Improving 3D dose prediction for breast radiotherapy using novel glowing masks and gradient-weighted loss functions.

BACKGROUND: The quality of treatment plans for breast cancer can vary greatly. This variation could be reduced by using dose prediction to automate treatment planning. Our work investigates novel methods for training deep-learning models that are capable of producing high-quality dose predictions for breast cancer treatment planning. PURPOSE: The goal of this work was to compare the performance impact of two novel techniques for deep learning dose prediction models for tangent field treatments for breast cancer. The first technique, a "glowing" mask algorithm, encodes the distance from a contour into each voxel in a mask. The second, a gradient-weighted mean squared error (MSE) loss function, emphasizes the error in high-dose gradient regions in the predicted image. METHODS: Four 3D U-Net deep learning models were trained using the planning CT and contours of the heart, lung, and tumor bed as inputs. The dataset consisted of 305 treatment plans split into 213/46/46 training/validation/test sets using a 70/15/15% split. We compared the impact of novel "glowing" anatomical mask inputs and a novel gradient-weighted MSE loss function to their standard counterparts, binary anatomical masks, and MSE loss, using an ablation study methodology. To assess performance, we examined the mean error and mean absolute error (ME/MAE) in dose across all within-body voxels, the error in mean dose to heart, ipsilateral lung, and tumor bed, dice similarity coefficient (DSC) across isodose volumes defined by 0%-100% prescribed dose thresholds, and gamma analysis (3%/3 mm). RESULTS: The combination of novel glowing masks and gradient weighted loss function yielded the best-performing model in this study. This model resulted in a mean ME of 0.40%, MAE of 2.70%, an error in mean dose to heart and lung of -0.10 and 0.01 Gy, and an error in mean dose to the tumor bed of -0.01%. The median DSC at 50/95/100% isodose levels were 0.91/0.87/0.82. The mean 3D gamma pass rate (3%/3 mm) was 93%. CONCLUSIONS: This study found the combination of novel anatomical mask inputs and loss function for dose prediction resulted in superior performance to their standard counterparts. These results have important implications for the field of radiotherapy dose prediction, as the methods used here can be easily incorporated into many other dose prediction models for other treatment sites. Additionally, this dose prediction model for breast radiotherapy has sufficient performance to be used in an automated planning pipeline for tangent field radiotherapy and has the major benefit of not requiring a PTV for accurate dose prediction.

Ultrafast optical currents in gapped graphene.

We theoretically study the interaction of ultrashort optical pulses with gapped graphene. Such a strong pulse results in a finite conduction band population and a corresponding electric current, both during and after the pulse. Since gapped graphene has broken inversion symmetry, it has an axial symmetry about the y -axis but not about the x-axis. We show that, in this case, if the linear pulse is polarized along the x-axis, the rectified electric current is generated in the y  direction. At the same time, the conduction band population distribution in the reciprocal space is symmetric about the x-axis. Thus, the rectified current in gapped graphene has an inter-band origin, while the intra-band contribution to the rectified current is zero.

The Effect of Percutaneous Laser Disc Decompression on Reducing Pain and Disability in Patients With Lumbar Disc Herniation.

Introduction: As low back pain incidence is increasing, noninvasive modalities are gaining attention for their ability to achieve the best possible outcome with the least complications. Percutaneous laser disc decompression (PLDD) is currently popular for this purpose. This study aims to evaluate the effect of PLDD on disability and pain reduction in patients with lumbar disc herniation. Methods: Thirty patients were enrolled in this study. Spinal nerve blocks were conducted by laser discectomy single stage injection of a needle into the disc space. The nucleus pulposus of herniated discs were irradiated with laser in order to vaporize a small part of the nucleus pulposus of the intervertebral discs and reduce the voluminosity of diseased discs. Patients were treated with 1000 J of 980 nm diode laser with 5 W energy. In order to measure the severity of pain, visual analog scale (VAS) and also ODI (Oswestry Disability Index) were used. Data were analyzed using SPSS version 12. Results: Thirty patients participated in this trial including 11 men and 19 women with a mean age (SD) of 40.8 (10.8) years. The mean patients VAS score and ODI level before and after discectomy showed statistically significant differences. The mean VAS and ODI scores showed no statistical difference between males and females (P<0.05) and percutaneous laser discectomy decreased the VAS and ODI at both groups of patients similarly. Conclusion: We found the use of PLDD reduces pain and disability in patients as a noninvasive procedure.

Restoring a post-traumatic partial edentulous mandible with the Toronto prosthesis: a clinical report.

Implants provide support, stability and retention for restorations used in fully and partially edentulous patients. This clinical report describes prosthetic treatment of a 30-year-old man suffering from a dentoalveolar deficiency due to an old gunshot trauma to the left side of the mandible. The patient was rehabilitated with implant-supported Toronto prosthesis following surgical placement of three implants with undesirable location and angulations due to lack of sufficient bone. This prosthetic option offers advantages of both screw-retained and cement-retained prostheses and provides acceptable aesthetic and functional results.

Stress distribution pattern of screw-retained restorations with segmented vs. non-segmented abutments: A finite element analysis.

Background. Screw-retained restorations are favored in some clinical situations such as limited inter-occlusal spaces. This study was designed to compare stresses developed in the peri-implant bone in two different types of screw-retained restorations (segmented vs. non-segmented abutment) using a finite element model. Methods. An implant, 4.1 mm in diameter and 10 mm in length, was placed in the first molar site of a mandibular model with 1 mm of cortical bone on the buccal and lingual sides. Segmented and non-segmented screw abutments with their crowns were placed on the simulated implant in each model. After loading (100 N, axial and 45° non-axial), von Mises stress was recorded using ANSYS software, version 12.0.1. Results. The maximum stresses in the non-segmented abutment screw were less than those of segmented abutment (87 vs. 100, and 375 vs. 430 MPa under axial and non-axial loading, respectively). The maximum stresses in the peri-implant bone for the model with segmented abutment were less than those of non-segmented ones (21 vs. 24 MPa, and 31 vs. 126 MPa under vertical and angular loading, respectively). In addition, the micro-strain of peri-implant bone for the segmented abutment restoration was less than that of non-segmented abutment. Conclusion. Under axial and non-axial loadings, non-segmented abutment showed less stress concentration in the screw, while there was less stress and strain in the peri-implant bone in the segmented abutment.

Cement Selection for Cement-Retained Implant-Supported Prostheses: A Literature Review.

Cement-retained implant-supported prostheses are widely used for restoring missing teeth; however, they show some complications in comparison to screw-retained restorations, such as difficulty in retrieving the restoration and biocompatibility of cement. Therefore, the practitioner should consider several important aspects when using this type of restoration. In this regard, one major concern is appropriate cement selection, with considerations including cement biologic compatibility, methods for limiting the excess cement, ease of removing the excess cement, radiographic view of the cement, and also the possibility of future retrieval of the prosthesis. The aim of this review article was to address most aspects related to this type of prosthesis in terms of cementation.

The intravenous laser blood irradiation in chronic pain and fibromyalgia.

Intravenous laser blood irradiation was first introduced into therapy by the Soviet scientists EN.Meschalkin and VS.Sergiewski in 1981. Originally this method was developed for the treatment of cardiovascular diseases. Improvement of rheologic properties of the blood as well as improvement of microcirculation and reduction of the area of infarction has been proved. Further, reduction of dysrhythmia and sudden cardiac death was achieved. At first, only the Helium-Neon laser (632.8 nm) was used in this therapy. For that, a power of 1-3mW and a period of exposure of 20-60 minutes were applied. The treatments were carried out once or twice a day up to ten appointments in all1. In the years after, many, and for the most part Russian studies showed that helium-neon laser had various effects on many organs and on the hematologic and immunologic system. The studies were published mainly in Russian which were little known in the West because of decades of political separation, and were regarded with disapproval. Besides clinical research and application for patients, the cell biological basis was developed by the Estonian cell biologist Tiina Karu at the same time. An abstract is to be found in her work "The Science of Low-Power Laser-Therapy"

Fabrication of an Implant-Supported Orbital Prosthesis with Bar-Magnetic Attachment: A Clinical Report.

Implant-supported craniofacial prostheses are made to restore defective areas in the face and cranium. This clinical report describes a technique for fabrication of an orbital prosthesis with three adjacent implants in the left lateral orbital rim of a 60-year-old woman. Selection of appropriate attachment system (individual magnetic abutments versus bar-clip attachment) for implant-supported orbital prostheses depends upon the position of implants. Bar-magnetic attachment has been selected as the retention mechanism in the present case.

Effect of cryoanalgesia on post-thoracotomy pain.

We prepared this study to determine the effect of cryoanalgesia on post-thoracotomy pain. In this double-blinded randomized clinical trial, 60 patients who underwent thoracotomy were divided into two groups (control and cryoanalgesia). Visual Analogue Scale (VAS, 0-10) was used for the measurement of severity of post-thoracotomy pain. It was classified into three categories: 0-1 (mild), 2-3 (moderate), and 4-10 (severe). Pethidine (0.5-1 mg/kg) was administered in case of need for both groups. Patients were visited at the hospital a week later, and were contacted by phone at the first, second, and third months post-operatively. Intensity of pain in the control group was higher than the cryoanalgesia group in all visits the follow-up period. On the second day, the frequencies of severe pain (4-10) were 33.3% and 0 in the control and cryoanalgesia groups, respectively. The mild pain on the seventh day was 13.3% and 83.3% in the control and cryoanalgesia groups, respectively (P < 0.01). Pethidine consumption was 151.6 ± 27 mg in the control group and 87.5 ±48 mg in the cryoanalgesia group on the first day post-operation (P < 0.001). Cryoanalgesia is a useful technique with not serious side effects in order to alleviate post-thoracotomy pain and reduce the need for opiate consumption.