Diagnosis of Cardiac Sarcoidosis
Sarcoidosis is a chronic systemic granulomatous disease ^ of unknown origin. Most deaths from sarcoidosis are attributable to involvement of the heart, making the early diagnosis and treatment of cardiac sarcoidosis essential. However, cardiac sarcoidosis shows no specific clinical symptoms or specific features on ECGs or echocardiograms, making it difficult to diagnose this condition. A definite diagnosis of this condition can be made when testing of an endomyocardial biopsy specimen is positive, but the rate of such biopsy results is low (around 20%).
Nuclear medicine is becoming increasingly important in the diagnosis of cardiac sarcoidosis. The development of single-photon emission CT (SPECT) scanning using I-metaiodobenzylguanidine, Tl (Tl), and 99mTc-sesta-mibi (Tc), has increased the diagnostic sensitivity of nuclear medicine. However, these modalities are not satisfactorily specific to cardiac sarcoidosis. Furthermore, the relationship between positive findings and the activity of the disease remains unclear when these SPECT scanning techniques are used for the diagnosis of cardiac sarcoidosis. Ga (Ga), on the other hand, is highly specific to cardiac sarcoidosis, since it is accumulated in inflamed areas and is expected to be useful in judging the responses of the disease to steroid therapy. canadian health and care mall
Some investigators have suggested that comparing Tl SPECT scanning with Ga SPECT scanning would increase the specificity of SPECT scanning to cardiac sarcoidosis, possibly allowing the evaluation of responses to steroid therapy. Even in cases of cardiac lesions that are too small to be visualized by systemic Ga scintigraphy, it is possible to detect abnormal radionuclide uptake in the myocardium by using Ga SPECT scanning. However, in cases in which the sarcoidosis activity is very high and organs other than the heart are intensely inflamed, abnormal nuclide uptake into the myocardium is difficult to visualize by Ga SPECT scanning because of the inability to distinguish between Ga uptake in other organs from that in the myocardium. We therefore hypothesized that if the myocardial outline depicted using another tracer is overlapped on a Ga SPECT image, it will be possible to detect abnormal Ga uptake in the myocardium and to increase the accuracy of localization of the lesion, leading to a more accurate diagnosis of cardiac sarcoidosis. It has been reported that Tc has higher energy and involves fewer artifacts than Tl, allowing sharper images to be obtained when used for SPECT scanning. Therefore, we attempted dual SPECT scanning using Ga and Tc and superimposing a Ga-SPECT image onto the myocardial traced outline of the Tc image (TcROI). The usefulness of this imaging technique in the diagnosis of cardiac sarcoidosis was investigated.