Characterization of mesothelioma and tissues present in contrast-enhanced thoracic CT scans

Our plain-English summary of Characterization of mesothelioma and tissues present in contrast-enhanced thoracic CT scans, by N. Corson, W.F. Sensakovic, C. Straus, et al (Medical Physics, 2011).

The study

• Authors: N. Corson, W.F. Sensakovic, C. Straus, A. Starkey, S.G. Armato
• Journal: Medical Physics
• Published: 2011;38(2):942-7
• Cited by: 19 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Purpose: The purpose of this study was to characterize the Hounsfield unit (HU) distributions of mesothelioma and other tissues present in contrast-enhanced thoracic CT scans, to compare the HU distributions of mesothelioma, muscle, and liver by scanner and reconstruction filter/kernel combination, and to assess interpatient HU distribution variability.

Methods: The database consisted of 28 contrast-enhanced thoracic CT scans from different patients. For each scan, regions of interest were manually outlined within each of 13 tissues, including mesothelioma. For each tissue, the empirical percentiles in HU values were calculated along with the interpatient variability. The HU distributions of select tissues were compared across three different scanner and reconstruction filter/kernel combinations.

Results: The HU distributions of blood-containing tissues demonstrated substantial overlap, as did the HU distributions of pleural effusion, mesothelioma, muscle, and liver. The HU distribution of fat had the least overlap with the other tissues. Fat and muscle had the lowest interpatient HU variability and the narrowest HU distributions, while blood-containing tissues had the highest interpatient HU variability. A soft-tissue reconstruction filter/kernel yielded the narrowest HU distribution, and fat with artifact had the widest HU distribution.

Conclusions: Characterization of tissues in CT scans enhances the understanding of those tissues' HU distributions. Due to their overlapping HU distributions and close spatial proximity to one another, separating pleural effusion, mesothelioma, muscle, and liver from one another is a difficult task based on HU value thresholding alone. The results illustrate the wide distributions and large variability that exist for tissues present in clinical thoracic CT scans.

In plain English

This study did not examine asbestos exposure. It examined how mesothelioma and other tissues appear on chest CT scans, to help design computer programs that outline tissues automatically. University of Chicago radiology researchers reviewed 28 contrast-enhanced chest CT scans from 28 mesothelioma patients (23 men and 5 women, aged 50 to 83). The scans were made on three Philips scanners. One observer outlined small areas within 13 tissues, including mesothelioma, pleural effusion, muscle, liver and fat. The authors then measured the spread of CT brightness values (Hounsfield units) in each tissue. Values for mesothelioma tended to fall between those of pleural effusion (lower) and those of muscle and liver (higher), and these four tissues overlapped heavily. Fat overlapped least with the other tissues, and fat and muscle varied least from patient to patient. For mesothelioma, muscle and liver, a soft-tissue image setting gave narrower ranges of values than a bone setting. The authors concluded that separating mesothelioma, effusion, muscle and liver by brightness thresholds alone is difficult. They noted that the study had only 28 patients and used scanners from one manufacturer.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Retrospective imaging analysis: measurement of CT brightness values (Hounsfield units) in hand-drawn regions of interest on existing CT scans
• Who was studied: 28 contrast-enhanced thoracic CT scans from 28 mesothelioma patients (23 male, 5 female, age 50–83), scanned at the University of Chicago Medical Center on three Philips CT scanners; dates of scanning not given
• Exposure: No asbestos or other exposure was studied. The variables compared were tissue type (13 tissues, including mesothelioma) and scanner/reconstruction filter combination (soft-tissue setting B/B versus bone setting D/D).
• Main results:
  • Across all scans, mesothelioma values tended to fall between those of pleural effusion (lower values) and those of muscle and liver (higher values), with overlap among these four tissues
  • Fat had a narrow distribution, low variability between patients, and limited overlap with other tissues
  • Fat and muscle had the lowest variability between patients; blood-containing tissues had the highest
  • For mesothelioma, muscle and liver (the only tissues compared across scanner settings), the soft-tissue reconstruction setting (B/B) gave narrower ranges of values than the bone setting (D/D)
  • For mesothelioma, between-patient variability on the 16P D/D and 64 D/D combinations was high because each had an outlier; with outliers removed it was 13 HU for each
  • Mesothelioma regions were available in fewer than all 28 scans, because the tissue was not present in every scan
• The authors' conclusion: The authors concluded that because of overlapping values and close placement in the body, computer outlining of mesothelioma, pleural effusion, muscle and liver will need methods more complex than simple brightness thresholding. They considered fat a good candidate for threshold-based outlining.
• Limitations the authors state:
  • Small database of 28 patients; a larger database would give more robust results
  • Only Philips scanners were examined
  • Variability due to other image acquisition settings was not evaluated
  • Variability within the same patient across repeated scans was not studied

Topics

The National Library of Medicine indexes this study under subjects our site covers: Mesothelioma.

Medical terms in this study, explained in our Lexicon: Mesothelioma, CT Scan, Pleural Effusion.

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