F(ab')2 fragments of several murine monoclonal antibodies have been labeled with 99mTc by a direct, pretinning method. The fragments were incubated with stannous ions overnight to split disulfide groups--a process which converts dimeric F(ab')2 to monomeric fragments. The pretinned fragments were then either directly labeled with 99mTc, frozen for subsequent labeling, or lyophilized to make kits for 99mTc-labeling at some later date. The 99mTc-labeled fragments were shown to be stable against transchelation when challenged with ethylenediaminetetraacetic acid, retained immunoreactivity, and were capable of binding to human tumor xenografts in nude mice.

Eleven children with reflex neurovascular dystrophy were investigated by technetium-labeled methylene diphosphonate bone scanning. Eight of 12 scans demonstrated abnormal findings, four showing diffusely decreased uptake and four diffusely increased uptake of the radionuclide in the affected site. Three scans showed normal findings initially, as did one previously abnormal scan when repeated in the asymptomatic patient 6 months later. Diffusely abnormal findings can be helpful in the diagnosis of childhood reflex neurovascular dystrophy, but a normal scan does not exclude the diagnosis.

The authors prospectively compared the ability of Tc-99m pyrophosphate (PYP) and Tc-99m methylene diphosphonate (MDP) to detect acute myocardial infarctions. The agents used were PYP (12 mg) with 3.4 mg of stannous chloride, MDP (10 mg) with 1.0 mg of stannous chloride, and MDP (10 mg) with 3.4 mg of stannous chloride. Imaging was performed on three consecutive days on 34 patients with proven myocardial infarctions, using the same agent on the first and third days of the study and an alternate agent on the second day. Agents were assigned randomly to each of six groups of patients. First images were obtained an average of 3.7 days (range, one to six days) following myocardial infarction. Seventeen of 23 patients (75%) had images positive for acute myocardial infarction with Tc-99m PYP, whereas only two of 21 patients (9.5%) had positive studies with Tc-99m MDP with 3.4 mg of stannous chloride and one of 24 patients (4.2%) had positive studies with Tc-99m MDP and 1.0 mg of stannous chloride. All three myocardial infarctions detected by Tc-99m MDP were extensive and transmural. When MDP and PYP were both positive in the same patient, the apparent size of the myocardial infarction was much smaller with the MDP. It is concluded that MDP can detect only large myocardial infarctions, has poor localization in the infarcted tissue, and varying the stannous chloride content of the preparation does not improve the ability of MDP to detect acute myocardial infarctions.

The authors, from their experience in 60 patients, demonstrate that technetium-99m-labelled red blood cell scintigraphy is a sensitive (91%) and specific (76%) diagnostic procedure with a high predictive value, when both positive (81%) and negative (92%). It is preferable to and more cost-effective than selective angiography as a first-line diagnostic test for occult gastrointestinal bleeding.

A case report is presented describing a 27-year-old woman with invasive trophoblastic hydatidiform mole metastatic to the lung. Gamma scintiscanning, using a polyclonal and monoclonal antibody specific to human chorionic gonadotropin, hCG, and labeled with Tc-99m, is described. The area of the primary lesion in the uterus was demonstrated with both antibodies tested without computer subtraction techniques; metastatic deposits in the lung were detected only with the aid of blood pool subtraction techniques.

A technetium-99m (99mTc) mouse monoclonal anti-hCGbeta antibody fragment labeled according to a novel pretinning method is shown in the present studies to be suitable for the in vivo detection of hCG-secreting and certain non-hCG-secreting human tumours. The advantages of this radiopharmaceutical over other radiolabeled antibody compositions previously described for in vivo tumor detection relate to its improved image quality, lower radiation exposure, and earlier scanning times.

It would appear that the best method of the three investigated for preparing a labelled fatty acid to be used in nuclear cardiology is to autoclave an omega-brominated fatty acid in the presence of radioiodine, resuspend the labelled preparation in Tween 80∶D5W: propylene glycol (10∶80∶10) and sonicate it for 30 minutes. Care must be taken when injecting Tween although no adverse effects were noted during the present study.

Mew, Daphne J.Y.; Alcorn, L. N.; Levy, J. G.; Lyster, D. M.; Morrison, R.T. Author Information

Lyster, Donald M.; Morrison, R. T.1; Szasz, I.1; Alcornn, 1; Rhodes, B.2; Breslow, K.2; Burchiel, S.2 Author Information

SZASZ, I M.D., F.R.C.S.(C)*; MORRISON, R T M.D., Ph.D., F.R.C.P. (C)*; LYSTER, D M Ph.D.*; NAIMAN, S C M.D., F.R.C.P. (C)† Author Information