Preoperative detection of pleural adhesions using dynamic chest radiography: prospective analysis

Recent trends in scientific research in chest radiology: What to do or not to do? That is the critical question in research

Hereby inviting young rising stars in chest radiology in Japan for contributing what they are working currently, we would like to show the potentials and directions of the near future research trends in the research field. I will provide a reflection on my own research topics. At the end, we also would like to discuss on how to choose the themes and topics of research: What to do or not to do? We strongly believe it will stimulate and help investigators in the field.

The utility of the low motion area ratio for the preoperative detection of pleural adhesions: dynamic chest radiography analysis

Background

Dynamic chest radiography (DCR) is useful for detecting preoperative pleural adhesions, predicting operation time and blood loss, and determining the surgical approach. However, since DCR evaluations are subjective, an objective index was needed. Therefore, we focused on the low motion area (LMA) ratio derived from the objective data obtained through DCR. The purpose of this study was to examine the relationship between the LMA ratio and pleural adhesions, as well as to evaluate its cutoff values, detectability, and overall utility.

Methods

The study encompassed patients who received DCR prior to thoracic surgery from January 2020 to December 2023. The LMA ratio was calculated using an analysis workstation for DCR. Pleural adhesions were defined as adhesions extending to >20% of the thoracic cavity and/or taking >5 min to dissect. The relationship between the presence of pleural adhesions and the LMA ratio was analyzed retrospectively.

Results

A total of 338 patients were analyzed, of whom 65 had pleural adhesions. The median LMA ratio for patients with adhesions was 56.0%, while that of patients without adhesions was 41.5%, which amounted to a significant difference (P<0.001). This was also true in the group of patients with pulmonary comorbidities (56.0% vs. 41.0%, P<0.001). When the analysis was limited to the group of patients with a large lung field change rate (>28.2%; n=169), the power of detection using the LMA ratio improved [52.0% vs. 36.9%, area under the curve (AUC) =0.748]. When the two groups were further divided according to the extent of adhesion, the LMA ratio was significantly higher for extensive adhesions (49.8% in grade 1, the narrow adhesion, and 66.1% in grades 2-4, the extensive adhesion).

Conclusions

The LMA ratio is a useful objective index for detecting pleural adhesions. Adding the cutoff value of the LMA ratio (approximately 50%) to the conventional criteria may allow for a more reproducible preoperative assessment.

Dynamic Digital Radiography (DDR) in the Diagnosis of a Diaphragm Dysfunction

Dynamic digital radiography (DDR) is a recent imaging technique that allows for real-time visualization of thoracic and pulmonary movement in synchronization with the breathing cycle, providing useful clinical information. A 46-year-old male, a former smoker, was evaluated for unexplained dyspnea and reduced exercise tolerance. His medical history included a SARS-CoV-2 infection in 2021. On physical examination, decreased breath sounds were noted at the right-lung base. Spirometry showed results below predicted values. A standard chest radiograph revealed an elevated right hemidiaphragm, a finding not present in a previous CT scan performed during his SARS-CoV-2 infection. To better assess the diaphragmatic function, a posteroanterior DDR study was performed in the standing position with X-ray equipment (AeroDR TX, Konica Minolta Inc., Tokyo, Japan) during forced breath, with the following acquisition parameters: tube voltage, 100 kV; tube current, 50 mA; pulse duration of pulsed X-ray, 1.6 ms; source-to-image distance, 2 m; additional filter, 0.5 mm Al + 0.1 mm Cu. The exposure time was 12 s. The pixel size was 388 × 388 μm, the matrix size was 1024 × 768, and the overall image area was 40 × 30 cm. The dynamic imaging, captured at 15 frames/s, was then assessed on a dedicated workstation (Konica Minolta Inc., Tokyo, Japan). The dynamic acquisition showed a markedly reduced motion of the right diaphragm. The diagnosis of diaphragm dysfunction can be challenging due to its range of symptoms, which can vary from mild to severe dyspnea. The standard chest X-ray is usually the first exam to detect an elevated hemidiaphragm, which may suggest motion impairment or paralysis but fails to predict diaphragm function. Ultrasound (US) allows for the direct visualization of the diaphragm and its motion. Still, its effectiveness depends highly on the operator's experience and could be limited by gas and abdominal fat. Moreover, ultrasound offers limited information regarding the lung parenchyma. On the other hand, high-resolution CT can be useful in identifying causes of diaphragmatic dysfunction, such as atrophy or eventration. However, it does not allow for the quantitative assessment of diaphragmatic movement and the differentiation between paralysis and dysfunction, especially in bilateral dysfunction, which is often overlooked due to the elevation of both hemidiaphragms. Dynamic Digital Radiography (DDR) has emerged as a valuable and innovative imaging technique due to its unique ability to evaluate diaphragm movement in real time, integrating dynamic functional information with static anatomical data. DDR provides both visual and quantitative analysis of the diaphragm's motion, including excursion and speed, which leads to a definitive diagnosis. Additionally, DDR offers a range of post-processing techniques that provide information on lung movement and pulmonary ventilation. Based on these findings, the patient was referred to a thoracic surgeon and deemed a candidate for surgical plication of the right diaphragm.