Multi-modality radiotherapy in cervical cancer: Impact on the 3D dose distribution

This thesis describes the impact of image and dose accumulation uncertainties on the cumulative 3D dose distribution in multimodality radiotherapy for cervical cancer. Image distortions for brachytherapy planning on 3T magnetic resonance (MR) images were evaluated with an MRI-only method. We conclude that it is safe to use 3T MRI scanners for applicator reconstruction during brachytherapy planning, because the dosimetric implications of these image distortions were clinically insignificant. We investigated the added value of non-rigid registration for the evaluation of cumulative external beam radiotherapy (EBRT) and brachytherapy (BT) dose volume histogram (DVH) parameters, for both the planned and delivered EBRT dose. With the current planning strategies, dose addition with non-rigid registration is not necessary and simple addition of DVH parameters is an adequate method to assess the toxicity from EBRT and BT. We investigated uncertainties related to non-rigid registration when accumulating the dose to the rectum of multiple BT fractions. We showed that, due to incorrect registration, dose addition with non-rigid registration is problematic for doses that have steep gradients such as brachytherapy doses. With the advent of novel techniques, such as MRI-guided radiotherapy, assessing the 3D dose distribution will become more important. For these new techniques with a high gradient dose distribution, it may be necessary to evaluate the cumulative dose using non-rigid registration. However, for the accumulation of 3D dose distributions with very steep gradients new registration algorithms/strategies need to be developed that take into account biomechanical properties

A Dietary Survey of Free-Living Middle-Aged White Males in the Westem Cape

A survey was conducted to determine the dietary intake of a sample of free-living normal middle-aged (40 - 59 years) White males from the Stellenbosch area. The 7-day food record method was employed, and the 44 subjects who completed the three recording periods represented a sample population drawn from 300 volunteers. The mean calorie intake of the sample (2.564jday) approximated the recommended daily allowance for the middle-aged reference male, and the mean ethanol intake was 24 g (SO ± 31) per day. The daily intake of 99 g of protein represents a high protein diet of mainly animal origin. The dietary fat provided about 38% of the total calories per day, and consisted of 41 g of saturated fatty acids, 33 g .of mono-unsaturated fatty acids and 12 9 of polyunsaturated fatty acids, with a resultant PjS ratio of 1 : 3. The mean value for the daily intake of dietary cholesterol (566 mgjday) is very close to the value reported in the National Diet-Heart Study of the USA. Of the 40% of calories derived from carbohydrates (256 gjday), half was contributed by mono- and disaccharides and half by polysaccharides. The highly saturated, high fat diet with a relatively high protein content of mainly animal origin, closely resembles that of a typical American diet of free-living males in a Western affluent community

The role of femoral venous pressure and femoral venous oxygen saturation in the setting of intra-abdominal hypertension: a pig model

Femoral venous access is frequently used in critically ill patients. Because raised intra-abdominal pressure (IAP) is also frequently found in this group of patients, we examined the impact of IAP and positive end-expiratory pressure (PEEP) on femoral venous pressure (FVP) and femoral venous oxygen saturation (Sfvo2) in an animal model. Thirteen adult pigs received standardized anesthesia and ventilation. Randomized levels of IAP (3 [baseline], 18, and 26 mmHg) were applied, with levels of PEEP (5, 8, 12, and 15 cmH2O) applied randomly at each IAP level. We measured bladder pressure (IAP), superior vena cava pressure, pulmonary artery pressure, pulmonary artery occlusion pressure, FVP, mixed venous oxygen saturation (Svo2), and Sfvo2. We found that FVP correlated well with IAP (FVP = 4.1 + [0.12 × PEEP] + [1.00 × IAP]; R = 0.89, P < 0.001) with a moderate bias and precision of 5.0 and 3.8 mmHg, respectively. Because the level of agreement did not meet the recommendations of the World Society of Abdominal Compartment Syndrome, FVP cannot currently be recommended to measure IAP, and further clinical trials are warranted. However, a raised FVP should prompt the measurement of the bladder pressure. Femoral venous oxygen saturation did correlate neither with Svo2 nor with abdominal perfusion pressure. Therefore, Sfvo2 is of no clinical use in the setting of raised IAP

Structure-based deformable image registration: Added value for dose accumulation of external beam radiotherapy and brachytherapy in cervical cancer

Background and purpose: Structure -based deformable image registration (DIR) can be used to calculate accumulated brachytherapy (BT) and external -beam radiation therapy (EBRT) dose-volume histogram (DVH) parameters in cervical cancer. Since direct parameter addition does not take dose non uniformity into account, the added value of DIR over addition methods was investigated for bladder and rectum.Materials and methods: For twelve patients (EBRT: 46 Gy, EBRT + BT: D-90 85-90 Gy(EQD2) in equivalent dose in 2 Gy fractions) the EBRT planning CT and BT planning MRI were registered using DIR. Affected lymph nodes, located far from the BT boost region, received an EBRT boost (9.2 Gy) not contributing to the BT boost dose. Cumulative bladder/rectum D-2cm3/D-1cm3 were calculated and compared to direct addition methods, assuming uniform EBRT doses (UD), or overlapping high dose volumes (OHD).Results: Between the three methods, the maximum differences in the cumulative DVH parameters were 3.2 GY(EQD2) (bladder) and 3.3 GY(EQD2) (rectum). The difference between DIR and UD was <1.8 GY(EQD2) for both organs.Conclusions: The UD method provides a better estimate of D2cm3/D1cm3 than the OHD method. There is no added value of DIR since differences with direct addition methods are clinically insignificant. EBRT dose distributions can be considered uniform in bladder and rectum for the evaluated dose parameters. (C) 2017 Elsevier B.V. All rights reserved.Biological, physical and clinical aspects of cancer treatment with ionising radiatio

Image Distortions on a Plastic Interstitial Computed Tomography/Magnetic Resonance Brachytherapy Applicator at 3 Tesla Magnetic Resonance Imaging and Their Dosimetric Impact

Purpose: To quantify magnetic resonance imaging (MRI)distortions on a plastic intracavitary/interstitial applicator with plastic needles at a field strength of 3 T and to determine the dosimetric impact, using patient data.Methods and Materials: For 11 cervical cancer patients, our clinical MRI protocol was extended with 3 scans. From the first scan, a multi-echo acquisition, a map of the magnetic field (B-0) was calculated and used to quantify the field inhomogeneity. The expected displacements of the applicator were quantified for the clinical sequence using the measured field inhomogeneity and the clinical sequence's bandwidth. The second and third scan were our routine clinical sequence (duration: <5 minutes each), acquired consecutively using opposing readout directions. The displacement of the applicator between these scans is approximately twice the displacement due to B0 inhomogeneity. The impact of the displacement on the dose was determined by reconstructing the applicator on both scans. The applicator was then shifted and rotated the same distance as the observed displacement to create a worst-case scenario (ie, twice the actual displacement due to B0 inhomogeneity). Next, the dose to 98%/90% (D98/D90) of the clinical target volume at high risk, as well as the dose to the most irradiated 2 cm 3 for bladder and rectum, were calculated for the original plan as well as the shifted plan.Results: For a volume of interest containing the intrauterine device and the ovoids the 95th percentile of the absolute displacement ranged between 0.2 and 0.75 mm, over all patients. For all patients, the difference in D98/D90 in the opposing readout scans with the original plan was at most 4.7%/ 4.3%. For the dose to the most irradiated 2 cm 3 of bladder/rectum, the difference was at most 6.0%/ 6.3%.Conclusions: The dosimetric impact of distortions on this plastic applicator with plastic needles is limited. Applicator reconstruction for brachytherapy planning purposes is feasible at 3 T MRI. (C) 2017 Elsevier Inc. All rights reserved.Biological, physical and clinical aspects of cancer treatment with ionising radiatio