We have developed a technique for inverse treatment planning of prostate therapy designed to improve the degree of conformation between the dose distribution and the target volume. We compared the inverse plan with a “standard” four-field box technique as well as a four-field technique using oblique fields (“cross technique”). We validated the dosimetry of the inverse plan using Fricke gel solution in phantom specifically designed for this purpose. The phantom is a Plexiglas tank with a cross section, which approximates the dimensions of the pelvis. Anatomical data from computed tomography (CT) images of a patient were used to simulate organs in our phantom. This allows us to calculate dose distributions with the external geometry of the phantom and internal anatomy of the patient. Dose–volume histograms (DVHs) for the three different plans were calculated. The phantom containing the Fricke gel was irradiated according to the inverse plan. Magnetic resonance (MR) images was used to determine the dose distribution delivered to the phantom. We observe, on DVHs, that the inverse plan significantly reduces the dose to the rectum and the bladder but slightly increases the inhomogeneity inside the target volume. Correlation is good between isodoses on MR images and calculated isodoses. We conclude that inverse planning software can greatly improve the conformal degree of treatment to the prostate. This technique could be applied to other complex anatomic sites at which dose to organs at risk is a limiting factor and increased dose to the target volume is indicated. Our phantom and the Fricke gel solution are convenient to carry out validation of conformal treatments.

Neurosurgery is by excellence afield of application for robots, based on multimodal image guidance Specific motorized tools have been already developped and routinely applied in stereotaxy to position ii probe holder or in conventional neurosurgery to hold a microscope oriented towards a given target. The potentialities of these approaches have triggered industrial developments currently commercially available These systems use data bases, primarily, coming from multimodal numerical images from X-ray radiology to magnetic resonance imaging. These spatially encoded data are transfered through digital networks to workstations where images can be processed and surgical procedures are preplanned then transferred to the robotic systems to which they are connected. We have been using a stereotactic robot since 1989 and a microscope robot since 1995 in various surgical routine procedures The future of these applications mainly rely on the technical progress in informatics, about image recognition to adapt the preplanning to the actual surgical situation to correct brain shifts for instance about image fusion, integrated knowledge such such as brain atlases, as well as virtual reality. The future developments, covering surgical procedure, research and teaching, will sure be far beyond our wildest expectations.

Brain tumor visualization has been improved significantly by Magnetic Resonance Imaging (MRI). This work shows that Sinerem(R), a superparamagnetic contrast agent can bring new information about rat brain tumor physiology, more particularly BBB permeability, neovascularization and edema. Sinerem(R) induces a strong hyposignal mainly in some central patches and in the periphery of the tumor, both corresponding to vessels. Furthermore, Sinerem(R) slowly diffuses from vessels to extravascular space due to BBB breakdown.

The authors report the findings of a national survey conducted at the request of the French Society for Rheumatology to list the rheumatic manifestations that can be inaugural in Hodgkin's disease or non-hodgkin's malignant lymphoma. This was an exploratory, retrospective, descriptive study of 146 patients from 22 rheumatology departments. A number of clinical features (young male, nocturnal sweats, generalized pruritus, protracted fever, central or peripheral lymphadenopathy) and laboratory test abnormalities (evidence of severe inflammation) considerably increased the likelihood of Hodgkin's disease rather than malignant lymphoma. The diagnosis of bony involvement requires multidisciplinary studies of tumor specimens.

Nine patients with haemangioblastoma of the posterior cerebral fossa were explored by computerized tomography (CT), then by magnetic resonance imaging (MRI) with enhancement by gadolinium in 4 cases. Following a review of clinical and laboratory data, the radiological images are detailed and distributed into three forms: cystic with mural nodule, solid, and annular. The usefulness of the different imaging techniques is specified, and the stress it put on the need to look for multiple sites in the entire central nervous system.

STUDY DESIGN:This study examined the effect of radio-frequency thermocoagulation on cadaveric disc material. Radio-frequency lesions are induced to decompress the nerve root by coagulating the nucleus pulposus.OBJECTIVES:The purpose of this study was to assess the potential of the radio-frequency lesion technique for treating lumbar disc herniation percutaneously. The effect of radio-frequency thermocoagulation on cadaveric disc material was studied.SUMMARY OF BACKGROUND DATA:An intradiscal bipolar electrode is used for the thermocoagulation of the nucleus pulposus.METHODS:Lumbar discs of 27 adult cadavers were used for the experiments within 72 hours of donors' deaths. The physical and thermal parameters of intradiscal radio-frequency thermocoagulation were determined experimentally. Acute macroscopic and histologic changes before and after thermocoagulation were investigated. The temperature distribution of the tissue surrounding the disc was measured during the operation using thermocouples to evaluate potential heat damage. Also, computed tomography and magnetic resonance imaging of the disc were performed before and after thermocoagulation.RESULTS:Macroscopic observation showed that the lesion induced by radio-frequency thermocoagulation is homogeneous and intense without necrosis, and is limited to the nucleus pulposus. Histologically, the endplates and vertebral bodies were unaffected and an architectural disorganization of the stroma of the nucleus pulposus was seen. The temperature increase of the tissue surrounding the discs did not exceed 3-4 C.CONCLUSION:A bipolar electrode and a radio-frequency alternating current permits percutaneous intradiscal thermocoagulation for destruction of a portion of disc material in a cadaveric spine.

The complex benzene-1,2,4,5-tetra(methylene-phosphonato)triferrate III 4, Fe3BTMP, is a contrast agent for liver MRI (magnetic resonance imaging). The stoichiometries 1:1 and 3:1 were found for FeBTMP 3 and Fe3BTMP 4 using polarography and P-31 NMR. At physiological pH and in aqueous solution these complexes are more stable than FeTTMP (5') and as stable as FeN3TMP (6'). It was found that 3 and 4 are polymers with linear and polydimensional structures respectively.

Doppler flowmeter and ultrasound imaging techniques, currently associated (duplex), have made important contributions to the simple and early non invasive diagnosis of carotid stenosis lesions in the cervical region for more than 20 years. These exploratory methods are reliable when a significant degree of stenosis (greater than about 60%) exists. Moderate degrees of stenoses or plaques are evaluated morphologicaly, calcifications and ulcerations being enhanced by staining techniques. But the evaluations have not really demonstrated exact correlations between anatomicopathologic and ultrasound images. The intracranial arteries and the circle of Willis are explored indirectly during the cervical examination by cautious compressive maneuvers or directly by trans-cranial Doppler. Whereas angiography competes with ultrasound imaging as a standard examination in the neck region, it nevertheless remains effective for the study of the intracranial arteries. Newer techniques, such as high-field MRI angiography, tridimensional ultrasonography or ultrasound recording of vascular flow rate without Doppler, will doubtlessly transform the diagnosis of symptomatic or asymptomatic carotid stenosis. From the strategic point of view, ultrasound imaging techniques will retain their role of a decisional pivot, since they are simple to use and are of very wide accessibility to competent vascular physicians in the context of an organized care network (J Mal Vasc, 1993, 18, pp. 187-190).

An impairment of muscle energy metabolism has been suggested as a predisposing factor for, as well as a consequence of exertional heatstroke (EHS). Thirteen young men were investigated 6 months after a well-documented EHS using 31Phosphorus Magnetic Resonance Spectroscopy (P-31-MRS). The relative concentrations of ATP, phosphocreatine (PCr), inorganic phosphate (Pi), phosphomonoesters (PME), and the intracellular pH (pHi) were determined at rest, during a graded standardized exercise protocol (360 active plantar flexions) and during recovery. Also the leg tissue blood flow was determined by venous occlusion plethysmography during the MRS procedure. Sixteen age-matched healthy male volunteers served as control group. In resting muscle, there were no significant differences between the groups as regards pHi, Pi/PCr, and ATP/PCr+Pi+PME ratios. During steady state exercise conditions, effective power outputs were similar for both groups at each level of exercise: 20, 35, and 50% of maximal voluntary contraction (MVC) of the calf muscle. No significant differences were shown between the two groups in Pi/PCr, pHi, or changes of leg blood flow at each level of exercise. At 50% MVC, Pi/PCr was 0.48 +/- 0.08 vs 0.47 +/- 0.05 (P = 0.96), pHi was 6.94 +/- 0.03 vs 6.99 +/- 0.02, respectively (P = 0.13). Finally, the rate of PCr resynthesis during recovery was not significantly different between the two groups: t1/2 PCr = 0.58 +/- 0.07 vs 0.50 +/- 0.05 min, respectively (P = 0.35). Therefore, no evidence of an impairment of muscle energy metabolism was shown in the EHS group during a standardized submaximal exercise using P-31-MRS performed 6 months after an EHS.

Initial signs of malignant lymphoma are rarely due to bone lesions. We reviewed 6 cases with early skeletal involvement, recently observed in the rheumatology and hematology departments. In 3 patients, magnetic resonance imaging (MRI) was added to traditional investigations, including radiography, radionuclide bone scan and computerized tomography. We stress the possibility of bone involvement in the clinical onset of malignant lymphoma and the usefulness of early bone assessment using MRI.

The complex 1,4,8,11-tetraazacyclotetradecane-1,4,8,11-tetra(methylenephosphonato)ferrate(III), FeTTMP, is a contrast agent for liver MRI. A stoichiometry 1:1 was found by polarography and NMR. The logarithmic stability constants beta11-1 = 21,2; beta110 = 30,6; beta111 = 38,7; beta112 = 45,2: beta113 = 50,5 were calculated by an original method based on P-31 NMR.

Using computed tomography and magnetic resonance imaging, we prospectively studied 100 patients hospitalized with a lacunar infarct. Our aim was to evaluate the capabilities of magnetic resonance imaging in the detection and delineation of lacunes in a project of clinicotopographic correlations. Seventy-nine patients had a classic lacunar syndrome; 35 had pure motor stroke, 26 had ataxic hemiparesis, seven had sensorimotor stroke, and 11 had pure sensory stroke. A miscellaneous group of 21 patients had less typical lacunar syndromes, primarily with brainstem signs and symptoms. Among a total of 153 lacunes, magnetic resonance imaging detected at least one lacune appropriate to the symptoms in 89 patients. In 16 patients at least two lesions correlated with the clinical features, and precise clinicotopographic correlations were possible in 68 patients. Magnetic resonance imaging was more effective when it was performed a few days after the stroke. Lesions causing different types of lacunar syndromes had significantly different volumes, suggesting that the size of the lesion may influence clinical features. Magnetic resonance imaging may be the imaging technique of choice in the study of lacunar syndromes.

We report a case of primary malignant melanoma of the cerebellopontine angle. This tumour showed RMI features that were totally different from those reported for secondary melanomas, and therefore its nature could not be suspected before surgery. Intracranial primary melanomas are so rare that no other published case is available for comparison, and our tentative explanations for the atypical RMI signals cannot be supported by evidence from the literature.