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/CNPurpose: 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 Sn- 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 - 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? YesEthics committee - additional information: The study received institutional review board approval and written informed consent was waived.