99mTc-methionine scintimammography in the evaluation of breast cancer.

OBJECTIVE: The diagnostic utility of a C-methionine scan has been established in breast cancer. We were able to radiolabel methionine with Tc at our institute. Thus, we undertook clinical trials to determine the role of Tc-methionine scans in the detection of breast cancer. METHODS: Scintimammography was performed in 47 female (median age 44 years, range 28-68 years) patients having palpable breast masses. All of them underwent ultrasound, mammography, fine-needle aspiration cytology, and Tc-methionine scintimammography before surgery. The final diagnosis was made after histopathological examination. Tc-methionine scintimammography was done after injecting 555 MBq of radiotracer intravenously. The results of scintimammography were compared with histopathology. RESULTS: The histopathological findings were malignant in 33 (70%) and benign in 14 (30%) cases. Scintimammography showed true-positive findings in 29 patients out of 33 cases of breast cancer. True-negative findings were found in 13 out of 14 patients having benign breast lesions. The sensitivity, specificity, and positive predictive value were found to be 87.8, 92.8, and 96.6% respectively. CONCLUSION: Tc-methionine imaging can provide useful information with reasonably high sensitivity and specificity in evaluating patients having breast masses.

Ventilation scintigraphy with lipophilic cationic compounds.

OBJECTIVE: On the basis of our hypothesis that lipophilic cations may be more suitable for ventilation lung scintigraphy than the conventional technetium-99m diethylenetriamine penta-acetic acid (Tc-DTPA), comparative studies were carried out. BASIC METHODS: The nebulization potential of nine routine radiopharmaceuticals was compared on medical and scintigraphy-specific nebulizers. This was followed by ventilation scintigraphy in 14 patients with chronic obstructive airway disease (n=13) or pulmonary embolism (n=1) where either 99mTc-methoxyisobutylisonitrile (n=10) or Tc-tetrofosmin (n=4) was used. Same-patient comparison with 99mTc-DTPA ventilation scan was available in six patients using the same acquisition protocol. Comparison with 99mTc-DTPA was made with respect to the nebulization rates, radioactivity delivered per unit of radioactivity available for inhalation, and regional distribution of inhaled counts. RESULTS: Lipophilic cation solutions had a significantly higher nebulization rate compared with 99mTc-DTPA using the medical nebulizer (235%, P<0.01) and 370% on scintigraphy-specific nebulizer (P<0.01). More than three times the counts of 99mTc-methoxyisobutylisonitrile or 99mTc-tetrofosmin was deposited in the body compared with Tc-DTPA aerosol per megabecquerel activity inhaled (1.5 vs. 0.4 kcounts/MBq) (P<0.001), preferentially in the lungs (75.2 vs. 65.2%), at the expense of oropharynx and stomach. Within the lungs, about 50% more counts were deposited in the outer one-third lung with lipophilic cations. Overall, therefore, more than 12 times the radioactivity deposition was achieved in the peripheral one-third of the lungs with the lipophilic cations. CONCLUSION: Ventilation lung scanning with lipophilic cations is a viable substitute of nanoparticle scintigraphy (technegas and pertechnegas, which are expensive and technically far more demanding).

Diagnosis, characterisation and evaluation of treatment response of frostbite using pertechnetate scintigraphy: a prospective study.

No large prospective study is available on use of a radionuclide method to assess frostbite and its response to conservative treatment. Recently, a large retrospective study using two-phase bone scintigraphy suggested that non-uptake (or low uptake) in frostbite lesions in the blood pool or bone phase had a strong correlation with the subsequent need for amputation. In the present study, we performed early blood pool scintigraphy with technetium-99m pertechnetate in 20 patients (10-180 days after frostbite injury; 71 clinical lesions) referred for a topical treatment protocol for mild to moderately severe frostbite, and in 22 asymptomatic controls. The aims of the study were to define the "normal" microcirculation of the hands and feet, to characterise the appearances of frostbite lesions on scintigraphy and correlate these with the clinical presentation, and to evaluate the usefulness of scintigraphy for assessing the treatment response. Six patients were "fresh", 12 had been undergoing conservative treatment (topical homeopathic) for several weeks and two had permanent fibrotic hand phalanges. Nine patients on treatment underwent serial scintigraphy a total of 22 times. Eleven patients were imaged only once, including the two with permanent fixed defects. Three distinct physiological microcirculation patterns were evident in control hands or feet: right- or left-handedness (seven subjects), subclinical inflammatory foci correlating with callosity or pressure points (36 lesions) and distinctly increased pooling of radiotracer at the thenar or hypothenar region (eight subjects). In frostbite patients, 128 lesions (48 inflammatory, 80 ischaemic) were seen on the scan. This number included all 71 lesions identified clinically, the rest being subclinical. Subclinical frostbite lesion as an entity has not been described previously. Microvasculature of normal muscle groups (in the hands, elbow or feet) was shown on scintigraphy to improve after topical treatment. The treatment resulted in improved or normalised perfusion scan in 25 of 45 ischaemic segments with matching clinical improvement, and reduction or normalisation of uptake in inflammatory lesions (n=30). The data confirm the vasodilator and anti-inflammatory action of the topical preparation, and the sensitivity of the radionuclide method in monitoring treatment response. In contrast to the previous findings that non-uptake on a scan performed 2 or more weeks after exposure correlates with the need for amputation, none of the 80 ischaemic lesions in our series required amputation while 60% showed improvement or normalisation in microvascular blood flow even though they were 10-180 days old. Our findings suggest that moderate to severe frostbite lesion can be classified as having infarcted, ischaemic or hibernating (viable) tissue, similar to the classification employed when using myocardial scintigraphy. Absence of uptake even after the initial 10 days does not necessarily indicate infarction and the need for amputation as many such lesions retain potential for vasodilation and recovery.