Dual-energy CT lung perfusion characteristics in pulmonary arterial hypertension (PAH) and pulmonary veno-occlusive disease and/or pulmonary capillary hemangiomatosis (PVOD/PCH): preliminary experience in 63 patients

Pulmonary Capillary Hemangiomatosis as a Rare Underlying Cause of Primary Pulmonary Hypertension: A Case Report in an Adolescent

Despite its rarity, pulmonary capillary hemangiomatosis (PCH) presents a significant diagnostic challenge. Due to its similarity to other pulmonary vascular diseases, such as pulmonary veno-occlusive disease, it is characterized by abnormal pulmonary capillary proliferation, which is a rare cause of primary pulmonary hypertension. This case was the first reported instance of PCH in Shahid Rajaee Heart Hospital in Tehran, Iran, in 2023, which was confirmed by genetic testing. It highlighted the importance of considering PCH among the differential diagnoses for pulmonary hypertension, even in adolescent patients. The 13-year-old patient's main complaints were progressive exertional dyspnea and chest pain. He had no previous medical history and had not taken any pharmaceutical or herbal medications. Critical clinical findings included a heart murmur, an electrocardiogram revealing right ventricular hypertrophy, and echocardiogram evidence of pulmonary hypertension. The main diagnosis was PCH, as shown by CT findings of pulmonary artery dilatation and diffuse nodular ground glass opacities. Genetic tests indicated pathogenic EIF2AK4 mutations and suspicion of PCH. Therapeutic intervention included vasodilator therapy, which exacerbated the patient's condition. This case emphasized the importance of maintaining a high index of suspicion for rare causes of pulmonary hypertension, such as PCH. The outcome was to prepare the patient for lung transplantation. To differentiate PCH from other pulmonary vascular diseases, a combination of clinical presentation, radiologic studies, genetic analysis, and response to treatment is required to determine appropriate management, particularly lung transplantation.

Pulmonary arterial hypertension associated with portal hypertension: Noninvasive comprehensive assessment using computed tomography

Pulmonary arterial hypertension associated with portal hypertension, known as portopulmonary hypertension (PoPH) is one of the important and serious pulmonary complications in patients with portal hypertension. Although there are a large number of patients with portal hypertension due to mainly liver cirrhosis, the number of cases diagnosed with PoPH are far fewer because the causes of dyspnea in patients with cirrhosis are diverse and the disease entity of PoPH is poorly recognized by clinicians. We report here the case with PoPH suggested and assessed comprehensively by dual energy computed tomography (CT) including high-resolution pulmonary CT angiography, pulmonary perfusion imaging, myocardial late iodine enhancement imaging, and myocardial extracellular volume analysis. This refined CT imaging protocol can be used in conjunction with standard chest evaluation and offers a practical and useful approach for the noninvasive "one-stop shop" evaluation of PoPH.

Thoracic Applications of Spectral CT Scan

TOPIC IMPORTANCE

Thoracic imaging with CT scan has become an essential component in the evaluation of respiratory and thoracic diseases. Providers have historically used conventional single-energy CT; however, prevalence of dual-energy CT (DECT) is increasing, and as such, it is important for thoracic physicians to recognize the utility and limitations of this technology.

REVIEW FINDINGS

The technical aspects of DECT are presented, and practical approaches to using DECT are provided. Imaging at multiple energy spectra allows for postprocessing of the data and the possibility of creating multiple distinct image reconstructions based on the clinical question being asked. The data regarding utility of DECT in pulmonary vascular disorders, ventilatory defects, and thoracic oncology are presented. A pictorial essay is provided to give examples of the strengths associated with DECT.

SUMMARY

DECT has been most heavily studied in chronic thromboembolic pulmonary hypertension; however, it is increasingly being used across a wide spectrum of thoracic diseases. DECT combines morphologic and functional assessments in a single imaging acquisition, providing clinicians with a powerful diagnostic tool. Its role in the evaluation and treatment of thoracic diseases will likely continue to expand in the coming years as clinicians become more experienced with the technology.

Pulmonary veno-occlusive disease: illustrative cases and literature review

Pulmonary veno-occlusive disease (PVOD), also known as "pulmonary arterial hypertension (PAH) with overt features of venous/capillary involvement", is a rare cause of PAH characterised by substantial small pulmonary vein and capillary involvement, leading to increased pulmonary vascular resistance and right ventricular failure. Environmental risk factors have been associated with the development of PVOD, such as occupational exposure to organic solvents and chemotherapy, notably mitomycin. PVOD may also be associated with a mutation in the EIF2AK4 gene in heritable forms of disease. Distinguishing PVOD from PAH is critical for guiding appropriate management. Chest computed tomography typically displays interlobular septal thickening, ground-glass opacities and mediastinal lymphadenopathy. Life-threatening pulmonary oedema is a complication of pulmonary vasodilator therapy that can occur with any class of PAH drugs in PVOD. Early referral to a lung transplant centre is essential due to the poor response to therapy when compared with other forms of PAH. Histopathological analysis of lung explants reveals microvascular remodelling with typical fibrous veno-occlusive lesions. This review covers the main features distinguishing PVOD from PAH and two clinical cases that illustrate the challenges of PVOD management.

Thoracic Diseases: Technique and Applications of Dual-Energy CT

Dual-energy computed tomography (DECT) is one of the most promising technological innovations made in the field of imaging in recent years. Thanks to its ability to provide quantitative and reproducible data, and to improve radiologists' confidence, especially in the less experienced, its applications are increasing in number and variety. In thoracic diseases, DECT is able to provide well-known benefits, although many recent articles have sought to investigate new perspectives. This narrative review aims to provide the reader with an overview of the applications and advantages of DECT in thoracic diseases, focusing on the most recent innovations. The research process was conducted on the databases of Pubmed and Cochrane. The article is organized according to the anatomical district: the review will focus on pleural, lung parenchymal, breast, mediastinal, lymph nodes, vascular and skeletal applications of DECT. In conclusion, considering the new potential applications and the evidence reported in the latest papers, DECT is progressively entering the daily practice of radiologists, and by reading this simple narrative review, every radiologist will know the state of the art of DECT in thoracic diseases.

Diagnosis and management of pulmonary veno-occlusive disease

INTRODUCTION

Pulmonary veno-occlusive disease (PVOD) is an orphan disease and uncommon etiology of pulmonary arterial hypertension (PAH) characterized by substantial small pulmonary vein and capillary involvement.

AREAS COVERED

PVOD, also known as 'PAH with features of venous/capillary involvement' in the current ESC/ERS classification.

EXPERT OPINION

In recent years, particular risk factors for PVOD have been recognized, including genetic susceptibilities and environmental factors (such as exposure to occupational organic solvents, chemotherapy, and potentially tobacco). The discovery of biallelic mutations in the EIF2AK4 gene as the cause of heritable PVOD has been a breakthrough in understanding the molecular basis of PVOD. Venous and capillary involvement (PVOD-like) has also been reported to be relatively common in connective tissue disease-associated PAH (especially systemic sclerosis), and in rare pulmonary diseases like sarcoidosis and pulmonary Langerhans cell granulomatosis. Although PVOD and pulmonary arterial hypertension (PAH) exhibit similarities, including severe precapillary PH, it is essential to differentiate between them since PVOD has a worse prognosis and requires specific management. Indeed, PVOD patients are characterized by poor response to PAH-approved drugs, which can lead to pulmonary edema and clinical deterioration. Due to the lack of effective treatments, early referral to a lung transplantation center is crucial.

The spatial-temporal dynamics of pulmonary blood flow are altered in pulmonary arterial hypertension

Global fluctuation dispersion (FDglobal), a spatial-temporal metric derived from serial images of the pulmonary perfusion obtained with MRI-arterial spin labeling, describes temporal fluctuations in the spatial distribution of perfusion. In healthy subjects, FDglobal is increased by hyperoxia, hypoxia, and inhaled nitric oxide. We evaluated patients with pulmonary arterial hypertension (PAH, 4F, aged 47 ± 15, mean pulmonary artery pressure 48 ± 7 mmHg) and healthy controls (CON, 7F, aged 47 ± 12) to test the hypothesis that FDglobal is increased in PAH. Images were acquired at ∼4-5 s intervals during voluntary respiratory gating, inspected for quality, registered using a deformable registration algorithm, and normalized. Spatial relative dispersion (RD = SD/mean) and the percent of the lung image with no measurable perfusion signal (%NMP) were also assessed. FDglobal was significantly increased in PAH (PAH = 0.40 ± 0.17, CON = 0.17 ± 0.02, P = 0.006, a 135% increase) with no overlap in values between the two groups, consistent with altered vascular regulation. Both spatial RD and %NMP were also markedly greater in PAH vs. CON (PAH RD = 1.46 ± 0.24, CON = 0.90 ± 0.10, P = 0.0004; PAH NMP = 13.4 ± 6.1%; CON = 2.3 ± 1.4%, P = 0.001 respectively) consistent with vascular remodeling resulting in poorly perfused regions of lung and increased spatial heterogeneity. The difference in FDglobal between normal subjects and patients with PAH in this small cohort suggests that spatial-temporal imaging of perfusion may be useful in the evaluation of patients with PAH. Since this MR imaging technique uses no injected contrast agents and has no ionizing radiation it may be suitable for use in diverse patient populations.NEW & NOTEWORTHY Using proton MRI-arterial spin labeling to obtain serial images of pulmonary perfusion, we show that global fluctuation dispersion (FDglobal), a metric of temporal fluctuations in the spatial distribution of perfusion, was significantly increased in female patients with pulmonary arterial hypertension (PAH) compared with healthy controls. This potentially indicates pulmonary vascular dysregulation. Dynamic measures using proton MRI may provide new tools for evaluating individuals at risk of PAH or for monitoring therapy in patients with PAH.

Perfusion imaging heterogeneity during NO inhalation distinguishes pulmonary arterial hypertension (PAH) from healthy subjects and has potential as an imaging biomarker

BACKGROUND

Without aggressive treatment, pulmonary arterial hypertension (PAH) has a 5-year mortality of approximately 40%. A patient's response to vasodilators at diagnosis impacts the therapeutic options and prognosis. We hypothesized that analyzing perfusion images acquired before and during vasodilation could identify characteristic differences between PAH and control subjects.

METHODS

We studied 5 controls and 4 subjects with PAH using HRCT and ¹³NN PET imaging of pulmonary perfusion and ventilation. The total spatial heterogeneity of perfusion (CV²_Qtotal) and its components in the vertical (CV²_Qvgrad) and cranio-caudal (CV²_Qzgrad) directions, and the residual heterogeneity (CV²_Qr), were assessed at baseline and while breathing oxygen and nitric oxide (O₂ + iNO). The length scale spectrum of CV²_Qr was determined from 10 to 110 mm, and the response of regional perfusion to O₂ + iNO was calculated as the mean of absolute differences. Vertical gradients in perfusion (Q_vgrad) were derived from perfusion images, and ventilation-perfusion distributions from images of ¹³NN washout kinetics.

RESULTS

O₂ + iNO significantly enhanced perfusion distribution differences between PAH and controls, allowing differentiation of PAH subjects from controls. During O₂ + iNO, CV²_Qvgrad was significantly higher in controls than in PAH (0.08 (0.055-0.10) vs. 6.7 × 10^-3 (2 × 10^-4-0.02), p < 0.001) with a considerable gap between groups. Q_vgrad and CV²_Qtotal showed smaller differences: - 7.3 vs. - 2.5, p = 0.002, and 0.12 vs. 0.06, p = 0.01. CV²_Qvgrad had the largest effect size among the primary parameters during O₂ + iNO. CV²_Qr, and its length scale spectrum were similar in PAH and controls. Ventilation-perfusion distributions showed a trend towards a difference between PAH and controls at baseline, but it was not statistically significant.

CONCLUSIONS

Perfusion imaging during O2 + iNO showed a significant difference in the heterogeneity associated with the vertical gradient in perfusion, distinguishing in this small cohort study PAH subjects from controls.