Autoradiographic studies of distribution in the stomach of 99mTc-pertechnetate

Gastric Mucosal Viability Assessment Using 99mTcO4 in a Case of Pure Esophageal Atresia After Isoperistaltic Gastric Tube Replacement

ABSTRACT

Gastric surface mucosal cells are responsible for the uptake and secretion of 99mTcO4, a feature that has been used in imaging heterotopic gastric mucosa. We used the same principle to look for gastric mucosal viability in this case of pure esophageal atresia admitted for cervical stomal closure after a previous isoperistaltic gastric tube (IGT) replacement procedure. 99mTcO4 scintigraphy was done after encountering a failure to maneuver the esophagoscope through the IGT. The study was helpful in assessing the loss of gastric mucosal viability in an intervening segment of the IGT.

Symptomatic paediatric Meckel's diverticulum: stratified diagnostic indicators and accuracy of Meckel's scan

PURPOSE

The aim of the study was to delineate stratified diagnostic indicants and evaluate the diagnostic accuracy of technetium-99m (Tc)-pertechnetate scintigraphy in children with symptomatic Meckel's diverticulum (MD).

MATERIALS AND METHODS

This was a prospective linear observational study conducted over a period of 5 years on 73 children with a diagnosis of symptomatic MD. The independent variables assessed were age, sex, weight-for-age z-scores, clinical presentation, complications of MD, laparoscopic findings, haematologic and biochemical results, radiological results, and histological findings. Stepwise multiple logistic regression analysis was performed to determine the diagnostic markers. The sensitivity and specificity of Tc-pertechnetate scintigraphy were assessed.

RESULTS

The incidence of MD with complications was 44%. The prevalence of ectopic gastric mucosa in histological specimens was 84%. There was a good correlation between rectal bleeding and the presence of ectopic gastric mucosa [r=0.94; 95% confidence interval (CI): 0.77-0.98]. Haematochezia associated with a drop in haemoglobin (>2 g/dl) was diagnostic of MD with ectopic gastric mucosa in children (n=42, 58%; P=0.006; odds ratio 1.99; 95% CI: 1.14-2.42). Bilious vomiting was diagnostic of complicated MD (n=12, 16%; P=0.007; odds ratio 1.89; 95% CI: 1.12-3.22). The sensitivity of Tc-pertechnetate scintigraphy was 84% and specificity was 22%. The positive predictive value was 0.64 and the negative predictive value was 0.22. The sensitivity and specificity of Tc-pertechnetate scintigraphy were dependent on the quantity and functional quality of the heterotopic gastric mucosa. The preoperative median z-score was -1.4 and the postoperative median z-score was -1.2.

CONCLUSION

Tc-pertechnetate scintigraphy had a truncated predictive value. Its contribution in clinical decision making was poor. Clinical suspicion of MD should be high in children presenting with haematochezia associated with a drop in haemoglobin by more than 2 g/dl. Laparoscopy is an effective diagnostic and therapeutic tool.

Planar scintigraphic imaging of the gastrointestinal tract in clinical practice

In the last 30 years, nuclear medicine has paralleled other imaging fields with the development of 3-dimensional techniques, including single-photon emission computed tomography and positron emission tomography. However, conventional nuclear medicine planar scintigraphy remains a common procedure at most imaging centers. Gastrointestinal studies constitute a significant portion of these planar procedures. The most common gastrointestinal studies, including hepatobiliary, gastric emptying, and gastrointestinal bleeding evaluations, resemble their original protocol. However, serial improvements have optimized the diagnostic efficacy of these procedures. Conventional Technetium-99m sulfur colloid liver/spleen imaging and hepatic blood pool imaging with labeled red blood cells now mainly serve an adjunctive role in the evaluation of equivocal findings on computed tomography. Salivary gland imaging is a less commonly requested evaluation, but can be used to evaluate functional capacity in some disease entities.

Perfusional evaluation of postesophagectomy gastroplasty with a radioisotopic study

Anastomotic fistula represents one of the frequent causes of postoperative morbidity and mortality following transhiatal esophageal resections. The main etiological factor is the ischemia of the gastric tube created for digestive transit reconstruction. Evidence suggests that per operative hypoperfusion can be maintained or even impaired after the surgery. Several methods have been employed in an attempt to assess the blood perfusion of the gastric flap, but they all pose limitations. However, there is a chronological relationship between perfusion assessments, which are almost exclusively performed per operatively, and the occurrence of a leak, which commonly appears several days after the surgery. The authors have developed a method of gastric perfusion evaluation by single photon emission computed tomography scintigraphy, which corrects that temporal matter, allowing the estimation of postoperative gastric perfusion. It is noninvasive, low cost, and may be applied by the time frame when most fistulas occur. High correlation between the event fistula and the low radiotracer uptake in the group of studied patients could be demonstrated. A role in the research of perfusion evaluation of different types of esophageal reconstruction is suggested.

Diagnosis of ectopic gastric mucosa using 99Tcm-pertechnetate: spectrum of scintigraphic findings

We highlight the spectrum of scintigraphic findings likely to be encountered in patients with ectopic gastric mucosa with illustrative cases for each such finding. 11 children (aged 4 months to 120 months, all males) underwent (99)Tc(m)-pertechnetate scintigraphic evaluation for ectopic gastric mucosa. Functioning ectopic gastric mucosa was detected in Meckel's diverticulae in three patients, in small bowel duplications in four, in a gastric duplication in one, and in intrathoracic foregut duplication cysts in three. Ectopic functioning gastric mucosa in Meckel's diverticulum, and gastric duplication is visualized simultaneously with the stomach while in intestinal duplications tracer activity can be visualized in the dynamic sequence and even before gastric tracer visualization. In the three patients with intrathoracic duplication cysts, the functioning ectopic gastric mucosa was evident only in the delayed (99)Tc(m)-pertechnetate images, much later than the visualization of stomach activity. Therefore, acquisition of delayed images are useful when the initial images are equivocal or negative in children with intrathoracic foregut duplication cysts. In addition, we suggest a hypothesis of a possible mechanism for the uptake of pertechnetate in ectopic gastric mucosa in some patients with intrathoracic forget duplication cysts. In conclusion, a variety of scintigraphic patterns may be found in patients with ectopic gastric mucosa undergoing (99)Tc(m)-pertechnetate scintigraphy depending upon the location and size of the ectopic tissue.

The spectrum of heterotopic gastric mucosa in children detected by Tc-99m pertechnetate scintigraphy

Meckel's diverticulum is the most common site of heterotopic gastric mucosa (HGM). Other sites include intestinal duplication and the small bowel proper. Tc-99m pertechnetate abdominal scintigraphy is used commonly to detect HGM. This article describes various scintigraphic patterns of HGM and reviews technical aspects of the procedure, with emphasis on pharmacologic enhancement.

Sodium iodide symporter in health and disease

Radioiodine-concentrating activity in thyroid tissues has allowed the use of radioiodine as a diagnostic and therapeutic agent for patients with thyroid disorders such as well-differentiated thyroid cancer. However, some extrathyroidal tissues also take up radioiodine, contributing to unwanted side effects of radioiodine therapy. Now that the molecule that mediates radioiodine uptake, the sodium iodide symporter (NIS), has been cloned and characterized, it may be possible to develop novel strategies to differentially modulate NIS expression and/or activity, enhancing it in target tissues and impeding it in others. In addition to restoring NIS expression/activity to ensure sufficient radioiodine uptake for the diagnosis and treatment of advanced thyroid cancers, we envision that it may be possible to selectively increase or confer NIS expression/activity in tumors of nonthyroidal tissues to facilitate the use of radioiodine in their diagnosis and treatment. We also consider the molecular basis of thyroid and nonthyroid disorders that may be complicated by NIS deregulation. Finally, we explore the use of NIS as an imaging reporter gene to monitor the expression profile of the transgene in transgenic mouse animal models and in patients undergoing gene therapy clinical trials.

The utility of technetium 99m pertechnetate scintigraphy in the evaluation of patients with Meckel's diverticulum

PURPOSE

The aim of this study was to assess the utility of technetium (Tc) 99m pertechnetate scintigraphy in the diagnostic workup of the pediatric patient with gastrointestinal (GI) bleeding and a suspected Meckel's diverticulum.

METHODS

The charts of 235 consecutive patients evaluated with a Meckel's scan (n = 165) or with the discharge diagnosis of Meckel's diverticulum (n = 70) between January 1975 and October 1997 were reviewed for presenting symptoms, bleeding characteristics, diagnostic studies and pathological diagnosis. Those patients with lower GI bleeding and a serum hemoglobin level less than 11.0 g/dL who underwent a 99mTc pertechnetate scan (n = 43) were assessed for utility of the scan.

RESULTS

In all patients the Meckel's scan had a positive and negative predictive value of 0.93. However, in patients with lower GI bleeding and a hemoglobin less than 11.0 g/dL the Meckel's scan had a sensitivity of 0.60, a positive predictive value of 1.0, a specificity of 0.96, but only a negative predictive value of 0.74. As such, the probability that a child who presents with GI bleeding and a serum hemoglobin less than 11 g/dL will have a Meckel's diverticulum despite a negative Meckel's scan of 0.26. We further evaluated the eight patients with a false-negative scan: ectopic gastric mucosa was present on pathological examination in all eight patients. Pentagastrin stimulation was performed at the time of scintigraphic study in three of eight. Six of these eight patients had duplicate scans that also were negative. Patients with a false-negative (FN) scan had significantly increased hospital charges when compared with those with a true positive (TP) scan (TP = $5012 +/- 1992; FN = $8554 +/- 1506; P = .0001). Clinical suspicion had a major effect on the decision-making process in these patients independent of the results of the Meckel's scan, and all eight patients ultimately underwent exploratory laparoscopy-laparotomy with Meckel's diverticulectomy despite the scan results.

CONCLUSIONS

The relatively low negative predictive value of the Meckel's scan may result in the need for operative evaluation despite the scan data. As such, the contribution of the scan to clinical decision making is low. These findings suggest that exploratory laparotomy or laparoscopy may be indicated instead of scintigraphic scanning in the assessment of the anemic (hemoglobin less than 11 g/dL) pediatric patient with lower GI bleeding, especially in patients in whom a high suspicion for a bleeding Meckel's diverticulum exists.

Physiological and pharmacological interventions in radionuclide imaging of the tubular gastrointestinal tract

Radionuclide studies of the gastrointestinal tract (GI) are used to measure GI function and to detect anatomic lesions such as Meckel's diverticuli. A variety of physiological and pharmacological interventions have been applied to both types of studies to gain a better understanding of GI function and to improve detection of disease. This article will review interventions useful in imaging the tubular GI tract. Discussed are the measurement of GI motility and function by gastric emptying and imaging studies for GI bleeding including the Meckel's scan. Interventions involving the hepatobiliary system are covered elsewhere in this issue.

Imaging Barrett's oesophagus

Eight patients who had Barrett's oesophagus confirmed by histology are presented. All had barium swallow examinations and technetium-99m sodium pertechnetate (99Tcm-pertechnetate) scintigraphy, the findings of which are reviewed and discussed. The most valuable diagnostic signs on barium swallow examination related to the site of the stricture and the presence of mucosal outpouchings. Scintigraphy was positive in all eight cases. Patients suspected of having Barrett's oesophagus on barium swallow examination should undergo scintigraphy. When the latter is positive, the endoscopist should be alerted to obtain biopsies not only at the site of stricture but serially as far as the gastrooesophageal junction.

Technetium pertechnetate scintigraphy to detect ectopic gastric mucosa in Meckel's diverticulum

Tc-pertechnetate scintigraphy was performed in 81 infants and children, clinically suspected to have Meckel's diverticulum with ectopic gastric mucosa. The predominant symptom was rectal bleeding and anemia. Twenty-two patients underwent laparotomy and 12 had Meckel's diverticulum with ectopic gastric mucosa. In operated patients the sensitivity of scintigraphy in detecting ectopic gastric mucosa was 0.75, the specificity 1.0 and the diagnostic accuracy 0.86; the diagnostic accuracy was estimated to 0.96 for the whole material. Histologic examination of the diverticula showed a smaller area of the ectopic mucosa in cases with negative scintigraphic findings. In addition, prominent fibrosis seemed to be a more consistent finding in cases with negative as opposed to those with positive scintigraphic findings. Presence of anemia may provide a guideline as to whether or not scintigraphy is indicated.

Biochemical studies of the renal radiopharmaceutical compound dimercaptosuccinate. III. Subcellular distribution and interaction of 99Tc-DMS complex with macromolecules in rat kidney homogenates in vitro

Rat kidney tissue homogenates, incubated in vitro with 99Tc-DMS were subjected to differential centrifugation. Specific radioactivities of subcellular fractions were as follows: cytosol 13,552, microsomes 3,600, mitochondria, 2,707 cpm/mg protein, and nuclei, 2,642 cpm/mg DNA. The cytosol fraction was further analyzed by ion-exchange chromatography on DEAE-Sephadex A-25 column. In this way it was separated into several distinct protein zones, three of them bearing a significant amount of 99Tc-DMS preparation. The highest specific radioactivities of proteins were eluted from the DEAE-Sephadex column with 30 mmol/l and 50-110 mmol/l NaCl solution. Total nucleic acids isolated from purified nuclei, mitochondria and microsomes contained a certain amount of bound 99Tc-DMS complex. Nuclear nucleic acids had the highest specific radioactivity, suggesting that 99Tc-DMS complex penetrates into the nuclei.

Biochemical studies of the renal radiopharmaceutical compound dimercaptosuccinate. II. Subcellular localization of 99Tc-DMS complex in the rat kidney in vivo

In order to extend and confirm our previous studies of in vivo behaviour of 99mTc-DMS in rat kidney cells, the intracellular localization of 99Tc-DMS complex in rat kidney tissue was examined. Animals were injected IV with 99Tc-DMS solution (37 kbq in 1.0 ml) 2 h before killing. Dissected kidneys were homogenized and submitted to differential centrifugation to obtain organelles. The following radioactivity distribution in relation to the total radioactivity of homogenate was obtained in nine experiments: nuclei 3.30% (+/-1.27), mitochondria 9.48% (+/-2.17), microsomes 7.03% (+/-2.34) and cytosol 57.45% (+/-8.01). The subcellular distribution pattern of 99Tc-DMS was in very good agreement with the pattern of 99Tc-DMS binding to kidney cell organelles obtained by the same procedure. Soluble cytoplasmic proteins binding 99Tc-DMS were excluded from a Sephadex G-25 column with the void volume. Their electrophoretic mobility after agarose gel electrophoresis corresponded to beta-lc- and alpha-2-macroglobulins. The results obtained show unambiguously that the investigated complex penetrates into the kidney cells where it binds mostly to soluble cytoplasmic proteins and mitochondria, and to a lesser extent to both microsomes and nuclei. In another series of six experiments, isolated kidney cortical tissue was used, the same procedure was repeated and similar results were obtained.

The role of radionuclide studies in pediatric gastrointestinal disorders

Radionuclide techniques are currently used to fully evaluate many congenital and acquired abnormalities of the gastrointestinal tract of children. Frequently, the anatomic and functional data provided by the nuclear examination are definitive. In the study of many disease entities, tracer techniques have replaced more cumbersome or invasive procedures. Although the radiopharmaceuticals and instrumentation are similar as applied to both children and adults, the uniqueness of children and their disease entities requires special consideration when performing and interpreting their studies. In this review, the principle radionuclide examinations used in the evaluation of pediatric gastrointestinal disorders are detailed and examples are illustrated.

Radionuclide diagnosis of Meckel's diverticulum

Meckel's diverticulum can be detected with a high degree of accuracy by radionuclide scintigraphy using technetium-99m pertechnetate. The technique is without risk and should precede roentgenographic studies when the diagnosis is suspected. The method is described and the causes for false positive and false negative examinations are discussed. False negatives are rare and false positive are usually secondary to other surgical entities. Overall accuracy is 85 to 90%.