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Results from a single-institution study support the need of a dose constraint for patients who have previously undergone hip replacement surgery. Our study provides evidence that a dose above 30 Gy to the area of hip prosthesis is significantly correlated with later hip arthroplasty dysfunction as measured by the Harris Hip Score. As total hip arthroplasty becomes more and more common, it is urgent to further look into radiation therapy treatment parameters that can be modified to improve the quality of life of patients who receive pelvic irradiation after hip arthroplasty. Further prospective studies are needed to extract safe conclusions.

Purpose The aim of this review article is to provide a useful reference for dose comparison techniques within the frame of treatment plan verification. Each technique is presented with a general description given along with advantages and disadvantage and the rationale for its development. Methods The review was conducted in PubMed from 1993 to 2019 including articles referring to the methodology of dose comparison for treatment plan verification. Results The search identified thirty-one dose comparison methods that were categorized according to the number of physical parameters that take into account for dose comparison. Conclusions Among the available methods for the comparison of two dose distributions, the γ-analysis (gamma analysis) has been widely adopted as the gold standard in verification procedures. However, due to various intrinsic limitations of gamma index, the development of a better metric taking into account both statistical and in clinical parameters is required.

Total Skin Electron Beam (TSEB) treatment, despite its proven effectiveness in skin malignancies, is a rather exhausting irradiation method, especially for feeble patients. In an effort to reduce treatment time by creating a clinically acceptable single TSEB field, various beam modifiers of different materials and shapes were tested. Using the TSEB immobilization device of our department and 3D printing technology, aluminum and thermoplastic modifiers were designed and constructed, according to the resulting profiles at treatment distance. Electron beam characteristics were measured and calculated both at SSD = 100 cm and at treatment level. Aluminum scatterers of the same thickness caused different modification according to the area of blocking. Aluminum modifiers reduced significantly central dose deposition for the same amount of MUs and therefore they expanded treatment time in undesirable levels. Plastic modifiers offer a good combination of field dimensions and treatment time. The final 3D printed modifier shaped the electron beam as desired resulting to a clinically acceptable 6 MeV field of 176 × 70 cm field with 10% inhomogeneity in vertical and 3% in the lateral dimension with adequate skin coverage at SSD = 400 cm. This modification offered approximately a two-minute treatment time reduction compared to the current technique. Underdosed areas appear near the edge of the field, but in regions that are far from the torso of the patient. Bremsstrahlung radiation was kept at clinically accepted levels ( 5%). This modification of the original six dual-field technique of our hospital could probably benefit fragile patients who could not easily tolerate a twenty-minute standing position without compromising the quality of their treatment.

PURPOSE Plastic phantoms are commonly used in daily routine for dosimetric tasks in radiation therapy. Although water is the reference medium according to the dosimetric protocols, measurements with nonwater phantoms are easier to be performed. To succeed absorbed dose determination, certain scaling factors have to be applied to the acquired measurements. Taking into account the increased availability of three-dimensional (3D) printing, we attempted to obtain scaling factors for polylactic acid (PLA), a commonly used thermoplastic material for 3D printing. METHODS Measurements were performed with a custom-made phantom from PLA material, which was designed and constructed using 3D printing technology. Depth and fluence scaling factors were obtained within the range of 6 to 20 MeV. Moreover, Monte Carlo simulations were performed to verify the measured results. RESULTS Experimental and Monte Carlo (MC) values showed a good agreement, especially in lower energies. Mean value of depth scaling factor (cpl ) over the whole range of energies was 0.946, while mean fluence scaling factor (hpl ) was found to be 1.050. For energies below 10 MeV, the corresponding mean values for cpl and hpl were 0.946 and 1.054, respectively. CONCLUSIONS PLA phantoms could be constructed and used for electron beam nonreference measurements, reproducing even more complex geometries, from simple quality assurance devices to geometrically complicated anthropomorphic phantoms.

Purpose Certain radiation responsive skin diseases may develop symptoms on the upper or the lower half of the body. The concept of a novel Hemi-Body Electron Irradiation (HBIe−) technique, described in this work, provides a low cost, LINAC based, intermediate treatment option in between extremely localized and Total Skin irradiation techniques. Materials and methods The HBIe− technique, developed in our department, incorporates a custom crafted treatment chamber equipped with adjustable Pb shielding and a single electron beam in extended Source-Skin Distance (SSD) setup. The patient is positioned in ‘Stanford’ technique positions. The geometrical setup provides both optimal dose homogeneity and dose deposition up to a depth of 2 cm. To confirm this, the following characteristics were measured and evaluated: a) percentage depth dose (PDD) on the treatment plane produced by a single electron beam at perpendicular incidence for six fields at ‘Stanford’ angles, b) 2D profile of the entrance dose on the treatment plane produced by a single field and c) the total surface dose on an anthropomorphic phantom delivered by all 6 fields. Results The resulting homogeneity of the surface dose in the treatment plane for an average patient was 5–6%, while surface dose homogeneity on the anthropomorphic phantom was 7% for both the upper and the lower HBIe− variants. The total PDD exhibits an almost linear decrease to a practical range of 2 g/cm2. Conclusion In conclusion, HBIe− was proven effective in delivering the prescribed dose to the target area, while protecting the healthy skin.

To investigate the accuracy of field junctioning planning techniques (monoisocentric and rotating couch technique) for 3D-conformal radiotherapy (3D-CRT).In vivo dosimetry has been performed using thermo- luminescence dosimeters (TLDs) in 10 head and neck cancer patients (treated with monoisocentric technique) and 10 breast cancer patients (treated with rotating couch technique) irradiated with a 6 MV photon beam. Entrance dose measurements were performed in selected regions including the field junction area.The mean deviation between measured and expected dose in the region of junction was significantly higher in breast cases compared to head and neck irradiation (-2.8±15.4% and 0.2±8.2% respectively; Mann-Whitney U test: p=0.002). A comparison between lateral head and neck fields and tangential breast fields revealed that the latter was associated with larger dose discrepancies (-2.2 ± 4.6% vs -3.5 ± 5.7% respectively; Mann-Whitney U test: p=0.029).The results indicate the superiority of monoisocentric technique compared to the rotating couch technique in terms of dose delivery accuracy for treatments with field junctioning planning techniques.

Interventional cardiology procedures result in substantial patient radiation doses due to prolonged fluoroscopy time and radiographic exposure. The procedures that are most frequently performed are coronary angiography, percutaneous coronary interventions, diagnostic electrophysiology studies and radiofrequency catheter ablation. Patient radiation dose in these procedures can be assessed either by measurements on a series of patients in real clinical practice or measurements using patient-equivalent phantoms. In this article we review the derived doses at non-pediatric patients from 72 relevant studies published during the last 22 years in international scientific literature. Published results indicate that patient radiation doses vary widely among the different interventional cardiology procedures but also among equivalent studies. Discrepancies of the derived results are patient-, procedure-, physician-, and fluoroscopic equipmentrelated. Nevertheless, interventional cardiology procedures can subject patients to considerable radiation doses. Efforts to minimize patient exposure should always be undertaken.

There is growing evidence to suggest that endothelial biology and atherosclerosis depend on arterial wall shear stress (WSS). We review the existing literature on in vivo measurements of WSS in healthy individuals using phase-contrast MRI, which is a promising, noninvasive technique for determinating various blood flow characteristics. WSS data exist for the following arteries: carotid, brachial, aorta and femoral. Measured values indicate that WSS is site specific, a finding which opposes the notion that physiological WSS values are maintained at a constant magnitude in all parts of the arterial system. Among the WSS values obtained at the same site by different investigators there is qualitative agreement; however, differences exist in absolute values mainly due to the dependence on the method used to obtain WSS values from velocity data.

Introduction There is growing evidence that atherosclerosis, as well as endothelial biology, depend on arterial wall shear stress (WSS). Several methods of WSS calculation with varying degrees of complexity have been proposed. This study aimed at investigating whether the most straightforward and easier to apply of these methods give comparable results in clinical practice. Methods Complete velocity encoding measurements using phase contrast magnetic resonance imaging were performed in 20 patients at a level perpendicular to the long axis of the ascending aorta approximately 2 cm above the aortic valve. WSS was calculated at this location on maximum systole. MR imaging was accomplished on a 1.5 T scanner. Four methods were applied to calculate WSS; three of them are based on the predictions of Poiseuille's theory of flow, while the last one is based on calculations resulting by the application of the definition of WSS. Results WSS calculated with the above mentioned methods was found to be in the range 4.2 ± 1.8 to 3.5 ± 1.7 dynes/m2. The velocity profile at the site of measurements can be described with a parabolic equation of the form u = a r 2 + b r + c with an average r2 = 0.83, which is in good agreement with Poiseuille's theory of flow. Comparison of the results shows no statistically significant differences between WSS measurements calculated with these methods. Discussion The four methods are equivalent in calculating WSS at the ascending aorta when blood flow velocities have a good parabolic distribution.