generate virtual monoenergetic images and iodine maps in a single acquisition, while reducing radiation dose. Preliminary studies indicate that PCCT can minimize motion artifacts, improve image quality, and enhance visualization of small pulmonary arteries, potentially increasing the detection of SSPE. This prospective observational cohort study will compare the diagnostic performance of PCCT with dual-source CT in patients with suspected acute PE. The primary outcome is the detection rate of SSPE. Secondary outcomes include image quality scores, radiation dose, and the added diagnostic value of PCCT in patients with negative findings on dual-source CT. By systematically evaluating image quality, detection yield, and radiation exposure, this study seeks to establish the potential role of PCCT as a superior diagnostic tool for SSPE in real-world clinical practice.
Interventions
None listed
Sponsors
Second Affiliated Hospital, School of Medicine, Zhejiang University
Study design
Observational model
COHORT
Time perspective
PROSPECTIVE
Eligibility
Sex/Gender
ALL
Age
18 Years to No maximum
Healthy volunteers
No
Inclusion criteria
1. Age ≥ 18 years 2. Clinical manifestations supporting the diagnosis of acute pulmonary embolism, including: Acute onset or progressive dyspnea Unexplained hypoxemia Chest pain Hemoptysis Syncope or presyncope Combined with abnormal findings on electrocardiogram, echocardiography, or pulse oximetry 3. Revised simplified Geneva score ≥ 3 4. Written informed consent obtained from the patient or the patient's legally authorized representative
Exclusion criteria
1. Patients requiring prophylactic or therapeutic doses of anticoagulant medication for reasons other than venous thromboembolism (VTE). 2. Life expectancy less than three months. 3. Patients unable to undergo CT scanning due to severe condition or hemodynamic instability. 4. History of allergy to contrast media, renal insufficiency (creatinine clearance \< 30 mL/min), or ongoing long-term dialysis. 5. Pregnancy. 6. Refusal to provide informed consent or inability to complete follow-up for any reason.
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| Detection rate of subsegmental pulmonary embolism (SSPE) using photon-counting CT versus dual-energy CT | perioperative period | The proportion of patients with suspected acute pulmonary embolism in whom SSPE is detected on photon-counting CT compared with dual-energy CT. All scans will be independently assessed by two blinded radiologists to determine diagnostic yield. |
Secondary
| Measure | Time frame | Description |
|---|---|---|
| Objective image quality scores for SSPE diagnosis | perioperative period | ignal-to-Noise Ratio (SNR) and Contrast-to-Noise Ratio (CNR) will be calculated based on CT attenuation and image noise measured in standardized Regions of Interest (ROIs) within pulmonary vessels, the aorta, and paraspinal muscles. Higher SNR and CNR values indicate better objective image quality. |
| Subjective image quality scores for SSPE diagnosis | perioperative period | Radiologists will qualitatively assess image noise and motion artifacts using a 5-point Likert scale (1 = Unacceptable, 5 = Excellent). The average score of the readers will be used, with higher scores indicating better subjective image quality |
| Incidence of Venous Thromboembolism (VTE) | 3 months | Occurrence of symptomatic VTE, defined as Deep Vein Thrombosis (DVT) or Pulmonary Embolism (PE), confirmed by objective imaging upon clinical suspicion |
Countries
China
Outcome results
None listed