The use of the source-skin distance measuring bridge indeed reduces skin teleangiectasia after interstitial boost in breast conserving therapy.

BACKGROUND AND PURPOSE: In 1990 the skin source measuring bridge was proposed as a tool to measure (1) the distance between the interstitial implant and the overlying skin during brachytherapy boost treatment as well as (2) the distances between the lateral source end and the exit point of the guide needle. The present study reports on the clinical experience using the source skin measuring bridge with respect to incidence and grade of teleangiectasia, and their relation to source skin distances and doses. PATIENTS AND METHODS: Two hundred and twenty-two breast cancer patients (229 breasts) treated between 1983 and 1996 with breast conserving therapy including a brachytherapy boost were scored on the occurrence of teleangiectasia. The minimum distance between the sources (above implant and laterally) and the skin surface were measured. RESULTS: If no bridge was used the appearance of teleangiectasia in the epiderm above the implant is 77, 63 and 50% for boost doses of 25, 20 and 15 Gy, respectively. For brachytherapy boost doses of 25 and 20 Gy and distances smaller than 10mm between the implant and the overlying epiderm, as determined with the skin source measuring bridge, the appearance of teleangiectasia was 78 and 46%, respectively. When respecting provisional dosimetry to spare the skin for a boost dose of 15 Gy, resulting in distances between 10 and 15 mm for the implant overlying skin and distances between 5 and 10 mm for the lateral skin, teleangiectasia can be reduced to a minimum (6.3% above and 3.3% laterally). While in a univariate analysis several parameters (use of the bridge, boost dose, boost modality, external beam therapy modality) were predictive factors, the use of the bridge remained the only significant variable in a multivariate analysis. CONCLUSIONS: The skin source measuring bridge reduces teleangiectasia after interstitial brachytherapy boost treatment. A hypothesis made previously relating teleangiectasia and source skin distances was verified and extended. Even when 3D planning is used, the bridge allows for a provisional calculation of the security margins between source positions and the skin at the time of BT implantation to assure a correct needle positioning from the beginning, instead of correcting dwell times later on to avoid unnecessary high skin doses.     

Connectomic assessment of injury burden and longitudinal structural network alterations in moderate‐to‐severe traumatic brain injury

Traumatic brain injury (TBI) is a major public health problem. Caused by external mechanical forces, a major characteristic of TBI is the shearing of axons across the white matter, which causes structural connectivity disruptions between brain regions. This diffuse injury leads to cognitive deficits, frequently requiring rehabilitation. Heterogeneity is another characteristic of TBI as severity and cognitive sequelae of the disease have a wide variation across patients, posing a big challenge for treatment. Thus, measures assessing network‐wide structural connectivity disruptions in TBI are necessary to quantify injury burden of individuals, which would help in achieving personalized treatment, patient monitoring, and rehabilitation planning. Despite TBI being a disconnectivity syndrome, connectomic assessment of structural disconnectivity has been relatively limited. In this study, we propose a novel connectomic measure that we call network normality score (NNS) to capture the integrity of structural connectivity in TBI patients by leveraging two major characteristics of the disease: diffuseness of axonal injury and heterogeneity of the disease. Over a longitudinal cohort of moderate‐to‐severe TBI patients, we demonstrate that structural network topology of patients is more heterogeneous and significantly different than that of healthy controls at 3 months postinjury, where dissimilarity further increases up to 12 months. We also show that NNS captures injury burden as quantified by posttraumatic amnesia and that alterations in the structural brain network is not related to cognitive recovery. Finally, we compare NNS to major graph theory measures used in TBI literature and demonstrate the superiority of NNS in characterizing the disease.