RESUMO
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.
Assuntos
Procedimentos de Cirurgia Plástica/métodos , Coluna Vertebral/diagnóstico por imagem , Coluna Vertebral/cirurgia , Tomografia Computadorizada de Emissão de Fóton Único , Feminino , Humanos , Masculino , Estudos Retrospectivos , Tomografia Computadorizada de Emissão de Fóton Único/normasRESUMO
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.
Assuntos
Câmaras gama/estatística & dados numéricos , Simulação por Computador , Distribuição de Poisson , Radiometria , Tomografia Computadorizada de Emissão de Fóton Único/estatística & dados numéricosRESUMO
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.
Assuntos
Coração/fisiologia , Hemodinâmica , Cintilografia , Adolescente , Adulto , Criança , Doença das Coronárias/fisiopatologia , Coração/fisiopatologia , Humanos , Educação Física e Treinamento , Artéria Pulmonar/fisiologia , Circulação Pulmonar , Tecnécio/administração & dosagem , Função VentricularRESUMO
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.
Assuntos
Medicina Nuclear , Radioisótopos , Temperatura Alta , Matemática , Técnica de Diluição de RadioisótoposRESUMO
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.
Assuntos
Tomografia Computadorizada de Emissão/métodos , Transtornos Cerebrovasculares/diagnóstico por imagem , Bócio Nodular/diagnóstico por imagem , Humanos , Modelos EstruturaisRESUMO
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.
Assuntos
Processamento de Imagem Assistida por Computador/métodos , Hepatopatias/diagnóstico por imagem , Neoplasias Hepáticas/diagnóstico por imagem , Tomografia Computadorizada de Emissão/métodos , Adulto , Idoso , Síndrome de Budd-Chiari/diagnóstico por imagem , Feminino , Hemangioma/diagnóstico por imagem , Humanos , Lactente , Neoplasias Hepáticas/secundário , Masculino , Pessoa de Meia-IdadeRESUMO
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).
Assuntos
Débito Cardíaco , Coração/diagnóstico por imagem , Volume Sistólico , Ventrículos do Coração , Humanos , Matemática , Métodos , Traçadores Radioativos , CintilografiaRESUMO
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.
Assuntos
Hemangioma/diagnóstico por imagem , Neoplasias Hepáticas/diagnóstico por imagem , Tomografia Computadorizada de Emissão de Fóton Único/métodos , Adulto , Idoso , Diagnóstico Diferencial , Feminino , Humanos , Fígado/diagnóstico por imagem , Masculino , Pessoa de Meia-Idade , Estudos RetrospectivosRESUMO
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.
Assuntos
Tempo de Circulação Sanguínea , Determinação do Volume Sanguíneo/métodos , Débito Cardíaco , Transporte Biológico , HumanosRESUMO
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.
Assuntos
Diagnóstico por Computador/métodos , Cardiopatias Congênitas/diagnóstico por imagem , Angiocardiografia , Cateterismo Cardíaco , Humanos , Lactente , Recém-Nascido , Artéria Pulmonar/diagnóstico por imagem , Cintilografia , Tetralogia de Fallot/diagnóstico por imagem , Transposição dos Grandes Vasos/diagnóstico por imagemRESUMO
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.
Assuntos
Coração/diagnóstico por imagem , Esforço Físico , Tálio , Adulto , Humanos , Masculino , Métodos , Pessoa de Meia-Idade , Radioisótopos , Cintilografia , Valores de ReferênciaRESUMO
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.
Assuntos
Débito Cardíaco , Volume Cardíaco , Ventrículos do Coração/diagnóstico por imagem , Angiografia , Cateterismo Cardíaco , Cardiografia de Impedância , Computadores/instrumentação , Eletrocardiografia/métodos , Humanos , CintilografiaAssuntos
Cintilografia , Computadores , Métodos , Modelos Teóricos , Radiação , Contagem de CintilaçãoAssuntos
Débito Cardíaco , Coração/diagnóstico por imagem , Volume Sistólico , Eritrócitos , Humanos , Cintilografia , TecnécioRESUMO
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.
Assuntos
Glândula Tireoide/diagnóstico por imagem , Tomografia Computadorizada de Emissão/métodos , Algoritmos , Feminino , Bócio Nodular/diagnóstico por imagem , Humanos , Masculino , Pessoa de Meia-Idade , Pertecnetato Tc 99m de SódioRESUMO
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.
Assuntos
Bócio/diagnóstico por imagem , Hipertireoidismo/diagnóstico por imagem , Pertecnetato Tc 99m de Sódio , Glândula Tireoide/diagnóstico por imagem , Humanos , Cintilografia , Sensibilidade e Especificidade , Testes de Função Tireóidea , UltrassonografiaRESUMO
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.
Assuntos
Bloqueadores dos Canais de Cálcio/uso terapêutico , Cardiomiopatia Dilatada/tratamento farmacológico , Hemodinâmica/efeitos dos fármacos , Adulto , Bloqueadores dos Canais de Cálcio/farmacologia , Volume Cardíaco/efeitos dos fármacos , Cardiomiopatia Dilatada/fisiopatologia , Diltiazem/uso terapêutico , Feminino , Frequência Cardíaca/efeitos dos fármacos , Humanos , Masculino , Pessoa de Meia-Idade , Nifedipino/uso terapêutico , Pressão Propulsora Pulmonar/efeitos dos fármacos , Volume Sistólico/efeitos dos fármacos , Verapamil/uso terapêuticoRESUMO
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)
Assuntos
Captopril/uso terapêutico , Insuficiência Cardíaca/tratamento farmacológico , Hemodinâmica/efeitos dos fármacos , Nifedipino/análogos & derivados , Vasodilatadores/uso terapêutico , Adulto , Idoso , Ensaios Clínicos como Assunto , Método Duplo-Cego , Feminino , Humanos , Assistência de Longa Duração , Masculino , Pessoa de Meia-Idade , Nifedipino/uso terapêutico , Nisoldipino , Distribuição AleatóriaRESUMO
We compared rectilinear scanning, analogous gamma-camera imaging and imaging using a gamma camera interfaced to a computer in order to determine which of these techniques is superior for thyroid scintigraphy. Forty patients with and without goitre and irregular activity distribution were imaged using each of the three techniques. The sets of three scintigrams per patient were rated by seven physicians. These ratings were statistically analysed using a new distribution-free test. Thyroid scintigraphy using a gamma camera interfaced to a computer turned out to be the best method, especially for detecting circumscribed areas of increased uptake. We conclude that this was due to a combination of the following factors: a computer matrix of 128 X 128 pixels in combination with an acquisition zoom of 1.5, the high count density of the scintigrams, computer-controlled documentation after data acquisition and the use of a continuous grey scale for documentation. The improved quality and information content of the scintigrams obtained using a gamma-camera/computer system could improve the diagnostic value of thyroid scintigraphy, especially when the scintigrams are also evaluated quantitatively.
Assuntos
Doenças da Glândula Tireoide/diagnóstico por imagem , Glândula Tireoide/diagnóstico por imagem , Tomografia Computadorizada de Emissão/métodos , Humanos , Tomografia Computadorizada de Emissão/instrumentaçãoRESUMO
The hemodynamic courses of 56 patients with congestive cardiomyopathy (CCM) were investigated. Fourteen patients died within 24 months after diagnosis. The hemodynamic courses of the remaining 42 patients were investigated in subsequent examinations by determination of left ventricular ejection fraction (LVEF), mean pulmonary arterial pressure at maximal workload, and peak systolic pressure/end-systolic volume index. During the study interval of 32.2 +/- 20.0 months the conditions of 20 patients (48%) deteriorated, according to their hemodynamic status, and at least five of these died of terminal heart failure. Surprisingly, the conditions of 22 patients (52%) improved or stabilized. One of these died of leukemia. Seven patients in the latter group with initial LVEFs of 0.30 or less experienced an average increase from 0.22 to 0.51. Retrospectively consideration of age, alcohol intake, exercise capacity, and hemodynamic status were not helpful in predicting the course of the disease. In 38 patients endomyocardial biopsy samples could be obtained at the time of diagnosis. Reduced myofibril volume fraction (less than 60%) had prognostic significance for both hemodynamic deterioration and death (sensitivity 23/24 = 96%), while 14 of 15 patients whose conditions improved or stabilized had a myofibril volume fraction of 60% or more (specificity 14/15 or 93%, p less than .002). A relationship between hemodynamic status and the myofibril volume fraction could not be found. Individual patients with CCM differ significantly with respect to course of the disease. A distinct separation of the patients by means of morphologic criteria is possible. This makes it more likely that the pathogenesis of the disease is not unique.