Imaging of acute pulmonary embolism

Use of the Pao2/Fio2 Ratio in Pulmonary Embolism: Evaluation of its Correlation with Pulmonary Arterial Computed Tomography Obstruction Index

RATIONALE AND OBJECTIVES

The pulmonary arterial computed tomography obstruction index ratio (PACTOIR) is a parameter that provides an idea of the clinical severity of acute pulmonary embolism (APE). This study aimed to examine the correlation between the PaO₂ /FiO₂ ratio and PACTOIR in patients who presented to the emergency department and received a preliminary diagnosis of APE.

MATERIALS AND METHODS

This study was conducted prospectively in the emergency department. The patients' sociodemographic characteristics, vital signs, PACTOIR, and PaO₂ /FiO₂ ratio were obtained. The correlation between PACTOIR and PaO₂ /FiO₂ ratio was then statistically evaluated.

RESULTS

The study included 50 patients, of whom 31 (62%) were women, and 19(38%) were men. The female patients had a PaO₂ /FiO₂ ratio of 209 ± 67 and PACTOIR of 36.3 ± 15.5. The male patients had a PaO₂ /FiO₂ ratio of 169 ± 43 and PACTOIR of 39.7 ± 19. The PaO₂ /FiO₂ ratio of the patients with APE was negatively correlated with the PACTOIR value at a statistically significant level (r = -0.308, p = 0.031). The regression equation was as follows: PACTOIR = (-0.0869) x (PaO₂ / FiO₂) + (54.489).

CONCLUSION

By calculating the PaO₂ /FiO₂ ratio in patients with APE, the degree of pulmonary artery obstruction and clinical severity can be predicted. Therefore, the ratio PaO₂ /FiO₂ can be used instead of PACTOIR.

Pulmonary vascular diseases

Pulmonary vascular diseases encompass a large and diverse group of underlying pathologies ranging from venous thromboembolism to congenital malformations to inflammatory vasculitides. As a result, patients can present either acutely with dyspnea and chest pain or chronically with dyspnea on exertion, hypoxia, and right heart failure. Imaging, particularly with multidetector CT, plays a key role in the evaluation and management of patients with suspected pulmonary vascular disease and, given the widespread routine use of high-quality CT pulmonary angiography, it is imperative that radiologists be familiar these pathologies.

Advanced Chest Imaging Interpretation of Acute Pulmonary Disorders

Bedside and advanced practice nurses in acute and critical care often view chest radiologic images of their patients. Correlation of findings on chest radiologic images with results of physical and other diagnostic assessments can provide information for making appropriate clinical judgments. Radiologic images of the chest available for acutely ill patients now include frontal/lateral chest radiographs and computed tomography (CT) scans. The purpose of this article is for the reader to review basic skills for interpreting chest radiographs, gain skill in reviewing CT scans of the chest, and be able to apply more advanced interpretation skills for both chest radiographs and chest CT scans. Several chest images are included for review.

High pitch, low voltage dual source CT pulmonary angiography: assessment of image quality and diagnostic acceptability with hybrid iterative reconstruction

Increased use of CT Pulmonary angiography in suspected pulmonary embolism (PE) has driven research to minimize radiation dose while maintaining image quality and diagnostic accuracy. Following institutional review board approval, we performed a retrospective comparison study in patients with suspected PE. Patients were scanned using an ultra high pitch dual source technique (pitch = 2.6) using 120 kV (SVCTPA) (n = 54) or 100 kV (RV-CTPA) (n = 52). SV-CTPA images were reconstructed using filtered back projection (SV-wFBP) and RV-CTPA images were reconstructed using both FBP (RV-wFBP) and Iterative Reconstruction (RV-IR). Comparison of radiation dose, diagnostic ability, subjective image noise, quality, and sharpness, diagnostic agreement, signal to noise (SNR) and contrast to noise ratios (CNR) were performed. Mean effective dose was 2.56 ± 0.19 mSv for the RV protocol compared to 5.36 ± 0.60 mSv for the SV. The RV-CTPA protocol resulted in a mean DLP reduction of 52 % and mean CTDI reduction of 51 %. Pulmonary artery SNR and CNR were significantly higher on RV-IR images than SV-wFBP (p = 0.007, p = 0.003). Mean subjective image noise, quality and sharpness scores did not differ significantly between the SV-wFBP and RVIR images (p > 0.05). Subjective quality scores were significantly better for the RV-IR group compared to the RV-wFBP group (p < 0.001). Agreement between readers for presence or absence of pulmonary emboli on RV-IR images was almost perfect (κ = 0.891, p < 0.001). Iterative reconstruction complements ultra high pitch dual source CTPA examinations acquired using a reduced voltage resulting in higher mean pulmonary artery SNR and CNR when compared to both RV-wFBP and SV-CTPA.