[Basic concepts of radiology physics]. / Bases physiques du radiodiagnostic.

An x-ray tube mainly emits low-energy X-rays, with few maximum energy E0 (equal in keV to the voltage U in kV) x-rays. Aluminium filtration (mandatory minimum thickness of 1.5 to 2.5 mm based on tube voltage) reduces soft X-rays and provides a mean energy equal to 2/3 E0. The half value layer of a reference material characterizes the spectrum. X-ray attenuation in tissues is due to secondary electron interactions: photoelectric effect at low-energy, especially in dense materials with high Z number; compton effect at intermediate-energy, proportional to density. The optimization of acquisition parameters of a medically necessary examination is based on appropriate selection of the highest voltage (U in kV) providing the best contrast and lowest tube current (Q in mAs) providing a diagnostic image.

[Concepts of dosimetry]. / Notions de dosimétrie.

The effects of exposure to ionizing radiation are determined by the absorbed dose D. The equivalent dose H takes into consideration the variation in probability of a stochastic effect (cancer, leukemia, genetic mutation) based on the quality of the exposure. The effective dose E takes into account the sensitivity of tissues (T) to stochastic effects from radiation exposure. Optimization of radiation exposure to patients in diagnostic radiology in based on diagnostic reference levels (DRL): entrance surface dose or dose-area product for conventional radiology; CT dose index and DLP for CT.

Comparison of jet and ultrasonic nebulizers for alveolar targeting of methylprednisolone.

The secondary systemic effects of oral corticosteroid therapy in chronic lung disease indicate the possible benefits of local therapy. The aim of this study was to show if alveolar targeting of a corticosteroid, methylprednisolone (MP), is possible, and to determine which type of nebulizer allows the most selective deposition into the alveoli. A jet nebulizer (Respirgard II) with 2 ml volume fill (R2), and an ultrasonic nebulizer (Ultraneb 99) with 4 ml volume fill (U4), were compared using a 40-mg dose of MP labelled 99Tcm human serum albumin. Particle size and MP-to-albumin binding were measured in the aerosol cloud. Each nebulizer was used in random order in five healthy volunteers. A dynamic posterior scan of 68 images of 15 s each was performed with a Gammatome II gamma camera during inhalation. Peripheral and central regions of interest were automatically defined with reproducible methods, and the peripheral-to-central ratio was used as a penetration index. Stomach and oropharynx activities were estimated on static anterior and static left lateral views, respectively, at the end of the examination. The mass median aerodynamic diameter (MMAD) was lower for R2 when unlabelled MP was used. The MMAD of MP+HSA was compatible with alveolar targeting. In the aerosol cloud, MP-albumin binding was 75% for R2 and 79% for U4. Peripheral and central activities at equilibrium (13-16 min) were higher with U4, but the penetration index was significantly higher with R2. Moreover, the stomach and oropharynx activities were significantly lower with R2.(ABSTRACT TRUNCATED AT 250 WORDS)

[Paracoccidioidomycosis assessed with 4 isotopic studies]. / La paracoccidioidomycose évaluée par quatre études isotopiques.

Paracoccidioidomycosis (south-american blastomycosis) is a consumptive granulomatous disease that is found in all Latin-America. The ethiological agent is a fungus (Paracoccidiosis brasiliensis) and mechanisms of disease transmission are not clear. Affection is frequent in the lungs, liver, spleen, ganglia, oropharynx and brain. Disease's response to therapy (Amphotericin, Ketoconazole) is good but recurrence is frequent. We have studied 12 patients with gallium-67, bone scintigraphy, bone marrow scintigraphy and lymph-scintigraphy. Six of these patients were re-studied after variable time of therapy. Gallium-67 accumulated in all patients's lungs. Other abnormal areas included ganglia, liver, spleen and bone. Bone scintigraphy was abnormal in all bone sites that were abnormal at the gallium study. Bone marrow scintigraphy showed expansion to the periphery in 6/12 cases and lymph nodes accumulated the radiopharmaceutical in 5 patients. Patients re-studied after the beginning of therapy presented decreased degrees or normalization of the radio-pharmaceutical's uptake (gallium and MDP), a regression of the bone marrow periphery expansion (bone marrow scintigraphy) and normalization of the lymph node aspects. These four radioisotopical studies may be useful for staging and for therapy follow-up. The sensitivity of the method is greater than the one noted for the conventional radiological studies.

[Keloid paracoccidioidomycosis assessed with gallium]. / La paracoccidioidomycose chéloïde étudiée avec le gallium.

This rare mycosis is caused by Paracoccidiodis loboii and is found mainly among indians of the Amazon forest. It is a cutaneous disease. No visceral affection was ever described, though generalized skin disease has been reported. One case of cheloid paracoccidioidomycosis was studied with gallium-67. The radiopharmaceutical has accumulated in the affected area and in a lymph node, although adenomegaly be rare. Degree of accumulation was discrete/moderate but the patient had been under irregular treatment for 10 years. As no laboratorial data are evaluable for this affection, gallium-67 may represent a means of disease extent and therapy efficacy evaluation.

[2 infectious granulomatous diseases (leprosy and cutaneous and mucous leishmaniasis) by scintigraphic methods]. / Contribution au début de l'étude de deux maladies infectieuses granulomateuses (la lèpre et la leishmaniose cutanée et muqueuse) par des méthodes scintigraphiques.

Leprosy is a multiform chronic infectious granulomatous disease caused by Mycobacterium leprae, that affects over 12 million people in the world. Cutaneous and mucous leishmaniasis (CML) is also a chronic granulomatous infectious disease, caused by Leishmania brasiliensis and transmitted to man by the mosquitoes of the Phlebotominae family. It is a worldwide spread disease. We studied one case of Borderline-wirchowian leprosy and 2 cases of CML with Gallium-67 (GA-67) scintigraphy. Ga-67 is a radiopharmaceutical known for its property of concentrating in inflammatory sites. In the leprosy patient, Ga-67 accumulated in the skin in a moderate, homogeneous and disseminated way (outlined skin); in the area of the face, the uptake was important and homogeneous (image in beard). Several internal organs accumulated Ga-67. As for the 2 CML patients, Ga-67 accumulated focally, in different degrees, in the affected anatomical areas. The leprosy patient was not under treatment and the 2 CML were under treatment (20 and 40 days, respectively). In the 3 cases, all affected areas accumulated Ga-67. Intensity differences of uptake may be explained both by different degrees of inflammatory processes (between leprosy and CML) and by treatment lasting. It is possible that Ga-67 scintigraphy may be useful for the evaluation of these 2 diseases extent and also for the therapy follow-up.

[Measurement by isotope study of the cardiac output in the elderly]. / Mesure par étude isotopique du débit cardiaque chez le vieillard.

Cardiac output and haemodynamic volumetric values (stroke volume, stroke index, left ventricular end-diastolic volume, blood volume, mean corpuscular volume and packed red cell volume) were measured in a population of 69 very old subjects (80 to 102 years) whose heart was regarded as normal on the basis of criteria determined, by radiocardiography and radionuclide ventriculography. These harmless and non-invasive techniques provided reference values in subjects of a seldom explored age group. Altogether, these values were lower than those of younger adults, and they decreased with age. Their reliability is due to the fact that they were obtained by true measurement and not by extrapolation of results observed in adults.

Evaluation of parathyroid autograft growth and function in hemodialysis patients.

The aim of our study was to evaluate the function and growth of parathyroid tissue autografted into the forearm of hemodialysis patients using several presently available methods. In a dynamic study, the secretory function of autografted tissue was evaluated in seven patients using either zero calcium dialysate or calcium infusion. In an additional prospective study, seven patients had repeated determinations of plasma immunoreactive parathyroid hormone (iPTH) concentration on samples from both forearms, a radionuclide evaluation of autograft function using thallium-201 chloride, and real time ultrasonography. Light microscopy analysis was performed in two patients. The dynamic study demonstrated that induction of hypocalcemia was followed by an increase, and induction of hypercalcemia by a decrease, in circulating iPTH in both forearms using three different radioimmunoassays, similar to what has been reported for normal parathyroid tissue. A significant gradient (ie, greater than 2.0) of plasma iPTH concentration in samples from both forearms was observed in only three out of the seven patients of the prospective study. Two of these patients disclosed an increased uptake of 201TI chloride at the site of autografted tissue and had an echographically detectable mass. In both, hyperplastic parathyroid tissue was removed. At present, the remaining third patient does not have other features of recurrent hyperparathyroidism. In conclusion, autotransplanted parathyroid tissue of hemodialysis patients shows an adequate response to physiologic stimuli such as hypo- and hypercalcemia. Dynamic tests, therefore, appear to be a useful tool in the assessment of its function. In addition, radionuclide and echographic studies may be reliable adjuncts in the detection of marked parathyroid autograft hyperplasia.

[Relative evaluation of arterial and portal perfusion of the liver during scintigraphy using technetium 99m sodium phytate]. / Evaluation relative des perfusions artérielle et portale du foie au cours d'une scintigraphie au technetium 99m phytate de sodium.

Quantitative assessment of the relative arterial and portal blood flows by calculation of the slopes of the arterial and venous components of the liver first-pass curve was performed in 67 patients with steatosis or cirrhosis referred for liver scintigraphy. In normal subjects, the portal venous blood flow amounts to 74.3 +/- 3% of total liver blood flow. In the present study, this figure was reduced to 58.6 +/- 8.6% in steatosis (n = 5) and 35.5 +/- 14.6% in cirrhosis (n = 33). Analysis of liver blood flow enhances the sensitivity of radioisotopic scans in diffuse liver diseases and is of considerable value for the indication, prognosis and follow-up of surgical shunts.