Jean-Luc Urbain

Electrogastrography and gastric emptying scintigraphy are complementary for assessment of dyspepsia.

We have tried to correlate abnormalities in electrogastrography (EGG) and gastric emptying (GE) with symptom severity in patients with functional dyspepsia. Seventy-two patients with functional dyspepsia underwent EGG, GE, and symptom severity quantitation. EGGs were assessed for dominant frequency (DF), percentage of time of DF in the 2 to 4 cpm range, and postprandial-fasting DF power ratio. Solid-phase GE scintigraphy was assessed for 2-hour percentage retention. Symptoms of upper abdominal discomfort, early satiety, postprandial abdominal distension, nausea, vomiting, and anorexia were graded as none (0), mild (1), moderate (2), and severe (3); the sum represented a total symptom score. The EGG was abnormal in 11 of 22 (50%) patients with delayed GE compared with 11 of 50 (22%) with normal GE (p < 0.025). The total symptom scores were higher in patients with both delayed GE and abnormal EGG compared with patients with normal GE and EGG, normal GE and abnormal EGG, and delayed GE and normal EGG. We conclude that EGG abnormalities are more common in dyspeptic patients with delayed GE. Patients with both delayed GE and abnormal EGG have more severe symptoms. Our results suggest that EGG and GE complement each other in correlating symptoms to gastric dysmotility.

The two-component stomach: effects of meal particle size on fundal and antral emptying

Using a dual-headed gamma camera and a standardized egg test meal labeled with 99mTc-sulfur colloid, the quantitative emptying of the total, proximal and distal stomach in five normal subjects was characterized. The same egg meal was given to the volunteers in 3 different forms: homogenized, and as 2.5 mm and 5.0 mm cubes on 3 separate occasions for a total of 15 studies. For the total stomach emptying, the lag phase and half emptying time (T1/2) obtained using a power exponential model were significantly shorter for the homogenized test meal than for the 2.5 mm and 5.0 mm cubed egg particles; the lag phases were 29±19 min (mean±SD) vs 55±56 (P<0.05) and 64±24 min (P<0.01), the T1/2′s were 71±30 min vs 91±26 (P<0.05) and 104±30 min (P<0.05), respectively. For the proximal stomach, no statistically significant difference was observed among the 3 test meals; the T1/2s for the homogenized, 2.5 mm and 5.0 mm cubed meals were 65±26 min, 53±18 min and 64±20 min, respectively. For the distal stomach, both the peak activity (%) and time to peak activity (min) were significantly higher for the 2.5 mm cubes (43%, 54 min) and the 5.0 mm cubes (38%, 60 min) than for the homogenized eggs (16.4%, 30 min) (P<0.01). The correlation between the lag phase for the total stomach and the time to peak activity in the distal stomach was excellent (r=0.85, P<0.001 suggesting that the lag phase may correspond to the maximum filling of the distal stomach. These results demonstrate quantitatively that the proximal portion of the stomach is mainly responsible for the receipt and storage of food and the emptying of liquids, while the distal stomach appears to be primarily involved with the processing of solid food before its passage through the pylorus.

Recent advances in gastric emptying scintigraphy

Gastric emptying scintigraphy was introduced more than 25 years ago by Griffith and still remains the gold standard to assess gastric emptying. Test meals, radiopharmaceutical and acquisition procedures have been refined and optimized over the years and the test procedure is now well standardized. However, in its most common use, gastric emptying scintigraphy provides little information on gastric physiology and pathophysiology. Over the last decade, modeling of the liquid- and solid-emptying curves has provided some insight into the complex gastric physiology. Compartmental analysis of the stomach has also provided information on the pathophysiological mechanisms of delayed gastric emptying. Over the past 5 years, the most dramatic development in gastric emptying scintigraphy has been the introduction of digital antral scintigraphy. Digital antral scintigraphy consists primarily of dynamic imaging of the stomach and a refined Fourier transform processing method. This new procedure allows for the visualization of antral contractions and, like manometry, permits quantitative characterization of the frequency and amplitude of these contractions. Overall, this new procedure provides a unique, noninvasive tool to characterize gastric motility, to define the pathophysiological mechanisms of gastric motor disorders, and to evaluate the effect of new gastrokinetic compounds.

How Useful is an Integrated SPECT/CT in Clinical Setting and Research?: Evaluation of a Low Radiation Dose 4 Slice System §

Hybrid imaging is becoming a popular technology in nuclear medicine. We have evaluated the added value of an integrated SPECT/low-dose multislice CT over conventional planar/SPECT nuclear imaging. Phantom and clinical studies were performed on the Infinia™ Hawkeye™ 4 slice (HWK-4) with an upgraded software package (Xeleris 2.05v) from GE Heatlthcare to assess 1) the benefit of CT for contrast-resolution, attenuation correction, and anatomic localisation; 2) the impact of hybrid imaging in 456 consecutive patients in a clinical setting. SPECT/CT data were compared to conventional planar/SPECT data and correlated to clinical, biochemical, morphological imaging, angiography, and pathology findings. SPECT/CT was well tolerated by the patients with minimal CT irradiation dose (< 2mSv). HWK-4 provided useful attenuation correction for its routine use in MPI and accurate anatomic localisation of physiological and pathological foci in 99m Tc-RBC, 99m Tc-HMPAO-WBC, 131/123 I-MIBG, Octreoscan ® , and 67 Ga studies. Low-dose multislice CT also helped detect gross morphological abnormalities. Hybrid imaging had a significant impact in ProstaScint ® and parathyroid imaging for image-guided intervention. In bone imaging and differentiated thyroid cancers, SPECT/CT was able to clarify equivocal findings from planar whole-body scan. SPECT/CT was also found useful to precisely localize sentinel lymph nodes. Research protocols are being evaluated for half-time acquisition with resolution recovery and quantification of tracer distribution. SPECT/low-dose multislice CT has been successfully implemented in routine clinical practice. CT provided added value for effective attenuation correction and accurate anatomic localisation of disease with an impact on patient management.

Complementary roles of low-dose SPECT-CT and high-resolution volume CT for detection of coronary artery disease.

A 70-year-old woman with a high pretest likelihood of coronary artery disease (CAD) underwent a Tc-99m MIBI SPECT-CT study for myocardial perfusion imaging (MPI), which was complemented by a high-resolution volume CT (VCT) study. After attenuation correction, an MPI pattern of ischemia was detected in the lateral wall of the myocardium. The CT calcium score (CTCS) was above the 75th percentile. The CT angiography (CTA) demonstrated a 70% stenosis at the ostial part of the circumflex artery, and incidentally revealed a saccular aneurysm. In todays nuclear cardiology, low-dose SPECT-CT plus high-resolution VCT allows anatofunctional assessment of suspected CAD.

Coagulation Factor and Theranostics: A New Paradigm in Molecular Imaging

In the current issue of The Journal of Nuclear Medicine, Nielsen et al. (1) illustrate the potentials and significant challenges of targeting cancer cells’ surface receptors for imaging and therapy. It is grossly estimated that the human body is made up of about 37 trillion cells (2). These cells communicate with each other through complex networks of extracellular molecules such as growth and inhibitory factors; hormones; neurotransmitters; and cytokines, which bind to specific membrane, cytoplasmic and nuclear receptors. Cell surface receptors are specialized membrane proteins that bind specific cognate ligands and, once activated, relay specific messages to the cell machinery via various molecular cascades under a process called signal transduction. Although cell surface receptors differ in the way they transmit information into the interior of the cell, in mammalian cells, most receptors can be generalized into 3 distinct and large families based on the mechanisms they use to transmit their signals: ion channel–linked receptors, which convert chemical signals to electrical ones; G-protein–linked receptors that trigger internal

Molecular Gastrointestinal Scintigraphy

Over the past 30 years, the description of the scintigraphic procedures to perform gastrointestinal imaging studies and their findings in multiple diseases have been described in journal articles and textbook chapters (Urbain et al. 2000, 2002). The aim of this contribution is to provide the nuclear medicine scientist with the basic genetic knowledge of various diseases as it relates to the gastrointestinal tract and may affect the result of gastrointestinal scintigraphic studies. First, the basic, molecular and genetic abnormalities of diseases affecting the motility of the gastrointestinal tract are explained. The molecular onco- genesis of gastrointestinal tumors is then described and illustrated with positron emission tomography (PET) examples. The neuroendocrine system of the gastrointestinal tract is then reviewed with a “molecular scope”. Finally, the most promising avenue in molecular gastrointestinal scintigraphy is evoked.