Estimation of deadtime in imaging human subjects

Deadtime count loss may cause significant errors in quantitative measurements performed by scintigraphic techniques. Deadtime depends on the scattering condition, and may vary among patients. The aim of this study was to estimate deadtime in imaging a human subject. A cylindrical phantom filled with various concentrations of technetium-99m solution was imaged with a gamma camera, and deadtime was assessed assuming the gamma camera to be a non-paralysable system (multi-dose method). Deadtime for the cylindrical phantom was also estimated using a point source to monitor counting efficiency (reference source method). Radionuclide angiography of the chest was performed in 38 patients with a reference source in the field of view, and temporal changes in count loss were assessed. The deadtime for each patient was calculated by the reference source method. The deadtime for the cylindrical phantom was estimated as 6.96±0.09 μs by the reference source method and was almost identical to that obtained by the multi-dose method (6.93 μs). Deadtime ranged from 6.01 to 9.58 μs in radionuclide angiography, and was positively correlated with the ratio of body weight in kg to body height in cm (y=8.566 x+5.611, r=0.869). Count loss was successfully corrected using the deadtime predicted with the regression line. In summary, the deadtime in imaging a human subject has a wide range and is related to the constitution of the subject. Correction for count loss using a deadtime predicted for each patient may be helpful in improving the reliability of quantitative nuclear medicine. Received 16 December and in revised form 28 April 1998     

Gastric carcinoma resected 95 months after being diagnosed: Report of a case

It is usually assumed that patients with gastric carcinoma will almost certainly die within 5 years if they do not receive treatment. We report herein a rare case of curative gastrectomy being performed 95 months after gastric carcinoma was diagnosed. A 37-year-old Japanese man had an upper gastrointestinal endoscopy with biopsy which revealed moderately differentiated adenocarcinoma of the stomach. This was diagnosed as type 11c early gastric carcinoma with ulceration but he refused surgery. At 45 years of age, 95 months later, he presented to our hospital with melena, at which time lesions in an identical location had enlarged to Borrmann type 3 advanced gastric carcinoma. Thus, a total gastrectomy with regional lymph node dissection was performed. Although there was no liver or peritoneal metastasis, the regional lymph nodes were involved; however, the patient recovered well and is still alive without any further recurrence roughly 4 years postoperatively. The natural history of gastric carcinoma and the malignant cycle are discussed following the presentation of this case.     

Usefulness and limitations in ultrasonography for diagnosing neck lymph node metastases in patients with hypopharyngeal squamous cell carcinoma: comparison with pathological findings following neck dissection

We evaluated the usefulness and limitations in ultrasonography (US) for diagnosing neck lymph node metastases in patients with hypopharyngeal cancer by comparing the results of preoperative US examinations with postoperative pathological findings following neck dissection. Seventy-five previously untreated patients with hypopharyngeal squamous cell carcinoma underwent a curative procedure that included neck dissection. Preoperatively, all patients were examined by palpation, computed tomography (CT), and US. Postoperatively, all dissected neck lymph nodes were submitted for pathological examination. Results of pre-and postoperative examinations were then compared. US accuracy for each lymph node was 93.9%, while sensitivity was 78.0%, since hypopharyngeal cancer metastasizes early and easily to the neck lymph nodes, and it is difficult to detect small, pathologically positive nodes. Nine of 75 cases showed latent neck recurrence, and two of these were underestimated by US. The major cause for neck recurrence was considered to be the high rate of metastases in such cases, rather than a reduced dissection field. It is not rare to find very small, pathologically positive lymph nodes that US cannot detect in hypopharyngeal cancer. Efforts must therefore be expanded to improve the accuracy of US diagnosis. Care must also be taken when selecting cases for no or limited neck dissection.     

A case of double common bile duct with gastric ulcer]

A 51-year-old man visited the Sasebo General Hospital because of a niche and a ductal lesion with reflux of barium in the lesser curvature of the gastric body in the upper gastrointestinal series of an annual medical checkup. Endoscopic examination showed an ulcer and a depressed lesion draining yellowish serous liquid in the stomach. Abdominal CT scan and MRCP revealed the ductal structure reached from the lesser curvature of the gastric body to the left lobe of the liver besides the ordinary pancreatobiliary system. ERCP showed normal common bile duct, gall bladder, and right intrahepatic bile duct, while the fistulography using cannula through the gastric depressed lesion revealed an accessory bile duct communicating to the left intrahepatic bile duct. The both biliary systems were completely separated, resulting in the diagnosis of double common bile duct of type IIIa.     

Arterial stiffness and progression to hypertension in Japanese male subjects with high normal blood pressure

OBJECTIVES: This observational study was conducted to compare the significance of the relationship between arterial stiffness and progression to higher blood pressure categories among middle-aged Japanese men with high normal blood pressure (HNP), normal blood pressure (NRP) and optimal blood pressure (OPP). METHODS AND RESULTS: During the 3-year observational period, 100 subjects with HNP developed hypertension (n=475; 42 +/- 9 years), and 175 of those with normal NRP (n=581; 41 +/- 8 years) and 249 of those with OPP (n=702; 39 +/- 8 years) showed progression to higher blood pressure categories. A binary logistic regression analysis adjusted for known risk factors revealed that values of the brachial-ankle pulse wave velocity, a surrogate marker of arterial stiffness, in the highest quartile, as compared with those in the lowest quartile, obtained at the start of the study were significantly predictive of the progression to hypertension [adjusted odds ratio = 9.4 (95% confidence interval, 3.0-29.8), P < 0.01]. The predictive value of this parameter for progression to higher blood pressure categories in subjects with HNP was more significant than that in those with NRP or OPP. CONCLUSIONS: Increased arterial stiffness and elevated blood pressure may be mutually causally related, and it appears that the significance of this relationship may increase with increasing blood pressure, even in subjects without hypertension. Assessment of arterial stiffness may be more reliable for predicting the progression to hypertension in cases of HNP than in cases with NRP or OPP.     

B-type natriuretic peptide and arterial stiffness in healthy Japanese men

BACKGROUND: Recent evidence suggests that even a slight increase in the plasma level of B-type natriuretic peptide (BNP) may be a marker of cardiovascular risk; however, the mechanisms underlying the association are currently unclear. Because increased arterial stiffness, as reflected by an increase of the pulse wave velocity (PWV) or pulse pressure (PP), may contribute to increasing plasma BNP levels, in the present study we investigated the relationships between the plasma BNP level and the PWV and PP, all of which are known markers of cardiovascular risk, in a healthy male Japanese cohort. METHODS: This was a cross-sectional study of 725 healthy Japanese men (age, 54 +/- 4 years). The PWV was assessed by the volume-rendering method. Plasma BNP levels were determined with a high-sensitivity noncompetitive immunoradiometric assay. RESULTS: A univariate linear regression analysis demonstrated that the plasma BNP level was significantly correlated with age (r = 0.20, P < .01), PWV (r = 0.12, P < .01), and PP (r = 0.17, P < .01). A stepwise multivariate linear regression analysis demonstrated that both the PWV and PP were significantly associated with the plasma BNP level, independent of age. CONCLUSION: In healthy Japanese men, stiffening of large arteries, as evidenced by an increase of the PWV or PP, may account at least in part for elevated plasma BNP levels, even within the so-called normal range.