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Biomedical subjects

H R Ham

Publications and source records attributed to H R Ham.

At least 127 records · Page 7Linked to original sources
PubMed1985

Influence of statistical noise on the determination of the single kidney 99Tcm-DTPA clearance.

Single kidney clearance can be obtained using the 99Tcm-DTPA complex and the scintillation camera. In order to evaluate the influence of statistical noise on the determination of the clearance, several non-noisy curves were constructed, simulating renal, background and precordial curves. Poisson noise was added to these curves and the clearance results were compared to those obtained on the original curves. It was shown that, in so far as a moderate curve smoothing was used, the statistical noise did not interfere considerably with the results of the renal clearance.

Glomerular Filtration Rate↗
PubMed1984

Quantitation of esophageal transit by means of 81mKr.

A method for quantifying esophageal transit by means of 81mKr is described. The principal advantage of 81mKr compared with 99mTc is its ultra-short half-life with its consequences on radiation dose and counting statistics. Factors which may influence the esophageal transit time such as body posture, volume of the tracer, and the nature of the tracer were studied. The reproducibility of the technique is quite good and its capacity to detect minor esophageal transit disorders is demonstrated.

Adult↗
PubMed1983

The evaluation of right ventricular performance using krypton-81m.

The availability of krypton-81m suitable for intravenous injection provides an easy means for assessing right ventricular function. The superimposition of the other heart chambers does not constitute a problem. The activity in the left heart is negligible and the study can be performed in the right anterior oblique position to obtain optimal separation between the right atrium and the right ventricle. Lung activity is quite high and should be corrected before computing the right ventricular ejection fraction. This correction can be accomplished by performing Tc-99m MAA perfusion scintigraphy. The measurement of the right ventricular ejection fraction appears to be reproducible with very small inter-and intraobserver variability. Good quality phase and amplitude images can be obtained with such high count rates.

Cardiac Output↗
PubMed1982

A co-operative study on the clinical value of dynamic renal scanning with deconvolution analysis.

An international project was set up to study the clinical usefulness of intrarenal transit times derived from the renogram by deconvolution. A common data sheet, to collect clinical, biochemical, radiological and isotopic information, was completed by the centres. Five hundred and ninety-one patients were studied and the results analysed. The mean transit time (MTT) in normal kidneys was found to be 3.6 +/- 1.1 min. If the MTT is greater than 7.6 min, a kidney is likely to be obstructed. In vesico-ureteric reflux, the transit times are prolonged, but they are normal in infection, hypertension, parenchymal disease and minimally irradiated kidneys. In transplantation, when the kidney is normal, the transit times are shorter than in the natural kidney; in acute rejection, transit time are prolonged.

Adult↗
PubMed1981

Radionuclide venography using continuous Kr-18 m infusion: preliminary note.

Continuous infusion of Kr-81m presents important advantages compared to the commonly used radionuclides for venography. High count rates can be accumulated, and a high resolution collimator can be employed to ensure good quality images. The study can be repeated immediately and multiple views can be performed until a satisfactory result is obtained. The production of radionuclide from a Rb-81--Kr-81m generator suitable for intravenous infusion is almost the same as that which is suitable for ventilation. The same generator can first be used for venography and then for ventilation imaging to complete the work-up patients suspected of having thromboembolic disease.

Evaluation Studies as Topic↗
PubMed1981

Radionuclide quantitation of left-to right cardiac shunts using deconvolution analysis: concise communication.

Quantitative radionuclide angiocardiography (QRAC) was performed with and without deconvolution analysis (DA) in 87 children with various heart disorders. QRAC shunt quantitation was possible without DA in 70% of the cases and with DA in 95%. Among 21 patients with prolonged bolus injections, quantitation of the shunt was possible in 52% of the cases without DA an in all cases with DA. Correlation between oximetry and QRAC with DA was better than between oximetry and QRAC without DA. It is concluded that QRAC with DA is a more reliable, noninvasive means for detection and quantitation of left-to-right cardiac shunts than QRAC without DA.

Adolescent↗
PubMed1980

Critical evaluation of lung scintigraphy in cystic fibrosis: study of 113 patients.

A long-term study has been performed on 285 lung perfusion scintigrams obtained from 113 patients with cystic fibrosis. Transverse and longitudinal comparisons with clinical and radiological scores, as well as retrospective analysis of the deceased patients, were the methods used in order to evaluate the importance of the scintigraphic images. It appears that lung scintigraphy is the best index of the regional lung impairment, and contributes, as does a chest radiograph, to the early detection of lung lesions, the two methods being complementary. The survival rate of CF patients reached 0.80 at 9 yr when initial scintigraphy was normal or only moderately impaired, but fell to 0.18 when severe lesions were seen on the first scintigrams.

Cystic Fibrosis↗
PubMed1978

A simple method for measuring separate glomerular filtration rate using a single injection of 99mTc-DTPA and the scintillation camera.

A new technique for measuring glomerular filtration in each kidney has been developed using a scintillation camera and the 99mTc-DTPA complex. The technique has been applied to 101 children with various uropathies. Correlations with the total and separate creatinine clearance, the HgCl2 uptake test, and the maximal urinary concentration have been good. The reproducibility of the method has been satisfactory in a small number of patients. The test is particularly adapted to children because of its simplicity, reduced trauma, short duration (20 minutes) and low-radiation dose. In contrast to some other radioisotope techniques, it can be carried out in infants.

Adolescent↗
PubMedDate not supplied

Determination of right ventricular ejection fraction in children with cystic fibrosis.

The radionuclide right ventricular ejection fraction (RVEF) determined by means of Krypton-81m represents a simple, noninvasive, and accurate procedure to quantify the right ventricular contractility. This procedure was applied to 25 young patients with cystic fibrosis. The RVEF tended to decrease with the progression of the lung disease, as assessed by the clinical S-K score, the degree of the defects on lung scintigraphy, the PaO2, and the lung function tests. However, the decrease of RVEF in patients with marked lung function tests. However, the decrease of RVEF in patients with marked lung involvement was moderate, and terminal lung disease was sometimes associated with normal right heart contractility.

Adolescent↗
PubMedDate not supplied

Cut-off point, timing and pitfalls of the 13C-urea breath test as measured by infrared spectrometry.

BACKGROUND: The best timing and the best cut-off level of the 13C-urea breath test have not yet been well established. AIMS: To evaluate the cut-off value and the influence of medication on the 13C-urea breath test as measured by infrared spectrometry. METHODS: A series of 223 patients, sent for endoscopy performed 13C-urea breath test in fasting conditions with 75 mg of 13C-urea and 20 ml of citric acid. Breath samples were collected before and then 10, 20, 25 and 30 minutes after ingestion. As gold standard, histological examination of gastric biopsies was used. A questionnaire was completed concerning the intake of medication, likely to influence the test, in the 2 months preceding the test. Sensitivity, specificity, positive predictive value and negative predictive value at 10, 20, 25 and 30 minutes at different cut-off values (3, 3. 5, 4, 4. 5, 5.0 0/00 DOB] were calculated. RESULTS: A total of 182 patients did not take medication. There was no significant difference between the different cut-off levels at different times. Compared with the group of 41 patients who did take medication, likely to influence the test, the differences were significant (Fisher exact test). CONCLUSION: There was no significant difference between the different cut-off values. A 10-minute test with a cut-off level between 4 and 5% delta over baseline (sensitivity: 100%, specificity: 95%) is, therefore, proposed. To avoid false negative results due to unknown intake of medication, every patient submitted to the 13C-urea breath test should fill out a questionnaire.

Breath Tests↗
PubMedDate not supplied

CT and 99mTc-DMSA scintigraphy in adult acute pyelonephritis: a comparative study.

PURPOSE: The aim of this prospective study was to evaluate the relative value of CT and (99m)Tc-DMSA scintigraphy in the diagnosis of acute pyelonephritis (APN) in adult patients suspected of having urinary tract infection. METHOD: The study was conducted in 36 patients presenting with symptoms suggestive of urinary tract infection. Plain B-mode sonography, CT with contrast medium, and (99m)Tc-DMSA scintigraphy of the kidneys were performed in all patients. Both CT and (99m)Tc-DMSA scintigraphy were performed within 72 h after admission. RESULTS: Twelve patients with clinical and biological signs of urinary tract infection had no CT or (99m)Tc-DMSA scintigraphy abnormalities. Among these patients, lower urinary tract infection was found in 10 patients and 2 patients had ureteral obstruction. In the 24 remaining patients, the diagnosis of APN was made. Among these patients, a correlation was found between CT and (99m)Tc-DMSA scintigraphy in 11 cases. In two cases, both examinations were normal, and in nine cases, both were abnormal. In 11 cases of the 13 remaining patients, abnormal CT was found with normal (99m)Tc-DMSA scintigraphy, whereas the 2 last cases had normal CT and abnormal (99m)Tc-DMSA scintigraphy results. In two cases, bilateral lesions found on CT manifested as unilateral abnormalities on (99m)Tc-DMSA scintigraphy images. CONCLUSION: The diagnosis of APN in adult patients is based on clinical presentation and biological findings. Few studies have compared (99m)Tc-DMSA scintigraphy with CT in the detection of parenchymal involvement in APN. We conclude that CT is more accurate than (99m)Tc-DMSA scintigraphy in the detection of APN lesions in adult patients.

Acute Disease↗
PubMedDate not supplied

Sensitivity of cortical transit and furosemide response in the diagnosis of renal obstruction. An experimental model.

Several radionuclide parameters are routinely used for the diagnosis of renal obstruction. In order to evaluate the sensitivity of those parameters, an experimental model of partial ureteral obstruction in rats was used. Neither the cortical transit time, nor the response to furosemide could serve to discriminate between obstructive and nonobstructive kidneys. These parameters were, however, more or less related to the degree of impairment of the single kidney glomerular filtration rate and should probably be considered as functional parameters reflecting the grade of the obstructive phenomenon.

Animals↗
PubMedDate not supplied

Evaluation of the 13C-aminopyrine breath test using nondispersive infrared spectrometry.

OBJECTIVE: The aim of the study was to assess the value of the 13C Aminopyrine Breath Test (ABT) when performed using the NonDispersive InfraRed Spectrometry (NDIRS), which is a simple and cheap alternative to the mass spectrometry. METHODS: The results obtained by using the NDIRS method for performing the ABT were compared to the results obtained by a reference method, the 14C Aminopyrine Breath Test. For this purpose, in 32 patients admitted for various liver problems, an ABT was performed by using the 2 methods simultaneously. The repeatability of the results obtained at 120 minutes by the NIDRS method as compared to the 14C test was assessed by the method of Bland and Altman. RESULTS: The mean of difference between the results obtained by both methods at 120 minutes was 0.06 +/- 0.46. The coefficient of repeatability between the two tests was 0.92 for a confidence interval of 95%. A good correlation (r = 0.93) was found between all individual results obtained in breath samples at different times of collection (30, 60, 90, 120 minutes), and between the results obtained at 120 minutes for both 13C and 14C tests (r = 0.94). CONCLUSION: The 13C ABT performed using NDIRS is a valid alternative to the 14C technique in routine clinical practice.

Aminopyrine↗