[Improvement of tomographic reconstruction in bone SPECT]. / Optimierung der tomographischen Rekonstruktion in der Skelett-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.

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.

[The effect of biological factors during functional scintigraphy of the heart (author's transl)]. / Der Einflub biologischer Faktoren bei der Funktionsszintigraphie des Herzens

The parameters relating to functional scintigraphy of the heart (average circulation time, peak time) depend not only on the method (injection technique, radiopharmaceutical), but also on biological factors. Failure to take these into consideration may result in an erroneous interpretation of the findings. Circulation time in normal children aged 6 to 14 years, as determined by isotope methods is significantly shorter than in normal adults. Patients with compensated heart disease, as well trained athletes, show significantly shorter than in normal adults. Patients with compensated heart disease, as well trained athletes, show significant increase in all portions of the circulation time, when compared with normals of similar ages. This indicates that deviation in the haemodynamics of the circulation as shown by functional scintigraphy, can only be interpreted in the light of clinical findings.

[An adaptation function for describing time-activity curves in nuclear medicine (author's transl)]. / Eine Anpassungsfunktion zur Beschreibung nuklearmedizinischer Zeit-Aktivitäts-Kurven.

Radioisotopic time-activity curves can be described by a function known from the physics of heat conduction. This function, called in this paper "tracer function", is a special solution of one-dimensional differential equation of heat conduction. The function is especially useful in the quantitation of left-to-right cardiac shunts by analysis of the pulmonary time-activity curve. The first transit curve is determined from the amplitudes on the ascending slope of the curve only including the maximum. The shunt curve analysis uses two parameters derived from the first transit curve and then the position and amplitude of the shunt curve maximum only.

[An iterative strategy for determining the source distribution in single photon tomography using a rotating gamma camera (SPECT)]. / Eine iterative Strategie zur Bestimmung der Quellverteilung bei der Einzelphotonen-Tomographie mit einer rotierenden Gammakamera (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.

[A nuclear medicine method for determining left ventricular stroke volume]. / Ein neues nuklearmedizinisches Verfahren zur Bestimmung des linksventrikulären Schlagvolumens.

A new non-invasive nuclear medicine procedure for determining the left ventricular stroke volume is described. The procedure exhibits the following features: 1. Individual calibration of scintigraphic counts in activity by first-pass evaluation; 2. no need for a delta-shaped bolus injection; and 3. determination of different stroke volumes, e.g. during different grades of exercise, by only one injection and by only one blood sample. 36 results obtained at rest and during exercise are compared with corresponding results of the thermodilution method (r = 0.86).

[Comparison of the clinical value of an iterative reconstruction procedure with that of a filtered back projection in SPECT of the liver]. / Vergleich der klinischen Wertigkeit eines iterativen Rekonstruktionsverfahrens mit der gefilterten Rück-projektion bei der SPECT der Leber.

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.

[Dynamic blood volume determination using the body transport function]. / Dynamische Blutvolumenbestimmung mit Hilfe der Körpertransportfunktion.

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.

[Typical presentation of sequential scintigraphy images in the diagnosis of cyanotic heart disease in the newborn, using a computer-assisted imaging technique (author's transl)]. / Typische Darstellung szintigraphischer Bildsequenzen zur Diagnose von zyanotischen Herzfehlern Neugeborener mit einer computergesteuerten Abbildungstechnik.

The technique of sequential scintigraphy in investigating newborn infants in order to exclude or detect cyanotic congenital heart disease has been improved. The primary scintigraphic data are recorded digitally (list mode, 1 ms, 128 by 128 pixels) and evaluated automatically as a sequence of 1/2 s frames in 1/8 s increments. A 35 mm film is exposed to a scanning pulsed light spot on a CRT-screen with quantitative correspondence between local count density and the local number of light pulses. A series of highly resolved images of the rapidly changing scintigraphic pattern is achieved in 30 min. The results of 3 investigations are discussed. They prove the importance of adequate spatial resolution and definition in time in nuclear angiocardiography in infancy. Three case results are discussed in detail. In one case cardiac catheterisation and angiocardiography had been omitted, since the radioisotopic findings excluded cyanotic congenital heart disease. Two further investigations are discussed with reference to the findings at cardiac catheterisation.

[Importance of iterative reconstruction ISA in the diagnosis of liver hemangioma]. / Bedeutung der iterativen Rekonstruktion ISA bei der Diagnostik von Leberhämangiomen.

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.

[The determination of the left ventrical volume curve without background correction and its validation by direct intercomparison with the ejection fractions as determined by biplane laevocardiography (author's transl)]. / Nuklearmedizinische Bestimmung linksventrikulärer Volumenkurven ohne Untergrundkorrektur und ihre Validisierung durch direkten Vergleich mit biplan laevokardiographisch ermittelten Auswurffraktionen.

Background corrections applied on the left ventricular volume curve determined by the "gated blood pool"--method are based on an estimated rather than on a directly measured background. This imposes an uncertainty on the values determined from the volume curve, especially on the ejection fraction. A method which does not require background correction may be applied if all available measurement and evaluation facilities are utilized fully. High temporal and spatial resolution is of fundamental importance, permitting the exact determination of the time-dependent scintigraphic contour variations of the left ventricle during the mechanical action of the heart. A good criterion of the validity of the volume curves with respect to interfering background radiation is the ejection fraction calculated from these curves. The direct intercomparison of 10 ejection fractions obtained by an expanded "gated blood pool"-method, employing cardiac catheterization, immediately before a biplane laevocardiography demonstrated very good agreement. A small systematic underestimation of the ejection fraction by the nuclear method was observed. This understimulation shows that the influence of the true background is small if other interfering count rate contributions or methodical uncertainties are excluded systematically.

[Quantitative exercise scintigraphy of the myocardium with 201Tl--methods and normal values (author's transl)]. / Quantitative Belastungs-Szintigraphie des Myokards mit 201Tl--Methodik und Normalverhalten.

Quantitative myocardial scintigraphy was performed in 20 normal individuals after maximum exercise and after two hours of rest. A mobile Anger camera with converging collimator and a Data-General computer with a 128 x 128 matrix were used. Quantitative analysis of data was performed on the basis of a 14-halfsegment model. Quantitative normal values after exercise and after redistribution of activity during rest are presented.

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.

[Verapamil, diltiazem or nifedipine in severe left ventricular functional disorder? A comparative study of the immediate hemodynamic effects]. / Verapamil, Diltiazem oder Nifedipin bei schwerer linksventrikulärer Funktionsstörung? Eine Vergleichsstudie der hämodynamischen Akutwirkungen.

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.

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.

[Clinical and hemodynamic effects of nisoldipine and captopril in heart failure: a double-blind comparative study of long and short-term effects]. / Klinische und hämodynamische Wirkungen von Nisoldipin und Captopril bei der Herzinsuffizienz: Eine doppelblinde Vergleichsstudie der Kurz- und Langzeitwirkungen.

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)

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.

[Differences in the non-invasive assessment of left ventricular filling in patients with dilated cardiomyopathy using Doppler echocardiography and radionuclide angiography]. / Unterschiede in der nichtinvasiven Beurteilung der linksventrikulären Füllung bei Patienten mit dilatativer Kardiomyopathie durch Dopplerechokardiographie und Radionuklidangiographie.

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)