Can the extent of coronary artery disease be predicted from thallium-201 myocardial images?

The accuracy with which the extent of coronary artery disease can be predicted from stress thallium-201 myocardial images has been assessed in 81 patients with chest pain. Whereas the appearance of the myocardial images was both a sensitive means of detecting coronary artery disease (images abnormal in 43 of 47 patients with abnormal coronary arteriograms) and specific in excluding it (images normal in 31 of 34 patients with normal arteriograms), there was poor correlation between the extent of disease predicted from the Tl-201 images and the findings at arteriography. It is concluded that although stress Tl-201 myocardial imaging is a useful method for the noninvasive diagnosis of coronary artery disease, it cannot be relied upon to predict the number of abnormal vessels.

The significance of the abnormal rest thallium-201 myocardial image in coronary artery disease.

Rest Thallium-201 myocardial images were abnormal in 20 out of 40 patients with arteriographically proven coronary artery disease. The myocardial image appearances did not accurately reflect the extent of coronary artery disease present. However, in 35 of the 40 patients (88%) the presence or absence of abnormalities on the rest myocardial image correleted respectively with the presence or absence of abnormal wall motion at left ventriculography. Most rest image abnormalities could be attributed to previous myocardial infarction, but in six patients myocardial ischaemia was possibly the cause. These results suggest that though myocardial fibrosis is usually the cause of rest myocardial image abnormalities in coronary artery disease, this is not invariably so. The possible therapeutic implications are discussed.

Chronic nephritis in a pony.

The clinical and pathological features of a case of chronic nephritis in a 17-year-old pony was described. Measurement of fluid intake and laboratory analysis of sequential blood and urine samples helped in establishing an accurate diagnosis. The case demonstrates that although chronic renal disease is not well documented in the horse it should nevertheless be considered in the differential diagnosis of conditions characterised by progressive loss of weight.

A clinical comparison of Tc-99m HEDP and Tc-99m MDP in the detection of bone metastases: concise communication.

We have compared bone scintigrams made with Tc-99m-tagged HEDP (1-hydroxyethylidene diphosphonate)and MDP (methylene diphosphonate), the former at 4 hr after injection, the latter at both 2 and 4 hr. In 17 patients with skeletal metastases, there was no significant difference in lesion count or scan quality between the 4-hr images. The tumor-to-bone ratio (T/B) was significantly higher with Tc-HEDP (p less than 0.02). Lesion detection rate and T/B ratios were both lower with Tc-MDP at 2 hr when compared with the 4-hr values for both Tc-HEDP (p less than 0.02, p less than 0.005) and Tc-MDP (p less than 0.02, p less than 0.01). The 4-hr Tc-MDP scan was of significantly higher quality than the 2 hr Tc-MDP scan (p less than 0.01). Although Tc-HEDP produces a higher T/B ratio at 4 hr, the present study does not suggest that either agent is superior in clinical practice.

Laryngeal malignancy following iodine-125 therapy for thyrotoxicosis.

A 52-year-old woman presented with a laryngeal sarcoma eight years after receiving two doses, each of 30 mCi, of iodine-125 for thyrotoxicosis. That extrathyroidal tissue receives a higher radiation dose of low-energy photon radiation from iodine-125 than from an equivalent microcurie dose of iodine-131 and that the tumour was of a type which rarely arises spontaneously in the larynx suggest a possible link between the development of the tumour and iodine-125 therapy.

The prognostic and therapeutic implications of the positive radionuclide bone scan in clinically early breast cancer.

Seventy-five women with clinical stage I or stage II carcinoma of the breast have had radionuclide bone scans at the time of presentation and at 6-monthly intervals during a mean follow-up period of 39 months. Patients with evidence of metastases on bone scan, either at the time of presentation or during follow-up, had significantly higher mortality and morbidity rates than those with persistently negative scans. Whatever the clinical stage, breast cancer patients with a positive bone scan have a very poor short term prognosis and local therapy to the breast is inadequate. A plan is outlined which incorporates the patient's bone scan status into the decision to introduce endocrine therapy or chemotherapy.

Clinical value of delayed thallium-201 myocardial imaging in suspected acute myocardial infarction.

Fifty patients with acute chest pain had thallium-201 myocardial imaging performed three to six days after emergency admission to hospital. The image was abnormal in 20 out of 22 patients with acute transmural myocardial infarcts but in only 1 of 5 with acute subendocardial infarcts. Indistinguishable scan abnormalities caused by old infarcts were seen in 7 patients, and caused by myocardial ischaemia in 1 patient. A single thallium-201 myocardial scan some days after the onset of symptoms appears to be of little value in the clinical assessment of patients with suspected acute myocardial infarction.

The use of whole-body retention of Tc-99m diphosphonate in the diagnosis of metabolic bone disease.

The limited role of bone scanning in the diagnosis of metabolic bone disease might be considerably improved by accurate quantification of skeletal uptake of the radiopharmaceutical. Using a standard shadow-shield whole-body monitor, we have measured whole-body retention (WBR) of Tc-99m HEDP up to 24 hr in 11 patients with renal osteodystrophy (mean WBR 88.6% at 24 hr); in ten patients with Paget's disease (mean 56.9%); in seven patients with osteomalacia (mean 40.7%); in five patients with primary hyperparathyroidism (mean 50.7%); in four patients with osteoporosis (mean 21.2%); and in 12 normals (mean 19.2%). The osteoporotic group could not be differentiated from the normal group, but the other groups were significantly different from the normal group at 24 hr (p less than 0.002), and each individual rest for the 24-hr WBR of Tc-99m HEDP in these groups lay outside our normal range. This test may, therefore, provide a sensitive means of detecting conditions with increased bone turnover. We obtained measurements of plasma activity of Tc-99m HEDP in these patients up to 24 hr, and 4-hr bone to soft-tissue ratios from bonescan images, but little additional information resulted.

The role of bone scanning in osteomalacia.

The presence of eight "metabolic features" was assessed on the bone scintigrams of ten patients with osteomalacia. In all of these bone images, sufficient features were present to strongly suggest a metabolic disorder. There scintiphotos were included in a controlled blind study using 30 normal bone scans and 20 scans of metastatic disease. Nine of the ten metabolic bone images were correctly identified by two independent observers. Skeletal uptake of radiotracer, expressed as bone-to-soft tissue ratio, was significantly higher in the osteomalacic patients than in a group of 80 controls.

A quantitative approach to the analysis of the normal thallium-201 myocardial image.

The visual interpretation of Thallium-201 myocardial images is made more difficult by nonhomogeneity of myocardial tracer uptake in normal studies. To increase the objectivity of the study, the variation in count density in different myocardial areas has been calculated using a computer regions of interest technique in 14 healthy, young subjects following intravenous injection of the radionuclide at rest and in 10 after injection during maximal exercise. The "normal ranges" for regional Thallium-201 uptake so obtained are presented and discussed.

A clinical comparison of 2 h and 4 h bone scans obtained with 99Tc H.E.D.P.

A comparison of 2 h and 4 h bone scan images obtained with technetium labelled H.E.D.P. in ten patients demonstrated no increase in lesion detection rate between the 2 h and 4 h scans. The 2 h bone scans were of sufficient quality to permit identification of tumours in all cases.

Absent kidney sign associated with symmetrical and uniformly increased uptake of radiopharmaceutical by the skeleton.

In 11 patients 99mTc-stannous H.E.D.P. bone scans showed absent renal images associated with symmetrical and uniformly increased uptake of radiopharmaceutical by the skeleton. These appearances are frequently seen in renal osteodystrophy but are uncommon in malignant disease. Their significance in hypervitaminosis D requires further evaluation.