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Thierry Duprez

Publications and source records attributed to Thierry Duprez.

At least 19 recordsLinked to original sources
PubMed2006

Suitability of helical multislice acquisition technique for routine unenhanced brain CT: an image quality study using a 16-row detector configuration.

Subjective and objective image quality (IQ) criteria, radiation doses, and acquisition times were compared using incremental monoslice, incremental multislice, and helical multislice acquisition techniques for routine unenhanced brain computed tomography (CT). Twenty-four patients were examined by two techniques in the same imaging session using a 16-row CT system equipped with 0.75-width detectors. Contiguous "native" 3-mm-thick slices were reconstructed for all acquisitions from four detectors for each slice (4x0.75 mm), with one channel available per detector. Two protocols were tailored to compare: (1) one-slice vs four-slice incremental images; (2) incremental vs helical four-slice images. Two trained observers independently scored 12 subjective items of IQ. Preference for the technique was assessed by one-tailed t test and the interobserver variation by two-tailed t test. The two observers gave very close IQ scores for the three techniques without significant interobserver variations. Measured IQ parameters failed to reveal any difference between techniques, and an approximate half radiation dose reduction was obtained by using the full 16-row configuration. Acquisition times were cumulatively shortened by using the multislice and the helical modality.

Aged↗
PubMed2006

Impact of the type of imaging modality on target volumes delineation and dose distribution in pharyngo-laryngeal squamous cell carcinoma: comparison between pre- and per-treatment studies.

BACKGROUND AND PURPOSE: It has been shown that the use of pre-treatment FDG-PET impacted on the GTV delineation of pharyngo-laryngeal tumors. The goals of this study were to evaluate (1) the impact of FDG-PET GTV on dose distribution, and (2) the impact of per-treatment re-imaging on target volume delineation and dose distribution. MATERIALS AND METHODS: Eighteen patients with squamous cell carcinoma of the oropharynx or larynx/hypopharynx were treated with curative intent by forward planning IMRT. Prior to treatment and on average after a dose of 46 Gy, all patients underwent contrast-enhanced CT, MRI and FDG-PET. After coregistration, GTVs were delineated manually on CT and MRI and automatically on FDG-PET. From these volumes, CTVs and PTVs were derived using consistent guidelines. Planning was performed using conformal radiotherapy. RESULTS: GTVs, CTVs and PTVs based on pre-treatment FDG-PET were significantly smaller than those based on pre-treatment CT. Such difference in target volumes (TV) translated into a significant reduction in the irradiated volumes (reduction of 13 and 18% of the V50 and V95, respectively), Dmean to ipsilateral parotids (30.7 and 38.6% for FDG-PET and CT based plans, respectively) and to controlateral parotids (11.2 and 14.4% for FDG-PET and CT based plans, respectively). TVs based on per-treatment CT or MRI were also significantly smaller compared to those delineated from pre-treatment CT. Volumes delineated with MRI were significantly smaller than those delineated with CT. Due to radiotherapy-induced peri-tumoral inflammation, automatic delineation of FDG-PET GTV could not be performed. Such reductions in TVs translated into a reduction of the irradiated volumes compared to pre-treatment CT planning (reduction for V50 of 19 and 32%, and for V95 of 22 and 40%, for CT and MRI, respectively); Dmean to the ipsilateral parotids were also reduced (ipsilateral parotid Dmean of 20.4% for CT and of 20.1% for MRI compared to 24.7% for pre-treatment CT). CONCLUSIONS: The use of pre-treatment FDG-PET and per-treatment CT or MRI significantly impacts on the delineation of TVs in pharyngo-laryngeal SCC, translating into more normal tissue sparing after conformal radiotherapy planning.

Body Burden↗
PubMed2006

Olfactory function assessed with orthonasal and retronasal testing, olfactory bulb volume, and chemosensory event-related potentials.

OBJECTIVE: To investigate whether differences in olfactory function between healthy individuals and patients with olfactory loss could be detected by various diagnostic tests. DESIGN: Psychophysical testing of orthonasal and retronasal olfactory functions, magnetic resonance imaging of olfactory bulb (OB) volume, and chemosensory event-related potential (ERP) measurement performed between January 1, 2005, and October 31, 2005. SETTING: Academic tertiary referral medical center. PATIENTS: Eleven healthy individuals with normal olfactory function (NL) and 11 patients with nasal polyposis (NP), 11 with posttraumatic olfactory loss (PT), and 11 with postinfectious olfactory loss (PI) were included in this study. MAIN OUTCOME MEASURES: Orthonasal and retronasal olfactory test results, magnetic resonance imaging-based OB volume, and ERPs to both olfactory and intranasal trigeminal stimulation. RESULTS: Orthonasal and retronasal testing revealed that NL individuals had higher scores than patients with NP, PT, or PI. Retronasal scores were higher in NP patients compared with PT and PI patients. The OB volumes were higher in NL individuals compared with NP, PT, and PI patients. The OB volumes in PT patients were significantly lower than those from NP and PI patients. Olfactory ERPs were different between NL individuals and NP, PT, and PI patients, and trigeminal ERPs were significantly different when comparing NL individuals with NP patients. For the entire cohort, a significant correlation was found between orthonasal testing and OB volume, between retronasal testing and OB volume, and between both orthonasal and retronasal testing and olfactory ERP amplitudes. Olfactory ERPs were recorded in the 11 NL individuals and in 3 NP, 3 PT, and 4 PI patients, defined as responders. Orthonasal and retronasal test scores, OB volume, and olfactory ERPs were significantly larger in responders compared with nonresponders. CONCLUSIONS: Significant differences in various tests that evaluate olfactory function were detectable in a cohort of NL individuals and NP, PT, and PI patients. This finding suggests that these diagnostic tools provide information in terms of the clinical assessment of olfactory function. Future studies will investigate their combined use in terms of the prognosis of olfactory function in patients with olfactory loss.

Action Potentials↗
PubMed2006

Olfactory function and olfactory bulb volume in patients with postinfectious olfactory loss.

OBJECTIVE: The study aimed to investigate whether the degree of postinfectious olfactory loss is reflected in volume of the olfactory bulb (OB). STUDY DESIGN: Retrospective study of 26 patients with postinfectious olfactory loss. MATERIALS AND METHODS: Olfactory function was assessed with the "Sniffin' Sticks" test kit, and the magnetic resonance imaging study focused on OB volume and the olfactory sulcus. RESULTS: The study revealed that 1) OB volume varies with regard to olfactory function, 2) OB volume decreases with duration of olfactory loss, and 3) patients with parosmia had smaller OB volumes than patients who did not report such smell distortions, although their overall olfactory function was not significantly different from each other. CONCLUSION: The study emphasizes that OB volume is a gauge of olfactory function.

Adult↗
PubMed2006

Retronasal and orthonasal olfactory function in relation to olfactory bulb volume in patients with posttraumatic loss of smell.

OBJECTIVE: The aims of this study were to evaluate olfactory function with orthonasal and retronasal testing in patients with posttraumatic olfactory loss and to investigate the relation between residual olfactory function and olfactory bulb (OB) volume. METHOD: A retrospective study of 25 patients with posttraumatic olfactory loss was performed. Orthonasal olfactory function was assessed with the Sniffin' Sticks test kit; retronasal olfactory function was assessed with intraorally applied odors. Magnetic resonance imaging was used to determine OB volume and cortical damage in the frontal and temporal areas. RESULTS: The main outcomes of the present study were the demonstration of a correlation between olfactory function and OB volume, which was more pronounced for retronasal than for orthonasal olfactory function; retronasal olfactory function was most affected in the patients with the most extensive cerebral damage and was least compromised in patients without such damage; OB volumes were smaller in patients with parosmia compared with those without; and the presence of parosmia was clearly associated with the presence of cerebral damage. CONCLUSION: The data confirm that OB volume is an indicator of olfactory function but, interestingly, in this study, it is largely determined by retronasal olfactory sensitivity. In addition, these results emphasize the role of higher cortical centers in olfactory function, and especially in parosmia, which may, at least in some cases, be related to lesions in the fronto-orbital and anterior temporal cortices. It would be of interest to investigate OB volume further in relation to the prognosis of the disorder.

Adult↗
PubMed2006

Influence of parasellar extension of macroprolactinomas defined by magnetic resonance imaging on their responsiveness to dopamine agonist therapy.

OBJECTIVE AND DESIGN: The resistance of macroprolactinomas to dopamine agonist (DA) therapy, whether defined as an absence of PRL normalization or the lack of significant tumour shrinkage after prolonged treatment at high doses, is usually regarded as unpredictable. The aim of this retrospective study, conducted in a teaching hospital, was to determine whether cavernous sinus (CS) invasion assessed by magnetic resonance imaging (MRI) is associated with a higher rate of resistance to DA therapy. METHODS: Forty-nine patients with a macroprolactinoma were included in this study and classified into four groups according to the percentage of encasement of the intracavernous internal carotid artery (ICA) by the tumour. All patients received DA as the primary treatment, mainly cabergoline (CAB). PRL normalization and tumour shrinkage during treatment were evaluated as a function of CS invasion. RESULTS: Tumours encasing more than three-quarters of the intracavernous ICA (group 4) were less responsive to DA therapy, exhibiting a lower rate of early (< or = 3 months) PRL normalization (8%vs. 69% in the others groups; P < 0.01) under a higher dose of CAB (median: 3.5 mg vs. 1.0 mg per week; P < 0.01). CS invasion was a strongly significant and independent predictor of hormonal resistance to CAB (P < 0.01). This hormonal resistance occurred in eight patients (16%), all but one belonging to group 4. Significant tumour shrinkage was observed in 31 out of 45 assessable cases (69%) and was more likely to occur in the case of PRL normalization (P < 0.01). CONCLUSIONS: Parasellar extension of macroprolactinomas, assessed on the basis of strict MRI criteria, may predict a negative response to DA. The responsiveness of noninvasive macroprolactinomas (over 90%) is similar to that reported in microprolactinomas, whereas invasive tumours are resistant to treatment in more than 50% of cases.

Adult↗
PubMed2006

The value of morphological neuroimaging after acute exposure to toxic substances.

Many toxic agents induce brain dysfunction and/or lesions. Modern neuroimaging techniques, such as CT and more recently magnetic resonance imaging (MRI), are able to demonstrate toxic brain lesions at both early and delayed phases of disease progression. In the early phase, neuroimaging enables the detection of acutely injured brain areas responsible for sudden onset of neurological dysfunction, but the severity and the extension of brain lesions on neuroimages do not necessarily parallel the severity of the clinical status. In the chronic phase, when neurological dysfunction has become permanent, neuroimaging allows precise identification of neuroanatomical sequelae that do not necessarily match the severity of the chronic neurological impairment. Papers in the medical imaging literature have dealt mainly with the brain changes induced by 'chronic exposure' to toxic substances such as solvents or heavy metals. This article selectively reviews the main radiological changes observed on CT/magnetic resonance (MR) neuroimages after 'acute exposure' to industrial products (methanol [methyl alcohol], ethylene glycol), environmental agents (cyanide, carbon monoxide), pharmaceuticals (insulin, valproic acid) and illicit substances (heroin, cocaine). Different kinds of lesions, which lack specificity for toxic injury, can be observed on radiological images, but deep grey matter lesions with symmetrical distribution throughout basal ganglia are most often seen. However, such findings have also been reported after anoxic-ischaemic insults or during severe metabolic disturbances. Lesions in the white matter may also be present in the case of acute exposure to toxic agents. The true prognostic value of toxic-induced brain changes in the acute phase in CT or MR studies is unclear, although serial MRI may add new information as may quantitative or molecular imaging techniques such as the MR diffusion-weighted imaging or MR spectroscopy.

Acute Disease↗
PubMed2005

Electrocardiographic changes after head trauma.

We report the case of a patient who developed, a few days after a closed head injury, marked electrocardiographic changes mimicking an acute coronary event, in the absence of actual cardiac damage. The electrocardiographic changes were fully reversible, paralleling the neurologic status. Neuroimaging examinations excluded subarachnoid hemorrhage or space-occupying hematoma, but demonstrated diffuse axonal injury using susceptibility-weighted magnetic resonance techniques. This kind of traumatic brain injury thus may be responsible for a pseudo-acute myocardial ischemic syndrome.

Adult↗
PubMed2005

Cerebral microembolization after protected carotid artery stenting in surgical high-risk patients: results of a 2-year prospective study.

BACKGROUND: This was a prospective single-center study to assess and analyze cerebral embolization resulting from carotid artery stenting with neuroprotective filter devices in patients considered as poor surgical candidates for surgical carotid endarterectomy. METHODS: Fifty-three consecutive patients with an internal carotid artery stenosis were treated by placement of carotid Wallstents with two different types of temporary distal filter protection devices: the Spider filter and the FilterWire. Diffusion-weighted magnetic resonance imaging (DWI) of the brain was obtained 24 hours before the procedure and within 5 to 30 hours after the procedure to detect ischemic brain lesions resulting from the procedure. Inclusion criteria were symptomatic (> or =70%) or asymptomatic (> or =80%) stenoses in surgical high-risk patients. RESULTS: Two (4%) regressive minor strokes occurred. Postprocedural DWI detected new focal ischemic lesions in 21 patients (40%). The average number of lesions was 5.9 per patient, and the mean lesion volume was 1 mL or less in 19 patients (90%). Small differences were found in the lesion distribution: homolateral anterior circulation in eight cases (15.1%), other vascular territories in seven cases (13.2%), and homolateral anterior circulation plus other vascular territories in six cases (11.3%). The microembolization risk seemed nonpredictable on the basis of clinical parameters and internal carotid artery lesion characteristics. An increased risk in the rate of ipsilateral hemispheric embolization has been observed in difficult carotid arch implantations (P = .04). CONCLUSIONS: The incidence of new focal ischemic lesions detected by DWI is higher than expected on the basis of previous reports. Embolization from the aortic arch or common carotid arteries could account for most of those events in patients considered as surgical high-risk patients. Although 90% of the events were clinically silent, this high rate of microembolization raises questions about the possible consequences on cerebral cognitive functions.

Aged↗
PubMed2005

Inter-observer variability in the delineation of pharyngo-laryngeal tumor, parotid glands and cervical spinal cord: comparison between CT-scan and MRI.

BACKGROUND AND PURPOSE: The goal of this study was to compare the inter-observer variability between CT and MRI for the delineation of pharyngo-laryngeal SCC, parotid glands and spinal cord. PATIENTS AND METHODS: Twenty pharyngo-laryngeal tumors were delineated by five observers on CT and MRI, using consistent delineation guidelines. Spinal cords and parotid glands were also delineated on CT and MRI by three observers. Mean GTVs and coefficients of variation were calculated for each observer and compared using ANOVA and its derived Pearson intra-class coefficient (R). For GTVs, a mismatch analysis (ratio between intersection and union volumes) was also performed. RESULTS: Regarding oropharyngeal GTVs (n=10), no significant difference was observed between observers either with CT (33.9, 31.1, 32, 34 and 34.7 ml, five observers, P=0.47) or with MRI (30.5, 29.4, 30.1 and 31.5 ml, four observers, P=0.59). CVs (13.6 vs 12.9%), (0.98 vs 0.99) and mismatches (0.43 vs 0.42) between CT and MRI did not significantly differ. Regarding laryngeal-hypopharyngeal GTVs (n=10), no significant difference was observed between observers either on CT (18.1, 20.7, 20.9, 19.3 and 21.9 ml, five observers, P=0.29) or on MRI (19.3, 21.5, 20, 22.1 and 21.8 ml, five observers, P=0.16). CVs (20.2 vs 13.8%), (0.94 vs 0.94) and mismatches (0.31 vs 0.41) were comparable. Regarding OARs, a small but significant difference in mean parotid volume was observed between observers (P<0.001) and between modalities (P<0.001) (CT: 34.8, 29.4, and 26.8 ml; MRI: 30.6, 27.9 and 20.4 ml). Similar results were obtained for mean spinal cord volumes (CT: 10.7, 10.6, and 9.5 ml; MRI: 8.7, 8.5 and 8.2 ml; P=0.05).

Carcinoma, Squamous Cell↗
PubMed2004

High signal intensity of intervertebral calcified disks on T1-weighted MR images resulting from fat content.

OBJECTIVE: To explain a cause of high signal intensity on T1-weighted MR images in calcified intervertebral disks associated with spinal fusion. DESIGN AND PATIENTS: Magnetic resonance and radiological examinations of 13 patients were reviewed, presenting one or several intervertebral disks showing a high signal intensity on T1-weighted MR images, associated both with the presence of calcifications in the disks and with peripheral fusion of the corresponding spinal segments. Fusion was due to ligament ossifications (n=8), ankylosing spondylitis (n=4), or posterior arthrodesis (n=1). Imaging files included X-rays and T1-weighted MR images in all cases, T2-weighted MR images in 12 cases, MR images with fat signal suppression in 7 cases, and a CT scan in 1 case. Histological study of a calcified disk from an anatomical specimen of an ankylosed lumbar spine resulting from ankylosing spondylitis was examined. RESULTS: The signal intensity of the disks was similar to that of the bone marrow or of perivertebral fat both on T1-weighted MR images and on all sequences, including those with fat signal suppression. In one of these disks, a strongly negative absorption coefficient was focally measured by CT scan, suggesting a fatty content. The histological examination of the ankylosed calcified disk revealed the presence of well-differentiated bone tissue and fatty marrow within the disk. CONCLUSION: The high signal intensity of some calcified intervertebral disks on T1-weighted MR images can result from the presence of fatty marrow, probably related to a disk ossification process in ankylosed spines.

Adipose Tissue↗
PubMed2004

Tumor volume in pharyngolaryngeal squamous cell carcinoma: comparison at CT, MR imaging, and FDG PET and validation with surgical specimen.

PURPOSE: To compare computed tomography (CT), magnetic resonance (MR) imaging, and fluorine 18 fluorodeoxyglucose (FDG) positron emission tomography (PET) for delineation of gross tumor volume (GTV) in pharyngolaryngeal squamous cell carcinoma and to validate results with the macroscopic surgical specimen when available. MATERIALS AND METHODS: Twenty-nine patients with stages II-IV squamous cell carcinoma treated with radiation therapy or chemotherapy and radiation therapy (n = 20) or with total laryngectomy (n = 9) were enrolled. Ten patients had oropharyngeal, 13 had laryngeal, and six had hypopharyngeal tumors. CT, MR imaging, and PET were performed with patients immobilized in a customized thermoplastic mask, and images were coregistered. GTVs obtained with the three modalities were compared quantitatively and qualitatively. If patients underwent total laryngectomy, images were validated with the surgical specimen after three-dimensional coregistration. The effect of each modality was estimated with linear mixed-effects models. Adjustments for multiple comparisons were made with the Bonferonni or Sidak method. RESULTS: For oropharyngeal tumors and for laryngeal or hypopharyngeal tumors, no significant difference (P >.99) was observed between average GTVs delineated at CT (32.0 and 21.4 cm(3), respectively) or MR imaging (27.9 and 21.4 cm(3), respectively), whereas average GTVs at PET were smaller (20.3 [P </=.10] and 16.4 cm(3) [P </=.01], respectively). GTVs from surgical specimens were significantly smaller (12.6 cm(3), P </=.06). In nine patients for whom a surgical specimen was available, no modality adequately depicted superficial tumor extension; this was due to limitations in spatial resolution. In addition, false-positive results were seen for cartilage, extralaryngeal, and preepiglottic extensions. CONCLUSION: Compared with GTVs at CT and MR imaging, GTVs at FDG PET were smaller. In nine patients for whom a surgical specimen was available, PET was found to be the most accurate modality. However, no modality managed to depict superficial tumor extension.

Adult↗
PubMed2004

Remitting/relapsing idiopathic hypertrophic spinal pachymeningitidis: comprehensive imaging work-up and MR monitoring.

We present the initial MR and PET work-up in a diabetic 31-year-old female patient presenting with spinal cord compression because of abnormal meningeal tissue and highlight the close correlation between the clinical course and the monitoring of the lesions on MR images. The combination of non-specific inflammatory signs at histopathological examination and of the negative results of a comprehensive bacteriological and serological testing led to the diagnosis of idiopathic hypertrophic spinal pachymeningitidis. The abnormal tissue showed mild glucose uptake at whole-body FDG-PET examination. Repeated MR follow-up examinations during corticoid treatment only demonstrated partial shrinkage of the abnormal tissue. Symptomatic relapse and re-increase in lesion size on MR images occurred concomitantly after an 11-month symptom-free remitting interval under tapering corticoid treatment.

Adult↗
PubMed2004

Comparison of clinical, magnetic resonance and evoked potentials data in a case of valproic-acid-related hyperammonemic coma.

Magnetic resonance (MR) multimodality evoked potentials (MEPs) and clinical findings were correlated in a 47-year-old epileptic man in whom parenteral valproic acid (VPA) therapy induced severe comatose hyperammonemic encephalopathy without biological signs of hepatotoxicity (or hepatocytic dysfunction). Although the plasma VPA level remained within a normal therapeutic range, the ammoniemia increased to a toxic peak level at 411 micromol/l 24 h after symptom onset, requiring VPA therapy discontinuation. Brain MR monitoring demonstrated early cytotoxic edema evolving into delayed vasogenic edema and final brain atrophy. Concomitantly to abnormalities within the brainstem on MR images, an increase in brainstem conduction at MEPs and clinical disturbance of brainstem reflexes were observed at the initial phase of the disease course. Later, the resolution of the MR and MEPs abnormalities paralleled the clinical recovery of the reflexes.

Atrophy↗
PubMed2004

MRI of hyperacute stroke in the AChA territory.

The purpose of our study was to derive from the anatomical literature an easy-to-use map of the brain areas supplied by the anterior choroidal artery (AChA) and to assess the correspondence between damage within the putative AChA areas and clinical symptoms. A thorough review of the literature led to the recognition of 16 anatomical areas which could be delineated on routine diffusion-weighted MR images. A database of 138 consecutive ischemic stroke patients examined with MRI less than 6 h after symptoms onset was thereafter processed in a retrospective way. Patients presenting with at least one damaged AChA area were selected so as to assess the prevalence of AChA infarction and the clinical correlates of the condition. Fifteen patients (11%) had at least one damaged AChA area. Only two of them had "pure" AChA-restricted infarction. Contralateral hemiparesis and contralateral hemianesthesia were best predicted by lesions within the tail of the caudate nucleus with a sensitivity of 87% and 83%, respectively. Homonymous hemianopsia best correlated with lesions within the posterior limb of the internal capsule and within the retrolenticular part of the internal capsule, with a sensitivity of 100% and a specificity of 70% for both areas. We concluded that the clinical-radiological correlations did not match the neurophysiological standards, thereby highlighting the limitation of this study, which involved a cohort of acute stroke patients recruited from clinical practice and investigated the clinical impact of these brain lesions, even when documented with the most sensitive imaging modality.

Acute Disease↗
PubMed2004

Surgical treatment of a syringomyelia associated with an idiopathic arachnoid malformation disclosed by preoperative MRI.

BACKGROUND: We describe the very rare condition of an idiopathic spinal arachnoid malformation associated with syringomyelia (SM) and depicted on preoperative magnetic resonance imaging (MRI) whose features were confirmed at surgery. CASE DESCRIPTION: A 34-year-old female suffered from progressive gait impairment because of lower limb palsy and sensory disturbances. MRI demonstrated a bulging membrane at the T6 level that was transversely stretched between the dorsal aspect of the spinal cord and the posterior dura mater. At this level, the spinal cord appeared atrophic and pushed anteriorly against the dura with enlargement of the posterior subarachnoid spaces (SAS) and focal collapse of an associated panmedullar SM. Surgery consisted in releasing the arachnoid malformation and opening the inferior segment of the syringomyelic cavity. Pathological examination revealed a fibro-sclerotic tissue with cellular areas of meningo-endothelial cells. Postoperative neurological status progressively improved but slightly. Three-months and 1 year postoperatively, MRI showed the collapse of the whole SM and restoration of cerebrospinal fluid (CSF) flow at the treated T6 level. CONCLUSION: Spinal arachnoid malformations associated with SM are very rare and have never been described up to now on MRI. Surgical removal of the causative malformation allows spinal cord decompression and prevents the recurrence of the SM by restoring normal CSF circulation.

Adult↗
PubMed2004

Unusual metastatic features in a patient with concomitant malignant orbital melanoma and prostate carcinoma.

A 73-year-old man with a history of malignant orbital melanoma and prostate carcinoma was admitted for progressive visual disturbance. Brain magnetic resonance imaging showed a suprasellar enhancing nodular lesion with major impingement on the anterior optical ways and sellar invasion. The extensive imaging work-up could not demonstrate with certainty its origin. Surprisingly, the transphenoidal biopsy of this patient revealed a prostate cancer metastasis outlining the importance of a histopathological diagnosis of cerebral metastases in patients with multiple malignancies when there is a doubt about the nature of the lesion.

Adenocarcinoma↗