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P Hannequin

Publications and source records attributed to P Hannequin.

16 recordsLinked to original sources
PubMed1991

Introducing simultaneous spatial resolution and attenuation correction after scatter removal in SPECT imaging.

A new approach to simultaneous spatial resolution and attenuation correction in SPECT imaging is presented. Before these corrections, scatter is removed on the projections. This removal is performed by spectral constrained factor analysis. The innovation reported here is the use of the different impulse responses of the system, according to the source-detector distance, and their integration in a generalized version of the Chang attenuation correction method. This novel algorithm is evaluated on computed and physical phantoms. In the computer-simulated phantom, the count rates after full-processing are very close to the initial values. In the physical phantom, the contrast is increased by 1.8 after full processing. The activity profiles drawn both on raw projections and reconstructed slices demonstrate the effectiveness of the algorithm for the restoration of spatial resolution. Furthermore, the method improves the quality of the images greatly. A clinical study is also presented. When the whole procedure is applied, the resulting slice matches the corresponding computed tomographic scan very well, which is not the case with the usual back-projected images. The process is fully automatic and the computing time performance allows its daily use for single photon emission tomographic examinations.

Algorithms↗
PubMed1991

[Prognostic value of exercise angioscintigraphy in coronary disease].

Multivariate survival analysis (MSA) was applied to 97 patients with coronary disease using the Cox model and a stepwise regression procedure. Seventeen variables including data based upon clinical examination, exercise testing (ET), and exercise angioscintigraphy (EAS) as well as coronary arteriography were studied in each patient. During the monitoring period (interval: 1-57 months), 38 patients sustained a cardiac event (recurrence of coronary disease or death). Neither resting left ventricular ejection fraction, nor coronary anatomy were significant prognostic variables. The only two variables identified by MSA were a variable of EAS: corrected ejection fraction at maximum exercise (p less than 0.008), and a variable of ET: maximum heart rate during exercise (p less than 0.03). This study shows that the prognosis of a coronary disease patient can best be assessed by two variables which are both exercise parameters.

Adult↗
PubMed1990

Scatter correction in planar imaging and SPECT by constrained factor analysis of dynamic structures (FADS).

The removal of Compton scattered photons included within the pulse height window is recognized as one of the most difficult noise problems in the restoration of nuclear medicine images. A new approach to Compton scatter correction based on factor analysis of dynamic structures (FADS) is presented in this study. The method requires all of the energy information. Acquisition of data can be performed either by list-mode or frame-mode. While the former presents some theoretical advantages, the latter is actually used in this work. Two factors are extracted by FADS, unfortunately no pure photopeak factor can be found by the algorithm. These rough factors lead to incorrect factor images. The innovation reported here is the use of a constrained photopeak factor. This novel algorithm is evaluated both on planar imaging and SPECT data using Monte Carlo simulations and real phantoms. A comparison with the modified method of Jaszczak is also presented. Different parameters are significantly improved with our recombination method in SPECT studies, particularly after attenuation compensation by the iterative method of Chang. Compared with the subtraction method the contrast is increased by 1.5 for planar Monte Carlo simulations and the scatter fraction is reduced four times with our recombination method.

Algorithms↗
PubMed1990

Cluster analysis for automatic image segmentation in dynamic scintigraphies.

An original and entirely automatic algorithm is proposed to select regions of interest (ROIs) on dynamic scintigrams. This algorithm is based on factor analysis and on cluster analysis. It consists of first extracting the orthogonal factor images of the series using factor analysis of correspondence. These factor images are then automatically segmented in ROIs using a hierarchical ascendant classification procedure. The distance used for the classification is the 'minimum added intra-class variance' distance. This algorithm has been implemented on a fast computer dedicated to nuclear medicine (Nodecrest Micas V system). The time of calculation on 1000 pixels from 40 images is less than 5 min when three factor images are used. This algorithm is validated using a numerical phantom and is illustrated using renal (99Tcm DTPA) and cardiac (equilibrium gated angiography) dynamic scintigraphies. The results show that the algorithm is able to recognize the bladder, the renal cavities and the renal parenchyma on the renal series, and the ventricules and the atria on the cardiac series.

Algorithms↗
PubMed1989

Immunoscintigraphy with indium-111 labeled monoclonal antibodies: the importance of a good display method.

A major drawback of In-111-labeled monoclonal antibodies (MoAb) is the presence of intense liver, renal, and bone marrow nonspecific activity. This makes the display of the images hardly optimal and their visual interpretation difficult. In this study, the "intrinsic color scale" (which consists of selecting the limits of the color scale as the highest and the lowest pixel value of the image) was compared to a new, simple algorithm for the determination of the limits of the color scale. This algorithm was based on the count density in the iliac crest areas. OC-125 or anti-CEA In-111 MoAb F(ab')2 fragments were used in 32 patients with suspected recurrence of ovarian (19 patients) or colorectal cancer (13 patients). Final diagnosis was assessed by surgery (21 patients), biopsy (five patients), or followup (six patients). A 10-minute abdomino-pelvic anterior view was recorded two days after injection. These views are displayed using the two methods and interpreted by two observers. Using their responses in each quadrant of the pelvis, the authors calculated two ROC curves. The comparison of the ROC curves showed better performances for the new method. For example, for the same specificity (73%), the sensitivity of the new method was significantly better (78% versus 68%). This result confirmed the importance of a good methodology for displaying immunoscintigraphic images.

Algorithms↗
PubMed1988

Superficial and deep lymphoscintigraphic findings before and after femoro popliteal bypass.

The aim of this work is to explore the patients operated on for a femoro popliteal bypass (FPB) with lymphoscintigraphy (LS) of the lower limbs. Data concerning 35 limbs from 33 patients operated on for a FPB have been included in a prospective study. Superficial and deep LS have been performed by injecting 74 MBq 99mTc-Rhenium Sulphide Colloid into the subcutaneous tissue of the first interdigital space and of the lateral malleolus region respectively. Both superficial and deep LS have been performed before and after surgery. A postoperative oedema was found in 17 of the 35 limbs. The value of the lymphatic flow indices and their variation after surgery do not significantly differ between the oedematous and non oedematous groups. Thirteen of the 17 limbs with oedema have presented an interruption of the lymphatic circulation or a diffuse activity outside the lymphatic vessels on the postoperative superficial and/or deep LS. This proportion is only 1/18 in the non oedematous group. The difference between the two groups is highly significant (P less than 0.001). By contrast, the proportion of lymph cyst does not differ significantly between the two groups. In conclusion, this study confirms the close relationship between the oedema following FPB and surgical damage to the lymphatics.

Colloids↗
PubMed1988

Multivariate analysis in solitary cold thyroid nodules for the diagnosis of malignancy.

A stepwise logistic regression (SLR) was performed on 162 patients with a solitary and cold thyroid nodule in order to discriminate between malignant and benign lesions. Sixteen variables were recorded for each patient. The predictions of the logistic regression model were compared to the histological diagnoses in order to evaluate the accuracy of the classification. The value of the logistic function (LF) was calculated for each patient. Using the ROC curve approach, an optimum threshold value (OTV) corresponding to a 100% sensitivity was defined. The classification obtained with the OTV was validated using a cross-validation procedure (CVP). The significant variables selected by the SLR are (from the most significant to the least significant): cytologic result, sex, irregular margin on the Tc scintigraphy and homogeneity on the ultrasound examination. The OTV corresponds to a specificity of 73% for a sensitivity of 100%. The specificity and the sensitivity obtained with the CVP are 73% and 96% respectively. In conclusion, the classification of the patients according to the value of the LF is a highly accurate diagnostic procedure.

Adult↗
PubMed1988

[Role of clinical manifestations, the exercise test and exertion angioscintigraphy in the diagnosis of coronary disease. A multivariate study].

Data of clinical examination, exercise electrocardiography and stress radionuclide angiography in 102 patients referred for assessment of chest pain was included in a logistic regression to optimise the diagnosis of coronary artery disease with coronary angiography as the reference investigation. None of the patients had other cardiac problems nor previous myocardial infarction. In the absence of symptoms exercise testing was continued until at least 80 p. 100 of the theoretical maximal heart rate was attained. Each patient was characterised by the value of the logistic function or probability of coronary artery disease. A threshold value corresponding to 80 p. 100 sensitivity was determined by the technique of ROC graphs. The significant variables were: a clinical variable--the type of chest pain as assessed by the clinical history; two radionuclide angiographic variables--the ejection fraction at peak effort and the corrected variation of ejection fraction between rest and stress, that is not taking into account possible decreases at the last increment of exercise. Coronary patients can be identified with an 80 p. 100 sensitivity and 77 p. 100 specificity on these criteria. This specificity is greater than that obtained by clinical examination and exercise electrocardiography alone (65 p. 100). Stress radionuclide angiography may therefore reduce the number of unnecessary coronary angiographies.

Adult↗
PubMed1987

ROC analysis in radioimmunoassay: an application to the interpretation of thyroglobulin measurement in the follow-up of thyroid carcinoma.

This study is an application of the ROC technique to the determination of threshold values (TV) for the interpretation of serum thyroglobulin (Tg) measurements in the follow-up of differentiated thyroid cancer. Serum Tg was assayed using the Henning kit in 1466 samples from 245 individuals. A local or distant recurrence was assessed by clinical examination, radiological and scintigraphic investigations, and was present in 23 patients. The measurements were divided into four groups: 1) measurements performed less than 6 months after thyroidectomy; 2) measurements performed more than 6 months after thyroidectomy; 3) measurements performed during the suppression of pituitary secretion; 4) measurements performed during withdrawal of the substitutive therapy. An ROC curve was calculated for each group and for each curve three TVs were determined: TV1, TV2, and TV3 corresponding to a high sensitivity, a high specificity and a high sum of sensitivity and specificity respectively. TV1 is 3.12 micrograms/l in the four groups. TV2 is 44 micrograms/l, 19 micrograms/l, 11 micrograms/l and 30 micrograms/l, in the first, second, third and fourth groups respectively. TV3 is 35 micrograms/l in the first group, 3.12 micrograms/l in both the second and third groups and 30 micrograms/l in the fourth group. When the classical method allows the determination of only one threshold value, the ROC technique allows us to determine threshold values adapted to both the patient clinical status and the chosen sensitivity or specificity.

Follow-Up Studies↗
PubMed1987

A new approach to image subtraction in immunoscintigraphy: preliminary results.

Recently proposed image comparison software is applied to immunoscintigraphy. The software performs geometric and gray level registration of two images and generates an image of the statistically significant differences. It permits the comparison of scintigraphic images recorded at different times. It is used to subtract 113mIn and 111Inphytate colloid liver scans and early (blood pool) images from 131I or 111In-monoclonal Ab images and to compare Ab images recorded at different times. Using the procedures made possible by this software, only images recorded using the same radionuclide or using radionuclides of about the same energy are compared. Anti CEA, 19-9 and OC 125 F(ab)2 fragments labeled with 131I or 111In are used in 32 patients with 47 demonstrated recurrences or metastases of colorectal or ovarian cancers. The overall sensitivities of the unprocessed and processed images are 25/47 and 41/47 respectively. The improvement in sensitivity is particularly high in the liver when In labelled Ab are used. This technique improves the contrast of the images, but the interpretation must take into account the components of the non target activity (kidney, bone marrow, colon...) which are not removed by the image subtraction method.

Antibodies, Monoclonal↗
PubMed1987

[Value of exploring the deep lymphatic system of the lower limbs using lymphoscintigraphy. Preliminary study of 18 patients with arteritis].

Lymphoscintigraphy of lower limbs generally involves bilateral subcutaneous injection of a radioactive colloid into the first or second interdigital space: only the superficial internal saphenous pathway is visualized in this way (superficial lymphoscintigraphy: SL). However, the external saphenous and deep pathways can be explored by an external retromalleolar injection as demonstrated in radiology. Isotopic exploration of the external saphenous pathway and deep lymphatics (deep lymphoscintigraphy: DL) was carried out in 18 patients with arteritis also investigated by SL. The study forms part of a prospective trial of edema developing after femoro-popliteal shunts. The deep lymphatics are correctly and easily visualized, and in about 20% of cases there exist anomalies of distribution of superficial or deep lymphatic flow, morphologic anomalies developing postoperatively in one pathway only, or in both pathways. DL is a simple, reliable method of investigation of deep lymphatics, and complete exploration of lymphatics of lower limbs should include both SL and DL.

Aged↗
PubMed1986

Multifactorial analysis of survival in thyroid cancer. Pitfalls of applying the results of published studies to another population.

Multifactorial analyses (MFAs) of survival data of thyroid carcinoma patients have already been published by the European Organization for Research and Treatment of Cancer EORTC, the Institut Curie (IC), and the Institut Gustave Roussy (IGR). The aim of this study was to find out if the results obtained in these MFAs could be applied to a new population of 480 patients. To determine this, three MFAs were carried out on the new population. Each of these MFAs is based on exactly the same methodology as one of the three reference studies. Using the EORTC methodology, five significant factors were retained: age, principal cell type, anaplastic, T-category, and metastatic sites (The significant factors in the EORTC study also included the sex factor, which was not significant for the current study). Using their own prognostic index instead of the EORTC index, gave the authors a better classification of the patients and better survival prediction. Using the IC methodology, four significant factors were retained: age, histology, T-category, and metastatic sites (the significant factors in the IC study were age, histology and sex). Using the IGR methodology, two significant factors were retained: age and N-category (the significant factors in the IGR study also included sex and histology). The authors' results differ from those published by the previous groups. Therefore, one should hesitate before applying the results obtained by other groups for thyroid carcinoma to another population. It would seem necessary to carry out one's own MFA before determining a prognostic index.

Age Factors↗
PubMed1986

Comparison of phase analysis with factor analysis in equilibrium gated radionuclide angiography.

This study is the intercomparison of phase analysis (PA), factor analysis of dynamic structures (FADS) and Karhunen-Loeve analysis (KLA) in the diagnosis of regional wall motion abnormalities, RWMA, of the LV. One hundred and twenty eight patients with proven or suspected CAD have been investigated by both X-ray angiography and radionuclide equilibrium angiography performed in the LOA view. FADS and KLA are performed twice, once on the whole-image (WI-FADS, WI-KLA), and once on the LV ROI (LV-FADS, LV-KLA) as suggested by Pavel. Resulting images and factors are interpreted by a well trained observer. In an attempt to quantify LV-FADS images, two numeric parameters, P1 and P2, are defined. They measure the relative weight of the so-called ventricular factor for 2 and 3 factor analysis, respectively. A ROC curve is calculated for each method, taking X-ray angiography as the gold-standard. The areas under the ROC curves are estimated by the maximum likelihood method and are compared using a test described by Hanley which takes into account the correlation between the responses. The areas are: 0.90 for PA, 0.84 for WI-FADS, 0.86 for LV-FADS, 0.83 for WI-KLA, 0.86 for LV-KLA, 0.65 for P1 and 0.72 for P2. The observed differences are significant (at 5% level) between PA and WI-FADS and between FA and WI-KLA; whereas they are not between PA and LV-FADS, between PA and LV-KLA and between LV-FADS and LV-KLA. The diagnostic value of the two numeric parameters is poor.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1986

The objective evaluation of the phase image: a comparison of different automated methods.

One hundred and twenty eight patients with suspected or proven CAD were investigated using both X-ray ventriculography and equilibrium gated radionuclide angiography. In order to diagnose regional wall motion abnormalities, the parametric images obtained by Fourier analysis of the radionuclide images were analysed by different automated methods based on the measurement of the homogeneity of the phase values within the LV ROI. The effect of a diastolic frames exclusion, smoothing the original data, weighting the phase histogram, using Bacharach's error corrected phase distribution functions, using different descriptors of the spread of the phase histograms or distribution functions were tested. Using the results of the X-ray examination as the gold standard, ROC curves were plotted for each method. The ROC curves were modelled by a binormal model using the maximum likelihood method. Statistical tests were applied on the area under the ROC curves. The results show that the diagnostic value of the automated methods depends mainly on the way the histograms or distribution functions are described and to a lesser extent on the type of histograms or distribution functions used. The best result is obtained after smoothing, diastolic frames exclusion, weighting the phase histogram by the amplitude and describing it by its standard deviation. Nevertheless, this result is not significantly different from the result obtained by visual analysis of the phase and amplitude images.

Adult↗
PubMed1986

[Thyroid cancer in Champagne-Ardenne: 1967-1984. Epidemiologic findings in a regional register].

Between 1967 and 1984, 600 cases of clinically diagnosed thyroid carcinoma were collected in an area (Champagne-Ardenne) of about 1,500,000 inhabitants. During this period, the complete collection of the cases was progressively ensured by involving all the general practitioners and by creating a cooperative multidisciplinary group. The collected data were sex, age at diagnosis, histological classification and clinical extension in TNM system. We found 19 patients with previous neck irradiation. Thyroid cancer was diagnosed in association with thyrotoxicosis in 36 patients: 13 Graves disease and 23 nodular hyperthyroidism. Incidence rates were estimated on a well defined population of two districts (850,000 inhabitants) and limited to the last four years. The following results were obtained: incidence 4.3/100,000/year, age-specific incidence progressively increasing up to a value of 10/000,000/year in the course of the fifth decade. Sex-ratio was 0.26.

Adolescent↗