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Biomedical subjects

S Delorme

Publications and source records attributed to S Delorme.

At least 37 records · Page 2Linked to original sources
PubMed2003

[Detection of prostate carcinomas with T1-weighted dynamic contrast-enhanced MRI. Value of two-compartment model].

AIM: The suitability of dynamic parameters of the two-compartment model for detecting prostate carcinomas and its correlation with tumor microvascular density were evaluated. METHODS: The study included 43 patients with biopsy-proven prostate carcinoma: 28 were examined by 1.0-T MRI (Turbo-FLASH) and 15 by 1.5-T MRI (FLASH) with infusion of 0.1 mmol/kg Gd-DTPA. Signal time curves were parametrized with an open two-compartment model in amplitude and exchange rate constants (k(ep)). The microvascular density of resected prostate carcinomas was determined. RESULTS: The microvascular density in the tumors was significantly higher than in the adjacent healthy prostate tissue and correlated in both sequences with k(ep). Prostate carcinomas of the peripheral zone were demarcated by amplitude and k(ep). In the Turbo-FLASH sequence there was a significant difference between the tumor tissue and healthy peripheral zone in terms of k(ep) and in the FLASH sequence in terms of amplitude. CONCLUSION: Prostate carcinomas can be visualized with dynamic T1-weighted MR sequences using a two-compartment model. Moreover, the parameter k(ep) reveals the microvascular density in the tumor and can thus provide valuable clinical information for characterizing the tumors.

Biopsy↗
PubMed2003

[Quantification of tissue perfusion with novel ultrasound methods].

Perfusion describes an important parameter of tissue vitality, e. g. of the myocardium, brain, or the kidney. In malign tumours, perfusion is of particular interest for characterization and prognosis. In addition, new pro- or anti-angiogenic therapies require a functional imaging which is suitable to quantify vascularity. Sonographic methods for the detection of microvascularity, particularly related smaller than those amenable to Doppler ultrasound, are reviewed. The main focus deals with the explanation of contrast-enhanced sonography using replenishment kinetics of microbubbles which provides a comprehensive quantification of tissue perfusion. Alterations of the microvascularity e. g., under anti-angiogenic therapy, can be depicted in experimental studies using this novel approach. Further clinical applications can be the quantification of the perfusion in the myocardium, the brain, or the kidney. New approaches to optimize the theoretical model to describe the replenishment, and novel technical developments are discussed.

Animals↗
PubMed2003

[Time-resolved multiphasic 3D MR angiography in the diagnosis of the pulmonary vascular system in children].

PURPOSE: To evaluate time-resolved, multiphasic 3D MR angiography (MRA) for the non-invasive assessment of the pulmonary vascular system in children. MATERIALS AND METHODS: 10 children aged 6 to 15 years (mean age 10 years) ware examined on a 1.5 T whole body MR system with time-resolved, multiphasic 3D MRA after injection of 0.2 mmol/kg body weight of Gd-DTPA. With the use of an ultrafast gradient echo pulse sequence with asymmetric k-space filling and very short echo and repetition times, a nominal spatial resolution of 1.4 x 1.4 x 2.0 mm3 could be achieved with a scan time of 5.6 and 6.2 seconds for a single 3D data set. Two radiologists, who were blinded to the clinical diagnosis, analyzed the image data in consensus. The image analysis included the assessment of the image contrast and artifacts as well as a quantitative analysis of the signal-to-noise (SNR) and contrast-to-noise ratios (CNR) for central and peripheral lung vessel segments. RESULTS: The children tolerated all examinations without any side effects. The referral diagnosis, which was based on echocardiography, catheter angiography and surgery, was confirmed by MRA in all cases. The image contrast was rated at least satisfactory in all but one case (19 of 20) and no artifacts were observed. The quantitative analysis of the SNR and CNR in the pulmonary arteries and veins confirmed the reader analysis of a high and uniform contrast throughout the entire pulmonary circulation. CONCLUSION: Time-resolved multiphasic 3D MRA allows a non-invasive diagnostic evaluation of the pulmonary circulation in children. In view of the excellent image quality, MRA may replace conventional diagnostic catheter angiography in the near future.

Adolescent↗
PubMed2003

Assessment of the 3-d reconstruction and high-resolution geometrical modeling of the human skeletal trunk from 2-D radiographic images.

This paper presents an in vivo validation of a method for the three-dimensional (3-D) high-resolution modeling of the human spine, rib cage, and pelvis for the study of spinal deformities. The method uses an adaptation of a standard close-range photogrammetry method called direct linear transformation to reconstruct the 3-D coordinates of anatomical landmarks from three radiographic images of the subject's trunk. It then deforms in 3-D 1-mm-resolution anatomical primitives (reference bones) obtained by serial computed tomography-scan reconstruction of a dry specimen. The free-form deformation is calculated using dual kriging equations. In vivo validation of this method on 40 scoliotic vertebrae gives an overall accuracy of 3.3 +/- 3.8 mm, making it an adequate tool for clinical studies and mechanical analysis purposes.

Humans↗
PubMed2003

Seroprevalence of antibodies against human herpesvirus 8 in a population of renal transplant recipients at Hôtel-Dieu de Québec Hospital.

We conducted a seroepidemiologic study to determine the prevalence of anti-human herpesvirus 8 antibodies in a renal transplant population at Hôtel-Dieu de Québec Hospital. Testing for immunoglobulin G antibodies against lytic and latent antigens was performed on serum samples from 150 renal transplant patients. Human immunodeficiency virus-positive patients with confirmed Kaposi's sarcoma were used as positive controls. None of the renal transplant patients tested positive.

Antibodies, Viral↗
PubMed2003

Morphofunctional visualization of MR-mammography in virtual reality.

In view of an increasing use of breast MRI supplementing X-ray mammography, the purpose of this study was the development of a method for fast and efficient analysis of dynamic MR image series of the female breast. The dynamic image data sets were analyzed by tracer kinetic modeling in order to describe the physiological processes underlying the contrast enhancement in mathematical terms and thus to enable the estimation of functional tissue specific parameters, reflecting the status of microcirculation. To display morphological and functional tissue information simultaneously, a multidimensional real-time visualization system (using 3D-texture mapping) was developed, which enables a practical and intuitive human-computer interface in virtual reality.

Breast Neoplasms↗
PubMed2003

Dynamic MR-mammography in virtual reality.

In view of an increasing use of breast MRI supplementing X-ray mammography, the purpose of this study was the development of a method for fast and efficient analysis of dynamic MR image series of the female breast. The image data sets were acquired with a saturation-recovery-turbo-FLASH sequence facilitating the detection of the kinetics of the contrast agent concentration in the whole breast with. In addition, a morphological 3D-FLASH data set was acquired. The dynamic image data sets were analyzed by tracer kinetic modeling in order to describe the physiological processes underlying the contrast enhancement in mathematical terms and thus to enable the estimation of functional tissue specific parameters, reflecting the status of microcirculation. To display morphological and functional tissue information simultaneously, a multidimensional real-time visualization system (using 3D-texture mapping) was developed, which enables a practical and intuitive human-computer interface in virtual reality. The spatially differentiated representation of the computed functional tissue parameters superimposed on the anatomical information offers several possibilities: improved discernibility of contrast enhancement; inspection of the data volume in 3D-space using the features of rotation and transparency variation; localization of lesions in space and thus fast and more natural recognition of topological coherencies. In a feasibility study, it could be demonstrated that multidimensional visualization of contrast enhancement in virtual reality is a practicable idea. Especially, detection and localization of multiple breast lesions may be an important application.

Computer Simulation↗
PubMed2002

Accuracy of tumor size measurement in breast cancer using MRI is influenced by histological regression induced by neoadjuvant chemotherapy.

The aim of this study was to evaluate whether regressive changes after neoadjuvant chemotherapy for breast cancer affect the accuracy of preoperative MRI measurements of tumor size. Thirty-one patients with breast cancer underwent MRI before and after neoadjuvant treatment. Besides pre- and post-contrast T1-weighted MRI, dynamic MRI with high temporal resolution (turbo-FLASH) was performed. Contrast enhancement in dynamic MRI was quantified using a pharmacokinetic two-compartment model, where two parameters, amplitude and k(ep), were calculated and color coded on transversal parameter maps. Considering the conventional MR images, tumor diameters were measured on the color maps and compared with histological tumor size. Histological regression was scored on a five-point scale regarding cytopathic effects, reactive changes, and tumor cell reduction. The correlation between tumor sizes measured by MRI and histopathology was 0.83 ( p<0.0007) in 12 tumors without regressive changes (score 0), and 0.48 ( p<0.051) in 17 tumors with regressive changes scored 1 or 2, without any tendency for systematic over- or underestimation. In two cases without residual tumor (score 4), MRI likewise showed no signs of persistent tumor. The decrease of the contrast enhancement parameters was significantly more marked in tumors with signs of histological regression than in those without. Whenever MRI is used to judge the response of breast cancer to chemotherapy, the reader must be aware that therapy-induced changes may cause significant over- or underestimation of tumor size. We saw a high precision only when there was either no response - according to histological criteria - or when the tumor had regressed completely.

Antineoplastic Agents↗
PubMed2002

Evaluation of neoadjuvant chemotherapeutic response of breast cancer using dynamic MRI with high temporal resolution.

The aim of this study was to evaluate changes in both size and contrast enhancement of breast tumors during neoadjuvant chemotherapy, using dynamic MRI with high temporal resolution. Patients with advanced breast cancer (n=21) underwent a 1.5-T MRI scan prior to and following neoadjuvant chemotherapy with four cycles. Dynamic contrast enhancement was measured using a fast turbo-FLASH sequence and quantified using a two-compartment model with the parameters k(ep) and amplitude. Image analysis was done on images overlayed with a color map of parameters. The correlation between tumor diameter measured by histopathology and MRI was 0.7 (p<0.003). A reduction of tumor size after chemotherapy of more than 25% was associated with a decrease of both analyzed contrast enhancement parameters (k(ep): p<0.002; amplitude: p<0.006), where k(ep) began to drop already after the first cycle of chemotherapy (p<0.008). A clear reduction of tumor size was only noted after the third cycle (p<0.008). In patients without tumor regression there was also a trend towards an early reduction of contrast enhancement. We assume that MRI with high temporal resolution and color mapping is a novel tool to assess therapeutic effects of neoadjuvant chemotherapy in breast tumors, which deserves further prospective evaluation.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed2002

Comparison of B-mode and conventional colour/power Doppler ultrasound, contrast-enhanced Doppler ultrasound and spiral CT in the diagnosis of focal lesions of the liver: Results of a multicentre study.

AIM: In patients with lesions of the liver we compared diagnoses based on different methods of ultrasound as well as spiral CT with the final diagnosis reached at the time of the patient's discharge from hospital. METHOD: From records of a prospective multicentre study including 90 liver lesions investigated with B-mode baseline and conventional colour/power Doppler ultrasound, contrast-enhanced colour/power Doppler ultrasound and spiral-CT, we evaluated only those where diagnoses for all modalities were available, and where the diagnosis at discharge comprising all clinical, laboratory and imaging data as well as histologic proof was at least "highly probable". RESULTS: 60 lesions met the inclusion criteria. 20 lesions were ultimately diagnosed as benign, and 40 as malignant. With respect to the diagnosis of malignancy, sensitivity was 92.5 % (37/40) with B-mode and unenhanced conventional colour/power Doppler US ultrasound, 97.5 % (39/40) with contrast-enhanced colour/ power Doppler ultrasound, and 100 % with CT; the corresponding specificities were 65 % (13/20), 85 % (17/20) and 80 % (16/20). 4 of 7 false positive, and 2 of 3 false negative results in the unenhanced technique were diagnosed correctly with contrast-enhanced Doppler ultrasound. CONCLUSION: Compared to conventional ultrasound, contrast-enhanced Doppler ultrasound improved the diagnostic accuracy in 10 % of the cases. Its accuracy in our study was equal to that of CT.

Contrast Media↗
PubMed2002

Magnetic resonance imaging of nude mice with heterotransplanted high-grade squamous cell carcinomas: use of a low-loaded, covalently bound Gd-Hsa conjugate as contrast agent with high tumor affinity.

RATIONALE: Malignant tumors often show an increased uptake and metabolism of plasma proteins, especially albumin. OBJECTIVES: Determine whether the accumulation of low loaded Gd-albumin improves visualization of malignant tumors by MRI. METHODS: Twelve nude mice with heterotransplanted squamous cell carcinomas were studied. The signal intensity of tumor, blood, liver, kidney and muscle tissue was studied in MR images after application of Gd-albumin during a period of 144 hours. MRI results were histologically correlated after simultaneously injection of Gd- and fluorescein-labeled albumins in 9 nude mice. RESULTS: Although liver and kidney had a maximum increase in signal intensity within 30 minutes, tumors showed a delayed 51% increase in the 24 hours after application. Histologic and fluorescence evaluation demonstrated albumin localization in tumors predominantly in stroma and necroses. CONCLUSIONS: Gd-albumin is efficiently accumulated in SCC transplants. MRI with low loaded Gd-albumin may offer relevant opportunities for recognizing tumors sensitive to a therapy with cyostic drug-labeled albumins.

Albumins↗
PubMed2002

Self-calibration of biplanar radiographs for a retrospective comparative study of the 3D correction of adolescent idiopathic scoliosis.

A novel technique for the 3D reconstruction of the spine from X-ray images is presented. The algorithm is based on the self-calibration of biplanar radiographs. It allows the 3D reconstruction of spines from old uncalibrated preoperative and postoperative radiographs. The reliability of the new self-calibration technique was investigated by validating its results against those of the Direct Linear Transform (DLT) on real images. An accuracy experiment was also performed using a dry spine specimen under controlled conditions. The results indicate that self-calibration is a viable technique, accurate enough to extract meaningful 3D clinical data for retrospective studies.

Adolescent↗
PubMed2001

[Radiotherapy planning for paraspinal tumors with CT-myelography].

BACKGROUND AND AIM: Artifacts due to metal implants are an important problem in diagnostic radiology and radiotherapy planning in tumors such as chordoma of the spine. A strict differentiation between target and radiosensitive structures e.g. spinal cord is absolutely essential for high-dose radiotherapy. Up to now CT and MRI techniques have provided only limited image quality in such situations. We introduce an approach to facilitate segmentation by using the technique of CT-myelography for radiation treatment. PATIENT AND METHOD: A 48-year-old woman with multiple inoperable relapses of a chordoma in the lumbar spine and extensive metal instrumentation in this area was given to radiotherapy using IMRT-technique (intensity modulated). MRI- and CT-planning images did not allow differentiation between myelon, cauda equina, dural sac and tumor. In this situation we performed a CT-myelography with the patient in treatment position. RESULT: CT-myelographic images enabled precise differentiation between myelon, cauda equina and intraspinal tumor. A substantial improvement of the segmentation of the spinal cord was obtained. There was no compression of the dural sac along the spine. This information provided the basis for a precise radiotherapy planning in IMRT-technique. CONCLUSION: In situations where CT- and MRI-techniques are not able to generate precise images which allow differentiation between tumor, myelon and cauda equina because of metal artifacts, CT-myelography is a promising technique which may help the diagnostic radiologist and radiation oncologist in planning radiotherapy.

Humans↗