Comparison of 99mTc Injected Activity with Prescribed Activity in Four Types of Nuclear Medicine Exams

Background: 99mTc is a radioactive isotope that is obtained by eluting a 99Mo/99mTc generator. (PINSTECH, Islamabad) and used for radionuclide scanning. Objectives: The objective of this work is to study the uncertainties in 99mTc activity that exist due to time delay between injection preparation and administration to patients, during the process of gamma camera scanning. Methods: Lead canisters were used for storing elution vials and dose calibrator for measuring 99mTc activity in mCi. The activity of preparing 99mTc injection and its administration to patients were compared with the prescribed values of activity recommended in the Society of Nuclear Medicine procedure guidelines. Results: This study showed that uncertainty in the activity existed in one thyroid patient, 38 bone patients, 5 renal patients and 45 cardiac patients. Conclusion: This uncertainty in activity exists due to time delay between injection preparation and administration to patients, as well as due to residual radionuclide that is not injected into patients and remains in the syringe.

The Prognostic Value of the Results of 123I-metaiodobenzylguanidine Myocardial Scintigraphy in the Examination of Patients with Atrial Fibrillation Referred for Its Interventional Treatment

Objective. To identify the scintigraphic predictors of the efficiency of interventional treatment for atrial fibrillation (AF) by cardiac 123I-metaiodobenzylguanidine (123I-MIBG) radionuclide scanning.Material and methods. The investigation enrolled 35 patients with AF concurrent with hypertensive disease (HD): 17 persons with persistent AF (PAF) and 18 patients with long-standing PAF (LPAF). In addition, 10 patients with HD without arrhythmia signs were examined as a comparison group. All the patients with AF before radiofrequency ablation (RFA) and those with sinus rhythm underwent 123I-MIBG myocardial scintigraphy to assess the sympathetic innervation of the heart. The efficiency of RFA was evaluated after 12 months by 24-hour ECG monitoring.Results. The patients of both groups were divided into subgroups according to the presence of recurrent arrhythmia one year after interventional treatment. ROC analysis could determine the main scintigraphic predictors of the efficiency of RFA. The preoperative indicators, in which the subgroups with and without recurrent AF showed significant differences, were studied. In the patients with PAF, the delayed Heart/ Mediastinum (H/M) ratio cutoff was ≥1.55 (the area under the ROC curve was 0.929; 100% sensitivity and 57% specificity), and the threshold value of 123I-MIBG washout rate was ≤22.3% (the area under ROC curve was 0.957; 100% sensitivity and 43% specificity) may suggest that RFA is effective. In the patients with LPAF, the threshold values of early H/M ratio were ≥1.69 (the area under the ROC curve was 0.849; 100% sensitivity and 62% specificity) and those of delayed H/M ratio were ≥1.66 (the area under the ROC curve was 0.938; 94% sensitivity and 23% specificity) allow the prediction of a risk for postoperative recurrent AF.Conclusion. The findings suggest that 123I-MIBG scintigraphy can be used to predict a high risk for recurrent AF after RFA of the pathological pathways of a pulse in the myocardium.

Is Routine Frozen Section Necessary for Parathyroid Surgery?

OBJECTIVE: Successful parathyroidectomy requires identification and excision of 1 or more abnormal parathyroid glands. The pathologist confirms or refutes the intraoperative presence of parathyroid tissue in excised material. With the advent of radionuclide scanning and rapid parathyroid hormone assays, the role of routine frozen section (FS) has once again been called into question. Our aim was to assess the need for routine FS in tissue identification during parathyroidectomy in a series of 50 consecutive cases. METHODS: We analyzed 50 consecutive parathyroidectomies performed by a single surgeon from December 2002 to August 2003. Diagnoses on gross examination (GE) of both the surgeon and the pathologist were recorded, cytologic smears made, and FSs performed. A cost analysis was also performed. RESULTS: Of the 50 parathyroidectomies performed (35 adenoma and 15 hyperplasia), both surgeon and pathologist's opinions on GE were concordant. Incorrect gross identification occurred by both in 6% (3) of the cases. GE is a cost-effective means of identifying parathyroid tissue. CONCLUSIONS: Experienced parathyroid surgeons need not routinely request FS examination. The decision to omit intraoperative FS examination must be balanced against the potential implications of misdiagnosis and a repeat operative procedure. EBM RATING: C