Pretherapeutic functional neuroimaging predicts tremor arrest after thalamotomy.

OBJECTIVE: Essential tremor (ET) represents the most common movement disorder. Drug-resistant ET can benefit from standard stereotactic procedures (deep brain stimulation or radiofrequency thalamotomy) or alternatively minimally invasive high-focused ultrasound or radiosurgery. All aim at same target, thalamic ventro-intermediate nucleus (Vim). METHODS: The study included a cohort of 17 consecutive patients, with ET, treated only with left unilateral stereotactic radiosurgical thalamotomy (SRS-T) between September 2014 and August 2015. The mean time to tremor improvement was 3.32 months (SD 2.7, 0.5-10). Neuroimaging data were collected at baseline (n = 17). Standard tremor scores, including activities of daily living (ADL) and tremor score on treated hand (TSTH), were completed pretherapeutically and 1 year later. We further correlate these scores with baseline inter-connectivity in twenty major large-scale brain networks. RESULTS: We report as predictive three networks, with the interconnected statistically significant clusters: primary motor cortex interconnected with inferior olivary nucleus, bilateral thalamus interconnected with motor cerebellum lobule V2 (ADL), and anterior default-mode network interconnected with Brodmann area 103 (TSTH). For all, more positive pretherapeutic interconnectivity correlated with higher drop in points on the respective scores. Age, disease duration, or time-to-response after SRS-T were not statistically correlated with pretherapeutic brain connectivity measures (P > .05). The same applied to pretherapeutic tremor scores, after using the same methodology described above. CONCLUSIONS: Our findings have clinical implications for predicting clinical response after SRS-T. Here, using pretherapeutic magnetic resonance imaging and data processing without prior hypothesis, we show that pretherapeutic network(s) interconnectivity strength predicts tremor arrest in drug-naïve ET, following stereotactic radiosurgical thalamotomy.

Comparison between the ICRU rectal point and modern volumetric parameters in brachytherapy for locally advanced cervical cancer.

PURPOSE: The implementation of image-guided brachytherapy in cervical cancer raises the problem of adapting the experience acquired with 2D brachytherapy to this technique. The GEC-ESTRO (Groupe européen de curiethérapie - European Society for Radiotherapy and Oncology) has recommended reporting the dose delivered to the rectum in the maximally exposed 2 cm(3) volume, but so far, the recommended dose constraints still rely on 2D data. The aim of this study was to evaluate the relationship between the doses evaluated at the ICRU rectal point and modern dosimetric parameters. MATERIAL AND METHODS: For each patient, dosimetric parameters were generated prospectively at the time of dosimetry and were reported. For analysis, they were converted in 2 Gy equivalent doses using an α/ß ratio of 3 with a half-time of repair of 1.5 hours. RESULTS: The dosimetric data from 229 consecutive patients treated for locally advanced cervical cancer was analyzed. The mean dose calculated at ICRU point (DICRU) was 55.75 Gy ± 4.15, while it was 59.27 Gy ± 6.16 in the maximally exposed 2 cm(3) of the rectum (P=0.0003). The D2 cm(3) was higher than the DICRU in 78% of the cases. The mean difference between D2 cm(3) and DICRU was 3.53 Gy ± 4.91. This difference represented 5.41% ± 7.40 of the total dose delivered to the rectum (EBRT and BT), and 15.49% ± 24.30 of the dose delivered when considering brachytherapy alone. The two parameters were significantly correlated (P=0.000001), and related by the equation: D2 cm(3)=0.902 × DICRU + 0.984. The r(2) coefficient was 0.369. CONCLUSION: In this large cohort of patients, the DICRU significantly underestimates the D2 cm(3). This difference probably results from the optimization process itself, which consists in increasing dwell times above the ICRU point in the cervix. Considering these findings, caution must be taken while implementing image-guided brachytherapy and dose escalation.

Volumetric evaluation of an alternative bladder point in brachytherapy for locally advanced cervical cancer.

PURPOSE: To evaluate an alternative dose point, so-called ALG (for Alain Gerbaulet), for the bladder in comparison to the International Commission on Radiation Units and Measurements (ICRU) point and D2cm(3) (minimal dose to maximally exposed 2 cm(3)) in a large cohort of patients with locally advanced cervical cancer treated with external beam radiotherapy followed by image-guided pulsed dose rate brachytherapy. METHODS AND MATERIALS: For each patient, the ALG point was constructed 1.5 cm above the ICRU bladder, parallel to the tandem (coronal and sagittal planes). The dosimetric data from 162 patients were reviewed. RESULTS: Average doses to ALG and bladder points were 19.40 Gy ± 7.93 and 17.14 ± 8.70, respectively (p=0.01). The 2 cm(3) bladder dose averaged 24.40 ± 6.77 Gy. Ratios between D2cm(3) and dose points were 1.37 ± 0.46 and 1.68 ± 0.74 (p<0.001) for ALG and ICRU points, respectively. Both dose points appeared correlated with D2cm(3) (p<0.001) with coefficients of determination (R(2)) of 0.331 and 0.399 respectively. The estimated dose to the ICRU point of the rectum was 12.77 ± 4.21 and 15.76 ± 5.94 for D2cm(3) (p<0.0001). Both values were significantly correlated (p<0.0001, R(2) = 0.485). CONCLUSION: The ALG point underestimates the D2cm(3), but its mean on a large cohort is closer to D2cm(3) than the dose to ICRU point. However, it shows great variability between cases and the weak strength of its correlation to D2cm(3) indicates that it is not a good surrogate for individual volumetric evaluation of the dose D2cm(3).

[Contribution of 3D imaging in brachytherapy: which kind of imaging for which localization?]. / Apport de l'imagerie 3D en curiethérapie : quel type d'imagerie pour quelle localisation ?

The use of image-guided brachytherapy has led to a significant change in application techniques and improvements in treatment planning. Today, 3D imaging has replaced orthogonal radiographs for a large number of treatments, providing a possibility of an optimization adapted to the anatomy of each patient. When properly selected and implemented, this imaging provides accurate 3D information of volumes and brachytherapy device, allowing moving from a dose to points assessment to a dose/volume evaluation. This article describes the contribution of different imaging modalities for the different brachytherapy techniques: gynecological brachytherapy, interstitial brachytherapy (breast, penis, etc.) and prostate brachytherapy. It reminds recommendations for the establishment of protocols of images acquisition and 3D reconstruction of brachytherapy devices (applicators, plastic tubes, needles, etc.).