Abstract: Objective To compare the sensitivity,specificity and accuracy between pulmonary V/Q SPECT and planar V/Q imaging using pigs with artificially engendered lung emboli labeled with ²⁰¹Tl.To investigate the value of ventilation imaging in the diagnosis of pulmonary embolism(PE).To investigate the value of V/Q imaging in the diagnosis of subsegmental pulmonary embolism(PE).To understand how the different acquisition parameters of V/Q SPECT imaging,i.e.different matrix size(64×64 matrix,128×128 matrix),type of collimator(low energy general purpose collimator,high resolution collimator) and different enlargement factor used will affect the data gathering process.Methods Using different acquisition parameters in ⁹⁹Tc^m windows,SPECT and planar pulmonary perfusion imaging were done on the sixteen small experimental pigs before being embolized.Each pigs was subsequently injected with zero to 3 latex flat emboli and a planar and SPECT pulmonary ventilation imaging was performed in ⁹⁹Tc^m and ²⁰¹Tl windows,followed with planar and SPECT pulmonary perfusion imaging in ⁹⁹Tc^m windows.Lastly,X-ray、CT scan and lung autopsy were done to ascertain the definite embolus position.Results Of the 28 emboli,17 are lodged in the left lungs and 11 are located in the right lungs.The planar images of these pig,sensitivity,specificity and accuracy were 75%,75% and 75%,respectively,whereas V/Q SPECT yielded 100%,75% and 96.9%,respectively.Conclusion Pulmonary V/Q SPECT imaging is more sensitive and more accurate than planar imaging,but specificity is the same for both.A combination of pulmonary ventilation imaging and perfusion imaging may enhance the diagnostic power of PE.Pulmonary V/Q SPECT imaging may enhance the diagnostic power for the detection of lesions at the subsegmental level.Using low energy general purpose collimator,128×128 matrix for planar imaging and Zoom 1.46 for SPECT will satisfy the demand of diagnosis and clinic.

Key words: pulmonary planar V/Q imaging, pulmonary V/Q SPECT imaging, pulmonary embolism(PE)