Computed chest radiography for total body irradiation: image quality and clinical feasibility

Abstract

Objective. In myeloablative total body irradiation (TBI), lung shielding
blocks are used to reduce the dose to the lungs and hence decrease the risk of radiation
pneumonitis. Some centers are still using mega-Volt (MV) imaging with dedicated
silver halide-based films during simulation and treatment for lung delineation and
position verification. However, the availability of these films has recently become
an issue. This study examines the clinical performance of a computed radiography
(CR) solution in comparison to radiographic films and potential improvement of image
quality by filtering and post-processing. Approach. We compared BaFBrI-based CR
plates to radiographic films. First, images of an aluminum block were analyzed to
assess filter impact on scatter reduction. Secondly, a dedicated image quality phantom
was used to assess signal linearity, signal-to-noise ratio (SNR), contrast and spatial
resolution. Ultimately, a clinical performance study involving two impartial observers
was conducted on an anthropomorphic chest phantom, employing visual grading
analysis (VGA). Various filter materials and positions as well as post-processing were
examined, and the workflow between CR and film was compared. Main results. CR
images exhibited high SNR and linearity but demonstrated lower spatial and contrast
resolution when compared to film. However, filtering improved contrast resolution
and SNR, while positioning filters inside the cassette additionally enhanced sharpness.
Image processing improved VGA scores, while additional filtering also resulted in
higher spine visibility scores. CR shortened TBI simulation by over 10 minutes for
one patient, alongside a dose reduction by order of 0.1 Gy. Significance. This study
highlights potential advantages of shifting from conventional radiographic film to CR
for TBI. Overall, CR with the incorporation of processing and filtering proves to
be suitable for TBI chest imaging. When compared to radiographic film, CR offers
advantages such as reduced simulation time and dose delivery, re-usability of image
plates and digital workflow integration.