Paul B. Hoffer

The role of gallium-67 in the clinical evaluation of cancer.

This review is based primarily on historic data, and it examines the indications for and limitations of gallium-67 scanning in the evaluation of patients with neoplasms. The use of gallium-67 scans is discussed according to tumor type, and data from the most representative and comprehensive studies are included. The results described, some of which were obtained primarily with older imaging techniques, should be regarded as representing the minimum that can be expected from application of this imaging procedure.

Comparison of computed tomography, ultrasonography, and gallium-67 scanning in the evaluation of suspected abdominal abscess.

A retrospective study was made of 29 consecutive patients who were evaluated for suspected abdominal abscess by at least two of three imaging modalities: gallium-67 scanning, ultrasonography, and computed tomography. No statistically significant difference in accuracy of the findings could be demonstrated. Consideration of the advantages and disadvantages of each imaging modality will often indicate which to use in an individual case. Findings from the three imaging techniques sometimes provided complementary rather than identical information.

99mTc-methylene diphosphonate bone imaging in the evaluation of total hip prostheses.

A retrospective study was performed to determine the accuracy of 99mTc-methylene diphosphonate bone imaging in the evaluation of total hip arthrosplasty for lossening and/or infection. Using focally increased activity at the tip of the femoral component or in the region of the acetabular component as a criterion, the examination was 77% specific and 100% sensitive for loosening and/or infection. A possible explanation for the increased uptake at the tip of the femoral component and the role of this examination in the management of a painful total hip prosthesis are discussed.

Fluorescent Thyroid Scanning: A New Method of Imaging the Thyroid

A method has been developed for imaging the thyroid gland through the use of K-shell fluorescence. This work was stimulated by the pioneer efforts of Jacobson (4) and Roy et al. (7), whose studies demonstrated the feasibility of radiologic detection of in vivo thyroidal iodine. Although it is well known that the thyroid gland selectively traps and incorporates significant amounts of iodine, it is not generally appreciated that the iodine content of the average thyroid gland is only 0.04 per cent by weight (6). Nevertheless, this quantity is sufficient to act as the target in the system to be described. The technic for imaging the thyroid gland which is presented in this communication incorporates the basic scheme of an x-ray fluorescent spectrometer. The equipment is a modification of the TMC Model 331 photon spectrometer used in conjunction with a dysprosium-159 radiation source. The dysprosium is placed in the flanges of a collimator, and a lithium-drifted silicon crystal (30 mm2 with 3 mm depleted regi...

Radionuclide joint imaging

Modern radionuclide techniques of joint imaging involve the use of either 99mTc-pertechnetate or 99mTc-phosphate compounds in conjunction with the Anger camera. In general, images obtained with both types of radiocompound are nonspecific--although increased uptake of 99mTc-pertechnetate usually denotes the presence of synovitis. The most popular uses of the technique are in documenting the extent and severity of inflammatory joint disease, assessing the effect of therapy, and establishing the diagnoses of Legg-Perthes disease and septic arthritis. The method is also useful in judging the extent of involvement in osteoarthritis of the knee prior to surgical intervention. Radionuclide joint imaging is more sensitive than clinical or radiographic techniques in detecting early joint involvement but usually it must be supplemented by other techniques to establish a specific diagnosis.

Perfusion Lung Scan in Normal Volunteers

The appearance of the lung scans in 61 clinically asymptomatic volunteers is described. Of the 61 volunteers, 16% (10 subjects) exhibited some type of perfusion defect. Six subjects exhibited subtle defects, the exact nature of which is unknown. Of the 4 other subjects with major perfusion abnormalities, 3 were indistinguishable from pulmonary embolism. The uncertain etiology of the positive lung scans in this series demonstrates the non-specificity of the positive perfusion lung scans.

Gallium-67 citrate imaging studies of the lung

In spite of localization of gallium in the lungs in a large variety of inflammatory pulmonary diseases, the chest radiograph is and will continue to be the principal diagnostic tool for evaluation of pulmonary inflammatory disease. The 67Ga-citrate scan, however, serves as a study complementary to chest radiography because it indicates the extent, localization, and degree of activity of the inflammatory disease with greater accuracy than do the radiographic studies. It also permits the physician to follow progression of the disease or response to treatment and possible to detect disseminated interstitial disease not visualized on radiographs. Gallium-67 scanning may be used in the evaluation of patients with lymphorecticular neoplasms (Hodgkins disease and malignant lymphomas) both during initial staging and in evaluation of the response to therapy. The 67Ga-citrate scan is useful in the evaluation of patients with lung cancer provided its limitations are kept in mind. It cannot and should not replace the pathologists microscope. The scan is useful as a screening test only in patients who have radiographic lesions not consistent with inflammatory disease and in whom invasive diagnostic procedures or exploratory surgery are contraindicated unless the probability of detecting a resectable tumor is high. However, the limited resolution of the scanning system restricts the possibility of detecting lesions before they become radiographically visible. The histologic type of the lesion appears to have no effect on the probability of detection. As a noninvasive procedure, the 67Ga-citrate scan complements mediastinoscopy by indicating which lymph nodes should be biopsied. It is also useful in evaluation of the controlateral hilar node region. The scan frequently detects clinically unsuspected extrathoracic lesions. It may therefore be a useful initial procedure in guiding the work-up of the patient with a known or strongly suspected tumor. The combination of the 67Ga scan with the chest radiograph could provide the information necessary for presurgical clinical staging in patients who have no symptoms that suggest distant metastases. Gallium-67 scans may be useful in indicating the effectiveness of treatment and the sensitivity of a tumor to radiation.

Clinical myocardial imaging with nitrogen-13 ammonia

Myocardial infarcts may be clearly imaged using intravenous nitrogen-13 as carrier-free ammonia in doses of 10–30 mCi. This positron emitter is well imaged with the Nuclear Chicago HP Anger Camera with heavy collimation. The rapid blood disappearance of the agent gives good image contrast, and the short half-life and high isotope dosage give high-count density images with little radiation absorbed dose (5 mrad∕mCi total body).

Radionuclide Imaging of the Bones and Joints of the Hand

Normal radionuclide patterns of the hand obtained with 99mTcO4 and 99mTc-Sn-EHDP are described and their validity supported by clinical, radiographic, and laboratory examinations performed to exclude articular disease in the control group. Comparison of the 99mTcO4 and 99mTc-Sn-EHDP images in patients with various articular diseases demonstrated higher sensitivity of 99mTc-Sn-EHDP in detection of involved joints; this was also true when the radionuclide images were compared with fine-detail radiographs in patients with rheumatoid arthritis.

Tomographic gallium-67 citrate scanning: useful new surveillance for metastatic melanoma.

Conventional gallium scans are not useful to evaluate patients with metastatic melanoma. We evaluated a new method of tomographic gallium imaging. One hundred fourteen tomographic scans were obtained in a prospective surveillance study of 67 patients over a 3-year period. Scans were evaluated and compared to findings of independent clinical evaluations. Sensitivity of gallium identification of tumor involving peripheral lymph nodes and soft tissues, abdomen, mediastinum, and osseous sites was 68% to 100%; overall sensitivity of this technique is 82% with specificity of 99% in 570 organ system assessments. Analysis of discordant findings when a site was clinically occult but gallium-positive showed gallium uptake to be true-positive in six of seven lymphatic sites, three of three lung and mediastinal sites, six of six abdominal sites, but in no brain or bone sites. Gallium lesions identified by computed tomographic scans proved to be false-positive at one lymphatic and one bone site, and false-negative at four otherwise clinically evident lymph node and soft tissue sites, seven pulmonary sites, and four brain sites. Gallium tomographic scanning provides a composite assessment of melanoma and may eliminate the need for other studies.