Is 'diaphragmatic' attenuation a misnomer?. Evaluation of the anatomic cause of 'diaphragmatic' attenuation in SPECT thallium scanning.

UNLABELLED

The most common artifact on thallium scans in our laboratory has been posterior myocardial attenuation, mostly in males. In the past this has been thought due to the position of the diaphragm.

METHODS

To evaluate this concept, matching chest x-rays were examined and measured. Eleven examples of posterior myocardial attenuation were consecutively pulled from our files and compared to eleven consecutive controls.

RESULTS

It was found that the diaphragm did not differ significantly. The ratio of the PA diameter of the chest to chest width was significantly (p < 0.03) less than controls.

CONCLUSIONS

It is suggested that a male with a flat, wide chest is more prone to posterior myocardial attenuation. If a posterior defect is present in this type of patient it is suggested he be further evaluated to rule out artifact.