Egg Labeling Methods for Gastric Emptying Scintigraphy Are Not Equivalent in Producing a Stable Solid Meal

Scintigraphy of Gastrointestinal Motility: Best Practices in Assessment of Gastric and Bowel Transit in Adults

Various radiologic examinations and other diagnostic tools exist for evaluating gastrointestinal diseases. When symptoms of gastrointestinal disease persist and no underlying anatomic or structural abnormality is identified, the diagnosis of functional gastrointestinal disorder is frequently applied. Given its physiologic and quantitative nature, scintigraphy often plays a central role in the diagnosis and treatment of patients with suspected functional gastrointestinal disorder. Most frequently, after functional gallbladder disease is excluded, gastric emptying scintigraphy (GES) is considered the next step in evaluating patients with suspected gastric motility disorder who present with upper gastrointestinal symptoms such as dyspepsia or bloating. GES is the standard modality for detecting delayed gastric emptying (gastroparesis) and the less commonly encountered clinical entity, gastric dumping syndrome. Additionally, GES can be used to assess abnormalities of intragastric distribution, suggesting specific disorders such as impaired fundal accommodation or antral dysfunction, as well as to evaluate gastric emptying of liquid. More recently, scintigraphic examinations for evaluating small bowel and large bowel transit have been developed and validated for routine diagnostic use. These can be performed individually or as part of a comprehensive whole-gut transit evaluation. Such scintigraphic examinations are of particular importance because clinical assessment of suspected functional gastrointestinal disorder frequently fails to accurately localize the site of disease, and those patients may have motility disorders involving multiple portions of the gastrointestinal tract. The authors comprehensively review the current practice of gastrointestinal transit scintigraphy, with diseases and best imaging practices illustrated by means of case review. ©RSNA, 2024 See the invited commentary by Maurer and Parkman in this issue.

An Evaluation of Gastric Emptying Scintigraphy Protocols in Health Care Institutions When Compared with the Society of Nuclear Medicine and Molecular Imaging Procedure Guidelines

This study aimed to analyze the compliance of health care institutions with the Society of Nuclear Medicine and Molecular Imaging (SNMMI) procedure guidelines for gastric emptying scintigraphy (GES). Methods: A 19-question survey on demographics and the GES protocol was conducted using a Google form. The demographic questions covered position, number of technologists in the department, location, type of health care institution, and number of GES studies per month. The protocol questions included patient preparation, meal preparation, withholding of scheduled medications, radiopharmaceutical type, and radiopharmaceutical dose. The survey was sent to 7 nuclear medicine Facebook groups and a list of clinical affiliates provided by the Indiana University School of Medicine Nuclear Medicine Program. Descriptive statistics were compiled for most questions. A Fisher exact test with a significance level of 0.05 was used to compare the type of health care institution with compliance with the SNMMI GES protocol regarding radiolabeling time, meal preparation, and meal components, as well as to compare the type of health care institution with the number of GES studies performed per institution. Results: In total, 240 people responded to the survey. Most were nonsupervisory nuclear medicine technologists (72%) in nonacademic institutions (72%) and groups with 4 or more technologists (62%). Of the respondents, 72% followed the SNMMI guideline of adding the radiopharmaceutical before cooking, but only 37% followed the meal component guideline. There was no significant association between the type of institution or the number of GES studies and compliance with radiolabeling time or with meal preparation or components. Most respondents asked patients to withhold medications per SNMMI guidelines and used the recommended radiopharmaceutical (99mTc-sulfur colloid, 95%) at the recommended dose (18.5-37 MBq, 84%). Conclusion: Although most respondents followed most aspects of the SNMMI guidelines for GES, more than half did not use the recommended meal of liquid egg whites. Compliance did not vary between academic and nonacademic institutions or between groups performing a large or a small number of GES studies.

The Efficacy of Radiolabeling the Albumin in Egg Whites with 99mTc-Sulfur Colloid

In 2009, the Society of Nuclear Medicine and Molecular Imaging published a standardized protocol guideline for gastric emptying scintigraphy that contains specific instructions on the exact meal and preparation procedure. Previous research has shown that the standardized meal and proper preparation of the meal for gastric emptying scintigraphy are not being adopted by some facilities. This research explores the differences of radiolabeling in the method of preparation of 99mTc-sulfur colloid (SC)-radiolabeled eggs. Methods: Liquid egg whites were mixed with 99mTc-SC before cooking in conjunction with the standardized protocol. A second sample set was prepared by adding the 99mTc-SC to eggs after they were cooked. Each sample set was placed in a solution of HCl and pepsin to simulate gestation. Radiolabeling efficacy was tested on each sample set at 2 and 4 h after gestating in HCl and pepsin. Results: 99mTc-SC added to the liquid egg whites before microwave cooking yielded radiolabeling efficacy of 70% 99mTc-SC after 2 and 4 h of simulated gastric fluid gestation. In contrast, radiolabeling after cooking the egg whites yielded 50% radiolabeling after simulated gestation. Conclusion: The results from this experiment showed that the method of mixing the 99mTc-SC with liquid egg whites before microwave cooking has higher binding efficacy than when adding 99mTc-SC onto already cooked egg whites. These results highlight the importance of following the standardized protocol for the meal preparation of a gastric emptying study.

Tagging Efficiency of 99m Tc-SC Radiolabeled Alternative Gastric Emptying Meals: A Quantitative Study

Objective  The aim of this study was to know the tagging efficiencies of technetium-99m labeled sulfur colloid (99mTc-SC) with different meals. Materials and Methods  Egg white sandwiches are the gold standard for gastric-emptying scan (GES); thus, an egg white omelet labeled with ^99m Tc-SC is taken as a standard meal. For evaluation, we included four meals, bread and butter, instant oatmeal, idli, and chapatti, and all meals were prepared by labeling them with ^99m Tc-SC. After preparation, food articles were chopped with the help of a metal fork and mixed in simulated gastric fluid. Four samples were taken simultaneously from each food article and analyzed for 1 to 4hours after agitation within the centrifuge. The samples were filtered and separated from the sediments and supernatants. We analyzed the activity in each sample before and after filtration. Results  The mean values of labeling efficiency in per cent of various meals were obtained. There was no significant difference in labeling stability for egg whites, chapatti, and idli meals labeled with ^99m Tc-SC from 1 to 4hours as their p -value (p>0.05) was insignificant. Conclusion  Radiolabeled chapatti and idli with ^99m Tc-SC show higher labeling stability, while oatmeal and bread and butter samples show relatively low stability. Thus, for GES, chapatti and idli labeled with ^99m Tc-SC can be used as alternatives to eggs for vegetarian people or for those allergic to eggs.

Pediatric Solid Gastric Emptying Scintigraphy: Normative Value Guidelines and Nonstandard Meal Alternatives

INTRODUCTION

Adult standards for gastric emptying scintigraphy, including the type of meal and range of normative values for percent gastric emptying, are routinely used in pediatric practice, but to date have not been validated. The purpose of this study is to determine whether the use of adult criteria for gastric emptying scintigraphy is valid for children and whether alternative nonstandard meals can also be offered based on these criteria.

METHODS

This retrospective study analyzed patients (n = 1,151 total) who underwent solid-phase gastric emptying scintigraphy. Patients were stratified into normal and delayed gastric emptying cohorts based on adult criteria, i.e., with normal gastric emptying defined as ≤10% gastric retention at 4 hours. Patients were further stratified based on the type of meal, namely complete or partial adult standard meals or alternative cheese-based meals. Percent gastric retention values at 1, 2, 3, and 4 hours were compared.

RESULTS

The median (95% upper reference limit) percentage gastric retention values for the complete standard meal were 72% (93%) at 1 hour, 39% (65%) at 2 hours, 15% (33%) at 3 hours, and 6% (10 %) at 4 hours. By comparison, the values for cheese-based meals were 60% (87%) at 1 hour, 29% (61%) at 2 hours, 10% (30%) at 3 hours, and 5% (10%) at 4 hours. Consumption of at least 50% of the standard meal yielded similar retention percentages; 68% (89%) at 1 hour, 32% (57%) at 2 hours, 10% (29%) at 3 hours, and 5% (10%) at 4 hours. There were no significant age- or sex-specific differences using the adult criteria.

DISCUSSION

The adult normative standards for gastric emptying scintigraphy are applicable for use in the pediatric population. These same standards can be also be applied to nonstandard meal options, including cheese-based alternative meals and partial standard meals.

Efficiency of Radiolabeling Eggs Before and After Microwave Cooking for Gastric Emptying Scintigraphy Studies

The accuracy and reproducibility of nuclear medicine gastric emptying scintigraphy (GES) require strict adherence to the Society of Nuclear Medicine and Molecular Imaging standardized protocol, which contains precise instructions for meal ingredients and preparation. Previous research demonstrated that many laboratories were using whole eggs in the test meal as opposed to the guideline-recommended liquid egg whites and that some laboratories were attempting to radiolabel the egg by adding the radiotracer after cooking. This study aimed to document the labeling efficiency of ^99mTc-sulfur colloid (SC) added to whole eggs before and after microwave cooking. Methods: Whole eggs were mixed with ^99mTc-SC before and after microwave cooking. The radiolabeling stability of the eggs was tested after 2 and 4 h of incubation in gastric fluid simulated using just hydrochloric acid (HCl) and using HCl with pepsin. Results: The experiment showed that no matter what the testing condition, radiolabeling by adding ^99mTc-SC to whole eggs before cooking resulted in a significantly higher labeling efficiency than radiolabeling by squirting the ^99mTc-SC on eggs after cooking. This finding persisted over time, with the precooking method still showing significantly higher radiolabeling at 2 and 4 h after the egg was placed in the incubation medium for both gastric fluid mediums. For simulated gastric fluid with pepsin at 2 h, the labeling was significantly higher, at 73.3%, when the radiotracer was added before cooking than the 43.3% when added after cooking (P < 0.001). The results of this study further showed that when egg labeling efficiency was tested in HCl without pepsin, the labeling was less stable than when tested in HCl with pepsin. In the HCl-only medium, the labeling efficiency decreased significantly between 2 and 4 h for both radiolabeling methods. Conclusion: The results of this study demonstrated that the addition of ^99mTc-SC to whole eggs after cooking resulted in considerably inferior binding of the radiotracer to the eggs and that binding deteriorated significantly over time. The study further demonstrated that the results of radiolabeling efficiency varied depending on whether HCl or HCl with pepsin was used to simulate gastric fluid. Radiolabeling stability decreased over time when HCl without pepsin was used. The findings emphasize the criticality of adhering to the standardized meal and preparation, as alternate cooking methods have different radiolabeling efficiencies.

Indirect vs direct assessment of gastric emptying: A randomized crossover trial comparing C-isotope breath analysis and MRI

BACKGROUND

Indirect methods to assess gastric emptying (GE), such as ¹³ C breath tests (BT), are commonly used. However, BT usually use a sampling time of 4+ hours. The current study aims to assess the validity of BT for four liquid meals differing in physicochemical properties. To this aim, we compared them to MRI GE-measurements.

METHODS

Fifteen healthy males (age 22.6 ± 2.4 years, BMI 22.6 ± 1.8 kg/m² ) participated in a randomized 2 × 2 crossover experiment. Test foods were liquid meals, which were either thin/thick and 100/500 kcal, labeled with 100 mg of ¹³ C-octanoate. GE was measured with MRI and assessed by ¹³ C recovery from breath. Participants were scanned every 10 minutes and at six time points breath samples were collected up to t = 90 minutes. Two curves were fitted to the data to estimate emptying halftime (t_{50 Ghoos} and t_{50 Bluck} ). T₅₀ times were ranked per participant and compared between methods.

KEY RESULTS

On average, MRI and BT showed similar t₅₀ rankings for the four liquid meals. In comparison to MRI, t_{50 Ghoos} overestimated, while t_{50 Bluck} underestimated GE time_. Moreover, more viscous foods were overestimated. In most participants individual t₅₀ time rankings differed significantly between methods.

CONCLUSIONS & INFERENCES

BT can assess relative emptying differences on group level and collecting breath data for 90 minutes constitutes a lower burden for participants and the research facility. However, BT has severe shortcomings compared to MRI for individual GE assessment. Notably, food matrix effects should be considered when interpreting the results of BT.

Nuclear Scintigraphy in Practice: Gastrointestinal Motility

OBJECTIVE

The purpose of this article is to describe the clinical utility of state-of-theart gastrointestinal transit scintigraphy, including the standardized esophageal transit, solid and liquid gastric emptying, small-bowel transit, colon transit, and whole-gut transit scintigraphy, with an emphasis on procedure performance.

CONCLUSION

Radionuclide gastrointestinal motility studies are noninvasive, quantitative, and physiologic diagnostic tools for evaluating patients with gastrointestinal complaints.

Comparative assessment of gastric emptying in obese patients before and after laparoscopic sleeve gastrectomy using radionuclide scintigraphy

Radionuclide scintigraphy provides a standard physiologic evaluation of gastric emptying (GE) after laparoscopic sleeve gastrectomy (LSG). This operation can be associated with motor gastric dysfunction and abnormal GE. The aim of this study was to evaluate the short-term effect of LSG on GE quantitative indices for liquids and solids compared with preoperative results. Forty obese patients were divided into two equal groups, the liquid and solid groups. Tc-sulfur colloid GE scintigraphy was performed on all patients submitted to LSG before and after surgery (1-4 weeks for liquids and 4-6 weeks for solids). The quantitative indices included half emptying time (T1/2) and percentage gastric retention at 15, 30, and 60 min for liquids and at 30, 60, 90, and 120 min for solids. A modified technique was used to label a boiled egg in order to be tolerated by the patients. T1/2 was significantly enhanced after LSG compared with baseline (25.3±4.4 vs. 11.8±3.0 min for liquids and 74.9±7.1 vs. 28.4±8.3 min for solids, respectively, P<0.001). The percentage of gastric retention in operated patients was significantly less than that at baseline for liquids at 15, 30, and 60 min (33.9±5.6, 17.7±3.9, and 7.5±2.8% vs. 69.4±10.5, 55.6±14.95, and 26.1±4.7%, respectively, P<0.001), as well as for solids at 30, 60, 90, and 120 min (42.0±11.1, 20.8±6.1, 11.0±5.9, and 3.8±2.7% vs. 79.9±8.7, 67.4±12.2, 37.0±10.9%, and 13.8±4.4%, respectively, P<0.001). The significant acceleration of GE of liquids and solids after LSG may have contributed to weight loss in the immediate postoperative period (4-6 weeks). It remains to be determined whether the weight loss will continue beyond that period.

In vitro evaluation of tc-99m radiopharmaceuticals for gastric emptying studies

Objective: Gastrointestinal motility and functional motility disorders causing either delayed or accelerated gastric emptying (GE) may result in similar symptoms including nausea, vomiting, early satiety, fullness, bloating, and abdominal discomfort or pain. Hence, it is important to evaluate patients for both rapid and delayed GE in the same test. The gold standard technique to measure GE is scintigraphy by radiolabeled test meals. The aim of this study was to test alternative Tc-99m agents to label eggs as the solid meal and compare to Tc-99m sulfur colloid (SC) for gastric emptying studies.

Methods: In search of alternative agents for gastric emptying studies, we mixed and fried eggs with four different particulate compounds (Tc-99m labeled SC, tin colloid, nanocolloid and MAA), as well as with free pertechnetate and Tc-99m DTPA. We then measured the stability of these compounds in simulated gastric juice.

Results: Our experiments demonstrated that in addition to Tc-99m sulfur colloid;Tc-99m MAA, Tc-99m nanocolloid and Tc-99m tin colloid also appear to make stable complexes with eggs in acidic environment.

Conclusion: Therefore, these agents may be used for gastric emptying studies which could be more practical in routine conditions.

Conflict of interest:None declared.

Update on gastrointestinal radiopharmaceuticals and dosimetry estimates

The gold standard technique for measuring gastric emptying is scintigraphy using radiolabeled test meals. Recently, a standardized radiolabeled solid meal has been proposed and adopted by many centers. There is still a need for alternative meals, and several such meals with demonstrated radiolabel stability have been evaluated in small numbers of subjects. Updated radiation dosimetry associated with these meals has been calculated for adult males and adult females with normal gastrointestinal transit as well as transit abnormalities.