Fiber tracking in q-ball fields using regularized particle trajectories

Most of the approaches dedicated to fiber tracking from diffusion-weighted MR data rely on a tensor model. However, the tensor model can only resolve a single fiber orientation within each imaging voxel. New emerging approaches have been proposed to obtain a better representation of the diffusion process occurring in fiber crossing. In this paper, we adapt a tracking algorithm to the q-ball representation, which results from a spherical Radon transform of high angular resolution data. This algorithm is based on a Monte-Carlo strategy, using regularized particle trajectories to sample the white matter geometry. The method is validated using a phantom of bundle crossing made up of haemodialysis fibers. The method is also applied to the detection of the auditory tract in three human subjects.

Thromboses veineuses superficielles des veines non variqueuses des membres inférieurs

Recent publications allow better understanding of superficial thrombophlebitis (ST) of the lower limb veins. However ST occurring in non varicose veins (NVV) and those occurring in varicose veins (VV) are seldom distinguished in literature.

AIMS OF THE STUDY

1) To estimate the potential gravity of ST occurring in NVV by putting a figure on the frequency of associated deep venous thrombosis (DVT) and symptomatic pulmonary embolism (PE); 2) to identify some risk factors (thrombophilia, systemic disease, thromboembolic events); 3) to assess the different types of thromboembolic recurrent events after superficial thrombophlebitis (TRST) and identify the risk factors for recurrence.

MATERIAL AND METHOD

Forty-two cases of ST occurring in NVV were included consecutively and prospectively in this series; TRST possible risk factors were evaluated. Patients were assessed at 1 month and followed up to 3 years. Isolated ST was treated with low-molecular-weight heparin at prophylactic dosage from 15 to 21 days and with elastic compression.

RESULTS

1) A DVT was combined in 12 cases (28.6%) located in the calf (n=9) or in the femoro-politeal axis (n=3). One symptomatic PE occurred confirmed by ventilation-perfusion lung scan; 2) The risk factor investigations identified a neoplasm in 2 patients (4.8%), a non neoplasic systemic disease in 4 (9.5%) and a thrombophilia in 20 patients. The most frequent thrombophilia was the heterozygous mutation of coagulation factor V (Leiden); 3) All patients were assessed at 1 month with a clinical examination and Duplex Scanning. We did not identify either new DTV, PE or extension of the previous DVT; 4) 17 TRST were identified in 13 patients. Three patients had 2 recurrences; one patient presented a TRST located at 2 different sites. In total 8 new ST and 9 DVT were identified.

DISCUSSION

The analysis of the literature shows that early complications or combinations (DVT and PE) occur with the same prevalence in NVV and VV groups. A risk factor was identified in 62% of patients in this series (thrombophilia was the most common) and TRST were statistically more frequent in this series than in groups of ST occurring in VV we had previously analyzed. A post-thrombotic syndrome and a DVT associated with the ST were identified as statistically significant risk factors for recurrence.

CONCLUSION

ST occurring in NVV, although representing 5 to 10% of all ST, is seldom reported in the literature. Like ST occurring in VV, they have a potential gravity (associated DVT and PE). However these two diseases should be distinguished. A risk factor is more often identified and TRST are more frequent in the group of ST occurring in NVV. We advise active management of these thromboses including screening for a risk factor, the implementation of measures for preventing venous thrombosis recurrence and patient follow-up.

[Surgery for deep venous reflux in the lower limb]

Surgery for deep venous reflux (DVR) in the lower limb had displayed, for various reasons a much more limited development than arterial surgery including endovascular techniques. Importance and frequency of DVR in chronic venous disease and particularly in chronic venous insufficiency (CVI) has been fully identified only in the last 20 Years, thanks to the development of duplex-scanning. Despite its effectiveness, deep reconstructive surgery remains controversial which probably explains why this specific surgery is performed by few units worldwide. Furthermore as deep reconstructive surgery is usually combined with superficial and perforator surgery, assessment of its specific benefit is difficult. In patients with severe CVI, venous valvular reflux involves deep vein as an isolated abnormality in less than 10%, but is associated with superficial reflux or/and perforator incompetence in 46%. The most common etiology in DVR is post-thrombotic syndrome accounting for an estimated 60-85% of patients with CVI. Primary reflux is the result of structural abnormalities in the vein wall and the valve itself. A very rare cause of reflux is the absence of valves secondary to agenesis. Surgical techniques for treating DVR can be classified into two groups: those that do and those that do not involve phlebotomy. The first group includes internal valvuloplasty, transposition, transplantation, neo valve and cryopreserved allograft. The second group involves wrapping, Psathakis II procedure, external valvuloplasty (transmural and transcommissural) angioscopy assisted or not, external valve construction and percutaneous placed devices. There are some clinical features that enable distinguishing superficial venous insufficiency from deep venous insufficiency but they are not reliable enough as both are frequently combined. In addition primary reflux is difficult to identify from secondary deep reflux.

INVESTIGATIONS

Duplex scanning provides both hemodynamic and anatomic information. Photoplethysmography as air plethysmography can help when superficial and deep venous reflux are combined to identify the predominant pathological component. It would seem logical to go beyond these investigations only in those patients in whom surgery for DVR may be considered. That means that the decision to continue investigations is dominated by the clinical context and absence of contraindication (uncorrectable coagulation disorder, ineffective calf pump). When surgery is considered, complementary investigations must be carried out: ambulatory venous pressure measurement and venography including ascending and descending phlebography. The goal of DVR surgery is to correct the reflux related to deep venous insufficiency at the subinguinal. But it must be kept in mind that DVR is frequently combined with superficial and perforator reflux, consequently all these mechanisms have to be corrected in order to reduce the permanent increased venous pressure. As mentioned previously, surgery results for DVR are somewhat difficult to assess as superficial venous surgery and/or perforator surgery have often been performed in combination with DVR surgery. Valvuloplasty is the most frequent procedure used for primary deep reflux. On the whole, valvuloplasty is credited with achieving a good result in 70% of cases in terms of clinical outcome defined as a freedom of ulcer recurrence and the reduction of pain, valve competence and hemodynamic improvement over a follow-up period of more than 5 years. In all series, a good correlation was observed between these three criteria. External transmural valvuloplasty does not seem to be as reliable as internal valvuloplasty in providing long-term valve competence or ulcer free-survival. In PTS, long-term results are available for transposition and transplantation. In terms of clinical result and valve competence, a meta-analysis demonstrates that a good result is achieved in 50% of cases over a follow-up period of more than 5 years, with a poor correlation between clinical and hemodynamic outcome. Results with others techniques including Psathakis II technique, neovalve and cryopreserved valves are less satisfactory. DVR surgery indications for reflux rely on clinical severity, hemodynamics and imaging: most of the authors recommend surgery in patients severe disease graded C4 and C 5-6. When superficial and perforator reflux are associated, they must be treated, for some Authors as a first step, for others shortly before DVR surgery in the same hospitalization stay. Contraindications as previously stipulated have to be kept in mind. Hemodynamics and imaging criteria: only reflux graded 3-4 according to Kistner are usually treated with DVR surgery. It is generally recognized that, to be significantly abnormal, venous refill time must be less than 12 s, and the difference between pressure at rest and after standardized exercise in the standing position must be less than 40%. The decision to operate should be based on the clinical status of the patient, not the non-invasive data, since the patient's symptoms and signs may not correlate with the laboratory findings. Indications according to etiology: the indications for surgery can be simplified according to the clinical, hemodynamic and imaging criteria described above. In primary reflux, reconstructive surgery is recommended after failure of conservative treatment and in young and active patients reluctant to wear permanent compression. Valvuloplasty is the most suitable technique, with Kistner, Perrin and Sottiurai favoring internal valvuloplasty and Raju transcommissural external valvuloplasty. In PTS, obstruction may be associated with reflux; most of the authors agree that when significant obstruction is localized above the inguinal ligament, obstruction must be treated first. Secondary deep venous reflux, mainly post-thrombotic syndrome may be treated only after failure of conservative treatment as the results achieved by subfascial endoscopic perforator surgery associated or not with superficial venous surgery are not convincing. It is recommended that this procedure might be carried out in combination with deep reconstructive surgery. The techniques to be used, given that valvuloplasty is rarely feasible, in order of recommendation, are: transposition, transplantation, neovalve and cryopreserved allograft. Patients must be informed that in PTS surgery for reflux has a relatively high failure rate.

CONCLUSION

as large randomized control trials comparing conservative treatment and DVR surgery for DVR shall or should be difficult to conduct we must rely on the outcome of present series treated by DVR surgery. Analysis of those series provides recommendation grade C. Better results are obtained in the treatment of primary reflux compared with secondary reflux. Such surgery is not however, often indicated, and the procedure must be performed on specialized and high-trained centers.

Traitement endovasculaire des varices des membres inférieurs

Endovenous treatment for varicose veins of the lower extremities is an old technique. New technologies such as radiofrequency and laser have revived its indications. Thermal energy which is delivered to the vein wall results in a fibrous retraction and eventually complete obstruction of the vessel.

Résultats d’une enquête sur les techniques compressives et contensives utilisées dans le traitement chirurgical des varices

OBJECTIVES

A survey on postoperative compression after varicose vein surgery was undertaken in 2001 among surgeons of the French-speaking Vascular Surgery Society as well as non-members with a heavy caseload in varicose vein surgery. The aims of the study were to 1) identify the various medical devices and protocols used postoperatively, 2) estimate the frequency and duration of use, and 3) identify the surgeon's rationale for prescribing postoperative compression. The first part of the inquiry was devoted to surgical procedures and has been previously published (J Mal Vasc 2003; 28: 277-86).

MATERIAL AND METHODS

A questionnaire with 11 items for postoperative treatments and a patient form was mailed to 675 surgeons.

RESULTS

The response rate was 41.5% (280 surgeons). Results were assessed by a scientific committee. Surgeons were classified into different groups according to their membership in the French-speaking Vascular Surgery Society or not, the type of practice (private, public hospital, mixed), and caseload. Compression was widely used (97.1%). It was the only postoperative treatment for 25.2% of the surgeons, was associated with anticoagulant treatment for 38.8% or non-steroidal antiinflammatory drugs for 11.2%. Prescription was evidence-based for only 11.6%. Compression therapy was mainly started postoperatively (93.2%). Elastic bandages (long stretch) were used by 87%. Duration of bandage therapy was variable (less than 8 days for 38.8%, 8-15 days for 24.5%). After bandage therapy, medical compression stockings (above knee 74.7%) or French class II (77.9%) were used. Compression stockings were prescribed for 8-15 days or 15-30 days by 12.7% and 84.6% of the surgeons respectively. Prolonged postoperative treatment was not common (28%) and was prescribed for patients with trophic changes.

[Surgical techniques used for the treatment of varicose veins: survey of practice in France]

This survey was undertaken in 2001 among surgeons of the French speaking Vascular Surgery Society (SCV-Société de Chirurgie Vasculaire de Langue Française) and SCV non-members with a heavy caseload in varicose vein surgery.

AIM OF THE STUDY

To identify --the various surgical procedures used for treating chronic venous disease and in particular varicose veins; --the current use of preoperative investigation with duplex ultrasound; --the type of anesthesia used; --the postoperative treatment prescribed, and specifically compression therapy.

MATERIAL AND METHODS

This survey was conducted by mail through a "half open" questionnaire including 17 questions and a patient form (see appendices I and II). 675 surgeons were questioned (501 were SCV members and 174 non members).

RESULTS

Two-hundred and eighty surgeons answered (41.5%). The level of replies for French surgeons was 45.3%. A scientific committee assessed these replies. The surgeons were classified into different groups according to their membership of the SCV, own practice, and caseload. The 2 most performed procedures were respectively high ligation + saphenous trunk stripping + tributaries stab avulsion (71.9%) and high ligation + saphenous trunk stripping (17.3%). Isolated phlebectomy was 5.6%, high ligation + tributaries stab avulsion + saphenous trunk preservation 2.8%, isolated high ligation 2.2%, and ambulatory hemodynamic and conservative treatment of venous insufficiency (CHIVA) 0.3% ). The various procedures used (total number, average and percentage) inside the different groups are displayed in, and. Concerning trunk stripping modality the 2 most frequently used techniques were invagination and Babcock techniques. Both were evaluated respectively for the great saphenous vein (invagination 78.1%, Babcock technique 44.2%) and the small saphenous vein (invagination 77.1%, Babcock technique 31.8%). Complete resection of the saphenous trunk was more frequently performed than partial stripping. Pre-operative duplex scanning was systematically undertaken by 85.4% of surgeons without a statistical difference between the different groups. General anesthesia remains the most used form of anesthesia (83.9%) followed by spinal or epidural anesthesia (70.4%), and local or loco-regional (29.2%). As multiple answers were allowed, the most frequent procedures associated with general anesthesia were spinal or epidural (36.9%). Responders prescribed postoperative compression and anticoagulation in 97.1% and 55.8% respectively. Intra-group comparison was then undertaken in order to determine if their practice was different. Annual caseload was significantly (P=0.001) higher in Group I (353) than in Group II (226) and Group III (152). There was no difference in terms of the various surgical procedures used between the different groups. Group 1 favored the trunk stripping modality invagination for avulsion of the great saphenous vein and small saphenous vein. Concerning anesthesia, local and loco-regional anesthesia was used more by Group I than by the other groups as was anticoagulation. Responders perform perforator ligation and deep venous reconstructive surgery respectively in 70.3% and 22.4% without any intra group difference, however we have no information on frequency and indications for this type of surgery as these items were not included in the questionnaire.

DISCUSSION

Total number of procedures recorded in this survey is in keeping with the yearly French data concerning surgical treatment of varicose veins (ie, approximately 200,000 procedures). Since the emphasis was on surgical procedures sparing the saphenous trunks in varicose vein treatment only 10.9% of the techniques used in this survey were compatible with this purpose. Invagination technique for stripping both the great and small saphenous trunk was preferentially used by the Group I. Although it is surprising that all groups favored total trunk stripping particularly for the small saphenous vein. It is not surprising that a large majority, despite very little controversy on this point, performed preoperative duplex scanning. Although postoperative compression can be only quoted as a grade C recommendation according to evidence-based medicine, it was prescribed in almost all cases.

CONCLUSION

Surgery for varicose veins is one of the most frequently performed surgical procedures in France, mainly by surgeons exercising in private practice. There is no significant difference between the various groups (SCV Member or not, type of practice and annual case load) concerning the various procedures used, although through careful analysis certain different tendencies may be identified. In addition postoperative compression is systematically prescribed.

Changes in CSF and plasma HIV-1 RNA and cognition after starting potent antiretroviral therapy

The authors assessed CSF and plasma HIV-1 RNA and neuropsychological test performance (composite neuropsychological test Z score [NPZ-4]) in 25 HIV-1-infected subjects 4 and 8 weeks after beginning potent antiretroviral therapy that included a protease inhibitor. In the 14 subjects who entered the study on no antiretroviral treatment, NPZ-4 improvement was associated with decline in CSF HIV-1 RNA at both visits (p = 0.001 and p = 0.02), and those treated with zidovudine or indinavir had greater improvement in NPZ-4 at both visits compared to those treated with other drugs (p = 0.003 and p = 0.01).

[Antibiotics resistance of Streptococcus pneumoniae. Results from the Brittany registry for 1999]

Throughout 1999, clinical microbiology laboratories of 13 hospitals in Brittany have recovered Streptococcus pneumoniae isolates in 832 patients, 312 (37.5%) female and 518 (62.2%) male. Two hundred fifty five of them (30.6%) were children. One hundred eighty eight isolates were recovered from blood cultures (22.6%), 16 from CSF (1.9%), 449 from lungs (54%), and 88 from ear exsudates (10.6%).A 5 microgram oxacillin-disk test was used to detect isolates with reduced susceptibility to penicillin G. Determination of MICs of penicillin G, amoxicillin and cefotaxime were then performed by agar dilution method on 402 strains previously categorized resistant or intermediate. Five hundred forty six isolates were PSDP, 33.5% of them were resistant to penicillin G, 2.2% to amoxicillin and 0.2% to cefotaxime. As expected, a decreased susceptibility to beta-lactamins was frequently associated with resistance to macrolides, cotrimoxazole and tetracycline. Among PSDP, the most prevalent serotypes were 23 (23.7%), 14 (23.5%) and 19 (19.1%). In Brittany, the constant rise of PSDP (1993-1994: 28.5%; 1997: 56.4%; 1999: 65.6 %) could be perhaps explain by analysis of social and demographic data.

Total synthesis of tricyclic azaspirane derivatives of tyrosine: FR901483 and TAN1251C

A solution to the long-standing problem presented by the oxidative cyclization of a phenolic 3-arylpropionamide to a spirolactam has been developed in this laboratory via oxazoline chemistry. This research was motivated by our interest in some novel tricyclic azaspirane natural products formally derived from tyrosine, such as FR901483 and TAN1251C. In this paper, we disclose full details of the total synthesis of these substances.

Phase transition in a radiation-matter interaction with recoil and collisions

The standard model introduced to describe the collective atomic recoil of an ensemble of atoms interacting with a strong electromagnetic field has been here extended by the inclusion of collisions with a buffer gas. As a result, we find that in the thermodynamic limit the coherent emission of radiation exhibits a continuous phase transition upon increasing the pump intensity. The output laser field is strictly larger than 0 only above a critical value. We find that the transition is not associated with the onset of spatial ordering but rather with the onset of a synchronization between the polarization phase and spatial position. A coherence parameter is introduced to characterize the phase transition.

[Superficial venous thrombosis of the lower limbs: prospective analysis in 100 patients]

OBJECTIVES

Our objectives were first to estimate the potential gravity of superficial venous thrombosis (SVT) of the lower limbs by determining the frequency of associated deep venous thrombosis (DVT), pulmonary embolism (PE) and extensions of the junction or a perforating vein and second to identify factors of risk (neoplasia, thrombophilia, connective tissue disease, thromboembolic events).

METHOD

We conducted a prospective study in 100 cases of SVT in 88 patients with varicose veins (VV) and 12 patients without varicose veins (NVV).

RESULTS

Superficial venous thrombosis was identified in 32 cases (32%): muscle vein in 23 (gastrocnemius, solesu), popliteo-femoro-iliac system in 5, and posterior tibial or fibular vein in 4. In 17 cases (17) the SVT extended to deep veins at distant localizations in 15 (15%). Pulmonary embolism was suspected clinically in 10 cases (10%) and confirmed in 3 (3%). An extension to the saphenous junction was observed in 17 cases (17%) and the thrombus migrated into a deep vein in 7. There were 6 cases of a unique extension to a perforating vein. Search for etiology was conducted in 86 cases: 64 were negative (74.4%), there was a neoplasia context in 5 (6%) and a hemostasis disorder in 17 (19.8%) including 6/12 (50%) in the NVV group and 11/74 (15%) in the VV group.

CONCLUSION

Superficial venous thrombosis is often considered to be benign although severe situations can occur in patients with a hemostatis disorder. Consideration of these different factors (risk factors, presence of a deep venous thrombus or pulmonary embolism) should be helpful in determining the etiology and for a better choice of a therapeutic option (medical/surgical) depending on the different subpopulations identified.