[Limits of dose constraint definition for organs at risk specific to stereotactic radiotherapy]. / Limites de la définition des contraintes de dose pour les organes à risque spécifiques à la radiothérapie stéréotaxique.

Stereotactic radiotherapy is a very hypofractionated radiotherapy (>7.5Gy per fraction), and therefore is more likely to induce late toxicities than conventional normofractionated irradiations. The present study examines four frequent and potentially serious late toxicities: brain radionecrosis, radiation pneumonitis, radiation myelitis, and radiation-induced pelvic toxicities. The critical review focuses on the toxicity scales, the definition of the dose constrained volume, the dosimetric parameters, and the non-dosimetric risk factors. The most commonly used toxicity scales remain: RTOG/EORTC or common terminology criteria for adverse events (CTCAE). The definition of organ-at-risk volume requiring protection is often controversial, which limits the comparability of studies and the possibility of accurate dose constraints. Nevertheless, for the brain, whatever the indication (arteriovenous malformation, benign tumor, metastasis of solid tumors...), the association between the volume of brain receiving 12Gy (V12Gy) and the risk of cerebral radionecrosis is well established for both single and multi-fraction stereotactic irradiation. For the lung, the average dose received by both lungs and the V20 seem to correlate well with the risk of radiation-induced pneumonitis. For the spinal cord, the maximum dose is the most consensual parameter. Clinical trial protocols are useful for nonconsensual dose constraints. Non-dosimetric risk factors should be considered when validating the treatment plan.

Independent 6D quality assurance of stereotactic radiotherapy repositioning on linacs.

PURPOSE: A high level of accuracy while positioning the patient is mandatory for frameless stereotactic radiotherapy (SRT), as large doses in multiple fractions can be delivered near organs at risk. The objective of this study is to propose an end-to-end quality assurance method to verify that submillimetre alignment can be achieved with stereotactic conventional linacs. METHODS: We used a TrueBeam® linear accelerator equipped with a 6DOF robotic couch. The "ISO Cube" phantom was used with a homemade stand designed to generate known translational and rotational offsets. A reference CT scan was performed with straight alignment of the phantom. The procedure introduced 1.6° angular offset for the couch pitch and roll, at various gantry angles. The couch base was also moved between 0° and 270°. We compared the results with the daily machine performance check tests (MPC, Varian). RESULTS: The mean isocentre size, MV and kV imager offsets were found to agree to within 0.1mm, 0.1mm and 0.3mm respectively, and were in close agreement between the methods. For a total four months data collection period, the mean deviation between requested and measured 6DOF couch shifts was 0.6mm and 0.2°. Errors on field size were smaller than 1mm for 97.7% of the 324 data points. CONCLUSION: Results demonstrate that the linac equipped with a 6DOF robotic positioner and CBCT imaging satisfies requirements for SRT. Our methodology, based on a modified Winston-Lutz quality control, allowed us to quantitatively assess end-to-end accuracy of a linac in order to safely deliver SRT.

[Technical aspects and indications of extracranial stereotactic radiotherapy]. / Place de la radiothérapie stéréotaxique extracrânienne dans la prise en charge des patients atteints de cancer.

Extracranial stereotactic radiotherapy has developed considerably in recent years and is now an important part of the therapeutic alternatives to be offered to patients with cancer. It offers opportunities that have progressively led physicians to reconsider the therapeutic strategy, for example in the case of local recurrence in irradiated territory or oligometastatic disease. The literature on the subject is rich but, yet, there is no real consensus on therapeutic indications. This is largely due to the lack of prospective, randomized studies that have evaluated this technique with sufficient recoil. We propose a review of the literature on the technical aspects and indications of extracranial stereotactic radiotherapy.

Image-guided IMRT for localized prostate cancer with daily repositioning: inferring the difference between planned dose and delivered dose distribution.

INTRODUCTION: To investigate the dosimetric impact of daily on-line repositioning during a full course of IMRT for prostate cancer. MATERIALS AND METHODS: Twenty patients were treated with image-guided IMRT. Each pre-treatment plan (Plan A) was compared with a post-treatment plan sum (Plan B) based on couch shifts measured. The delivered dose to the prostate without a daily repositioning was inferred by considering each daily couch shift during the whole course of image-guided IMRT (i.e., plan B). Dose metrics were compared for prostate CTV (P-CTV) and PTV (P-PTV) and for organs at risk. Ten patients were treated with a 5 mm margin and 10 patients with a 10 mm margin. RESULTS: For plan A vs. plan B: the average D95, D98, D50, D mean and EUD were: 76.4 Gy vs. 73.9 Gy (p = 0.0007), 75.4 Gy vs. 72.3 Gy (p = 0.001), 78.9 Gy vs. 78.4 Gy (p = 0.014), 78.7 Gy vs. 77.8 Gy (p = 0.003) and 78.1 Gy vs. 75.9 Gy (p = 0.002), respectively for P-CTV, and 73.2 Gy vs. 69.3 Gy (p = 0.0006), 70.7 Gy vs. 66.0 Gy (p = 0.0008), 78.3 Gy vs. 77.5 Gy (p = 0.001), 77.8 Gy vs. 76.4 Gy (p = 0.0002) and 74.4 Gy vs. 69.2 Gy (p = 0.003), respectively for P-PTV. Margin comparison showed no differences in dose metrics between the two plans except for D98 of the rectum in plan B which was significantly higher with a 10 mm margin. CONCLUSIONS: The absence of daily image-guided IMRT resulted in a significantly less uniform and less homogeneous dose distribution to the prostate. A reduction in PTV margin showed neither a lower target coverage nor a better spare of OAR with and without daily image-guided IMRT.

Cognitive function and 99mTc-ECD brain SPECT are significantly correlated in patients with primary Sjogren syndrome: a case-control study.

OBJECTIVES: To assess subclinical central nervous system (CNS) involvement in primary Sjögren syndrome (pSS), by comparing standard brain MRI, in-depth neuropsychological testing and (99m)Tc-ECD brain single-photon emission computed tomography (SPECT) of patients with pSS with matched controls. METHODS: 10 women (<55 years old), with pSS defined using European-American criteria, presence of anti-SSA and/or anti-SSB antibodies and no history of neurological involvement were prospectively investigated, and compared with 10 age- and sex-matched controls. All subjects underwent, within 1 month, brain MRI, neuropsychological testing, including overall evaluation and focal cognitive function assessment, and (99m)Tc-ECD brain SPECT. RESULTS: (99m)Tc-ECD brain SPECT abnormalities were significantly more common in patients with pSS (10/10) than controls (2/10; p<0.05). Cognitive dysfunctions, mainly expressed as executive and visuospatial disorders, were also significantly more common in patients with pSS (8/10) than controls (0/10; p<0.01). Notably, between-group comparisons enabled a significant correlation to be established between neuropsychological assessment and (99m)Tc-ECD brain SPECT abnormalities in patients with pSS (r(s) = 0.49, p<0.01). MRI abnormalities in patients and controls did not differ significantly. CONCLUSIONS: Neuropsychological testing and (99m)Tc-ECD brain SPECT seem to be the most sensitive tools to detect subclinical CNS dysfunction in pSS. The strong correlation between cortical hypoperfusion in (99m)Tc-ECD brain SPECT and cognitive dysfunction suggests an organic aetiology of CNS dysfunction in pSS. These data should be confirmed in a larger study.

[MRI features of spinal neurosarcoidosis associed with cervical spondylosis]. / Myélopathie sarcoïdosique associée à un canal cervical rétréci : aspects IRM.

INTRODUCTION: Spinal neurosarcoidosis is rare and exceptionally inaugural. OBSERVATION: A 49-year-old African woman developed a progressive left Brown-Sequard syndrome. Magnetic resonance imaging (MRI) scans of the cervical spinal cord revealed an intramedullary lesion from C2 to T1 with intense pial enhancement after administration of contrast material associated with cervical spondylosis. The diagnostic of sarcoidosis was confirmed by liver biopsy which demonstrated noncaseating granulomas. CONCLUSIONS: MRI features of spinal neurosarcoidosis were reviewed by the authors with focus on differential diagnosis.

[Dosimetric impact of the 2D motion of a platform simulating breathing during a dynamic mode treatment]. / Impact dosimétrique du mouvement 2D d'une plateforme simulant la respiration lors d'un traitement en mode dynamique.

Breathing-adapted techniques in external radiotherapy lead to the improvement of the taken into account of the tumour motion during the patient treatment. Indeed, this motion involves dosimetric uncertainties, in particular during a dynamic treatment (intensity-modulated radiation therapy, dynamic wedge...). As tumoral movement is complex and is carried out in various directions of space, a dynamic platform moving in one or two plans was conceived. This article approaches the technical aspects of design and functioning of this prototype. A study of the dosimetric effects of the respiratory movement on one and two plans during a dynamic treatment without gating will be presented. Films were irradiated while varying the rates with wedged fields at various speeds. The penumbra of beams were compared with the static case and appeared twice broader in the majority of the cases. The results highlighted the contributions of the longitudinal and the axial components of the motion on the form of the dose distribution. These results were completed with gamma index measurements to determine an internal margin. Moreover, this platform proves to be a promising tool for breathing-adapted treatment, in particularly to test the synchronisation of RPM system in fluoroscopic mode in board imaging system.

[MR and CT features of craniocervical junction tuberculosis: a report of 5 cases]. / Caractéristiques IRM et TDM de la tuberculose de la jonction crânio-vertébrale: à propos de 5 cas.

Tuberculosis of the craniocervical junction is rare but may cause significant complications with severe sequelae due to the nearby presence of important neurovascular structures. The CT and MR features of 5 cases are presented with correlation with reports from the literature. The differential diagnosis is reviewed.

MR diffusion tensor imaging and fiber tracking in spinal cord arteriovenous malformations: a preliminary study.

BACKGROUND AND PURPOSE: Diffusion tensor imaging (DTI) of the spinal cord in patients harboring spinal arteriovenous malformations (AVMs) was carried out to evaluate the feasibility of this new technique to determine the displacement of the spinal cord tracts and to correlate morphologic and functional DTI data (fractional anisotropy [FA] and apparent diffusion coefficient [ADC]) with the clinical symptoms. MATERIALS AND METHODS: Nine patients with spinal cord AVMs were investigated at 1.5T using a sagittal spin-echo single-shot echo-planar generalized autocalibrating partially parallel acquisition diffusion-weighted imaging sequence. ADC and FA maps were computed in different regions of interest (both above and below the nidus), and tractography was used to visualize the course of the tracts. The data were correlated with the clinical symptoms and compared with 12 healthy control subjects. RESULTS: At the level of the nidus, tracts were normal, shifted, separated, or interrupted but not intermingled with the nidus. Interruption of the tracts was coherent with the clinical symptoms. In patients with severe neurologic deficits, FA values caudal to the nidus showed a reduced anisotropy consistent with loss of white matter tracts. CONCLUSIONS: We demonstrate that AVMs may interrupt, displace, or separate the fiber tracts and that clinical symptoms may be reflected by the quantitative FA results and the morphologic loss of fibers distant to the lesion. DTI with fiber tracking offers a novel approach to image spinal cord AVMs and may open a window to understand the complex pathophysiology of these lesions.

[Practical recommendations for breathing-adapted radiotherapy]. / Bonnes pratiques pour la radiothérapie asservie à la respiration.

Respiration-gated radiotherapy offers a significant potential for improvement in the irradiation of tumor sites affected by respiratory motion such as lung, breast and liver tumors. An increased conformality of irradiation fields leading to decreased complications rates of organs at risk (lung, heart...) is expected. Respiratory gating is in line with the need for improved precision required by radiotherapy techniques such as 3D conformal radiotherapy or intensity modulated radiotherapy. Reduction of respiratory motion can be achieved by using either breath-hold techniques or respiration synchronized gating techniques. Breath-hold techniques can be achieved with active techniques, in which airflow of the patient is temporarily blocked by a valve, or passive techniques, in which the patient voluntarily holds his/her breath. Synchronized gating techniques use external devices to predict the phase of the respiration cycle while the patient breaths freely. This work summarizes the different experiences of the centers of the STIC 2003 project. It describes the different techniques, gives an overview of the literature and proposes a practice based on our experience.

Equivalent uniform dose concept evaluated by theoretical dose volume histograms for thoracic irradiation.

BACKGROUND AND PURPOSE: The goal of our study was to quantify the limits of the EUD models for use in score functions in inverse planning software, and for clinical application. MATERIALS AND METHODS: We focused on oesophagus cancer irradiation. Our evaluation was based on theoretical dose volume histograms (DVH), and we analyzed them using volumetric and linear quadratic EUD models, average and maximum dose concepts, the linear quadratic model and the differential area between each DVH. RESULTS: We evaluated our models using theoretical and more complex DVHs for the above regions of interest. We studied three types of DVH for the target volume: the first followed the ICRU dose homogeneity recommendations; the second was built out of the first requirements and the same average dose was built in for all cases; the third was truncated by a small dose hole. We also built theoretical DVHs for the organs at risk, in order to evaluate the limits of, and the ways to use both EUD(1) and EUD/LQ models, comparing them to the traditional ways of scoring a treatment plan. For each volume of interest we built theoretical treatment plans with differences in the fractionation. CONCLUSION: We concluded that both volumetric and linear quadratic EUDs should be used. Volumetric EUD(1) takes into account neither hot-cold spot compensation nor the differences in fractionation, but it is more sensitive to the increase of the irradiated volume. With linear quadratic EUD/LQ, a volumetric analysis of fractionation variation effort can be performed.

[Listeria monocytogenes encephalitis revealed by left progressive hemiparesis]. / Hémiparésie d'installation progressive révélant une encéphalite à listéria monocytogènes.

INTRODUCTION: Central nervous system listeriosis is a diagnostic and therapeutic challenge for the clinician. CASE REPORT: We report the case of a 66-year-old woman who was admitted for a left progressive hemiparesis associated with headaches. She was treated for one year by immunosuppressive drugs for vulgaris pemphigus. At the time of admission, examination revealed left hemiparesis without fever, and a computed tomography brain scan demonstrated a focal lesion in the right frontal lobe. Blood analyses were normal. Two days after, she suddenly developed fever (40 degrees C), and aggravation of her motor deficit followed by partial motor seizures. The cerebrospinal fluid was normal. Treatment with amoxicillin (3g IV q6h), cefotaxim, gentamycin (120mg IV q12h) and aciclovir was started empirically. The brain MRI without gadolinium displayed infiltrative lesions in the right hemisphere and in the mildbrain. The blood culture grew Listeria monocytogenes. The antimicrobial regimen was changed to amoxicillin for seven weeks and gentamicin for the first ten days. Four days after beginning the antimicrobial regimen, the brain MRI with gadolinium displayed several abscesses measuring less than one cm diameter. The clinical and imaging outcome excellent. CONCLUSION: Meningitis is by far the most central nervous system listeriosis. In our patient, the diagnosis of listeria monocytogenes encephalitis was established on the basis of positive blood cultures, as such patients do not have sterile cerebrospinal fluid.

Esophageal cancer: determination of internal target volume for conformal radiotherapy.

BACKGROUND AND PURPOSE: To evaluate esophageal tumor and OAR movement during the respiratory cycle in order to obtain optimal values for ITV and PRV. To correlate tumor motion with chest wall displacement - information of value in the free-breathing gating system. MATERIAL AND METHOD: Inclusion criteria were: histologically proven squamous-cell carcinoma (SCC) or adenocarcinoma at stage T3 - T4 NX or TX N1 M0 according to the UICC 1997 classification. Two spiral scans were performed with breath-hold respiration under spirometric control: one at end expiration (EBH) and the other at end inspiration (IBH). Displacements between exhalation and inhalation were calculated according to ICRU report 42 recommendations. For the correlation study, CT-scan acquisition was performed at the isocenter over a 20 - 40 s period. After Fourier Transform, frequency spectra for amplitude and phase of tumor and chest wall motions were performed for each patient. RESULTS: Cumulative distribution of CTV motion in absolute values showed that 95% of data ranged from 0 to 1 cm. Cumulative distribution of GTV motion in absolute values showed that 95% of data ranged from 0 to 0.8 cm. The correlation study demonstrated no specific relationship between respiratory and esophageal motions. CONCLUSION: The ITV margin for 3D conformal radiotherapy in esophageal cancer was 1 cm when 95% of motions were taken into account in this clinical study involving eight patients. Before using a free-breathing gating system, the correlation between external markers and target displacement during irradiation must be established for each patient.

Dosimetric consequences of breath-hold respiration in conformal radiotherapy of esophageal cancer.

The objective of this paper is to study the dosimetric impact of respiratory gated radiotherapy in locally advanced esophageal carcinomaand to define the optimal respiratory phase for this treatment. The study included 8 consecutive patients with squamous-cell carcinoma (SCC) or histologically proved adenocarcinoma, for both at least T3-T4 NX or TX N1 M0 stage. Informed consent was obtained before beginning the study. Three spiral scans were performed in breath-hold respiration: one acquisition in end expiration (EBH), one in end inspiration (IBH) and one in deep inspiration breathhold (DIBH); and one acquisition was performed in Free Breathing (FB). A 3 mm-margin was defined as Internal Target Volume (ITV) on FB CT-scan. No ITV was applied on EBH, IBH and DIBH CT-scan. Target volumes were analyzed and we performed dosimetric comparisons on DVH data of each CT-scan for PTV and Organs at Risk (OAR) (Conformity Index, V(dose), D(mean), Equivalent Uniform Dose). DIBH and IBH correlated with a 32% (p=0.77) and 20% (p=0.52) decrease in lung V(20) respectively as compared to FB (13.5%and 15.6% respectively versus 19.9%). DIBH and IBH correlated with a 25% (p=0.25) and 17% (p=0.39) decrease in cardiac V(40) respectively, as compared with FB (16.9% and 18.9% respectively versus 22.7%). For spinal cord irradiation, the minimum dose was obtained in IBH (36.5 Gy). Conformal radiotherapy with respiratory gating for esophageal cancer decreases the irradiated dose to OAR. We suggest that DIBH technique should be used when irradiation is performed using the spirometric system. In the Tidal Volume, the inspiration phase is the most favourable and should be chosen for irradiation with a free breathing gating system.

The value of phase-contrast magnetic resonance angiography of the circle of Willis in predicting cerebral ischemia-hypoxia (shunt need) during carotid endarterectomy.

BACKGROUND: Cerebral perfusion during carotid cross-clamping depends on collateral function of the circle of Willis. The aim of this study was to determine the value of 3D Phase-Contrast (3D PC) MR angiography in predicting pre-operatively the need of shunting. METHODS: 3D PC MR angiography were performed in 121 patients before carotid endarterectomy under locoregional anaesthesia. Based on the MR analysis, the risk of cerebral ischemia-hypoxia during clamping was classified as high, moderate and low. The analysis was then correlated with intraoperative neurological examination. RESULTS: In patients with high risk of cerebral ischemia (n=9), immediate cerebral ischemia developed in all patients within one min of clamping (P<0.001). All nine underwent shunt placement. In six of the patients with moderate risk (n=46), cerebral ischemia occurred between 20 and 25 min after clamping; All occurred during intraoperative hypotension. CONCLUSION: 3D PC MR angiography can significantly determine the need of shunting in patients with important risk of immediate intraoperative cerebral ischemia. It also focuses on the intraoperative blood pressure stability in patients with moderate risk of ischemia.

[Value of imaging in sarcoidosis]. / Apport de l'imagerie dans la sarcoïdose.

Imaging plays an important role in identifying thoracic, abdominal and neurological localizations of sarcoidosis as well as ENT and bone localizations. It contributes to disease detection and is helpful for diagnostic, prognostic and therapeutic decision making and useful for therapeutic monitoring. The chest x-ray is particularly important in the initial work-up and to follow well-tolerated disease. Other investigations, depending on the localization, are helpful to follow the course of severe or chronic sarcoidosis.

Study of the "sniffing position" by magnetic resonance imaging.

BACKGROUND: The "sniffing position" is widely considered essential to the performance of orotracheal intubation and has become the cornerstone of training in anesthesiology. However, the anatomic superiority of this patient head position has not been established. METHODS: Eight healthy young adult volunteers underwent magnetic resonance imaging scanning in three anatomic positions: head in neutral position, in simple extension, and in the "sniffing position" (neck flexed and head extended by means of a pillow). The following measurements were made on each scan: (1) the axis of the mouth (MA); (2) the pharyngeal axis (PA); (3) the laryngeal axis (LA); and (4) the line of vision. The various angles between these axes were defined: alpha angle between the MA and PA, beta angle between PA and LA, and delta angle between line of vision and LA. RESULTS: Both simple extension and sniffing positions significantly improved (P < 0.05) the delta angle associated with best laryngoscopic view. Our results show that the beta value increases significantly (P < 0.05) when the head position is shifted from the neutral position (beta = 7 +/- 6 degrees ) to the sniffing position (beta = 13 +/- 6 degrees ), and the alpha value slightly (but significantly) decreases (from 87 +/- 10 degrees to 63 +/- 11 degrees; P < 0.05). Anatomic alignment of the LA, PA, and MA axes is impossible to achieve in any of the three positions tested. There were no significant differences between angles observed in simple extension and sniffing positions. CONCLUSIONS: The sniffing position does not achieve alignment of the three important axes (MA, PA, and LA) in awake patients with normal airway anatomy.

Central nervous system sarcoidosis: follow-up at MR imaging during steroid therapy.

PURPOSE: To document the changes observed at sequential magnetic resonance (MR) imaging of sarcoidosis lesions of the central nervous system (CNS) during treatment with corticosteroids. MATERIALS AND METHODS: The abnormalities detected in 24 patients (mean follow-up, 36 months) were compared before and after therapeutic periods (n = 75) that were divided into attack (high-dose), upkeep (decreased-dose), and minimal (low-dose) periods. Parenchymal lesions were classified as type 1 (enhanced with gadolinium), type 2 (demyelinating), or type 3 (lacunar) and were assessed as regressing, stable, or progressing. RESULTS: Seven of the 24 patients had several types of lesions. Isolated type 3 lesions (six patients) were the only lesions not associated with neurologic deficit. Type 1 lesions (13 patients) regressed in 22 of 22 attack periods and progressed in nine of 27 upkeep and minimal periods. MR imaging depicted relapses in patients with multifocal CNS involvement or long-standing CNS impairment or in those who had previously received steroid therapy. Type 2 (seven patients) and type 3 (13 patients) lesions remained stable in 68 of 68 therapeutic periods. Type 1 lesions appeared in three patients with type 2 and type 3 lesions during two upkeep and three minimal periods. Findings at follow-up MR imaging contributed to the reintroduction of high-dose corticosteroid therapy in eight patients. CONCLUSION: MR imaging can be used to differentiate between reversible and irreversible lesions in CNS sarcoidosis. MR imaging can be a useful tool for adjusting treatment to prevent irreversible CNS damage.