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Biomedical subjects

H Luig

Publications and source records attributed to H Luig.

At least 19 recordsLinked to original sources
PubMed2006

[Improvement of tomographic reconstruction in bone SPECT].

AIM: The comparison between iterative reconstruction and filtered backprojection in the reconstruction of bone SPECT in the diagnosis of skeletal metastases. PATIENTS, METHODS: 47 consecutive patients (vertebral segments: n = 435), with suspected malignancy of the vertebral column, were examined by bone scintigraphy and MRI (maximal interval between the two procedures +/- 5 weeks). The SPECT-data were reconstructed with an iterative algorithm (ISA) and with filtered backprojection. We defined semiquantitative criteria in order to assess the quality of the tomograms. Conventional reconstruction was performed both by a Wiener-filter and a low-pass-filter. Iterative reconstruction was performed by the ISA algorithm. The clinical evaluation of the different reconstruction algorithms was performed by MRI as the gold-standard. RESULTS: Sensitivity (%): 87.3 (ISA), 86.4 (low-pass), 79.7 (Wiener); specificity (%): 95.3 (ISA), 95 (low-pass), 85.4 (Wiener). The sensitivity of iterative reconstructed SPECT and low-pass reconstructed SPECT was significantly higher (p < 0.05) compared with the sensitivity of SPECT reconstructed by the Wiener-filter. The specificity of iterative reconstruction ISA and low-pass-filter reconstructed SPECT were significantly higher compared with the SPECT data reconstructed by the Wiener-filter. ISA was significantly superior to the Wiener-SPECT relating to all criteria of quality. Iterative reconstruction was significantly superior to the low-pass-SPECT relating to 2 of 3 criteria. In addition the Wiener-SPECT was significantly inferior to the low-pass-SPECT regarding to 2 of 3 criteria. CONCLUSION: In our series the iterative algorithm ISA was the method of choice in the reconstruction of bone SPECT data. In comparison with conventional algorithms ISA offers a significantly higher quality of the tomograms and yields a high diagnostic accuracy.

Female↗
PubMed2000

Fever of unknown origin: prospective comparison of [18F]FDG imaging with a double-head coincidence camera and gallium-67 citrate SPET.

Gallium-67 citrate is currently considered as the tracer of first choice in the diagnostic workup of fever of unknown origin (FUO). Fluorine-18 2'-deoxy-2-fluoro-D-glucose (FDG) has been shown to accumulate in malignant tumours but also in inflammatory processes. The aim of this study was to prospectively evaluate FDG imaging with a double-head coincidence camera (DHCC) in patients with FUO in comparison with planar and single-photon emission tomography (SPET) 67Ga citrate scanning. Twenty FUO patients underwent FDG imaging with a DHCC which included transaxial and longitudinal whole-body tomography. In 18 of these subjects, 67Ga citrate whole-body and SPET imaging was performed. The 67Ga citrate and FDG images were interpreted by two investigators, both blinded to the results of other diagnostic modalities. Forty percent (8/20) of the patients had infection, 25% (5/20) had auto-immune diseases, 10% (2/20) had neoplasms and 15% (3/20) had other diseases. Fever remained unexplained in 10% (2/20) of the patients. Of the 20 patients studied, FDG imaging was positive and essentially contributed to the final diagnosis in 11 (55%). The sensitivity of transaxial FDG tomography in detecting the focus of fever was 84% and the specificity, 86%. Positive and negative predictive values were 92% and 75%, respectively. If the analysis was restricted to the 18 patients who were investigated both with 67Ga citrate and FDG, sensitivity was 81% and specificity, 86%. Positive and negative predictive values were 90% and 75%, respectively. The diagnostic accuracy of whole-body FDG tomography (again restricted to the aforementioned 18 patients) was lower (sensitivity, 36%; specificity, 86%; positive and negative predictive values, 80% and 46%, respectively). 67Ga citrate SPET yielded a sensitivity of 67% in detecting the focus of fever and a specificity of 78%. Positive and negative predictive values were 75% and 70%, respectively. A low sensitivity (45%), but combined with a high specificity (100%), was found in planar 67Ga imaging. Positive and negative predictive values were 100% and 54%, respectively. It is concluded that in the context of FUO, transaxial FDG tomography performed with a DHCC is superior to 67Ga citrate SPET. This seems to be the consequence of superior tracer kinetics of FDG compared with those of 67Ga citrate and of a better spatial resolution of a DHCC system compared with SPET imaging. In patients with FUO, FDG imaging with either dedicated PET or DHCC should be considered the procedure of choice.

Adult↗
PubMed1998

Count-rate statistics of the gamma camera.

The temporal distribution of decay events recorded by a gamma camera in 'list mode' differs from the Poisson distribution because of dead-time effects. We propose a new model for the dead-time behaviour of a gamma camera. The most important feature of our model is that the loss of events occurs in pairs or higher multiples due to the so-called 'pile-up' effect. We analyse the consequences of pile-up for the temporal distribution of events recorded by a gamma camera. The probability distribution for the time intervals between events recorded by the camera is calculated from first principles. We construct estimators for the parameter of the new distribution. We distinguish between the estimation of the total count rate and the estimation of a certain subset of the total count rate. Computer simulation confirms that our estimators are less influenced by dead-time effects than the standard estimator.

Computer Simulation↗
PubMed1997

Cardiac phase-synchronized myocardial thallium-201 single-photon emission tomography using list mode data acquisition and iterative tomographic reconstruction.

The purpose of this study was to determine whether data acquisition in the list mode and iterative tomographic reconstruction would render feasible cardiac phase-synchronized thallium-201 single-photon emission tomography (SPET) of the myocardium under routine conditions without modifications in tracer dose, acquisition time, or number of steps of the a gamma camera. Seventy non-selected patients underwent 201T1 SPET imaging according to a routine protocol (74 MBq/2 mCi 201T1, 180 degrees rotation of the gamma camera, 32 steps, 30 min). Gamma camera data, ECG, and a time signal were recorded in list mode. The cardiac cycle was divided into eight phases, the end-diastolic phase encompassing the QRS complex, and the end-systolic phase the T wave. Both phase- and non-phase-synchronized tomograms based on the same list mode data were reconstructed iteratively. Phase-synchronized and non-synchronized images were compared. Patients were divided into two groups depending on whether or not coronary artery disease had been definitely diagnosed prior to SPET imaging. The numbers of patients in both groups demonstrating defects visible on the phase-synchronized but not on the non-synchronized images were compared. It was found that both postexercise and redistribution phase tomograms were suited for interpretation. The changes from end-diastolic to end-systolic images allowed a comparative assessment of regional wall motility and tracer uptake. End-diastolic tomograms provided the best definition of defects. Additional defects not apparent on non-synchronized images were visible in 40 patients, six of whom did not show any defect on the non-synchronized images. Of 42 patients in whom coronary artery disease had been definitely diagnosed, 19 had additional defects not visible on the non-synchronized images, in comparison to 21 of 28 in whom coronary artery disease was suspected (P < 0.02; chi 2). It is concluded that cardiac phase-synchronized 201T1 SPET of the myocardium was made feasible by list mode data acquisition and iterative reconstruction. The additional findings on the phase-synchronized tomograms, not visible on the non-synchronized ones, represented genuine defects. Cardiac phase-synchronized 201T1 SPET is advantageous in allowing simultaneous assessment of regional wall motion and tracer uptake, and in visualizing smaller defects.

Algorithms↗
PubMed1997

[Importance of iterative reconstruction ISA in the diagnosis of liver hemangioma].

AIM: To evaluate whether the iterative reconstruction methodology ISA is superior to the standard technique of filtered back-projection. METHODS: In a retrospective study, we evaluated images of 39 patients with solitary or multiple liver tumors who underwent blood pool imaging in SPECT technique in order to prove or exclude the presence of hemangioma. RESULTS: Activity accumulations in accordance with the diagnosis of liver hemangioma could be visualized in 34 cases by the iterative, in 31 cases by the filtered back-projection methodology. As compared to filtered back-projection, the iteratively reconstructed lesions showed higher tumor-to-background ratios and were more easily distinguished from structures in their neighborhood. Furthermore, the iterative methodology resulted in a more homogeneous activity distribution in the liver, whereas the inhomogeneous "patchy" structure of the liver parenchyma in filtered back-projection provokes difficulties in the distinction from reconstruction artifacts. A clearer visualization of vessels and a better distinction between the right kidney and the liver was possible by the iterative algorithm, leading to advantages in the recognition of centrally or dorsally located lesions in the right hepatic lobe. CONCLUSION: These data indicate that the use of our iterative algorithm in performing liver blood pool imaging yields a higher sensitivity and a better diagnostic accuracy in diagnosing liver hemangioma.

Adult↗
PubMed1994

[Dynamic blood volume determination using the body transport function].

This paper describes a dynamic blood volume determination which is faster and more accurate than the classic method. The new method determines blood volume by means of the product of the mean transit time of the circulation and the cardiac output. The mean transit time is calculated from the body transport function. To examine the precision of the dynamic method the blood volume of 24 patients was determined in both the dynamic and the classical way, using radioactively labelled erythrocytes. The comparison of the two methods resulted in a correlation coefficient of r = 0.77. The dynamic method of blood volume determination will be helpful especially in risk patients to accurately determine the quantities of fluids to be administered.

Biological Transport↗
PubMed1993

Determination of the autonomously functioning volume of the thyroid.

The aim of this work was to determine the autonomously functioning volume in euthyroid and hyperthyroid goitres for prognostic and therapeutic purposes. To this end, various groups of patients were selected: individuals without evidence of thyroid disease, euthyroid patients with diffuse goitre of normal structure and function, euthyroid patients with evidence of autonomy and patients with hyperthyroidism due to autonomy. In all of them the thyroid uptake of technetium-99m was determined under exogenous suppression (TcUs) in the euthyroid state and under endogenous suppression (TcU) in the hyperthyroid state. It was demonstrated that: 1. In patients with unifocal autonomy the TcUs and TcU correlated linearly with the autonomous volume delineated and measured by sonography. 2. A nearly identical result was obtained if the mean autonomous volume in individuals without thyroid disease of 2.2 +/- 1.1 ml calculated by TcUs/TcU x total thyroid volume was used as a basis. 3. The critical autonomous volume, i.e. the volume at which hyperthyroidism will occur, was found to be 16 ml at a cumulated sensitivity and specificity of > 0.9. The method can be used to select patients for definitive treatment before hyperthyroidism occurs and to measure the autonomously functioning volume independent of its distribution within the thyroid for treatment with radioiodine. The method is easy to perform and is also an example of how a relative parameter of a function can be converted into an absolute parameter of a functioning volume.

Goiter↗
PubMed1992

[Differences in the non-invasive assessment of left ventricular filling in patients with dilated cardiomyopathy using Doppler echocardiography and radionuclide angiography].

Doppler echocardiography and radionuclide angiography were shown to provide valuable tools with comparable functional parameters for the noninvasive assessment of left ventricular (LV) diastolic function in patients with coronary artery disease or LV hypertrophy. In order to examine the influence of an impaired systolic function on both methods, we studied LV filling simultaneously by Doppler echocardiography and radionuclide angiography in 47 patients with idiopathic dilated cardiomyopathy and stable sinus rhythm. The Doppler echocardiographic peak velocities (VE, VA) and radionuclide angiographic peak filling rates (PFRFF, PFRA) normalized to either left ventricular enddiastolic volume or stroke volume were measured and systolic function was assessed by obtaining the ejection fraction (EF) with the radionuclide angiography. Patients were divided into two groups with moderately (group 1: EF > or = 35%) or severely impaired (group 2: EF < 35%) systolic function. In group 2 the PFRFF (1.8 +/- 0.5 vs. 3.3 +/- 0.8 SV/s; p < 0.01) and PFRA (1.2 +/- 0.6 vs. 2.5 +/- 1.0 SV/s; p < 0.01) were both lower than in group 1, as was the Doppler echocardiographic VA (0.44 +/- 0.20 vs. 0.63 +/- 0.17 m/s; p < 0.01). However, VE was increased with reduced systolic function (0.75 +/- 0.20 vs. 0.53 +/- 0.16 m/s; p < 0.01). No relation was found between PFRFF and VE and only a weak relation between the atrial filling parameters of Doppler echocardiography and radionuclide angiography. The peak filling rates were closely correlated with the systolic function (PFRFF:r = 0.86; p < 0.001) and were reduced with an impaired systolic function.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Flow Velocity↗
PubMed1989

[Comparison of the clinical value of an iterative reconstruction procedure with that of a filtered back projection in SPECT of the liver].

We have tested an iterative reconstruction procedure against the usual filtered back-projection in 14 patients with SPECT-examinations of various liver diseases. The aim of the examinations was to assess the presence of liver tumors in most cases. Further indications were Budd-Chiari syndromes and a liver malconfiguration in one case. Three of six haemangiomas and both liver metastases were better delineated with the iterative method, in one patient the haemangioma was visible only with this method. An irregular pattern after filtered back-projection led to misinterpretation as multiple metastases in another patient in whom there was no irregularity after iteration. Diagnostic improvement was not reached in the Budd-Chiari syndromes or in an atypical liver configuration, with a more homogeneous pattern after iteration however. The iterative reconstruction procedure was superior to the filtered back-projection method in the detection of small focal liver diseases.

Adult↗
PubMed1988

[An iterative strategy for determining the source distribution in single photon tomography using a rotating gamma camera (SPECT)].

A new iterative strategy for determination of the source distribution in single-photon emission tomography (SPECT) simulates mathematically the scintigraphic imaging process during direction sum computation. Limited spatial resolution and gamma-ray attenuation are taken into account using simplifying approximations. Highly resolved low-noise tomograms without obvious artifacts are obtained. Results of phantom measurements as well as cases of thyroid and brain perfusion imaging are presented to demonstrate the capabilities of the method.

Cerebrovascular Disorders↗
PubMed1987

Intensive short-term chemotherapy in patients with advanced breast cancer.

Aiming at a high complete remission rate with an intensive induction regimen, 27 patients with advanced breast cancer were given three cycles of VAC chemotherapy consisting of vindesine 3 mg/m2 i.v. on days 1 and 12, adriamycin 40 mg/m2 i.v. on days 1 and 12, and cyclophosphamide 200 mg/m2 p.o. on days 3-6 and 14-17 together with medroxyprogesterone acetate (MPA) 1,500 mg p.o. daily during the induction phase and 1,000 mg p.o. thereafter until relapse. These VAC double cycles were repeated twice with 3-weekly intervals for a total induction period of 15 weeks. In responders, including no change, the chemotherapy was discontinued thereafter, and the patients were observed until relapse with a maintenance therapy of MPA 1,000 mg p.o. daily. A complete remission (CR) was achieved in 8 (29.6%) and a partial remission (PR) in 13 (48.2%) of the 27 patients (CR + PR 77.8%). A no change (NC) status was found in 6 patients (22.2%). There were no nonresponders. The median duration of the CR was 20 (5-42) months with two patients still in CR at 33 and 36 months, of the PR 8.3 (4-13.5) months, and of the NC 6.7 (2-13) months. The treatment was tolerated without life-threatening toxicity or interval prolongation by all patients. No dose-limiting cardiac toxicity was observed in these patients regularly controlled by left ventricular ejection fraction (LVEF). The high response rate of this intensive induction regimen warrants further investigation. Complete remission was achieved only in patients without previous chemotherapy, with marked tumor regression after the first chemotherapy cycle and when there was no extensive bone involvement.

Adult↗
PubMed1987

Iterative reconstruction of thyroidal SPECT images.

First SPECT results using a multiplicative iterative reconstruction algorithm are presented. The superiority of the iterative technique over filtered backprojection is demonstrated in two thyroid SPECT studies. Obvious benefits of the new reconstruction technique are better defined outlines of the imaged organ and patient body as well as negligible artificial image amplitudes outside the patient.

Algorithms↗
PubMed1987

[Doppler echocardiography determination of the minute heart volume in ergometric stress].

To prove the use of Doppler-echocardiography in the determination of cardiac output during supine bicycle exercise, 14 patients suffering from dilatative cardiomyopathy were studied. Cardiac output was simultaneously determined by Doppler-echocardiography and with radionuclide ventriculography. In some cases, cardiac output was additionally measured using the thermodilution technique. In 12 patients (success rate 86%) flow velocity signals from the ascending aorta could be recorded with sufficient quality. Both methods were closely correlated, the r-value was 0.91 and the standard error of estimate was found to be 2.09 l/min. Mean deviation was 1.50 l/min (0.09-5.45 l/min) or 13% (1%-64%) respectively. For changes in cardiac output with exercise, the correlation was r = 0.88 with a mean deviation of 69% (2%-453%). The coefficient of variation for exercise measurements was 19% and did not differ from the resting value of 20%. Comparing the mean values of the whole group, no differences between the two methods could be found at rest, during exercise or for changes from rest to maximal exercise. Using the suprasternal approach, aortic flow velocities can be assessed by Doppler-echocardiography during exercise. Gross estimation of cardiac output during exercise seems possible; judgement of changes in cardiac output in individual cases appears to be uncertain.

Adult↗
PubMed1987

[Clinical and hemodynamic effects of nisoldipine and captopril in heart failure: a double-blind comparative study of long and short-term effects].

Afterload reduction with angiotensin-converting enzyme inhibitors (ACE-inhibitors), such as captopril, is an established therapeutic measure in the adjunctive treatment of severe chronic heart failure. Unfortunately, several side effects and adverse reactions are related to this form of therapy. Calcium antagonists of the dihydropyridine group can also induce a similar afterload reduction, and substances of this group exhibit only a few adverse reactions. In the present double-blind study, the acute and chronic hemodynamic and clinical benefits of the calcium antagonist nisoldipine (= BAY K 5552) were compared with captopril in the adjunctive treatment of patients with heart failure (NYHA III or IV). The study group consisted of 17 patients. After randomization, 9 were treated with captopril (25 mg orally t.i.d.) and 8 with nisoldipine (3 were given 20 mg orally t.i.d., and 5 were given 20 mg b.i.d.). The following hemodynamic variables were obtained in the control phase after 3 days and 3 months' duration of treatment: heart rate, LVEF, SVI, ESVI, EDVI, PSP/ESVI (ratio of peak systolic pressure and end-systolic volume index), CI and systemic vascular resistance. The clinical status of the patients was assessed by means of seven criteria on an arbitrary scale. The following results were obtained: for the nisoldipine group, the average LVEF increased significantly from 0.26 to 0.31 within 3 days of treatment, but after 3 months, this increase had disappeared. All other hemodynamic parameters did not change significantly within either 3 days or 3 months of treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1986

[Verapamil, diltiazem or nifedipine in severe left ventricular functional disorder? A comparative study of the immediate hemodynamic effects].

High doses of verapamil, diltiazem or nifedipin were administered to three groups of eight patients each, with severely abnormal left-ventricular (LV) function (mean ejection fraction 0.29). Various haemodynamic measurements were made immediately before and 30 minutes after drug administration: LV ejection fraction, ratio of peak systolic pressure to endsystolic volume index, stroke index, pulmonary capillary closing pressure, and maximal diastolic filling rate. None of these were reduced. In fact, ejection fraction rose by a mean of 0.05, stroke index by a mean of 5 ml/m2, while p.c. closing pressure and contractility did not alter significantly. Verapamil and diltiazem reduced the pressure X rate product (an important determinant of oxygen consumption); nifedipine reduced total systemic resistance. It is concluded that verapamil and diltiazem can be used with advantage in cases of unstable angina, if there are severe abnormalities of LV function; they are to be preferred to beta-blockers in this situation. Nifedipin is the calcium antagonist of choice in hypertension and abnormal LV function.

Adult↗