Scintigraphic detection of osteomyelitis with Tc-99m MDP and Ga-67 citrate: concise communication

Using both Tc-99m methylene diphosphonate and gallium-67 citrate, images of the lower extremities in New Zealand white rabbits were obtained on sequential days after inoculation of tibias with Staphylococcus aureus. Gallium-67 scintigraphy was positive earlier in the course of infection than Tc-99m MDP scintigraphy. In addition to 4-hr Ga-67 scintigrams, 24-hr and 48-hr scintigrams were obtained, contributing substantially to interpretation. However, 72-hr Ga-67 scintigrams contributed little additional information.     

A Ga-68-labeled tetrabromophthalein (Ga-68 BP-IDA) for positron imaging of hepatobiliary function: concise communication

We describe the chemical synthesis of an iminodiacetic-acid-substituted tetrabromo-o-cresolphthalein (BP-IDA), which complexes Ga-68 tightly. The liver uptake, bile excretion, and urinary excretion of the complex were examined in rats. Maximum liver uptake reached 60%, and 1-hr cumulative bile excretion was 75% of injected dose. Urinary excretion in rats with ligated common bile duct remained below 1%. Competitive action of exogenous bilirubin on hepatobiliary excretion of the Ga complex was less pronounced than that of bromosulfophthalein. The absolute activity determination of the positron emitter Ga-68, the high accumulation in the liver, the low urinary excretion, and the weak competition from exogenous bilirubin are promising features of this radiopharmaceutical for the quantitative study of hepatobiliary function.     

Gallium-67 scanning in Sj?gren's syndrome: concise communication

We performed gallium-67 scans in 12 patients with primary or secondary Sj?gren's syndrome (SS). Salivary-gland uptake of gallium-67 was noted in four of five patients with primary SS. Pulmonary uptake was observed in ten of 12 patients. Chest radiographs were essentially normal in all patients, although 60% complained of significant dyspnea with exertion. The gallium-67 scan may prove to be a sensitive noninvasive diagnostic test for lung and mediastinal involvement by either primary or secondary SS, and for salivary-gland involvement in primary SS.     

Pharmacokinetics of hepatobiliary imaging agents in rats: concise communication.

The distribution and elimination kinetics of Tc-99m pyridoxlidene glutamate (Tc-99m PG), of Tc-99m N-(2,6-dimethyl-phenylcarbamoylmethyl) iminodiacetic acid (Tc-99m HIDA), and of I-131 rose bengal in blood were quantitated after i.v. injection in rats. This was performed by use of a unique indwelling catheter that externalizes the systemic circulation, permitting continuous monitoring of blood radioactivity. The blood activity-time curves of Tc-99m PG and Tc-99m HIDA are described by the sum of three exponential functions. Only two exponentials are required in the case of I-131 rose bengal. The rank order for the rates of loss from blood was Tc-99m HIDA less than Tc-99m PG less than I-131 rose bengal. Bile was collected after administration of Tc-99m HIDA and Tc-99m PG. The total excretion of radioactivity over a 70-min period amounted to 95.7% and 42.8% of the dose of Tc-99m HIDA and Tc-99m PG, respectively. A linear compartmental kinetic model was developed to account for the disappearance from blood and the biliary excretion of these radiopharmaceuticals in rats.     

Clinical evaluation of some phosphorus bone-imaging agents: concise communication.

Four different Tc-99m labeled phosphorus-based bone-imaging agents were compared by a scan-evaluation technique in which the skeletal uptake was visually assessed at selected sites. A detailed statisticalanalysis of scans, by each of three independent evaluators, on a total of 140 different patients showed that two of the agents (based on pyro- and on trimetaphosphate) were superior. The statistical analysis showed good agreement between the investigators and consistency in thier repeat evaluations.     

Gallium-67 scanning in the diagnosis of postoperative sternal osteomyelitis: concise communication

Sternal osteomyelitis is an uncommon but serious complication of the median sternotomy incision. Definite diagnosis is clinically difficult and radionuclide scanning is of uncertain value in the early postoperative period. We conducted a prospective blind study of gallium scanning in the early period after cardiac surgery and reviewed clinically diagnosed cases that also had scans. Clinical status and scan interpretation were each independently assessed by three raters. Thirty-eight scans included six true positives, five true negatives (no sternotomy) and 27 post-sternotomy, clinically uninfected patients. Using categories of high, medium, and low for scan interpretation, the radiologic assessors agreed 90% of the time. Normal postoperative Ga-67 uptake could usually be differentiated from uptake by an infected sternum. The test had a sensitivity of 83% and specificity 96%. If the clinical (pretest) likelihood of sternal osteomyelitis is 30%, then the gallium scan will have a 90% positive predictive value and a 93% negative predictive value. This study of observer variation and validity indicates that Ga-67 scanning may be useful in confirming the diagnosis of poststernotomy sternal osteomyelitis.     

Rectal perchlorate for unconscious patients prior to brain scintigraphy with pertechnetate: concise communication.

Patients undergoing brain scintigraphy with pertechnetate are frequently premedicated with oral perchlorate. However, the oral route is difficult to employ in unconscious or uncooperative patients or when oral intake is restricted. In such situations, rectal administration of sodium perchlorate dissolved in water is an effective alternative to oral administration.     

The specificity of pyrophosphate myocardial scintigrams in patients with prior myocardial infarction: concise communication.

Fifty-five patients with old (9 days to 10 yr) transmural infarcts but with no evidence of recent infarction, were imaged with Tc-99m pyrophosphate. Discrete uptake was rare in the setting of an old infarct. Diffuse uptake was neither sensitive to, nor specific for, acute infarction. Prior infarction will rarely cause diagnostic error if the discrete pattern is required for a positive diagnosis.     

The mechanism of adsorption of Ga-67 citrate to cultured cells

Gallium adsorption was investigated at various pH values, with and without chelating agents or buffers. Evidence was obtained that Ga-67 citrate was adsorbed to cells in a polymeric form at a certain pH. Adsorption of Ga-67 to cells and to a glass surface reached a maximum at pH 4.5. When Ga-67 solutions were centrifuged to separate the precipitate, the highest precipitated radioactivity was found at the stated pH. With the addition of chelating agents which interact strongly with gallium, the adsorption to either cells or a glass surface was stoichiometrically inhibited. No such inhibition occurred, however, when counter ions unbound to gallium were added. The amount of Ga-67 released from the cell depended on the pH, suggesting that most of the gallium is deposited on the cell surface. Our results support Glickson's conclusion that gallium citrate forms a polymer at a certain acidic pH, which results in an increased cellular uptake by unknown mechanisms, presumably by pynocytosis.     

Effect of food intake on the tissue distribution of gallium-67: concise communication

Fasting affects the body retention and tissue distribution of Ga-67 in experimental animals. In Ga-67 experiments, therefore, a difference in food intake between treated and control animals might result in confusing side effects. We have observed this in irradiation studies. It is suggested that a fasting regimen should be imposed in any Ga-67 animal study where an alteration in food intake might be experienced in the treated group.     

The association of Ga-67 and lactoferrin.

Activity was seen in the breasts of a patient with galactorrhea 72 h after intravenous injection of Ga-67 citrate. Differential protein separation of breast secretion, extracted from the breast, revealed that the Ga-67 was contained primarily in the lactoferrin-rich protein fraction. Additional studies on partially purified lactoferrin revealed that lactoferrin binds Ga-67 more avidly than does transferrin. Since lactoferrin is present in high concentration non only in human colostrum and milk, but also in neutrophilic leukocytes, bone marrow, spleen, colon, tears, and in genital, salivary, and nasopharyngeal secretions, binding of Ga-67 to lactoferrin may explain the localization of Ga-67 in certain normal tissues and inflammatory lesions.     

The role of Ga-67 citrate imaging in pancreatitis

Two patients with pancreatitis in whom an area of predominant uptake of Ga-67 citrate was demonstrated involving the entire pancreas are presented. Ultrasound and x-ray CT did not reveal any morphologic abnormalities in the pancreas, whereas Ga-67 citrate imaging indicated the presence of active inflammatory change. Ga-67 citrate imaging may be useful in confirming the diagnosis of acute pancreatitis or acute exacerbation of chronic pancreatitis based on clinical and laboratory data, especially when ultrasound and/or x-ray CT cannot reveal any morphologic abnormalities in the pancreas.     

Gallium-67 citrate scanning--a new adjunct in the detection and follow-up of extrapulmonary tuberculosis: concise communication

Gallium-67 citrate scans were obtained in 11 patients considered at risk for extrapulmonary tuberculosis. Radiographic and bacteriologic studies were performed routinely and tissue biopsy selectively. Of five patients with proven extrapulmonary tuberculosis, there were three with renal tuberculosis, one with Pott's disease, and one with peritoneal tuberculosis. The Ga-67 scan correctly predicted presence or absence of active extrapulmonary foci in all 11 patients. Follow-up scans correlated well with clinical response to therapy. The diagnosis of extrapulmonary tuberculosis is often overlooked because of nonspecific symptoms and frequent lack of concurrent lung involvement. Scanning with Ga-67 citrate offers a reliable and simple means of screening patients at risk and of monitoring response to treatment.     

The evaluation of the bone marrow accumulation of Ga-67 citrate

The bone marrow distribution of Ga-67 citrate may be influenced by various elements in serum. In order to make these points clear, 1,955 whole body images were reviewed on the relationship between the accumulation of bone marrow and laboratory examination data of each patients. Increasing accumulation in the bone marrow was determined as positive when the bones of lower extremities were deposited on the images, because these bones was not visualized in normal gallium image. Laboratory data of 20 patients without having bone marrow accumulation was used as control. The positive findings of bone marrow accumulation was observed in 38 patients (2%) including 23 malignancies and 15 benign disease. The malignant tumor infiltration to the bone marrow was demonstrated by bone marrow aspiration biopsy in 2 out of 7 patients with bone marrow accumulation of Ga-67. Seven out of 15 patients with benign disease were collagen disease such as aortitis syndrome or SLE. The values of hemoglobin, hematocrit, serum iron and creatinine clearance were significantly lower in the patients with positive findings in comparison with control. These results suggest that the lower level of serum iron and anemia may cause increasing bone marrow accumulation of Ga-67 citrate.     

Ga-67 SPECT to detect endocarditis after replacement of an aortic valve

Ga-67 SPECT was crucial in making the diagnosis of infectious endocarditis in a 28-year-old man with a history of aortic valve replacement who was referred to the nuclear medicine service because of persistent fever. In the planar left anterior oblique view, an area of slight, diffuse activity was noted. The shape and site of the infectious focus were well defined by Ga-67 SPECT. After Ga-67 imaging, results of a computed tomographic (CT) scan were negative and the patient was treated with antibiotics and discharged from the hospital after showing clinical improvement. However, the fever returned and he was readmitted. A second Ga-67 SPECT was also positive, but a spiral CT scan showed only minor inflammatory changes. Finally, transesophageal ultrasonographic images suggested vegetation on the prosthetic valve. Cultures of the graft and the valve were obtained surgically and showed staphylococcal endocarditis. Exaggerated confidence in negative CT scan results led to unnecessarily delayed surgical treatment of the infection. Ga-67 SPECT was a powerful noninvasive tool in the diagnosis of infectious complications after prosthetic valve surgery.     

Lymphoma: predictive value of Ga-67 scintigraphy after treatment.

The negative predictive value (PV-) and positive predictive value (PV+) of gallium-67 scintigraphy and computed tomography (CT) were compared after treatment in 43 patients with Hodgkin disease and in 56 patients with non-Hodgkin lymphoma. The usefulness of these studies in predicting survival was also evaluated. In patients with Hodgkin disease, the PV- of Ga-67 scintigraphy was 0.84 and of CT was 0.88. The PV+ was 0.80 for Ga-67 studies and only 0.29 for CT. In patients with non-Hodgkin lymphoma, the PV- of Ga-67 scintigraphy was 0.84 and of CT was 0.80. The PV+ was 0.73 and 0.35, respectively. For both groups, the differences in disease-free survival between patients with negative and positive Ga-67 studies were significant (P less than .05 in Hodgkin disease and P less than .001 in non-Hodgkin lymphoma), but the differences were not significant for CT. These data show that, after treatment of patients with lymphoma, Ga-67 scintigraphy is a good predictor of clinical outcome and can be used beneficially in patient treatment.