The Bone Scintigraphy with ^99mTc-Labeled Phosphorus Compounds

Abstract

A fundamental and clinical comparative study of three kinds of^99mTc-labeled phosphorus compounds—^99mTc-polyphosphate, ^99mTc-pyrophosphate and^99mTc-diphosphonate (EHDP) —, was made and the diagnostic efficiency of these agents in metastatic bone tumors is discussed.
Paperchromatographic study revealed the labeling efficiency of^99mTc-poly phosphate was 70 percent which was worse than those of^99mTc-pyrophosphate and^99mTc-di phosphonate in both of which more than 95 percent of^99mTcwas labeled.
A comparison between^99mTc-pyrophosphate and^99mTc-diphosphonate in the rat organs 3 hours after i.v. administration revealed that the distribution of^99mTc-diphosphonate was less than that of^99mTc-pyrophosphate in the soft tissue such as the blood or the muscle. The spine/blood uptake ratio was 9.3 in^99mTc-diphosphonate and 5.0 in^99mTc-pyrophosphate.
The disappearance of the radioactivity from the blood in human was essentially the same in^99mTc-pyrophosphate and^99mTc-diphosphonate which were faster than that in^99mTc-polyphosphate.
Clinically, with^99mTc-polyphosphate, the thyroid or the liver was occasionally imaged but was seldom with other two agents. No essential difference was found in bone imaging between^99mTC-pyrophosphate and^99mTc-diphosphonate.
Bone scintigram of the metastatic bone tumors taken with these three agents was compared with bone X-ray photo and value for serum alkaline-phosphatase. Of 28 cases of positive scintigram, 9 cases had no abnormal lesions on X-ray photo and 11 cases had negative X-ray lesions and positive scan lesions as well as positive X-ray and scan lesions. All of these scan positive lesions had been strongly suspected of bone metastases by symptoms and histories but not proved histologically. In 4 X-ray photo positive cases, the scintigrams were negative. All of these 4 cases were long standing after radiation or hormone therapy and had no symptoms. In 24 scan positive cases, the values for serum alkaline phosphatase were high in 13 cases.
As was said about⁸⁵Sr, ^87mSr, ¹⁸F and other agents, the scintigraphy with^99mTc-labeled phosphorus compounds was more useful in early diagnosis of bone metastasis than X-ray examination or value for serum alkaline phosphatase.
Other skeletal disorders than metastatic bone tumor were not discussed in detail in this paper, but some interesting cases in which bone scintigrams were very useful diagnostics were presented: metastatic calcification in the lung in tertiary hyperpara-thyroidism; metastatic osteogenic sarcoma in the peritoneunt, the lung and the brain; metastatic brain tumor; hydronephrosis.