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Biomedical subjects

F Joffre

Publications and source records attributed to F Joffre.

At least 19 recordsLinked to original sources
PubMed2003

Measurements of extracellular volume fraction and capillary permeability in tissues using dynamic spin-lattice relaxometry: studies in rabbit muscles.

Dynamic MR longitudinal R(1) relaxometry after administration of a gadolinium contrast bolus (Gd-DTPA) has been used for in vivo measurements of the extracellular volume fraction (v) and the capillary permeability (k min(-1)) in rabbit muscles to distinguish between red slow- and white fast-twitch muscle fiber types. For this purpose a protocol imaging sequence has been used which allows fast R(1) measurements during the contrast agent uptake. Physiological tissue parameters, k and v, were obtained by computing procedures assuming a simplified monoexponential plasma model. These were shown to be about twice as large in the slow-twitch semimembranosous proprius muscle (SP), containing 100% oxidative type-I fiber, that in the fast-twitch rectus femorus muscle (RF), containing only 6% type-I fiber type. The capillary permeability has been found to be 0.25 +/- 0.02 min(-1) for the (SP) and 0.10 +/- 0.01 min(-1) for the (RF). Similarly, the extracellular volume fractions were 0.189 +/- 0.015 and 0.082 +/- 0.006 respectively, in close agreement with literature data and experimental results obtained by invasive radionuclide measurements. For the pool of the 10 studied animals, no significant variation among animals was observed in the extracellular volume fraction and the capillary permeability for the different muscle fiber types. The dynamic relaxometry method used is easy to implement on conventional MR imagers and has potential applications in muscle diseases. The method has also potential applications for tissue characterization based on extracellular volume and capillary permeability quantification. In particular, the method can be used for the evaluation of tumors and their responses to therapies.

Animals↗
PubMed2002

[Local staging of prostate carcinoma with phased array MR imaging: prospective study over 5 years].

PURPOSE: To assess by MRI, using a pelvic phased array coil, the accuracy for staging prostate carcinoma and to correlate the results with the rate of positive surgical margins. MATERIALS AND METHODS: Between January 1995 and December 1999, 176 patients with localized prostate carcinoma underwent a preoperative MRI examination using a pelvic phased-array coil (1 Tesla). MRI and histological results were compared in a prospective study. RESULTS: 131 were classified T2 and 45 were classified T3 at MRI. Pathologic findings showed 103 pT2 and 73 pT3. The accuracy of MRI (extra capsular or vesicle extension) was 75%. The risk for a patient labelled T2 or T3 at MRI to have a positive surgical margin was respectively 13.7% and 31%. CONCLUSION: This study shows that the phased-array coil has a low sensitivity but a good specificity to distinguish between organ-confined cancer or not. It shows that the risk of positive surgical margins is higher for T3 lesions at MRI. The low sensitivity should be improved by using a multi coil phased array.

Adenocarcinoma↗
PubMed2002

[Imaging of adrenal tumors].

Adrenal masses may be discovered incidentally by sonography. Nevertheless, CT is the modality of choice for the detection of adrenal mass when primary or secondary neoplasm is suspected. The distinction between benign and metastatic lesions relies mainly on the relatively high lipid content of most of the adenomas. CT (evaluation of non-enhanced attenuation) and MRI (chemical shift imaging) have comparable performances in the evaluation of lipid content. Lipid-poor adenomas benefit from the evaluation of tumoral wash-out, and, if necessary, CT-guided biopsy. Primary neoplasms are uncommon, reliability of biopsy is poor and surgical resection is generally performed.

Adrenal Gland Neoplasms↗
PubMed2001

Long-term results of endovascular stent placement in the superior caval venous system.

PURPOSE: To present the long-term results in superior caval stenting for symptomatic obstruction. METHODS: Forty-nine stents were placed in 30 patients: 16 (53%) with malignant lesions, five (17%) with benign lesions and nine (30%) hemodialysis patients. Self-expandable stents were deployed on a first-line basis. Patients were followed clinically as well as by various imaging techniques and survival analysis was performed. RESULTS: Stent deployment was possible in all cases. Reocclusion was seen in 13 patients, of whom eight belonged to the hemodialysis group. Primary and secondary patency rates for malignant, benign and hemodialysis patients were respectively 74%, 50% and 22%, and 74%, 75% and 56% at 1 year. We had 7% complications and one death from iatrogenic superior vena cava injury. CONCLUSION: Primary stenting of superior caval obstruction is a first-choice treatment method achieving good mid-term patency. Patients with hemodialysis shunts must be closely monitored for early reintervention.

Adenocarcinoma↗
PubMed2001

[Risk of embolism in diagnostic and therapeutic intravascular procedures--in vitro model].

The purpose of the study was to evaluate the risk of distal embolisation in a silicon model during different endovascular diagnostic and therapeutic procedures. Endovascular technics, such as guidewire and catheter advancement, metal stent placement, balloon angioplasty and thrombectomy device were compared. Clots were produced from human blood sample. The transparent silicon model was filled with saline, flow was generated by an hydraulic pump. Stenosis was created by mechanical compression. The size of the circulating particles were measured with a mesh of nylon filters. No loose particles were detected using guidewire, pigtail and straight catheters. Balloon inflation induced embolisation of particles ranging from 100 microns-12 mm in length. Deployment of self expandable metallic stents did not result in particle migration but secondary angioplasty inside the stent detached particles (ranging from 400 microns to 12 mm in length). Use of thrombectomy device resulted in significant particle migration (ranging from 400 microns to 1500 microns in length).

Angioplasty, Balloon↗
PubMed2001

Imaging of retroperitoneal ganglioneuroma.

The aim of this study was to describe the radiological appearance of retroperitoneal ganglioneuroma. We retrospectively reviewed seven cases of histologically proven retroperitoneal ganglioneuroma. Ultrasound and enhanced CT were obtained in all cases, and MRI in three cases. The masses were well-circumscribed, ranged in size from 5 x 3 x 3 to 10 x 6 x 4 cm. In three cases close relationships between the tumor mass and major blood vessels were noted, resulting in vessel displacement or surrounding, but without compression or occlusion. On ultrasound examination the tumor showed a heterogeneous solid echostructure. Non-enhanced CT showed homogeneous or mildly heterogeneous low attenuation, and a punctate calcification was seen in one case. Contrast uptake was absent (n = 1) or delayed (n = 6). Progressive but incomplete enhancement was observed in three cases. On MRI, T2-weighted images showed a high signal intensity. Dynamic studies depicted the same enhancement pattern as described on CT. Ganglioneuroma is a rare tumor which should nevertheless be included in differential diagnosis of retroperitoneal masses when presenting as a well-delimited tumor with possible tendency to surround or displace major blood vessels, low density on non-enhanced CT, and delayed progressive enhancement on CT and MRI.

Adult↗
PubMed2001

Assessment of the risk of positive surgical margins with pelvic phased-array magnetic resonance imaging in patients with clinically localized prostate cancer: a prospective study.

OBJECTIVES: We assessed magnetic resonance imaging (MRI) performance in the prediction of positive surgical margins (PSMs) before radical prostatectomy in a prospective study correlating the MRI results and pathologic findings. METHODS: Between January 1995 and December 1999, 176 patients (mean age 64.2 years, range 49 to 75), with localized prostate cancer (49 with Stage T1 and 127 with Stage T2) underwent preoperative MRI with a pelvic phased-array coil (Tesla-1, Siemens) at a mean interval of 35 days after randomized transrectal biopsies. The mean preoperative prostate-specific antigen level was 10.9 ng/mL (range 1.2 to 39). The MRI studies and specimen analysis were performed by one radiologist unaware of the clinical and biopsy findings and by one pathologist, respectively. Multivariate analysis was performed to compare the predictive value of MRI staging, prostate-specific antigen value, and preoperative Gleason score to identify the PSM rate. RESULTS: Of the 176 patients, 131 (74%) had Stage T2 disease by MRI and 45 (26%) Stage T3 disease by MRI. Pathologic staging showed 103 with pT2 and 73 with pT3. Overall, the PSM rate of the series was 18%. The PSM rate was 13.7% and 31% for patients with T2 and T3 disease by MRI, respectively. For the T3 MRI cases, the PSM rate was 2.32-fold higher. MRI staging, like the prostate-specific antigen value, was a predictive factor of PSMs (P = 0.05). CONCLUSIONS: The results of this study show that preoperative MRI staging with the phased-array coil may be helpful in predicting the PSM risk in radical prostatectomy candidates with clinically localized prostate cancer.

Aged↗
PubMed2001

Kinetic parameters of hepatic oxidation of cyclic fatty acid monomers formed from linoleic and linolenic acids.

Cyclic fatty acid monomers (CFAM) occur from linoleic (CFAM-18:2) or linolenic (CFAM-18:3) acids present in some edible oils as a result of domestic frying or industrial refining. They present adverse effects in pups and weaning rats. In the present work, we studied the importance of hepatic oxidation in the metabolism of CFAM. For this purpose, kinetic parameters of Carnitine Palmitoyl Transferase I (key enzyme of the channeling of the fatty acids into the mitochondrial beta-oxidation pathway) and Acyl CoA Oxidase (key enzyme of the peroxisomal oxidation pathway) towards CFAM-18:2 and CFAM-18:3 were calculated on hepatic sub-cellular fractions of rats. For mitochondrial oxidation of CFAM, we observed a lower oxygen consumption and a lower activity of Carnitine Palmitoyl Transferase compared to 18:2w6 and 16:0. For peroxisomal oxidation, CFAM-18:2 showed the same kinetic parameters (Vm and K(0.5)) as 18:2w6 and 16:0, used for oxidative controls, whereas CFAM-18:3 presented a lower Vm (-50%). This difference should induce a lower catabolism of CFAM-18:3 in liver. This could contribute to their accumulation and probably to their toxic effect.

Journal Article↗
PubMed2001

Macroporous polyester-covered stent in an experimental abdominal aortic aneurysm model.

PURPOSE: To validate a recently described animal model of abdominal aortic aneurysm (AAA) and to assess a new macroporous polyester-covered stent for endovascular AAA exclusion. METHODS: Twenty adult sheep had AAAs surgically created by replacing a segment of the infrarenal aorta with an autologous jugular venous graft. Three months later, surviving animals underwent percutaneous implantation of macroporous polyester-covered nitinol stents; 3 animals with untreated AAAs served as controls. Follow-up surveillance included spiral computed tomography at 1 month and digital subtraction angiography at 3 and 6 months. Endografted animals were sacrificed at 1, 3, and 6 months after implantation; specimens from all animals were examined grossly and microscopically. RESULTS: Seven (35%) animals died within 24 hours of causes related to the technique; 1 animal developed paraplegia and was sacrificed on day 1. Three (25%) animals died of spontaneous aneurysm rupture at <10 days, and 6 received the stent-graft at 3 months. The macroporous cover did not prevent continued perfusion of the sac early after stent-graft deployment, but all aneurysms were excluded on the 1-month CT. CONCLUSIONS: Spontaneous AAA rupture occurred earlier and was not as frequent as previously described for this model. Implantation of the covered stent was feasible, but aneurysm exclusion was not immediate.

Animals↗
PubMed2001

Pseudoaneurysm and aortobronchial fistula after surgical bypass for aortic coarctation: management with endovascular stent-graft.

PURPOSE: To report the endovascular repair of an aortobronchial fistula at the distal anastomosis of a complex thoracic graft. CASE REPORT: A 61-year-old man operated 18 years prior for aortic coarctation presented with hemoptysis. An aortobronchial fistula was suspected, but spiral computed tomography and angiography showed only a small pseudoaneurysm at the distal anastomosis without revealing the fistulous tract. A Talent stent-graft was successfully deployed through a femoral access, but the large delivery system injured the external iliac artery, producing a retroperitoneal hemorrhage. Prompt balloon occlusion of the aorta and subsequent bypass graft repair of the arterial injury prevented serious sequelae. The patient recovered without further complications. Follow-up imaging to 2 years has documented exclusion of the pseudoaneurysm with no hemoptysis or signs of new false aneurysm formation. CONCLUSIONS: Endovascular exclusion of anastomotic pseudoaneurysms even in complicated cases can be an efficient treatment option, but the procedure must be carefully planned and executed in order to achieve good results.

Anastomosis, Surgical↗
PubMed2001

[Radiologic study of renal colic].

Ureterolithiasis is a common disease responsible for a large number of admissions in emergency departments and a wide utilization of imaging studies. The purpose of this review was to analyze the respective role of the different available imaging techniques. Intravenous urography is the gold-standard for diagnosis of acute obstruction, but positive detection of a stone may prove difficult at times. US is less accurate than urography for both diagnoses of obstruction and lithiasis, but it represents a non invasive alternative to IVU (no ionizing radiation and no IV contrast). The information obtained from measurements of intra-renal resistive index is poorly contributive. Non contrast helical CT has become the gold-standard for the diagnosis of ureterolithiasis, the two main factors limiting its widespread use are its accessibility and the radiation exposure. Nevertheless, its excellent diagnostic performance tends to dramatically reduce the need for IVU.

Colic↗
PubMed2001

[Endoluminal treatment of peripheral aneurysm with covered endoprosthesis].

PURPOSE: To evaluate the feasibility and middle term patency results, for endovascular treatment of peripheral aneurysms, using covered stents. MATERIALS AND METHODS: Between December 1993 and may 2000 25 peripheral aneurysms on 24 patients, mean age 67.8 years (42-81), were treated with covered stents (Cragg EndoPro system or passenger, hemobahn, Word Medical). Aneurysm locations were: 17 iliac, 4 popliteal, 1 femoral, 1 subclavian, 1 carotid. The follow-up range from 1 to 75 months (mean 30.1 months). RESULTS: Successful aneurysm exclusion was achieved in all patients, while maintaining good lower extremity perfusion. All but one stent remained patent during the early follow-up period. At one year 94.4% stents were patent, at two years 90.2. CONCLUSION: Treatment of peripheral aneurysms with covered stents has a high rate of immediate procedural and clinical success. At middle term follow-up patency is encouraging except with popliteal procedure, however long term follow-up and larger series is warranted to assess the place of this procedure as an alternative to the surgery.

Adult↗
PubMed2000

Rapid relaxation times measurements by MRI: an in vivo application to contrast agent modeling for muscle fiber types characterization.

This paper is a description of a simulation method to evaluate the contrast in NMR imaging and its aim is to help to optimize the use of contrast media in clinical imaging. Indeed, there is a need to define objective criteria in order to choose among several contrast media the ones that are the most effective and to define their optimal conditions of use, such as: the dose to be injected, the required time after injection to obtain the best enhancement and the optimal imaging sequence parameter values. The method is based on NMR signal simulation in the presence of contrast media and requires the fast measurement of the T1 and T2 relaxation times to obtain the dynamic relaxometry variation of tissues after contrast injection. In this work the fast imaging techniques that are to be described enable the measurement of T1 and T2 with a 30sec temporal resolution on 128*256 matrix images. The accuracy of the method was assessed in rabbit muscles after the injection of two gadolinium chelates (Gd-DTPA and Gd-DOTA) with the aim of improving the in vivo characterization of fast-twitch and slow-twitch muscle fiber types. The simulation results were in close agreement with contrast image analysis and showed, for relevant clinical doses, a small efficacy for both chelates. The interest of the proposed simulation method lies in the fact that it enables to objectively compare the efficacy of different contrast agents, to forecast the efficacy of a given contrast reagent and to define the optimal dose and the optimal imaging sequence parameters that give the best contrast. This simulation method obviates numerous prior experiments to evaluate the benefit expected from different contrast media. The method, which has been evaluated here for muscle investigations is applicable to any tissue analysis and can help to guide the best condition of use of contrast agents in MR imaging.

Animals↗
PubMed2000

Aortoduodenal fistula after endovascular stent-graft of an abdominal aortic aneurysm.

Despite satisfying short- and middle-term effectiveness and feasibility, endovascular stent-grafting for abdominal aortic aneurysm is still under evaluation. We report a case of an aortoduodenal fistula after the use of this technique. Enlargement of the upper aneurysmal neck was followed by caudal migration of the major portion of the stent-graft, which resulted in kinking of the device in the aneurysmal sac. Ulcerations were found on adjacent portions of both the aneurysmal sac and the adjacent duodenum. Only the textile portion of the prosthetic contralateral limb separated the aortic lumen from the corresponding duodenal lumen. Early detection of complications after stent-grafting is essential to allow successful treatment, either surgical or endoluminal.

Angioplasty↗
PubMed2000

Transjugular intrahepatic portosystemic shunts in the treatment of refractory ascites: results in 48 consecutive patients.

PURPOSE: To assess the efficacy, morbidity, and mortality involved in the creation of transjugular intrahepatic portosystemic shunts (TIPS) in the treatment of patients with refractory ascites in Child-Pugh classes B and C. MATERIALS AND METHODS: Forty-eight consecutive patients with refractory ascites were treated with TIPS creation in a tertiary care institution. They were followed for a median of 337 days (range, 3-1376 d). RESULTS: TIPS significantly decreased the portohepatic pressure gradient (20.7 +/- 5.9 mm Hg vs. 6.8 +/- 4.1 mm Hg; P < .0001). Seventy-three percent of patients had complete or partial response. One year after TIPS creation, survival was 73% in Child class B patients and 56% in Child class C patients. Thirteen patients experienced procedural complications (portal vein thrombosis, peritoneal bleeding, acute renal failure, pneumothorax, hemoptysis, spontaneous bacterial peritonitis, and heart failure) and TIPS creation was considered the cause of death in five patients (10.4%). Primary patency was 65% at 3 months and 23% at 1 year, but shunt obstruction was accessible for a second intervention. Ten patients (21%) had de novo encephalopathy after TIPS creation. CONCLUSIONS: This series suggests that TIPS is an effective treatment for refractory ascites; however, it is a challenging procedure and serious complications--usually renal and heart failure--can be seen. A careful selection of patients is mandatory.

Ascites↗