Research Presentation Session: Chest

RPS 1704 - Novel technological developments in chest imaging: from research to practice

March 2, 08:00 - 09:00 CET

7 min
Assessment of lung perfusion using dynamic digital radiography and comparison with nuclear medicine lung scintigraphy
Satinder Singh, Birmingham / United States
Author Block: S. Singh, R. Sai, P. Manapragada, D. Benson; Birmingham, AL/US
Purpose: Assessment of lung perfusion is required in the preoperative evaluation of patients being considered for lung transplant or resection. Dynamic digital radiography (DDR) is a newer radiographic technique that acquires rapid sequential diagnostic radiographs of the chest throughout multiple respiratory cycles. The regional lung perfusion can be estimated using DDR by assessing pixel signal changes throughout the cardiac cycle. This study will compare the results of the differential lung perfusion estimated using DDR with the same results obtained from lung scintigraphy, a conventional imaging modality.
Methods or Background: A retrospective review of patients evaluated with both nuclear medicine lung scintigraphy and DDR was performed. The DDR examinations were performed between January 14, 2022, and July 27, 2023. Each patient had a lung scintigraphy perfusion study within six months of the DDR examination. The percent differential of perfusion between the lungs was calculated using both modalities and the results were analyzed for statistical correlation.
Results or Findings: Results for 75 patients were reviewed (mean age - 56 years, 32 Females). The mean absolute percent differential in perfusion between the right and left lungs was (14.7 ± 23.1%) using DDR and (15.08 ± 24.76%) using lung scintigraphy. There were five patients in which there was a discrepancy between the two modalities in determining which lung was better perfused. The Pearson coefficient of correlation was (0.915) indicating a strong correlation between the perfusion results obtained by the two modalities.
Conclusion: Differential lung perfusion estimated by DDR is strongly correlated with the same result obtained using lung scintigraphy. The speed and cost-effectiveness of DDR make it an attractive option for clinicians, potentially reducing wait times and healthcare costs for patients.
Limitations: Small numbers. Need more refined computer analysis.
Funding for this study: No funding was received for this study.
Has your study been approved by an ethics committee? Yes
Ethics committee - additional information: The study is IRB approved.
7 min
Silver x-ray spectrum modulation filter for lung cancer screening: comparison of capability for radiation dose reduction and detection performance with copper filter
Yoshiharu Ohno, Toyoake / Japan
Author Block: Y. Ohno1, H. KImata2, Y. Ito2, K. Fujii2, N. Akino2, H. Nagata1, M. Nomura1, T. Ueda1, Y. Ozawa1; 1Toyoake/JP, 2Otawara/JP
Purpose: The purpose of this study was to compare the capability of low-dose lung cancer CT screening between silver (Ag) and copper (Cu) x-ray spectral modulation filters at in vitro and in vivo studies.
Methods or Background: A chest CT phantom including simulated ground-glass and part-solid nodules was scanned with a 320-detector row CT with Ag and Cu filters at 0.6, 1.6 and 2.5 mGy at in vitro study. Then, 95 patients underwent low-dose CT lung cancer screening with Ag and Cu filters at the same radiation dose level (i.e. 1.6 mGy) as in the in vivo study. At in vitro study, SNR at each nodule were determined by region of interest (ROI) measurements at all protocols. At in vivo study, SNR of normal lung parenchyma was also determined by ROI measurement at each CT. Then, the probability of a nodule was assessed with 5-point visual score by two board-certified chest radiologists at both studies. Student's t-test was performed to compare SNR between Ag and Cu filters at each study. ROC and JAFROC analyses were performed to compare nodule detection capability between Ag and Cu filters.
Results or Findings: At in vitro study, SNR and AUC of Ag filter were significantly better than those of Cu filter at each dose level (p <0.05). At in vivo study, SNR of Ag filter was significantly higher than that of Cu filter (p <0.05), although no significant differences of averaged figure of merit were determined.
Conclusion: Low-dose CT screening with Ag filter can significantly improve image quality compared to screening using a Cu filter.
Limitations: This was a single institution study.
Funding for this study: This study received funding via a research grant from Canon Medical Systems Corporation.
Has your study been approved by an ethics committee? Yes
Ethics committee - additional information: IRB approval was received (Fujita Health University Hospital).
7 min
Ultra-low-dose photon-counting detector CT for imaging follow-up after lung transplantation
Ruxandra-Iulia Milos, Vienna / Austria
Author Block: L. Lechner, R-I. Milos, A. Korajac, D. Kifjak, D. Tamandl, M. Stuempflen, M. Watzenböck, A. E. Strassl, H. Prosch; Vienna/AT
Purpose: CT surveillance is performed in patients after lung transplantation for the detection of subclinical abnormalities. We assessed the potential of ultra-low-dose (ULD) photon-counting detector computed tomography (PCD-CT) when compared to routinely performed low-dose (LD) PCD-CT for the follow-up in lung transplanted patients.
Methods or Background: For this prospective study adult patients underwent same-day ULD and LD PCD-CT (with inspiration and expiration scans for each radiation dose protocol) between March and May 2023. The 1 mm reconstructions ULD and LD scans were reviewed by three readers who independently assessed the subjective image quality of anatomical structures (using visual grading analysis, VGA, scores) and the presence of lung abnormalities (evaluated as present or absent). Interrater agreement was calculated using Fleiss' kappa.
Results or Findings: 83 patients (median age 62 years, 36 women) were included. The radiation dose of the ULD protocol comprised on average 15% of the one for LD protocol. For anatomical structures all readers rated ULD scans adequate to excellent in the majority of patients (92.8 - 97.6% for bronchial wall, 91.6 - 94% for fissures, and 80.7 - 100% for peripheral vessels). Interrater agreement was better on the LD protocol for the detection of ground glass opacities, consolidations, and atherosclerosis (0.61 vs 0.50; 0.68 vs 0.6; 0.94 vs 0.72), and better for the ULD protocol for the detection of air trapping, tree-in-bud, bronchial wall thickening and nodules greater than 5 mm (0.66 vs 0.57; 0.69 vs 0.56; 0.44 vs 0.31; 0.45 vs 0.19). Both LD and ULD protocols showed comparable agreement for the detection of reticulations, linear atelectasis and distal bronchiectasis (between 0.18 and 0.37).
Conclusion: ULD PCD-CT offers sufficient image quality and is a feasible option for post-lung transplantation patient surveillance.
Limitations: No limitations were identified.
Funding for this study: No funding was provided for this study.
Has your study been approved by an ethics committee? Yes
Ethics committee - additional information: The ethics committee notification can be found under the number EK Nr: 1891/2022.
7 min
Low-dose high-resolution photon-counting CT in patients with cycstic fibrosis: radiation dose and image quality in the clinical routine
Marko Frings, Essen / Germany
Author Block: M. Frings, M. Welsner, S. Zensen, J. Haubold, D. Bos, L. Umutlu, B. M. Schaarschmidt, M. Forsting, M. Opitz; Essen/DE
Purpose: Patients with cystic fibrosis routinely undergo low-dose high-resolution (LD-HR) CT scans as part of their clinical management, primarily for monitoring chronic exacerbations or assessing treatment response with the triple-combination CFTR modulator therapy elexacaftor/tezacaftor/ivacaftor. The aim of this study is to compare the radiation dose and image quality of LD-HR protocols between photon-counting CT (PCCT) and CT scanner with an energy-integrating detector system (EID-CT) in this patient cohort.
Methods or Background: Thirty-five patients who underwent a LD-HR chest CT scan with PCCT and had previously undergone a LD-HR chest CT with a standard EID-CT scanner were retrospectively included in this study. The dose-length product (DLP), volumetric CT-dose index (CTDIvol) and singal-to-noise ratio (SNR) were determined and explorative data analysis was performed. The overall image quality, image sharpness, and image noise of both full lung scans and enlarged sections highlighting specific findings were assessed by three radiologists using a 5-point Likert scale.
Results or Findings: The PCCT used significantly less radiation dose compared to the EID-CT (P <0.001), approximately 36%. PCCT consistently received significantly better ratings for overall image quality and image sharpness compared to EID CT (P <0.003). Additionally, PCCT exhibited significantly lower image noise (P <0.004) and a lower average signal-to-noise ratio (SNR) compared to EID CT (P <0.005).
Conclusion: Lung PCCT scans in patients with CF offer superior image quality while utilising substantially lower radiation doses in comparison to EID-CT scans.
Limitations: The limitations of this study are its retrospective and single-centre study design.
Funding for this study: No funding was received for this study.
Has your study been approved by an ethics committee? Yes
Ethics committee - additional information: This study was approved by an ethics committee.
7 min
Optimal slice thickness and quantum iterative reconstruction level in low-dose ultra-high-resolution photon-counting detector CT of the lungs
Dirk Graafen, Mainz / Germany
Author Block: D. Graafen1, M. C. Halfmann1, T. S. Emrich1, Y. Yang1, C. Düber1, R. Klöckner2, L. Müller1, T. Jorg1; 1Mainz/DE, 2Lübeck/DE
Purpose: Using photon-counting detector computed tomography (PCD-CT) alongside an innovative iterative reconstruction technique called quantum iterative reconstruction (QIR) holds the promise of significantly improving the quality of lung images. This research aimed to investigate how various QIR levels and different slice thicknesses affect the image quality of low-dose ultra-high-resolution (UHR) PCD-CT in lung examinations.
Methods or Background: The study involved 51 patients who underwent unenhanced UHR-PCD-CT scans. The images were reconstructed using a 1024 matrix. Three slice thicknesses (1.0 mm, 0.4 mm, and 0.2 mm) were employed, along with three different QIR levels (2 to 4). Noise levels were calculated for all reconstructions. To evaluate the image quality in comparison to the clinical reference reconstruction (1.0 mm QIR-3), three radiologists rated the sharpness of different lung structures and the conspicuity of various lung abnormalities in the images using a 5-point Likert scale.
Results or Findings: The highest QIR level (QIR-4) reduced image noise effectively and received the best image quality ratings. Decreasing the slice thickness to 0.4 mm enhanced the sharpness of pulmonary structures and the conspicuity of different pathologies. However, when the thickness was reduced to 0.2 mm, the images were significantly affected by noise, resulting in a notable decline in quality scores.
Conclusion: The ideal reconstruction approach for low-dose UHR-PCD-CT lung imaging is to use a slice thickness of 0.4 mm together with the highest QIR level. The clinical implementation of this optimised UHR-PCD-CT protocol could potentially enhance the accuracy of diagnoses and boost confidence in lung imaging.
Limitations: Limitations of the study are the single-centre design and the small sample size of some lung pathologies.
Funding for this study: This research received no external funding.
Has your study been approved by an ethics committee? Yes
Ethics committee - additional information: The study was approved by the Institutional Ethics Committee of Rhineland-Palatinate (Reg. Nr. 2022-16359).
7 min
The feasibility and accuracy of using low- and ultra-low-dose photon counting detector CT to detect metastatic lung nodules in paediatric and young adults with malignant bone tumours
Shanshui Zhou, Shanghai / China
Author Block: S. Zhou, L. Qin, Z. Xu, F. Yan; Shanghai/CN
Purpose: We aimed to investigate the feasibility of low- and ultra-low-dose photon counting detector CT (PCD-CT) for chest CT follow-ups in paediatric and young adults with pulmonary metastasis of bone malignant tumours, and compare the accuracy of PCD-CT with intra-patient previous energy-integrating detector CT (EID-CT).
Methods or Background: 83 subjects (male/female, 52/31) aged 19 [15; 21] years with prior chest EID-CT scans participated in low-dose (IQ level=16, n=43) and ultra-low-dose (IQ level=10, n=40) chest PCD-CT scanning with a tube voltage of Sn100. The contrast-noise-ratio (CNR), figure of merit for CNR (FOMCNR, normalising the CNR to effective dose), and edge sharpness of maximum nodule were calculated. Moreover, a 5-point Likert scale was used to subjectively evaluate the image quality.
Results or Findings: The low-dose and ultra-low-dose groups with effective doses of 0.40 [0.35; 0.44] and 0.22 [0.16; 0.27] mSv, which were 7.67 and 14.42 times lower than EID-CT, achieved a mean detection rate of 93.56% and 84.48% for preexisting lung nodules, respectively. PCD-CT with higher FOMCNR and sharpness but lower CNR than EID-CT (all P <0.05). In the low-dose group, in detail, the CNR, FOMCNR, and sharpness were 18.7 [14.8; 24.0] vs 19.7 [14.1; 26.2], 915 [632; 1578] vs 128 [63.2; 268], and 543 [446; 704] vs 422 [344; 545] Hounsfield Unit (HU)/pixel for PCD-CT and EID-CT, respectively. In the ultra-low-dose group, these values were 17.1 [15.4; 20.7] vs 22.4 [16.6; 26.6], 1490 [955; 2441] vs 150 [96; 207], and 594 [464; 752] vs 445 [362; 617] HU/pixel, respectively. PCD-CT showed statistically significant superiority in the image quality, motion artifacts, and display of lung nodules and skeleton, but inferior in the presentation of mediastinal lymph nodes and lung markings compared to EID-CT (P <0.05).
Conclusion: PCD-CT allowed reliable detection of metastatic lung nodules with significant radiation dose reduction.
Limitations: This technique has relatively poor visualisation of soft tissues, but it does not compromise the detection of crucial structures like lymph nodes.
Funding for this study: No funding was received for this study.
Has your study been approved by an ethics committee? Yes
Ethics committee - additional information: The study received institutional review board approval and written informed consent was waived.

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