Use of SPECT/CT to assess changes in regional lung function following radical radiotherapy

  • Ms Elizabeth Bailey, Dept Nuclear Medicine, Royal North Shore Hospital and University of Sydney, Discipline of Medical Radiation Sciences, Sydney, Australia
  • A/Prof Dale Bailey, Dept Nuclear Medicine, Royal North Shore Hospital and University of Sydney, Discipline of Medical Radiation Sciences, Sydney, Australia
  • Dr Ben Harris, Dept Respiratory Medicine, Royal North Shore Hospital and Woolcock Institute of Medical Research, Sydney, Australia, Australia
  • Dr Gillian Lamoury, Radiation Oncology Department, Royal North Shore Hospital, Sydney, Australia, Australia
  • Dr Thomas Eade, Radiation Oncology Department, Royal North Shore Hospital, Sydney, Australia, Australia
  • Dr Greg King, Respiratory Medicine, Royal North Shore Hospital and Woolcock Institute of Medical Research, Sydney, Australia, Australia
  • Prof Jenny Cox, University of Sydney, Discipline of Medical Radiation Sciences, Sydney, Australia, Australia

    • Background: Radiotherapy to lungs gives large dose to surrounding lung, resulting in regional lung damage.

    Aim: Assess regional lung function for ventilation (V) and perfusion (Q) using individual patient dose fields to determine if dose delivered to lung tissue correlates with degree of change in lung function.

    Methods: Subjects with non-resectable lung cancer treated with radiotherapy (RT) underwent V/Q SPECT/CT at baseline, 3 and 6 months post treatment. Lung V20, V30, mean lung dose and prescribed dose recorded, including history pneumonitis. V/Q SPECT/CT reconstructed using OSEM with CT-based scatter and attenuation correction, and registered to RT planning CT. RT dose fields segmented into discrete ROIs for 1-20Gy, 21-30Gy, 31-40Gy, 41-50Gy and >50Gy, to calculate fractional lung function (%) in these regions for V&Q at baseline, 3 and 6 months.

    Results: Total 11 subjects recruited with 7 having 3 month follow-up (FU) and 3 having 6 month FU, receiving between 44Gy and 66Gy, with 1 not completing treatment. Decrease in lung function for V and Q between baseline and 3 month FU at dose >50Gy seen in all cases, with average V=3.7% (0.34-13.2%) and Q=4% (0.92-10.5%). Corresponding increase in relative function seen in regions receiving <20Gy, with average V=6.1% (1.4-16.9%) and Q=6.3% (1.75-12.7%).

    Conclusion: Following radiotherapy to chest, ventilation and perfusion lung function changes due to dose delivered. Areas receiving high doses (>50Gy) have decrease in function with corresponding increase at doses <20Gy, possibly resulting from function being shunted to these areas due to regional lung damage in high dose fields.