Dosimetric characterization of foam padding with posterior fields in palliative radiation therapy

Patients undergoing external beam radiation therapy for the palliative treatment of painful bony metastases may have difficulty maintaining a still position on a rigid uncovered couch top, both during CT simulation as well as during patient setup, image guidance, and treatment on the linear accelerator. For these patients, a thin foam pad or mattress is sometimes used to mitigate patient discomfort. It was desired to quantify the effect of the padding in cases in which the patient is to be treated supine with posterior beams when the majority of the beam weighting traverses both the couch and the pad. Ion chamber measurements in-phantom were acquired with 6 MV, 10 MV, and 15 MV photon beams. At depths of maximum dose, the pad resulted in a difference of signal collected ≤1%. At the phantom surface, the pad resulted in an increase in signal ranging from 1% to 6.5% for the measured beams. CT data of the pad, both with and without applied pressure, indicated that the pad had average HU values close to air.

CryoEM single particle reconstruction with a complex-valued particle stack

Single particle reconstruction (SPR) in cryoEM is an image processing task with an elaborate hierarchy that starts with many very noisy multi-frame images. Efficient representation of the intermediary image structures is critical for keeping the calculations manageable. One such intermediary structure is called a particle stack and contains cut-out images of particles in square boxes of predefined size. The micrograph that is the source of the boxed images is usually corrected for motion between frames prior to particle stack creation. However, the contrast transfer function (CTF) or its Fourier Transform point spread function (PSF) are not considered at this step. Historically, the particle stack was intended for large particles and for a tighter PSF, which is characteristic of lower resolution data. The field now performs analyses of smaller particles and to higher resolution, and these conditions result in a broader PSF that requires larger padding and slower calculations to integrate information for each particle. Consequently, the approach to handling structures such as the particle stack should be reexamined to optimize data processing. Here we propose to use as a source image for the particle stack a complex-valued image, in which CTF correction is implicitly applied as a real component of the image. We can achieve it by applying an initial CTF correction to the entire micrograph first and perform box cutouts as a subsequent step. The final CTF correction that we refine and apply later has a very narrow PSF, and so cutting out particles from micrographs that were approximately corrected for CTF does not require extended buffering, i.e. the boxes during the analysis only have to be large enough to encompass the particle. The Fourier Transform of an exit-wave reconstruction creates an image that has complex values. This is a complex value image considered in real space, opposed to standard SPR data processing where complex numbers appear only in Fourier space. This extension of the micrograph concept provides multiple advantages because the particle box size can be small and calculations crucial for high resolution reconstruction such as Ewald sphere correction, aberration refinement, and particle-specific defocus refinement can be performed on the small box data.

Examining ski area padding for head and neck injury mitigation

OBJECTIVES

The injury mitigation capabilities of foam, ski-area padding was examined for headfirst impacts.

DESIGN AND METHODS

A custom-made pendulum impactor system was constructed using an instrumented, partial 50th-percentile-male Hybrid-III anthropomorphic testing device (ATD). For each test, the ATD was raised 1.0m, released, and swung into a 20-cm diameter wooden pole. Test trials were conducted with the wooden pole covered by ski area padding (five conditions of various foam types and thicknesses) or unpadded. Linear (linear acceleration and HIC₁₅) and angular (angular velocity, angular acceleration, and BrIC) kinematics were examined and used to estimate the likelihood of severe brain injury. Cervical spine loads were compared to the injury assessment reference values for serious injury. Further tests were conducted to examine the changes produced by the addition of a snowsport helmet.

RESULTS

38 test trials were recorded with a mean (±sd) impact speed of 4.2 (±0.03) m/s. Head, resultant linear acceleration, HIC₁₅, and associated injury likelihoods were tempered by ski area padding at the impact speed tested. Ski area padding did not reduce brain injury likelihood from rotational kinematics (p>0.05 for all comparisons) or reduce the cervical spine compression below injury assessment reference values. The addition of a helmet did not reduce significantly the likelihoods of brain or cervical spine injury.

CONCLUSIONS

At the impact speed tested, ski area padding provided limited impact protection for the head (for linear kinematics) but did not protect against severe brain injuries due to rotational kinematics or serious cervical spine injuries.

Practical issues and limitations of brain attenuation correction on a simultaneous PET-MR scanner

BACKGROUND

Despite the advent of clinical PET-MR imaging for routine use in 2011 and the development of several methods to address the problem of attenuation correction, some challenges remain. We have identified and investigated several issues that might affect the reliability and accuracy of current attenuation correction methods when these are implemented for clinical and research studies of the brain. These are (1) the accuracy of converting CT Hounsfield units, obtained from an independently acquired CT scan, to 511 keV linear attenuation coefficients; (2) the effect of padding used in the MR head coil; (3) the presence of close-packed hair; (4) the effect of headphones. For each of these, we have examined the effect on reconstructed PET images and evaluated practical mitigating measures.

RESULTS

Our major findings were (1) for both Siemens and GE PET-MR systems, CT data from either a Siemens or a GE PET-CT scanner may be used, provided the conversion to 511 keV μ-map is performed by the PET-MR vendor's own method, as implemented on their PET-CT scanner; (2) the effect of the head coil pads is minimal; (3) the effect of dense hair in the field of view is marked (> 10% error in reconstructed PET images); and (4) using headphones and not including them in the attenuation map causes significant errors in reconstructed PET images, but the risk of scanning without them may be acceptable following sound level measurements.

CONCLUSIONS

It is important that the limitations of attenuation correction in PET-MR are considered when designing research and clinical PET-MR protocols in order to enable accurate quantification of brain PET scans. Whilst the effect of pads is not significant, dense hair, the use of headphones and the use of an independently acquired CT-scan can all lead to non-negligible effects on PET quantification. Although seemingly trivial, these effects add complications to setting up protocols for clinical and research PET-MR studies that do not occur with PET-CT. In the absence of more sophisticated PET-MR brain attenuation correction, the effect of all of the issues above can be minimised if the pragmatic approaches presented in this work are followed.

Medical Image Encryption: An Application for Improved Padding Based GGH Encryption Algorithm

Medical images are regarded as important and sensitive data in the medical informatics systems. For transferring medical images over an insecure network, developing a secure encryption algorithm is necessary. Among the three main properties of security services (i.e., confidentiality, integrity, and availability), the confidentiality is the most essential feature for exchanging medical images among physicians. The Goldreich Goldwasser Halevi (GGH) algorithm can be a good choice for encrypting medical images as both the algorithm and sensitive data are represented by numeric matrices. Additionally, the GGH algorithm does not increase the size of the image and hence, its complexity will remain as simple as O(n²). However, one of the disadvantages of using the GGH algorithm is the Chosen Cipher Text attack. In our strategy, this shortcoming of GGH algorithm has been taken in to consideration and has been improved by applying the padding (i.e., snail tour XORing), before the GGH encryption process. For evaluating their performances, three measurement criteria are considered including (i) Number of Pixels Change Rate (NPCR), (ii) Unified Average Changing Intensity (UACI), and (iii) Avalanche effect. The results on three different sizes of images showed that padding GGH approach has improved UACI, NPCR, and Avalanche by almost 100%, 35%, and 45%, respectively, in comparison to the standard GGH algorithm. Also, the outcomes will make the padding GGH resist against the cipher text, the chosen cipher text, and the statistical attacks. Furthermore, increasing the avalanche effect of more than 50% is a promising achievement in comparison to the increased complexities of the proposed method in terms of encryption and decryption processes.

Comfort and compressional characteristics of padding bandages

BACKGROUND

Padding bandage is an essential component of the multi-layer compression system used for chronic venous management. Padding plays a critical role in managing pressure over bony prominences and ensuring uniform pressure distribution around the limb circumference. Moreover, it helps in the management of heat, moisture and body fluids or exudates during the course of treatment to provide comfort to the patients.

OBJECTIVE

To study the effect of structural and constructional parameters on the compressional (pressure absorption or distribution) and comfort (air, moisture and heat transmission) characteristics of the padding.

METHODS

This research focuses on the examination of polypropylene based nonwoven padding samples. Critical factors, i.e., fiber linear density, needling density and mass per unit area, have been chosen for this study to find their significance on the performance of padding. Simple laboratory based methods have been proposed to examine pressure reduction and comfort characteristics of the padding.

RESULTS

Pressure absorption by the padding decreases with increase in mass per unit area and needling density of the padding. A padding composed of thicker fiber absorbs more pressure compared to padding made from thinner fiber. On examining comfort, it was found that the air and moisture vapor transmission increase with decrease in mass per unit area and needling density but have opposite effects with fiber linear density (p<0.01). The heat transmission decreases with increase in both mass per unit area and fiber linear density but has opposite effect for needling density.

CONCLUSION

Padding composed of thick fiber with low mass per unit area and needling density could be more effective in pressure management and ensuring comfort. These results could be very useful for health practitioners, fabric engineers and manufactures to understand the significance of fibrous materials and their role in compression management, and could be further used as design consideration to optimized padding performance.

Liquid transmission characteristics of padding bandages under pressure

Padding is an essential component in a multilayer compression bandaging system, used inside the compression bandage through which substantial amount of pressure is exerted on the limb of patient for treatment of venous leg ulcers. As a result, the liquid transmission behavior of padding is also critical in managing body fluids or sweat exuded from the affected limb, reducing the excessive moisture build-up around the wound and thereby ensuring comfort to and hence a better compliance from the patients. This study investigates the in-plane fluid transport characteristics of needle-punched nonwoven padding bandages. It first reviewed the existing studies related to the problems, and discussed their limits and possible improvements in dealing with complex fluid transport issues in textile porous media. The measurement of fluid transport under different pressure levels was then done using a newly designed apparatus capable of simultaneously tracing the liquid in-plane spreading along different directions, and obtaining several transport characteristics of a testing sample, e.g. the liquid flow anisotropy, the rate of movement, the area of wet surface with time, etc. Also the effects of several important factors, such as the levels of pressure applied, the specimen bulk density, and needling density of the padding products, have been experimentally investigated. In addition, based on an extended Lucas-Washburn theory, we calculated the liquid flow distance, both instantaneous speed and a more useful time-averaged speed v(av) at any given direction, and also defined a flow anisotropy index I(A) as a convenient parameter to represent the material flow anisotropy. The applications of v(av) and I(A) to actual samples have demonstrated the usefulness of these parameters in characterizing the flow nature and behavior of the materials.

Quilting Sutures Reduces Seroma in Mastectomy

BACKGROUND

Drainage duration and seroma formation occurring after mastectomy with or without axillary surgery lengthens hospitalization and delays adjuvant treatment. The aim of the study was to evaluate the effect of quilting in the prevention of seroma after mastectomy for breast cancer.

PATIENTS AND METHODS

Eighty-two breast cancer patients about to undergo mastectomy with or without axillary surgery lymphadenectomy were enrolled in the study. We conducted an observational comparison between 41 patients in whom quilting with closed suction drainage was used and 41 patients in whom drainage only was used.

RESULTS

The mean drained volume was significantly lower in the quilting group compared with the control group on days 1 and 2 (day 1: 107.1 mL vs. 156.5 mL; P = .02; day 2: 108.4 mL vs. 162.8 mL; P = .01). The mean drainage period was shorter in the quilting group (4.6 vs. 5.3 days; P = .046). There were fewer needle aspirations for seroma in the padding group (n = 14, 34.1% vs. n = 24, 58.5%; P = .03).

CONCLUSION

The use of padding after mastectomy seems to reduce seroma formation, volume drained, and length of drainage time.

[Prevention of seroma post-mastectomy by surgical padding technique]

INTRODUCTION

Every year, 20,000 mastectomy are realized. The most common complication of these surgical procedure is seroma, occurring in a range of 10 to 85% of the cases, which may be responsible for an increased morbidity by complications: disunity of surgical flap, infection, and delay in administrating adjuvant therapies.

OBJECTIVE

We focused on a post-mastectomy padding technique, aiming at decreasing incidence of postoperative seromas.

PATIENTS AND METHODS

We conducted a retrospective study of patients treated with mastectomy from January 2012 to March 2014 in Amiens University Hospital. Forty-two patients were included: 20 to the "padding's" group and 22 to the "control's" group.

RESULTS

Drainage flow was significantly decreased at Day 1, Day 2, Day 3 and throughout hospitalization after padding (358.5mL versus 685mL; P=0.02). Hospital stays were significantly shortened by 2 days (5.3 versus 7.3 days; P<0.05) for patients receiving padding surgery.

DISCUSSION AND CONCLUSION

Our results show a benefit in the mastectomy padding flap. However, the retrospective character of our study and its strength character imply bias and data not available such as complications in type of wound dehiscence, pain, necrosis, the period from the establishment of the adjuvant therapies and aesthetic evaluation of technique. As such, we initiated a prospective randomized multicenter study late 2013, named PRELYMCA, which should be able to answer the pending questions.

Pneumatic tourniquet use in foot and ankle surgery--is padding necessary?

BACKGROUND

The majority of foot and ankle surgery is carried out in a bloodless field achieved by the use of a pneumatic tourniquet. The risks of tourniquet use may be divided into those resulting from direct mechanical pressure from the cuff and those secondary to prolonged limb ischaemia. Current peri-operative guidelines advise the use of padding beneath the cuff, in particular to reduce skin complication.

OBJECTIVES

To assess the complication rate of tourniquet use when the cuff is applied directly to the skin.

METHOD

Patients undergoing foot and ankle surgery under tourniquet control without use of padding were assessed pre and post operatively for soft tissue complication, neurological deficit and post-tourniquet syndrome.

RESULTS

We recorded findings for 97 patients, 47 thigh and 50 ankle tourniquets. We found a complication rate of 0%. There were no cases of skin blistering, abrasion, bruising, laceration or burn.

CONCLUSIONS

These findings are contrary to published RCTs supporting the use of padding. Our study demonstrates the safe use of pneumatic tourniquets without padding in foot and ankle surgery.