Pediatric Gastrointestinal Nuclear Medicine

Update on Pediatric Nuclear Medicine in Acute Care

Various radiopharmaceuticals are available for imaging pediatric patients in the acute care setting. This article focuses on the common applications used on a pediatric patient in acute care. To confirm the clinical diagnosis of brain death, brain scintigraphy is considered accurate and has been favorably compared with other methods of detecting the presence or absence of cerebral blood flow. Ventilation-perfusion lung scans are easy and safe to perform with less radiation exposure than computed tomography pulmonary angiography and remain an appropriate procedure to perform on children with suspected pulmonary embolism as a first imaging test in a hemodynamically stable patient with no history of lung disease and normal chest radiograph. 99mTc-pertechnetate scintigraphy (Meckel's scan) is the best noninvasive procedure to establish the diagnosis of ectopic gastric mucosa in Meckel's diverticulum. 99mTcred blood cell scintigraphy generally is useful for assessing lower GI bleeding in patients from any cause. Hepatobiliary scintigraphy is the most accurate diagnostic imaging modality for acute cholecystitis. 99mTc-dimercaptosuccinic acid scintigraphy is the simplest, and the most reliable and sensitive method for the early diagnosis of focal or diffuse functional cortical damage. 99mTcmercaptoacetyltriglycine scintigraphy is used to evaluate for early and late complications of renal transplantation. Bone scintigraphy is a sensitive and noninvasive technique for diagnosis of bone disorders such as osteomyelitis and fracture. 18F-fluorodeoxyglucose-positron emission tomography could be valuable in the evaluation of fever of unknown origin in pediatric patients, with better sensitivity and significantly less radiation exposure than a gallium scan. Moving forward, further refinement of pediatric radiopharmaceutical administered activities, including dose reduction, greater radiopharmaceutical applications, and updated consensus guidelines is warranted, with the use of radionuclide imaging likely to increase.

Gender-based differences in pediatric nuclear medicine

Gender-based differences commonly encountered in pediatric nuclear medicine reflect both basic embryologic differences of the sexes, which are evident from infancy, and evolving physiological changes due to gender, which occur as the pediatric patient grows, undergoes puberty, and matures to adulthood. It is important for a nuclear medicine physician or radiologist to know both the gender and the age of a patient when interpreting her or his studies. It is also important that the reading physician be familiar with the normally evolving physiological changes that are specific for that patient's stage of development. It is particularly important that the reading physician consider such changes when comparing serial studies of the patient that are acquired during the patient's transitions through her or his different significant stages of development. Many pediatric nuclear medicine imaging protocols are modifications or adaptations of the protocols for adult imaging. Physicians reading pediatric studies must routinely incorporate knowledge on age and gender that is relevant to the patient for any given study. The age-defined gender-based subtleties of potential findings in pediatric nuclear medicine studies are often underrecognized. However, they are often of interest and at times important in the workup of both benign entities and pathologic processes of the pediatric patient.

Hepatobiliary scintigraphy during cholestatic and noncholestatic periods in patients with progressive familial intrahepatic cholestasis after partial external biliary diversion

BACKGROUND

The purpose of the study was to determine the distribution of excreted bile during cholestatic periods and in remission in patients with progressive familial intrahepatic cholestasis (PFIC) after surgery with partial external biliary diversion (PEBD), using hepatobiliary scintigraphy.

METHODS

Using intravenously administered technetium Tc 99m-labeled mebrofenin, the distribution of bile during periods of biochemical cholestasis and in remission was investigated in patients with PFIC operated with PEBD. Stomal bile, urine, and feces from the patients were collected during 24 hours after administration of technetium Tc 99m-labeled mebrofenin; and the fractions of remaining radioactivity in the 3 compartments and the remaining isotopic activity in the body were quantified using scintigraphy.

RESULTS

Nine patients (4 boys and 5 girls) were studied. The median age was 13 (range, 5-24) years, and they had been operated with PEBD at a median time of 10 (range, 4-14) years before entering the study. Thirteen scintigraphic examinations were analyzed: 8 during noncholestatic remission (n = 7 patients) and 5 during cholestasis (n = 3 patients). The patients studied during remission discharged a significantly larger fraction of isotopic activity through the stoma (median, 90% vs 22%; P < .05) and a significantly lower fraction through the urine (median, 2.5% vs 15%; P < .05) compared with the patients studied during cholestasis.

CONCLUSION

Hepatobiliary scintigraphy could detect substantial differences in the output of bile. Further studies are needed to determine whether these differences may explain the mechanism of the PEBD operation or merely are secondary to the degree of cholestasis.

The role of coughing as a gastroesophageal-reflux provoking maneuver: the scintigraphical evaluation

BACKGROUND

Attempts have been made to improve the positivity of the radionuclide detection of gastroesophageal reflux (GER). The aim of this study was to examine the possible contribution of coughing as a provoking maneuver in GER scintigraphy.

METHODS

One hundred and twenty-five patients (mean age: 9.2+/-3.2 years) who had a clinical probability of having GER and were fully able to cooperate for coughing on command were included in the study. The patients were asked to cough gently four to six times per minute in the 2nd, 4th, and 6th 10-min periods within a 60-min total study time. The presence and number of GER episodes were noted for each period in all patients.

RESULTS

Sixty-one of 125 patients (48.8%) showed no scintigraphic finding of GER and were interpreted as normal. In the remaining 64 patients (51.2%), GER was observed and these patients were interpreted as abnormal (GER+). Among patients with abnormal results, 25 (39%) presented GER episodes only during the coughing intervals of the study. In 33 (51.6%) patients, the reflux was seen both at coughing and noncoughing periods. In only six patients (9.4%) with GER in noncoughing periods, coughing did not provoke any reflux episodes. No overall correlation between cough-provoked frequency of reflux, number of GER episodes, and symptom severity was found in 64 GER+ patients (P>0.5); but in the subgroup of patients presenting GER episodes only during the coughing intervals, 60% (15 of 25), presented GER episodes only in one of the three cough-provoked intervals and also had the lowest symptom severity scores.

CONCLUSION

The results of our study showed that 39% (25 of 64) of the observed GER findings were achieved exclusively by means of cough provocation.

Effects of anatomical position on esophageal transit time: A biomagnetic diagnostic technique

AIM: To study the esophageal transit time (ETT) and compare its mean value among three anatomical inclinations of the body; and to analyze the correlation of ETT to body mass index (BMI).

METHODS: A biomagnetic technique was implemented to perform this study: (1) The transit time of a magnetic marker (MM) through the esophagus was measured using two fluxgate sensors placed over the chest of 14 healthy subjects; (2) the ETT was assessed in three anatomical positions (at upright, fowler, and supine positions; 90º, 45º and 0º, respectively).

RESULTS: ANOVA and Tuckey post-hoc tests demonstrated significant differences between ETT mean of the different positions. The ETT means were 5.2 ± 1.1 s, 6.1 ± 1.5 s, and 23.6 ± 9.2 s for 90º, 45º and 0º, respectively. Pearson correlation results were r = -0.716 and P < 0.001 by subjects’ anatomical position, and r = -0.024 and P > 0.05 according the subject’s BMI.

CONCLUSION: We demonstrated that using this biomagnetic technique, it is possible to measure the ETT and the effects of the anatomical position on the ETT.