Quantification Of Dose Research Articles

SU‐FF‐J‐174: Volume Rendered Cardiac Segmentation and Analysis for Breast Radiotherapy

Purpose: Development of a non‐rigid deformable template algorithm for the segmentation of cardiac anatomy allowing for quantification of dose delivered to the heart during breast irradiation. Method and Materials: A high resolution, contrast enhanced, cardiac CT scan was used for manual delineation of cardiac? anatomy. This reference scan consisted of 163 slices, 0.75 mm thick. In‐plane reconstruction voxel dimension of the scan was 0.373×0.373×0.75mm. Manual contours were generated to delineate cardiac anatomy, describing in detail position of relevant anatomy such as the left anterior descending coronary artery (LAD). This set of segmented structures, along with the corresponding cardiac CT image, define a reference set of cardiac data, to be used to match corresponding structures in our patient population. Plastimatch, a b‐spline, non‐rigid registration algorithm, was employed to determine the vector fields necessary to deform the reference CT image to match the designated patient volume. Using this vector field, the segmented model may then be deformed and registered to the new patient anatomy. Using the Fovia High Definition® Volume Rendering platform, the segmented volume may be analyzed volumetrically, visualizing anatomy, segmented volumes and delivered dose in near real‐time. Results: Retrospective application of this algorithm upon a selection of previously irradiated free breathing and breath hold left breast patients shows good agreement with expected geometry. However, alignment issues persist where significant thoracic and pulmonary motion obscures the registration image of the patients heart, resulting in poor registration of the treated anatomy with the cardiac template. Conclusion: Risk of late cardiopulmonary toxicity from left breast irradiation has motivated new treatment techniques to reduce cardiac exposure during radiotherapy. Implementation of a deformable segmentation model imaged volumetrically allows for careful analysis of delivered cardiac dose.

Quantification of radiation dose from short-lived positron emitters formed in human tissue under proton therapy conditions

The dose distribution in proton therapy is mainly due to primary particles and secondary electrons. The contribution of short-lived β + emitters formed in the interactions of protons with the light mass elements C, N and O has hitherto not been considered. We estimated the formation of 11C, 13N and 15O in irradiation of tissue with 200 MeV protons. The integral yields at 150 MeV were compared with a literature phantom measurement. The results for 11C and 15O agreed very well; for 13N, however, appreciable deviation was observed. The activities were also calculated in the region around the Bragg peak as well as over the path length after entrance of the beam. Dose calculations were then done using the medical internal radiation dose (MIRD) formalism. Furthermore, a dose calculation was simulated for a 150 MeV proton beam (2 nA, 2 min) in a brain tumour. The dose deposited by the positron emitters in the Bragg peak region was found to be about 1.5 mGy, i.e. less than 1% of the dose estimated from the electronic interactions of protons. The absorbed dose in the whole brain amounted to 5.5 mGy.

High-dose-rate prostate brachytherapy in a patient with bilateral hip prostheses planned using megavoltage computed tomography images acquired with a helical tomotherapy unit

Purpose The presence of hip prostheses results in significant image artifacts making delineation of anatomy for planning difficult with traditional kilovoltage CT images. This report presents the use of megavoltage computed tomography (MVCT) imaging acquired with a helical tomotherapy unit to plan a high-dose-rate (HDR) prostate brachytherapy treatment for a patient with bilateral hip prostheses. Methods and Materials A 77-year-old man presented with a localized clinical Stage T3a, Gleason 7 prostate cancer. Past history was also significant for bilateral hip prostheses. Staging workup included a negative bone scan and CT of abdomen and pelvis. The pelvic CT exhibited significant streak artifacts obscuring the prostate. HDR monotherapy with adjuvant androgen deprivation therapy was proposed. On the day of the implant and after catheter insertion, MVCT imaging of the pelvic area of the patient was obtained using a commercial helical tomotherapy unit. The MVCT images were transferred to Nucletron PLATO (v14.3.2) for planning with optimization of catheter dwell positions and times. Results MVCT images acquired with the helical tomotherapy unit allow good visualization of bony anatomy and of the hip prosthesis. No reconstruction streak artifacts are visible in the images as seen in the diagnostic kilovoltage CT images. Sufficient soft tissue contrast exists to allow delineation of the bladder and rectum. The absence of streak artifacts provides good quantification of Hounsfield number in the region surrounding the hip prosthesis and allows for good dose quantification. Conclusions MVCT images obtained using the commercial helical tomotherapy unit have been shown to provide good soft tissue contrast and no streak artifacts when planning a patient for prostate HDR brachytherapy having bilateral prosthetic hip replacements. The rectum and bladder can be clearly seen in the MVCT images and contoured independently. Prostate delineation is assumed from the position of the brachytherapy catheters.

Quantification of the infectious dose of Leishmania major transmitted to the skin by single sand flies.

Leishmaniasis is transmitted between mammalian hosts by the bites of bloodsucking vector sand flies. The dose of parasites transmitted to the mammalian host has never been directly determined. We developed a real-time PCR-based method to determine the number of Leishmania major parasites inoculated into the ears of living mice during feeding by individual infected flies (Phlebotomus duboscqi). The number of parasites transmitted varied over a wide range in the 58 ears in which Leishmania were detected and demonstrated a clear bimodal distribution. Most of the infected mice were inoculated with a low dose of <600 parasites. One in four received a higher dose of >1,000 and up to 100,000 cells. High-dose transmission was associated with a heavy midgut infection of >30,000 parasites, incomplete blood feeding, and transmission of a high percentage of the parasite load in the fly. To test the impact of inoculum size on infection outcome, we compared representative high- (5,000) and low- (100) dose intradermal needle infections in the ears of C57BL/6 mice. To mimic natural transmission, we used sand fly-derived metacyclic forms of L. major and preexposed the injection site to the bites of uninfected flies. Large lesions developed rapidly in the ears of mice receiving the high-dose inoculum. The low dose resulted in only minor pathology but a higher parasite titer in the chronic phase, and it established the host as an efficient long-term reservoir of infection back to vector sand flies.

Ozone Flux Measurement and Modelling on Leaf/Shoot and Canopy Scale

The quantitative study of the ozone effects on agricultural and forest vegetation requires the knowledge of the pollutant dose absorbed by plants via leaf stomata, i.e. the stomatal flux. Nevertheless, the toxicologically effective dose can differ from the stomatal flux because a pool of scavenging and detoxification processes reduce the amount of pollutant responsible of the expression of the harmful effects. The measurement of the stomatal flux is not immediate and the quantification of the effective dose is still troublesome. The paper examines the conceptual aspects of ozone flux measurement and modelling in agricultural and ecological research. The ozone flux paradigm is conceptualized into a toxicological frame and faced at two different scales: leaf/shoot and canopy scales. Leaf and shoot scale flux measurements require gas-exchange enclosure techniques, while canopy scale flux measurements need a micrometeorological approach including techniques such as eddy covariance and the aerodynamical gradient. At both scales, not all the measured ozone flux is stomatal flux. In fact, a not negligible amount of ozone is destroyed on external plant surfaces, like leaf cuticles, or by gas phase reaction with biogenic volatile compounds. The stomatal portion of flux can be calculated from concurrent measurements of water vapour fluxes at both scales. Canopy level flux measurements require very fast sensors and the fulfilment of many conditions to ensure that the measurements made above the canopy really reflect the canopy fluxes (constant flux hypothesis). Again, adjustments are necessary in order to correct for air density fluctuations and sensor-surface alignment break. As far as regards flux modelling, at leaf level the stomatal flux is simply obtained by multiplying the ozone concentration on the leaf with the stomatal conductance predicted by means of physiological models fed by meteorological parameter. At canopy level the stomatal flux is calculated by SVAT models often based on the energy balance of the soil-vegetation-atmosphere system and on the big-leaf concept. This latter assumes the canopy as equivalent to a single leaf having a leaf area equal to the total area of all the plant’s leaves and lying at a certain height above the ground. The complexity of SVAT models ranges from one-dimensional to three-dimensional models. The most used are one-dimensional models in single-layer, dual-source or multi-layer version. The main uncertainties in flux modelling are currently associated to the estimation of the non-stomatal flux component and to the up-scaling process from leaf to canopy and stand level. For the latter a separate representation of sunlit and shaded leaves is recommended.

Aerosol Delivery through Nasal Cannulas: An In Vitro Study

In most circumstances, a nasal route for the delivery of pulmonary aerosol medications is rarely considered; however, in specific instances, this route may be quite useful. Consider, for example, the delivery of aerosol treatments during humidified high-flow nasal cannula use in pediatric critical care, or continuous aerosol delivery via cannula for medications with short durations of action. The goal of this study was to evaluate the potential for delivering aerosols via nasal cannula through in vitro studies of aerosol output and size. The system utilized for testing included an Aerogen Solo nebulizer downstream of a heater/humidifier system, followed by a nasal cannula and an aerosol collection apparatus. Adult, pediatric, and infant cannulas were tested with and without an inhalation-only breathing simulator. The cannulas were driven by 3 lpm (50 psig) oxygen flows. Dose quantification was performed using radioisotope techniques. Total cannula output and system losses were measured. Aerosol size measurements were made from the nebulizer, from the heating tube, and from the prongs of the adult and pediatric cannulas, using laser-diffraction techniques. Total cannula output ranged from 8.4-25.1% and 18.6-26.9% of loaded dose, without and with the addition of inhalation flows. Volume median diameters were 2.2 +/- 0.2 microm from the adult cannula and 1.9 +/- 0.3 microm from the pediatric cannula. Ninety percent of the aerosol volume was in sizes smaller than 4.2 +/- 0.4 microm (adult) and 3.8 +/- 0.5 microm (pediatric). System losses were highest in the nebulizer-humidifier connectors, heated tube, and humidifier. Losses in the nebulizer were very low (2.2-3.5%). This study demonstrates that aerosols can be efficiently delivered through a humidified high-flow nasal cannula system. Further study is required to determine if this route is viable for pulmonary delivery.

Disease Severity Adversely Affects Delivery of Dialysis in Acute Renal Failure

Background/Aims: Methods of intermittent hemodialysis (IHD) dose quantification in acute renal failure (ARF) are not well defined. This observational study was designed to evaluate the impact of disease activity on delivered single pool Kt/V_urea in ARF patients. Methods: 100 patients with severe ARF (acute intrinsic renal disease in 18 patients, nephrotoxic acute tubular necrosis in 38 patients, and septic ARF in 44 patients) were analyzed during four consecutive sessions of IHD, performed for 3.5–5 h every other day or daily. Target IHD dose was a single pool Kt/V_urea of 1.2 or more per dialysis session for all patients. Prescribed Kt/V_urea was calculated from desired dialyzer clearance (K), desired treatment time (t) and anthropometric estimates for urea distribution volume (V). The desired clearance (K) was estimated from prescribed blood flow rate and manufacturer’s charts of in vivo data obtained in maintenance dialysis patients. Delivered single pool Kt/V_urea was calculated using the Daugirdas equation. Results: None of the patients had prescription failure of the target dose. The delivered IHD doses were substantially lower than the prescribed Kt/V values, particularly in ARF patients with sepsis/septic shock. Stratification according to disease severity revealed that all patients with isolated ARF, but none with 3 or more organ failures and none who needed vasopressive support received the target dose. Conclusion: Prescription of target IHD dose by single pool Kt/V_urea resulted in suboptimal dialysis dose delivery in critically ill patients. Numerous patient-related and treatment-immanent factors acting in concert reduced the delivered dose.

Quantification of incidental dose to potential clinical target volume (CTV) under different stereotactic body radiation therapy (SBRT) techniques for non-small cell lung cancer – Tumor motion and using internal target volume (ITV) could improve dose distribution in CTV

Clinical target volume (CTV), although present, is usually not considered during stereotactic body radiation therapy (SBRT) for non-small cell lung cancer. This study aimed to quantify the incidental dose to the potential CTV under different SBRT techniques. Ten patients with various tumor motions were included in the study. Gated-4DCT was performed for all patients. Three treatment plans were generated. Plan A was based on free breathing gross tumor volume (GTV) from a regular CT. Plan B was based on internal target volume (ITV) from gated 4DCT. Plan C was a perfect gated treatment at the exhale phase. The hypothetical CTV was represented by three CTV shells (5, 10, and 15 mm). Time-averaged dose for different respiratory phases was calculated for 18 representative points in each shell. The minimum doses for plans A, B, and C were 84+/-20%, 94+/-3%, and 80+/-17% of the isocenter dose to the 5mm shell, 72+/-27%, 64+/-7%, and 20+/-11% to the 10mm shell, and 38+/-27%, 27+/-17%, and 6+/-7% to the 15 mm shell, respectively. The caudal and cranial ends of each shell usually had lower dose compared to the other points on the shell. Plan B had the most uniform and reasonable doses to the CTV shells, and patients with large respiratory motion had significantly higher minimum dose than patients with less motion. The potential CTV may incidentally receive adequate and relatively homogeneous doses when ITV is used and the patients have large respiratory motion. However, it could be underdosed for gated treatment or for patients with little motion.

Toxicity of dimethoate and fenoxycarb to honey bee brood (Apis mellifera), using a new in vitro standardized feeding method

A new in vitro method was devised to assess the effects of pesticides on honey bee brood. The method allowed the quantification of doses ingested by larvae and the assessment of larval and pupal mortality. Larval mortality in control samples was lower than 10%. Two active substances were tested: dimethoate and fenoxycarb. The LD(50) of dimethoate was 1.9 microg larva(-1) 48 h after oral exposure of larvae at day 4. Additional dose-related effects on pupal mortality were noted. After a chronic intoxication, the NOAEC (No Observed Adverse Effect Concentration) for larval mortality at day 7 was 2.5 mg kg(-1), whereas a NOAEC of 5 mg kg(-1) was found at day 22 for delayed effects on the reduction of adult emergence. Fenoxycarb applied at day 4 showed no effect on larvae, whereas emergence of adults was affected at doses higher than 6 ng larva(-1).

Internal microdosimetry of inhaled radon progeny in bronchial airways: advantages and limitations

The objective of the present study was to identify advantages and limitations of the application of microdosimetric concepts for inhaled radon progeny activities in the lungs. The methods employed for this analysis were a recently developed Monte-Carlo microdosimetry code for the calculation of energy deposition in bronchial target cells and the Probability Per Unit Track Length (PPUTL) model, which relates these microdosimetric parameters to cellular radiation effects. The major advantages of internal microdosimetry of radon progeny in bronchial airways are: (i) quantitative characterisation of non-uniform dose distributions and identification of target sites with enhanced carcinogenic potential, (ii) quantification of low doses of alpha particles by the number of cells hit and the dose received by those cells, (iii) illustration of the random variations of cellular doses by specific energy distributions and (iv) establishment of a direct link to cellular radiobiological effects. At present, a major limitation of microdosimetry is the extrapolation of the response of individual cells to the resulting tissue response, which is still not fully explored.

Ionic dialysance shows promise for quantification of dialysis dose in acute renal failure

Ionic dialysance shows promise for quantification of dialysis dose in acute renal failure

Renal Replacement Therapy in Acute Renal Failure: Which Index is Best for Dialysis dose Quantification?

The "delivered dose" of dialysis may significantly affect the outcome of acute renal failure (ARF) patients requiring dialysis. Our study aimed to elucidate which dose quantification method offers an appropriate parameter to compare different treatments in ARF patients. Six sustained low-efficiency daily dialysis (SLEDD), and 7 continuous venovenous hemofiltration (CVVH) patients with a prescribed Kt/V of 1.0 were studied during a single treatment. CVVH was studied over the first 24 hours after initiation. SLEDD was performed for 6-12 h. Solute clearance (K) was determined by direct dialysate quantification (DDQ). The single-pool Kt/V (spKt/V), equilibrated Kt/V (eqKt/V), equivalent renal urea clearance (EKRc), and solute removal index (SRI) were calculated. There were no significant differences at enrollment between the SLEDD and the CVVH groups in any patient characteristics except for the serum creatinine levels. The prescribed Kt/V of both groups was similar (SLEDD, 0.9+/-0.22; CVVH, 1.10+/-0.12, p=NS). The EKRc, which is used to verify kinetic equivalence among patients treated with differing renal replacement therapies (RRT), was higher in CVVH (15.7 in SLEDD; 27.4 in CVVH, p<0.0001), despite the fact that there was no difference between the delivered spKt/V for the SLEDD (1.05+/-0.40) and the CVVH (1.10+/-0.11) groups. The values for SRIurea (0.61 in SLEDD; 1.04 in CVVH, p=0.001), SRIcreatinine (0.55 in SLED; 1.02 in CVVH, p<0.0001), and SRIphosphate (1.81 in SLED; 3.60 in CVVH, p=0.03) were higher in CVVH. The EKRc is calculated assuming a steady state, which is an incorrect assumption in ARF patients with hypercatabolism. The SRI calculated using direct dialysate effluent quantification appears to be more reliable as an index of the dialysis dose compared to other methods in ARF patients. However, the use of the dialysate-side SRI is limited by the difficulty of dialysate effluent collection.

Radiation dose to contra lateral breast during treatment of breast malignancy by radiotherapy

External beam radiotherapy is being used regularly to treat the breast malignancy postoperatively. The contribution of collimator leakage and scatter radiation dose to contralateral breast is of concern because of high radio sensitivity of breast tissue for carcinogenesis. This becomes more important when the treated cancer breast patient is younger than 45 years and therefore the contralateral breast must be treated as organ at risk. Quantification of contralateral dose during primary breast irradiation is helpful to estimate the risk of radiation induced secondary breast malignancy. In present study contralateral breast dose was measured in 30 cancer breast patients undergoing external beam therapy by Co-60 teletherapy machine. Postoperative radiotherapy was delivered by medial and lateral tangential fields on alternate days in addition to supraclavicle field daily with 200 cGy/F to a total dose of 5000 cGy in 25 fractions. CaSO4: Dy thermoluminescence dosimeter discs were employed for these measurements. Three TLD discs were put on the surface of skin of contralateral breast, one at the level of nipple and two at 3 cms away from nipple on both side along the midline for each field. At the end treatment of each filed, TLD discs were removed and measured for dose after 24 h on Thelmador-6000 TLD reader. The dose at the contralateral breast nipple was to be 152.5 to 254.75 cGy for total primary breast dose of 5000 cGy in 25 equal fractions which amounted to 3.05-6.05% of total dose to diseased breast. Further it was observed that the maximum contribution of contralateral breast dose was due to medical tangential half blocked field. CaSO4; Dy thermoluminescence dosimetry is quite easy, accurate and convenient method to measure the contralateral breast dose.

Du sodium à la quantification de la dialyse

Sodium measurements are usually substituted by conductivity measurements in hemodialysis monitors. Ionic dialysance can be calculated from conductivity measurements and used for quantification of dialysis dose (Kt). Quantification of dialysis efficiency is based on the concept of clearance. The clearance of a solute is the blood volume fully depurated per unit time. The dialysance of a solute is the blood volume fully equilibrated with the dialysate entered into the dialyzer per unit time. For a solute absent from the diatysate delivered to the dialyzer, dia[ysance is equal to clearance. Because ions of quantitative importance (largely sodium) and urea have similar transfer characteristics through the dialyzer membrane, it can be expected that ionic dialysance is equal to urea dialysance and thus to urea clearance. Actually several studies have shown that ionic dialysance is a very good estimation of urea clearance. In comparison with the measurement of urea clearance, the measurement of ionic dialysance can be performed on-line, repeatedly and fully automatically, and is totally in expensive.

SU‐EE‐A3‐01: A Novel Filtering Approach for Local PET Verification of Proton Radiotherapy

Purpose: Proton radiotherapy activates positron emitters in tissue, which can be imaged with PET. However, the resulting PET image is not directly proportional to the delivered dose. We are investigating the spatial relationship between the dose distribution and its PET image without reverting to Monte Carlo methods. The first goal is to validate the proton range in the patient, and ultimately to reconstruct the spatial distribution of the actually delivered dose from its PET image. Method and Materials: The relationship between the proton dose and its PET image can be described mathematically as a convolution (filtering). We derive the convolution kernel analytically. This filter is unique for a given activation channel, independent of beam energy and specific absorber. The straightforward application of the method to determine the PET signal by locally filtering the planned dose distribution was validated through comparisons with Monte Carlo calculations and measured PET data in homogeneous and inhomogeneous media. The challenging inversion of the relationship, determining the dose from the PET signal, was initially explored for a simplified mono‐energetic case in a homogeneous absorber. Results: Activity depth profiles obtained with the convolution approach agreed with measured and Monte Carlo data within 1 mm in depth. In terms of absolute intensity, the agreement was within 1.5% between filtered and simulated profiles and 10% between filtered and measured data in the distal region. Attempts to recover the dose distribution from its PET image through a de‐convolution yielded promising results for idealized data but were strongly noise dependent. Conclusion: We have derived the spatial relationship between dose and positron activation and demonstrated the possibility to obtain the PET image measured after proton treatment by locally filtering the planned dose distribution. The inverse approach, i.e., direct dose quantification from the measured PET, seems possible but is very sensitive to noise.

Current status of dosing and quantification of acute renal replacement therapy. Part 2: Dosing paradigms and clinical implementation (Review Article)

The dosing and quantification of acute renal replacement therapy has emerged as one of the most pressing issues in the management of critically-ill patients with acute kidney injury. Although there is ongoing debate as to the best marker of uraemic injury in this setting, several landmark studies have identified clearance-related expressions of acute renal replacement therapy dose as important determinants of survival. Part 1 of this review examined the factors affecting the delivery of prescribed acute renal replacement therapy dose. Part 2 summarises and contextualises findings from recent dose-outcome studies, and reviews clinical tools to assist in the prescription and quantification of acute renal replacement therapy dose.

Dose distribution to the mediastinum and heart

CorrespondenceDose distribution to the mediastinum and heartB Jones and Y AkineB Jones1University Hospital Birmingham, Birmingham, B15 2TH, UK;2Proton Medical Research Centre, University of Tzukuba, JapanSearch for more papers by this author and Y Akine1University Hospital Birmingham, Birmingham, B15 2TH, UK;2Proton Medical Research Centre, University of Tzukuba, JapanSearch for more papers by this authorPublished Online:28 Jan 2014https://doi.org/10.1259/bjr/88462532SectionsPDF/EPUBFull Text ToolsAdd to favoritesDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InEmail About"Dose distribution to the mediastinum and heart." The British Journal of Radiology, 79(941), p. 448 References 1 Cominos M, Mosleh-Shirazi MA, Tait D, Henrys A, Cornes P. Quantification and reduction of cardiac dose in radical radiotherapy for oesophageal cancer. Br J Radiol 2005;78:1069–74. Link ISI, Google Scholar2 Satoshi I, Keiji N. Atushi O, Narikasu B. Long term toxicity after definitive chemoradiation of oesophageal and gastro-oesophageal junction cancers. J Clin Oncol 2003;21:115–20. Google Scholar3 Sugahara S, Tokuuye K, Okumura T, Nakahara A, Saida Y, Kagei K, et al. Clinical results of proton beam therapy for cancer of the oesophagus. Int J Radiat Oncol Biol Phys 2005;61:76–84. Crossref Medline ISI, Google Scholar Previous article Next article FiguresReferencesRelatedDetailsCited byCharged particle therapy for cancer: The inheritance of the Cavendish scientists?Applied Radiation and Isotopes, Vol. 67, No. 3Impact of Intrafractional Bowel Gas Movement on Carbon Ion Beam Dose Distribution in Pancreatic RadiotherapyInternational Journal of Radiation Oncology*Biology*Physics, Vol. 73, No. 4Effects of Interfractional Anatomical Changes on Water-Equivalent Pathlength in Charged-Particle Radiotherapy of Lung CancerJournal of Radiation Research, Vol. 50, No. 6The Potential Clinical Advantages of Charged Particle Radiotherapy using Protons or Light IonsClinical Oncology, Vol. 20, No. 7Effects of Intrafractional Motion on Water Equivalent Pathlength in Respiratory-Gated Heavy Charged Particle Beam RadiotherapyInternational Journal of Radiation Oncology*Biology*Physics, Vol. 69, No. 1 Volume 79, Issue 941May 2006Pages: 365-451 © The British Institute of Radiology History RevisedJanuary 18,2006ReceivedJanuary 03,2006AcceptedJanuary 18,2006Published onlineJanuary 28,2014 Metrics Download PDF

Reduction in urea distribution volume over time in clinically stable dialysis patients

We have previously shown that, assuming urea distribution volume (V) remains constant for 1 month, ionic dialysance (ID) allows the dialysis dose to be calculated without the need for blood sampling. The aim of this multicenter study was to verify whether the assumption of a constant V can be extended to 1 year. In clinically stable patients receiving thrice-weekly hemodialysis at 13 dialysis centers, V and Kt/V were assessed during three dialysis sessions at baseline and 1 year later using ID as dialyzer urea clearance and the single-pool urea kinetic model. Baseline albumin, hemoglobin, and C reactive protein were prespecified covariates for predicting the change in V over time. Of the 52 enrolled patients, 40 (25 males; age 63.0+/-13.5 years) completed the study. Baseline end-dialysis body weight (62.4+/-13.7 kg) showed a non-significant 1% reduction during follow-up (-0.6+/-2.8 kg; P=0.175), whereas V significantly decreased from 29.0+/-6.8 to 27.4+/-6.0 l (-1.6+/-3.0 l or 4.5%; P=0.002). The reduction in V was greater when baseline albumin was lower (P=0.001) and baseline V was higher (P=0.005). The single-pool K(t)/V calculated using baseline V underestimated the actual value by 0.07+/-0.16 (P=0.008). The slight underestimate of Kt/V during follow-up suggests that annual V evaluations may be sufficient for dialysis dose quantification as the only risk is underestimating the actually delivered dialysis dose. However, the relationship between baseline albumin and the reduction in V over time may have nutritional value, and suggests more frequent V evaluations.

High-performance liquid chromatography of lactose with evaporative light scattering detection, applied to determine fine particle dose of carrier in dry powder inhalation products

A method for quantification of the fine particle dose of lactose is described, using a hydrophilic interaction chromatography (HILIC) method and evaporative light scattering detection. The HILIC method used an aminopropyl column and a mobile phase consisting of acetonitril/water (80/20, v/v) for isocratic elution. Sensitive chromatography was obtained using a low concentration of water in the extraction solvent. The detection limit (RSD < 10%) at an injection volume of 10 μL is 10 μg/mL. Linearity was obtained in the range of 10–80 μg/mL ( R 2 > 0.99). A relative standard deviation (RSD) of 0.5% ( N = 6) demonstrated good precision of the optimized method.

Evaluation of scatter dose of dental titanium implants exposed to photon beams of different energies and irradiation angles in head and neck radiotherapy

In this study, quantification of backscatter doses between scattering titanium dental implant and the thermoluminescent dosimeter (TLD(100)) radiation detector at axial beam irradiation-angle range of 0-90 degrees in head and neck radiotherapy is done to evaluate irradiation angle dependency of dose enhancement contributing to osteoradionecrosis. A cylindrical titanium dental implant with diameter of 4 mm and length of 9 mm was implanted into a specially-designed human mandible phantom with a TLD100 chip placed on the buccal site and irradiated with 6 MV X, 25 MV X and Co-60 gamma sources at 19 different irradiation angles. Dose enhancement on a buccal site of the titanium implant depends on the incident beam angle. At angles of 65 degrees, 60 degrees and 40 degrees the maximum detected scatter doses over the titanium implant are 36%, 32% and 23% for Co-60 gamma, 6 MV X-ray and 25 MV X-ray, respectively. The dose enhancement at different beam angles was less pronounced in 25 MV X and more pronounced in Co-60 gamma irradiation. For the different radiation beams studied, the irradiation angle between scattering titanium dental implants and the central axis does not significantly affect the total dose that may lead to osteoradionecrosis of the mandible.