An automated method for the normalization of scintigraphic images.

The computer comparison of two images of the same organ requires normalization of the images. We propose an iterative, automated method of normalization that is highly insensitive to structural modifications in the images. The normalization factor is calculated by maximizing the number of sign changes in the scanned subtraction image with a unidimensionnal optimization method. This algorithm is efficient, computationally cheap, and can be implemented on most nuclear medicine data-processing systems.

Automated comparison of scintigraphic images.

New algorithms for automated comparison of scintigraphic images have been developed and are described here. The first step presented here is the registration of the images, performed by optimizing, with respect to the registration parameters (two translational shifts, one angle of rotation, the two parameters of a linear transformation of the gray levels), the stochastic sign change (SSC) criterion. The optimization of this criterion is demonstrated to be efficiently performed using the adaptative random search strategy; a more limited but less time-consuming method is also presented. The second step described is the point-by-point comparison of the registered images. The pixel-by-pixel application of Poisson variable statistical tests permits the generation of the significant image differences. From such images it is possible to detect modifications which escape visual inspection. Examples of applications are given in controlled and routine conditions. These algorithms are useful for the processing of many investigations and are proposed for implementation on all nuclear medicine data processing systems.

An automated system for the registration and comparison of photographic images in medicine.

A system is presented for digitization and automated comparison of photographic images of patients obtained at different times using a high-precision video camera. The images can be acquired either directly or from slides. The two images to be compared are registered using a complex geometrical and gray-level registration model including six parameters (planar, translation, rotation, magnification, linear transformation of the gray levels). The values of the registration parameters are automatically calculated by maximizing an integer similarity measure selected for robustness. The optimization of this function with respect to the registration parameters is performed using an adaptive random search strategy. The analysis of the differences between the registered images can be carried out through visual inspection of the subtraction image in which artifacts due to remaining infrapixel shifts have been suppressed.

In vitro adrenal cortex lesions characterization by NMR spectroscopy.

Percentage of lipid content of 22 adrenal cortex lesions and their water proton longitudinal relaxation time were measured in vitro at 60 MHz. Although water relaxation times obtained on benign and malignant samples overlap each other, measurements of the percentage of lipids performed on the same tissues allow us to distinguish the two pathologies. The specific tool of characterization should be possible to obtain through in vivo spectroscopic imaging techniques.

[Study of shunts using isotopic technics]. / Etude des shunts par méthodes isotopiques.

Isotopic techniques and in particular 99m Tc sequential angiography are accurate methods of assessing left-right and right-left intracardiac shunts. The results obtained are so reliable that these methods have become the investigation of choice for diagnosis and follow-up of intracardiac shunts in children and young adults, for post-operative control of repaired septal defects and for rapid diagnosis of asymptomatic murmurs. Radio-isotope methods are more accurate than oxymetry and in addition scintigraphy using a scintillation camera outlines the cardiac cavities and the site of left-right shunts may be localised in most cases. These methods have the advantage of being quick, non-invasive and less irradiating than oxymetry or conventional contrast angiography. The recent introduction of isotopes with very short half lives and radioactive gases probably heralds new advances in an already proven field.

[Myocardial scintigraphy]. / La scintigraphie du myocarde.

Myocardial scintigraphy may be performed at rest or after stress testing using potassium-like cations, labeled metabolites or infarct-fixing tracers. It is an in vivo method of studying myocardial ischaemia and infarction and may provide diagnostic information when other techniques fail. The diagnostic possibilities of myocardial scintigraphy have been increased by the introduction of tomographic techniques and new radioisotopes with very short half lives.

[Scintigraphy of the myocardium following injection of thallium 201 during an exercise test. Value in the study of myocardial ischemia]. / La scintigraphie du myocarde, après injection de thallium 201 au cours d'une épreuve d'effort. Intérêt dans l'étude de l'ischémie myocardique

Thallium 201 is fixed rapidly by the healthy mocardium, and its emissions are easily recordable with a scintillation camera; it was used to discover and localise zones of ischaemia. This radio-isotope was injected into 40 patients during an exercise test. The results from this so-called exercise scintigraphy were compared with those of the exercise ECG, with the findings on coronary arteriography in 32 cases, and in 14 cases with those obtained by injecting thallium 201 into the patient while at rest (the so-called scintigram at rest). The results obtained from exercise scintigraphy correlate well with those from the exercise ECG and coronary arteriography. It would seem to have an important place in monitoring the permeability of aorto-coronary bypasses.

Myocardial scintigraphy with technetium 99m pyrophosphate. / La scintigraphie du myocarde au pyrophosphate technetium 99m

The pyrophosphate of Tc99m attaches itself to ischaemic myocardial cells, and therefore makes it possible to obtain a scintigram of necrotic or necrosing myocardium. In a series of 65 cases the scintigram was positive in every case in which there had been a recent transmural infarct (17 cases). The results showed greater variation in the other ischaemic conditions involving the myocardium (limited infarcts or simple angina). The progress as a function of time was stuided in a series of fairly recent and older infarcts. The limitations and future prospects of this investigations are discussed.

[Value and limitations of sequential technetium 99m angiocardiography in the detection, localization and quantification of left-right intracardiac shunts apropos of 110 cases]. / Valeurs et limites de l'angiocardiographie séquentielle au technétium 99 m pour la détection, la localisation et la quantification des shunts intra-cardiaques gauche-droite. A propos de 110 observations.

A comparative study of the diagnosis of intracardiac left-to-right shunts by isotope radiography on the one hand and oxymetry, abnormal catheter trajectory and angiocardiography on the other, was performed on a series of 110 patients, comprising 12 normals, 46 valvulopathies or cardiomyopathies without shunts, 23 ASDs, 22 VSDs, and 7 other shunts. Intravenous injection of Technetium 99 m with scintigraphic imagery and interpretation of time-activity curves detected even small left-to-right shunts and appeared to be more sensitive than oxumetry. The estimation of the size of the shunt correlated well with oxymetry for VSDs but not for ASDs. The localisation of the shunt was more difficult. The atrial level of the defect was detected in some but not the majority of cases. The isotopic technique appeared unreliable in the presence of severe haemodynamic disturbances. The isotopic method is a quick means of detecting left-to-right shunts without measurable risk, particularly useful in the investigation of children and young adults thought to have left-to-right shunts.

[Angioscintigraphy in venous pathology. Comparison of isotope angioscintigraphy and radiologic examination]. / L'angioscintigraphie en pathologie veineuse. Confrontation entre l'angioscintigraphie isotopique et l'examen radiologique.

Results of vascular radiology and isotope examinations were compared in 48 patients with suspected ileocaval lesions (37 cases) or affections of the veins of the upper limb or superior vena cava (11 cases). Isotopic examination, which can be performed in ambulatory patients, respects normal hemodynamic conditions, is painless, and can be repeated, was found to give valid results, positive correlations with radiological investigation findings being present in 43 cases. Lack of correlation in the remaining 5 patients could have resulted from the period of time elapsed between the two examinations or the techniques employed during each investigation.

[Osteonecrosis of the femoral head. MRI study of 60 cases]. / L'ostéonécrose de la tête fémorale. Etude par IRM de 60 cas.

Normal and pathologic femoral heads have been studied by MRI at 1.5 Tesla. The study was centered upon avascular necrosis (53 lesions). Twenty normal subjects and three patients with algodystrophy were examined. The osteonecrosis patterns were established from known lesions. A low signal rim surrounds an upper polar zone of conserved (Type I) or decreased (Type II) signal. The lesions age correlates significantly with their type: amongst type I lesions, 6 are asymptomatic and the 21 others have a mean age of 5.5 months; Type II lesions have a mean age of 12.7 months. Fourteen lesions were not seen on plain radiographs and six were not detected by bone scan. The older lesions with femoral head deformation are better depicted by standard radiologic techniques. Conservatively MRI is the most efficient examination for recent avascular necrosis lesions.

[Magnetic resonance imaging in the diagnosis of adrenal pathology]. / Apport de l'I.R.M. au diagnostic en pathologie surrénalienne.

M.R.I. allows a good delineation of adrenals, due to the high contrast with fat and to the use of frontal planes. We showed on post operative adrenal lesions samples that the lipid percentages, high in normal and hyperplasic glands, was still high in most benign adenomas, and very low (under 5%) in adrenal carcinomas. MRI, with Dixon sequence, allows to evaluate this lipid percentage in adrenal lesions. Post-operative controls show a good agreement between in vivo and in vitro measurements. This simple technique should allow to discriminate between malignant and benign adrenal cortex lesions.