How to Study Smart?

How to Study Smart By Dr Sumer Sethi, where he explains how students can utilize Feynman technique for deep understanding of concepts. Dr Sumer Sethi is author of the book Fire in the Belly and is a famous teacher and motivator.

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Volumetric MRI Analysis of Plexiform Neurofibromas in Neurofibromatosis Type 1

Publication date: Available online 31 October 2017
Source:Academic Radiology
Author(s): Wenli Cai, Seth M. Steinberg, Miriam A. Bredella, Gina Basinsky, Bhanusupriya Somarouthu, Scott R. Plotkin, Jeffrey Solomon, Brigitte C. Widemann, Gordon J. Harris, Eva Dombi
ObjectivesPlexiform neurofibromas (PNs) are complex, histologically benign peripheral nerve sheath tumors that are challenging to measure by simple line measurements. Computer-aided volumetric segmentation of PN has become the recommended method to assess response in clinical trials directed at PN. Different methods for volumetric analysis of PN have been developed. The goal of this study is to test the level of agreement in volume measurements and in interval changes using two separate methods of volumetric magnetic resonance imaging analysis.MethodsThree independent volume measurements were performed on 15 PN imaged at three time-points using 3DQI software at Massachusetts General Hospital (MGH) and National Cancer Institute (NCI) and MEDx software at NCI.ResultsMedian volume differences at each time-point comparing MGH-3DQI and NCI-3DQI were −0.5, −4.2, and −19.9 mL; comparing NCI-3DQI and NCI-MEDx were −21.0, −47.0, and −21.0 mL; comparing MGH-3DQI and NCI-MEDx were −10.0, −70.3, and −29.9 mL. Median differences in percentage change over time comparing MGH-3DQI and NCI-3DQI were −1.7, 1.1, and −1.0%; comparing NCI-3DQI and NCI-MEDx were −2.3, 3.3, and −1.1%; comparing MGH-3DQI and NCI-MEDx were −0.4, 2.0, and −1.5%. Volume differences were <20% of the mean of the two measurements in 117 of 135 comparisons (86.7%). Difference in interval change was <20% in 120 of the 135 comparisons (88.9%), while disease status classification was concordant in 115 of 135 comparisons (85.2%).ConclusionsThe volumes, interval changes, and progression status classifications were in good agreement. The comparison of two volumetric analysis methods suggests no systematic differences in tumor assessment. A prospective comparison of the two methods is planned.



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Comparison of intensity modulated radiotherapy with simultaneous integrated boost (IMRT-SIB) and a 3-dimensional conformal parotid gland-sparing radiotherapy (ConPas 3D-CRT) in treatment of nasopharyngeal carcinoma: a mono-institutional experience

Abstract

Aim

To compare intensity modulated radiotherapy with simultaneous integrated boost (IMRT-SIB) and a 3-dimensional conformal parotid gland-sparing radiotherapy (ConPas 3D-CRT) in treatment of nasopharyngeal carcinoma with regard to outcomes and dose distribution to the planning target volumes (PTVs) and to the organs at risk (OARs).

Methods

The treatment records of 24 patients with histologically proven carcinoma of the nasopharynx treated with ConPas 3D-CRT or IMRT-SIB technique between May 2009 and December 2016 were assessed.

Results

The mean dose and dose to 50% parotid glands volume as well as the maximal dose to the spinal cord were significantly lower in the IMRT-SIB than in the ConPas 3-CRT group (p < 0.05; p < 0.05; p < 0.01, respectively). IMRT-SIB was also superior in coverage of PTVs. The 3-year overall survival (OS) and disease-free survival (DFS) of patients in the IMRT-SIB and ConPas 3D-CRT groups were 77 and 81% (p = 0.93), 51.9 and 70.7% (p = 0.83), respectively.

Conclusion

IMRT-SIB provided additional spearing to parotid glands and spinal cord in comparison to ConPas 3D-CRT technique but without improvement of OS and DFS.

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Automated, reference-free local error assessment of multimodal deformable image registration for radiotherapy in the head and neck

Publication date: Available online 31 October 2017
Source:Radiotherapy and Oncology
Author(s): Michael G. Nix, Robin J.D. Prestwich, Richard Speight
BackgroundHead and neck MR-CT deformable image registration (DIR) for radiotherapy planning is hindered by the lack of both ground-truth and per-patient accuracy assessment methods. This study assesses novel post-registration reference-free error assessment algorithms, based on local rigid re-registration of native and pseudomodality images.MethodsHead and neck MR obtained in and out of the treatment position underwent DIR to planning CT. Block-wise mutual information (b-MI) and pseudomodality mutual information (b-pmMI) algorithms were validated against applied rotations and translations. Inherent registration error detection was compared across 14 patient datasets.ResultsUsing radiotherapy position MR-CT DIR, quantitative comparison of applied rotations and translations revealed that errors between 1 and 4 mm were accurately determined by both algorithms. Using diagnostic position MR-CT DIR, translations of up to 5 mm were accurately detected within the gross tumour volume by both methods. In 14 patient datasets, b-MI and b-pmMI detected similar errors with improved stability in regions of low contrast or CT artefact and a 10-fold speedup for b-pmMI.Conclusionsb-MI and b-pmMI algorithms have been validated as providing accurate reference-free quantitative assessment of DIR accuracy on a per-patient basis. b-pmMI is faster and more robust in the presence of modality-specific information.



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Glucose starvation impairs DNA repair in tumour cells selectively by blocking histone acetylation

Publication date: Available online 31 October 2017
Source:Radiotherapy and Oncology
Author(s): Rena Ampferl, Hans Peter Rodemann, Claus Mayer, Tobias Tim Alexander Höfling, Klaus Dittmann
Background and purposeTumour cells are characterized by aerobic glycolysis and thus have high glucose consumption. Because repairing radiation-induced DNA damage is an energy-demanding process, we hypothesized that glucose starvation combined with radiotherapy could be an effective strategy to selectively target tumour cells.Material and methodsWe glucose-starved tumour cells (A549, FaDu) in vitro and analysed their radiation-induced cell responses compared to normal fibroblasts (HSF7).ResultsIrradiation depleted intracellular ATP levels preferentially in cancer cells. Consequently, glucose starvation impaired DNA double-strand break (DSB) repair and radiosensitized confluent tumour cells but not normal fibroblasts. In proliferating tumour cells glucose starvation resulted in a reduction of proliferation, but failed to radiosensitize cells. Glucose supply was indispensable during the late DSB repair in confluent tumour cells starting approximately 13 h after irradiation, and glucose starvation inhibited radiation-induced histone acetylation, which is essential for chromatin relaxation. Sirtinol – an inhibitor of histone deacetylases – reverted the effects of glucose depletion on histone acetylation and DNA DSB repair in tumour cells. Furthermore, a glucose concentration of 2.8 mmol/L was sufficient to impair DSB repair in tumour cells and reduced their clonogenic survival under a fractionated irradiation regimen.ConclusionsIn resting tumour cells, glucose starvation combined with irradiation resulted in the impairment of late DSB repair and the reduction of clonogenic survival, which was associated with disrupted radiation-induced histone acetylation. However, in normal cells, DNA repair and radiosensitivity were not affected by glucose depletion.



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Prognostic impact of HPV-associated p16-expression and smoking status on outcomes following radiotherapy for oropharyngeal cancer: The MARCH-HPV project

Publication date: Available online 31 October 2017
Source:Radiotherapy and Oncology
Author(s): Pernille Lassen, Benjamin Lacas, Jean-Pierre Pignon, Andy Trotti, Bjorn Zackrisson, Qiang Zhang, Jens Overgaard, Pierre Blanchard
Background and purposeEvaluate the prognostic and predictive impact of HPV-associated p16-expression and assess the combined prognostic impact of p16 and smoking on altered fractionated radiotherapy (AFRT) for oropharyngeal cancer (OPC) within the frames of the update of the Meta-Analysis of Radiotherapy in Carcinomas of Head and neck (MARCH).Materials and methodsPatients with OPC, known tumor p16-status and smoking history were identified from the MARCH update, resulting in a dataset of 815 patients from four randomized trials (RTOG9003, DAHANCA6&7, RTOG0129, ARTSCAN). Analysis was performed using a Cox model stratified by trial and adjusted on gender, age, T-stage, N-stage, type of radiotherapy fractionation, p16, smoking. Primary endpoint was progression-free survival (PFS).ResultsIn total, 465 patients (57%) had p16-positive tumors and 350 (43%) p16-negative. Compared to p16-negative, p16-positive patients had significantly better PFS (HR = 0.42 [95% CI: 0.34–0.51], 28.9% absolute increase at 10 years) and OS (HR = 0.40 [0.32–0.49], 32.1% absolute increase at 10 years). No interaction between p16-status and fractionation schedule was detected. Smoking negatively impacted outcome; in the p16-positive subgroup, never smokers had significantly better PFS than former/current smokers (HR = 0.49 [0.33–0.75], 24.2% survival benefit at 10 years).ConclusionsNo predictive impact of p16-status on response to AFRT could be detected but the strong prognostic impact of p16-status was confirmed and especially p16-positive never smoking patients have superior outcome after RT.



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Robustness of patient positioning for interfractional error in carbon ion radiotherapy for stage I lung cancer: Bone matching versus tumor matching

Publication date: Available online 31 October 2017
Source:Radiotherapy and Oncology
Author(s): Makoto Sakai, Yoshiki Kubota, Jun-ichi Saitoh, Daisuke Irie, Katsuyuki Shirai, Ryosuke Okada, Masami Torikoshi, Tatsuya Ohno, Takashi Nakano
Background and purposePatient positioning was compared by tumor matching (TM) and conventional bony structure matching (BM) in carbon ion radiotherapy for stage I non-small cell lung cancer to evaluate the robustness of TM and BM in determining interfractional error.Material and methodsSixty irradiation fields were analyzed. Computed tomography (CT) images acquired before treatment initiation for confirmation (Conf-CT) were obtained under the same settings as the treatment planning CT images and used to evaluate both positioning methods. The dose distributions were recalculated for Conf-CT using both BM and TM, and the dose–volume histogram parameters [V95% of clinical target volume, V5Gy(RBE) of normal lung, and acceptance ratio (ratio of cases with V95% > 95%)] were evaluated. The required margin, which in 90% of cases achieved the acceptable condition, was also examined.ResultsUsing BM and TM, the median V95% was 98.93% and 100% (p < 0.001) and the mean V5Gy(RBE) was 135.9 and 125.8 (p = 0.694), respectively. The estimated required margins were 7.9 and 3.3 mm and increased by 53.9% and 2.5% of V5Gy(RBE), respectively, compared with planning.ConclusionsTM ensured a better dose distribution than did BM. To enable TM, volumetric imaging is crucial and should replace 2D radiographs for carbon therapy of stage I lung cancer.



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