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D. Moses



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    P1.08 - Poster Session 1 - Radiotherapy (ID 195)

    • Event: WCLC 2013
    • Type: Poster Session
    • Track: Radiation Oncology + Radiotherapy
    • Presentations: 1
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      P1.08-006 - Inter-observer variability of GTV delineation based on Lung MRI: impact of radiologist led workshop (ID 779)

      09:30 - 09:30  |  Author(s): D. Moses

      • Abstract

      Background
      Magnetic Resonance Imaging (MRI) with its superior soft tissue contrast resolution has the potential to improve Gross Tumour Volume (GTV) delineation of lung cancer. The aim of this study was to assess the inter-observer variability between observers for MRI based GTV delineation for Lung cancer and evaluate whether this factor changed following a GTV delineation workshop with a thoracic radiologist.

      Methods
      Five radiation oncologists from three different institutions were asked to delineate GTV on 3 patient datasets. Each observer was given a planning CT, PET, T1 and T2 weighted 1.5 T MRI datasets along with patient history and relevant diagnostic test results. Each observer was instructed to delineate a primary GTV and nodal GTV as required on the T1 and T2 weighted MRI datasets (pre workshop contours). A workshop was then conducted. The aim of the workshop was to discuss each case with a thoracic radiologist and for the radiologist to educate each of the observers in how to review thoracic MRI for both T1 and T2 weighted images. Following the workshop each observer delineated a post workshop GTV. Conformity index (CI) was used to evaluate improvement in inter-observer variability between pre and post workshop contours.

      Results
      Results of two observers are presented here. For patients 1 and 3 slight improvement in CI was noted between pre and post primary and nodal GTV for T1 and T2 weighted datasets. Similarly for patient 3 slight improvements were noted in inter-observer variability for primary GTV for both T1 and T2 weighted images. However there was significant improvement in both T1 and T2 weighted nodal GTV. CI improved from 0.2 to 0.6 and 0-0.6 for T1 and T2 weighted images respectively.

      Conclusion
      Preliminary results from this study indicate that a radiologist led workshop assisted in improving inter-observer variability for MRI based GTV delineation. Further analysis of all observers is required to assess the significance of the impact of a radiologist led contouring workshop in improving inter-observer variability on MRI delineation of lung cancer.

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    P3.08 - Poster Session 3 - Radiotherapy (ID 199)

    • Event: WCLC 2013
    • Type: Poster Session
    • Track: Radiation Oncology + Radiotherapy
    • Presentations: 1
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      P3.08-010 - The potential use of MRI to delineate lung cancer volumes for radiotherapy (ID 1344)

      09:30 - 09:30  |  Author(s): D. Moses

      • Abstract

      Background
      The use of MRI for lung cancer volume delineation for radiotherapy is rare. This has been due to poor image quality as a result of physical and physiological factors such as low proton density, susceptibility effects and respiratory and cardiac motion. However as MRI technology has improved, imaging of lung abnormalities has become more feasible. A prospective study was therefore conducted to evaluate image quality for lung tumour delineation on a 1.5T (Tesla) and 3T MRI scanner. The aim of the study was to identify potential scan sequences that could be used clinically for tumour delineation for radiation therapy treatment.

      Methods
      Ten patients with lung cancer underwent MRI, five on a 1.5T GE scanner using a body phased array coil and five on a 3T Phillips scanner. Scans on the 1.5T scanner were undertaken with breath hold and scans on the 3T scanner were performed with respiratory and peripheral pulse gating to give optimal image quality. The thorax was imaged with T2 and T1 weighted sequences on both field strengths. Cine mode imaging to compare tumour motion was also acquired. Scan sequence was matched for the 1.5T and 3T scanners. The quality of images for lung cancer delineation was assessed by an experienced thoracic radiologist and thoracic radiation oncologist using a four point scale. A consensus score ranging from 1(superior) to 4 (inferior) was given for each sequence based on four categories; tumour edge detection, image artefacts, noise affecting edge detection and overall image quality. A score of 2 or below was considered clinically acceptable

      Results
      Both magnet strengths provided reasonable image quality to define tumour volume on lung MRI. The average score for overall image quality between the two scanners was 1.8 for 1.5T and 1.3 for the 3T scanner. For the 1.5T scanner the sagittal and coronal T2 weighted scan scored the best for overall image quality for tumour delineation (1.53), due to limited respiratory motion distortion. However these image planes are not compatible with radiotherapy planning systems. For the 3T scanner the axial T2 images scored best for overall image quality (1.05). For tumour edge detection the sagittal and coronal and T1 weighted images scored best (1.75) for the 1.5T scanner. The axial T2 weighted image and the sagittal cine mode performed best for tumour edge detection (1). Overall sequences on the 3T scanner were rated higher than those on the 1.5T scanner

      Conclusion
      It is feasible to utilise commercially available MRI sequences to acquire images of acceptable quality for the purposes of lung cancer delineation in radiotherapy. Both magnet strengths gave acceptable image quality for clinical use in radiotherapy, with the 3T magnet displaying slightly better image quality. A future study will compare lung cancer delineation between the current standard practice of CT&PET with MRI.