ABSTRACT
In emission tomography, the spread of regional tracer uptake to surrounding areas caused by limited spatial resolution of the tomograph must be taken into account when quantitating activity concentrations in vivo. Assuming linearity and stationarity, the relationship between imaged activity concentration and true activity concentration is only dependent on the geometric relationship between the limited spatial resolution of the tomograph in all three dimensions and the three-dimensional size and shape of the object. In particular it is independent of the type of object studied. This concept is characterized by the term "recovery coefficient". Recovery effects can be corrected for by recovery coefficients determined in a calibration measurement for lesions of simple geometrical shape. This method works on anatomical structures that can be approximated to simple geometrical objects. The aim of this study was to investigate whether recovery correction of appropriate structures is feasible in a clinical setting. Measurements were done on a positron emission tomography (PET) scanner in the 2D and 3D acquisition mode and on an analogue and digital single-photon emission tomography (SPET) system using commercially available software for image reconstruction and correction of absorption and scatter effects. The results of hot spot and cold spot phantom measurements were compared to validate the assumed conditions of linearity and stationarity. It can be concluded that a recovery correction is feasible for PET scanners down to lesions measuring about 1.5xFWHM in size, whereas with simple correction schemes, which are widely available, an object-independent recovery correction for SPET cannot be performed. This result can be attributed to imperfections in the commercially available methods for attenuation and scatter correction in SPET, which are only approximate.
Subject(s)
Tomography, Emission-Computed, Single-Photon/methods , Tomography, Emission-Computed/methods , Feasibility Studies , Humans , Image Processing, Computer-Assisted , Phantoms, Imaging , TechnetiumSubject(s)
Nuclear Medicine/standards , Radioisotopes , Argentina , Calibration/standards , RadioactivityABSTRACT
Se determino tiroxina libre serica (T4L) utilizando un RIA de fase solida en 253 pacientes: 122 controles, 27 hipertiroideos, 15 hipotiroideos, 4 eutiroideas en tratamiento estrogenico, 9 hipotiroideos tratados con levotiroxina, 1 hipertiroideo en tratamiento con antitiroideos y betabloqueantes y 1 hipertiroideo con defecto de TBG. En las mismas muestras se determino tiroxina total (T4), triiodotironina (T3) y tirotrofina (TSH) por RIA.Los valores normales de T4L fueron de 1.42 ng/100 ml +/- 0.03 (e.s.); en los hipertiroideos: 4.66 ng/100 ml +/- 0.48 y entre los hipotiroideos: 0.05 ng/100 ml +/- 0.06. En los restantes grupos los valores de T4L se mostraron acordes con el estado clinico.Los valores de T4 y T3 se correlacionaron con los de T4L, excepto en aquellos pacientes con alteraciones de la capacidad de transpoete, iatrogenicas o patologicas.Los analisis de decision clinica (curvas "ROC") indicaron que la T4L es el mejor metodo entre los estudiados para el diagnostico del hipertiroidismo y T4 lo es para el hipotiroidismo. La relacion costo beneficio es mejor para T4L en conjunto
Subject(s)
Child , Adolescent , Adult , Middle Aged , Humans , Male , Female , Radioimmunoassay , Thyroxine , Hyperthyroidism , HypothyroidismABSTRACT
Se determino tiroxina libre serica (T4L) utilizando un RIA de fase solida en 253 pacientes: 122 controles, 27 hipertiroideos, 15 hipotiroideos, 4 eutiroideas en tratamiento estrogenico, 9 hipotiroideos tratados con levotiroxina, 1 hipertiroideo en tratamiento con antitiroideos y betabloqueantes y 1 hipertiroideo con defecto de TBG. En las mismas muestras se determino tiroxina total (T4), triiodotironina (T3) y tirotrofina (TSH) por RIA.Los valores normales de T4L fueron de 1.42 ng/100 ml +/- 0.03 (e.s.); en los hipertiroideos: 4.66 ng/100 ml +/- 0.48 y entre los hipotiroideos: 0.05 ng/100 ml +/- 0.06. En los restantes grupos los valores de T4L se mostraron acordes con el estado clinico.Los valores de T4 y T3 se correlacionaron con los de T4L, excepto en aquellos pacientes con alteraciones de la capacidad de transpoete, iatrogenicas o patologicas.Los analisis de decision clinica (curvas "ROC") indicaron que la T4L es el mejor metodo entre los estudiados para el diagnostico del hipertiroidismo y T4 lo es para el hipotiroidismo. La relacion costo beneficio es mejor para T4L en conjunto
Subject(s)
Child , Adolescent , Adult , Middle Aged , Aged , Humans , Male , Female , Radioimmunoassay , Thyroxine , Hyperthyroidism , HypothyroidismSubject(s)
Intestinal Absorption , Phosphates/metabolism , Adolescent , Adult , Aged , Body Burden , Feces/analysis , Female , Humans , Male , Methods , Middle Aged , Phosphates/administration & dosage , Phosphates/urine , Phosphorus Radioisotopes , Radioactive TracersSubject(s)
Hypertension/genetics , Norepinephrine/urine , Renin/blood , Adolescent , Adult , Aged , Angiotensin II/pharmacology , Child , Female , Furosemide/pharmacology , Humans , Hypertension/metabolism , Male , Middle Aged , Sex Factors , Sodium/urineSubject(s)
Intestinal Absorption , Phosphates/metabolism , Adolescent , Adult , Aged , Body Surface Area , Female , Humans , Male , Middle Aged , Phosphates/urine , Phosphorus Radioisotopes , Whole-Body CountingABSTRACT
A 23-year-old white woman suffering pycnodysostosis whose parents and five siblings were unaffected was investigated. Chromosomal morphology was normal. Histologic examination of a biopsy specimen obtained from the distal phalanx of the left thumb, corresponding to an area on an x-ray film of osteolysis, showed a fibrous dysplasia-like picture. Kinetic studies of calcium metabolism revealed that exchangeable pool size, turnover, and bone accretion rate were all decreased. Intestinal calcium absorption was investigated simultaneously by a double isotope technique and by deconvolution of the plasmatic specific activity curve of 47Ca given per os. Results obtained by both methods coincided in that values were found to be similarly increased. Endogenous fecal calcium was also determined and revealed a similar increase. Some physiopathological implications of these findings are discussed.
