Keywords:
Thorax, Pulmonary vessels, CT, Plain radiographic studies, Computer Applications-General, Computer Applications-Detection, diagnosis, Education and training, Image verification
Authors:
J. Shin, A. Gupta; WA/AU
DOI:
10.26044/ranzcr2019/R-0026
Purpose
Anatomical structures depicted on the lateral chest radiograph have been studied as far back as the mid to late 1900’s (1-9). Bachman et al studied the effect of a mild degree of rotation on the lateral chest radiograph and the appearance of anatomical structures with slight rotation (1). These studies have given an anatomical basis for radiographic findings on the lateral chest radiograph, but there were limitations in these studies, and more thorough investigation is possible with current advancements in technologies, particularly CT reformat images.
One of the limitations is that plain radiographs are 2-dimensional representations of 3-dimensional structures (5). This means the superimposition of various structures may give a false representation of these structures and making it difficult for accurate analysis.
Secondly, the previous studies were conducted by physical rotation of the individuals at the time of taking the chest radiograph. Bachman investigated 10-degree rotation in both right and left anterior oblique as per “acceptable” range of rotation (1). While this showed good comparison between the right anterior oblique to the left anterior oblique rotations, the margin of error in how many degrees an individual was rotated as compared to a different individual may have been significant.
Third, the technologies used at the time these studies were conducted may have contributed to the limitations in accurately viewing structures. X-ray machine, imaging plate, image processing, and monitor has improved tremendously as compared to its quality in the 20th centuries (10,11). This means better resolution and fewer artefacts when viewing lateral chest radiograph which would improve the viewing of the image, thus more accurate analysis of the anatomy can be achieved.
In today’s age of multi-slice CT, there has been deskilling in the interpretation of the lateral chest radiograph. This paper illustrates hilar anatomy on the lateral chest radiograph using CT datasets, which can be reformatted to look like a chest radiograph. In 1978, Bachman had demonstrated that the lateral chest radiograph with the right side anterior by 10 degrees unravels hilar structures which improve visualisation and diagnosis (1). The anatomical basis for this is revealed in this paper using 3D volume CT datasets in normal patients.