bluuebunny/crossref_metadata_2025 huggingface dataset:
TASTE PERCEPTION OF UMAMI‐RICH DISHES IN ITALIAN CULINARY TRADITION
Authors: SINESIO FIORELLA , COMENDADOR FRANCISCO JAVIER , PEPARAIO MARINA , MONETA ELISABETTA
Published: April 2009

The aim of this research project was to investigate umami taste properties of recipes based on Italian culinary tradition and prepared with umami‐rich ingredients, focusing on the impact of the preparation and ingredient combination. Gustative profiles were prepared for a traditional Italian dish, tender beef bouillon, usually consumed with pasta stuffed with beef. Four different samples were designed by changing the ingredients (with or without integrating Parmigiano cheese) and the preparation (cooking time) of the recipe. Panelists were rigorously trained for umami taste evaluation using monosodium L‐glutamate (MSG) aqueous solutions and were then asked to evaluate umami sensation in tender beef bouillon with or without added Parmigiano Reggiano. A majority of the panelists were able to distinguish correctly umami sensations induced by MSG. The level of umami enhancement induced by Parmigiano Reggiano was clearly perceived by the panelists, and this enhancement positively affected also other basic tastes; whereas the cooking time had no clear effect on the gustative perception.

PRACTICAL APPLICATIONS

In western countries, people do not know much about umami. This taste is defined as the “savoriness” of the glutamate. Umami‐taste substances are present in several foods, but whereas the taste of monosodium glutamate and 5′ nucleotides can be without difficulty identified in water solutions, which are usually employed for panel training, the ability to identify this primary taste decreases enormously in more complex matrices like food. This study describes a procedure for screening and training sensory panels and could serve as a guide in teaching panelists to recognize and quantify the umami taste in a multistimuli matrix like a food recipe or product.

It also provides a practical application in a recipe in which the umami taste is modulated by the culinary preparation and ingredients.
Indirect evidence for increased mechanosensitivity of jejunal secretomotor neurones in patients with idiopathic bile acid malabsorption
Authors: Bajor A. , Ung K.‐A. , Öhman L. , Simren M. , Thomas E. A. , Bornstein J. C. , Sjövall H.
Published: April 2009

Aim:  The interdigestive motor rhythm, the migrating motor complex (MMC), is accompanied by active secretion of chloride during periods of distally propagating maximal motor activity (MMC phase III). We studied the behaviour of this system in bile acid malabsorption (BAM), a relative common cause of chronic diarrhoea. We measured motor activity and transmucosal potential difference (PD, reflecting active chloride secretion), in the proximal jejunum in healthy controls (n = 18) and in a group of patients with BAM (n = 11). The phase III‐generated voltage was related to the degree of BAM quantified by the 75SeHCAT test.

Methods:  We used a multi‐channel intestinal infusion system to simultaneously measure jejunal pressure and PD. Saline passing calomel half‐cells was infused into the jejunum and subcutaneously. Pressure and PD were recorded in the fasting state and after a test meal.

Results:  In the absence of motor activity, jejunal PD was not significantly different from zero in either group. During MMC phase III, PD reached significantly higher mean and peak levels in BAM patients. The product of MMC phase III length multiplied by voltage, over 3 h, was also significantly higher in BAM patients (controls: median 307 mV × cm, range 70–398; BAM: median 511, range 274–2271, P < 0.01). This value was also significantly correlated with the degree of BAM as reflected by the 75SeHCAT test (P < 0.05).

Conclusion:  Phase III induced jejunal secretion may be upregulated in BAM patients, resulting in overload of colonic reabsorption capacity.
Greater growth hormone and insulin response in women than in men during repeated bouts of sprint exercise
Authors: Esbjörnsson M. , Norman B. , Suchdev S. , Viru M. , Lindhgren A. , Jansson E.
Published: April 2009

Aim:  In a previous study, sprint training has been shown to increase muscle cross‐sectional area in women but not in men [Eur J Appl Physiol Occup Physiol 74 (1996) 375]. We hypothesized that sprint exercise induces a different hormonal response in women than in men. Such a difference may contribute to explaining the observed gender difference in training response.

Method:  Metabolic and hormonal response to three 30‐s sprints with 20‐min rest between the sprints was studied in 18 physically active men and women.

Results:  Accumulation of blood lactate [interaction term gender (g) × time (t): P = 0.022], and plasma ammonia (g × t: P < 0.001) after sprint exercise was greater in men. Serum insulin increased after sprint exercise more so in women than in men (g × t: P = 0.020), while plasma glucose increased in men, but not in women (g × t: P < 0.001). Serum growth hormone (GH) increased in both women and men reaching similar peak levels, but with different time courses. In women the peak serum GH level was observed after sprint 1, whereas in men the peak was observed after sprint 3 (g × t; P < 0.001). Serum testosterone tended to decrease in men and increase in women (g × t: P = 0.065). Serum cortisol increased approx. 10–15% after sprint exercise, independent of gender (time: P = 0.005).

Conclusion:  Women elicited a greater response of serum GH and insulin to sprint exercise. This may contribute to explaining the earlier observed muscle hypertrophy in women in response to sprint training.
Integrated Water Resources Optimization Models: An Assessment of a Multidisciplinary Tool for Sustainable Water Resources Management Strategies
Authors: Mayer Alex , Muñoz‐Hernandez Andrea
Published: April 2009

Integrated water resources optimization models (IWROM) are tools that have been developed over the last decade for determining optimal water allocations among competing sectors. This article describes the state of the art of IWROMs. We illustrate the various approaches that have been taken to determine and maximize economic benefits of withdrawing water for various use categories in IWROM applications, including off‐stream human uses and in‐stream uses such as ecological flows. First, we describe the hydrologic simulators used in IWROM applications, and the mathematical methods used to solve the optimization problems. It is suggested that IWROMs (a) seek to model coupled human–nature relationships and mimic the impact of water resources management strategies on the environment at the basin scale; (b) allow for the simulation and assessment of economic policies and strategies on water resources management; (c) can support basin‐wide decision‐making; and (d) are particularly useful for water‐scarce regions. Finally, we have identify the need for improvements in (a) simulating biophysical systems; (b) handling model uncertainty; (c) inclusion of environmental flows and other relevant environmental factors through economic benefit functions; (d) accounting for social impacts related to shifts in water allocations among users; and (e) inclusion of stakeholders in the development of IWROMs.
Observing Forest Change to Enhance Border Sustainability in Chihuahua, Mexico
Authors: Currit Nate
Published: April 2009

The US–Mexico border is a place of great social and economic contrasts. Environmental systems straddle the border without regard for social or economic differences, and degradation is rarely confined to a single side of the border. Of major concern to the border region is the quantity and quality of water resources in the Rio Grande and its tributaries. The forests of the Sierra Madre Occidental in Chihuahua State are the source of much of this water and are an ideal place to study the impact of distant border influences, and this article examines remote sensing applications of Chihuahua's forest resources. Efforts to map Mexico's land‐cover are reviewed, and specific examples relating to Chihuahua are provided. Forest fire analysis at the national level is discussed, and opportunities for applying remotely sensed data and analysis to Chihuahua are identified. These include (i) long‐term monitoring of Chihuahua's forests; (ii) the estimation of biophysical forest parameters; and (iii) assessment of pre‐fire, active fire, and post‐fire forest characteristics and burn severity. Remote sensing of Chihuahua's forests will facilitate studies of downstream water quantity and quality and point to management practices that will create a sustainable border environment.
Climate change alters reproductive isolation and potential gene flow in an annual plant
Authors: Franks Steven J. , Weis Arthur E.
Published: April 2009

Climate change will likely cause evolution due not only to selection but also to changes in reproductive isolation within and among populations. We examined the effects of a natural drought on the timing of flowering in two populations of Brassica rapa and the consequences for predicted reproductive isolation and potential gene flow. Seeds were collected before and after a 5‐year drought in southern California from two populations varying in soil moisture. Lines derived from these seeds were raised in the greenhouse under wet and drought conditions. We found that the natural drought caused changes in reproductive timing and that the changes were greater for plants from the wet than from the dry site. This differential shift caused the populations to become more phenological similar, which should lead to less reproductive isolation and increased gene flow. We estimated a high level of assortative mating by flowering time, which potentially contributed to the rapid evolution of phenological traits following the drought. Estimates of assortative mating were higher for the wet site population, and assortative mating was reduced following the drought. This study shows that climate change can potentially alter gene flow and reproductive isolation within and among populations, strongly influencing evolution.
Radiopathological review of small bowel carcinoid tumours
Authors: Wong M , Kong A , Constantine S , Pathi R , Parrish FJ , Verma R , Lim C , Steer C
Published: April 2009

Small bowel carcinoid tumours are endocrine tumours of the gastrointestinal tract. This pictorial essay will review the pathology, clinical features, treatment and prognosis and illustrate the radiographic, computed tomographic, sonographic, magnetic resonance and nuclear medicine appearances of small bowel carcinoid tumours.
Cerebral hyperperfusion syndrome post‐carotid artery stenting
Authors: Tan GS‐S , Phatouros CC
Published: April 2009

Cerebral hyperperfusion syndrome is increasingly recognized as a complication in carotid artery stenting for severe internal carotid artery stenosis. This study reviews the cases of hyperperfusion syndrome occurring after this procedure. We reviewed our database of 170 cases of internal carotid artery stenting carried out at our hospital between January 1999 and June 2006. A radiology search was also carried out to identify those who had CT or MRI within 1 month of post‐carotid artery stenting. We had four patients who developed cerebral hyperperfusion syndrome. One patient developed cerebral oedema, one patient had petechial intracerebral haemorrhage and two patients had large intracerebral haemorrhages, one of whom died. This gives a risk of 2.3% (95% confidence interval 2.27–2.323). All patients with cerebral haemorrhage presented within 6 h. Both patients with large intracerebral haemorrhage had carotid stenting within 3 weeks after presentation of symptoms and all had critically severe stenosis of 95% or more. In our series, large intracerebral haemorrhage has occurred only in patients who have been treated early. Cerebral hyperperfusion is an uncommon but serious complication post‐carotid stenting. Further studies comparing early treatment of endarterectomy and carotid stenting are awaited.
Comprehensive Australasian multicentre dosimetric intercomparison: Issues, logistics and recommendations
Authors: Ebert MA , Harrison KM , Cornes D , Howlett SJ , Joseph DJ , Kron T , Hamilton CS , Denham JW
Published: April 2009

The present paper describes the logistics of the 2004–2008 Australasian Level III Dosimetry Intercomparison. Dosimetric intercomparisons (or ‘audits’) can be used in radiotherapy to evaluate the accuracy and quality of radiation delivery. An intercomparison was undertaken in New Zealand and Australia to evaluate the feasibility and logistics of ongoing dosimetric intercomparisons that evaluate all steps in the radiotherapy treatment process, known as a ‘Level III’ intercomparison. The study commenced in 2002 with the establishment of a study team, definition of the study protocol, acquisition of appropriate equipment and recruitment of participating radiotherapy centres. Measurements were undertaken between October 2004 and March 2008, and included collation of data on time, costs and logistics of the study. Forty independent Australian and New Zealand radiotherapy centres agreed to participate. Measurement visits were made to 37 of these centres. Data is presented on the costs of the study and the level of support required. The study involved the participation of 16 staff at the study centre who invested over 4000 hours in the study, and of over 200 professionals at participating centres. Recommendations are provided for future phantom‐based intercomparisons. It is hoped that the present paper will be of benefit to any centres or groups contemplating similar activities by identifying the processes involved in establishing the study, the potential hazards and pitfalls, and expected resource requirements.
Macular function after intravitreal triamcinolone acetonide injection for diabetic macular oedema
Authors: Karacorlu Murat , Ozdemir Hakan , Senturk Fevzi , Karacorlu Serra Arf , Uysal Omer
Published: April 2009

Purpose:  We aimed to evaluate the effect of intravitreal triamcinolone acetonide (IVTA) on macular function in patients with diabetic macular oedema (DMO).

Methods:  Eleven eyes in 11 patients with DMO were enrolled. In each eye, at baseline and at 30 days after IVTA injection, logMAR visual acuity (VA), macular sensitivity, fixation stability and fixation location by MP‐1 microperimetry and optical coherence tomography (OCT) foveal thickness were assessed.

Results:  Thirty days after IVTA injection, eyes with DMO showed a significant (p < 0.001) reduction in foveal thickness and significant (p < 0.01) increases in logMAR VA and MP‐1 retinal sensitivity (p < 0.001). There was also significant (p = 0.046) improvement in fixation location and some improvement in fixation stability, although the latter was not significant (p = 0.08).

Conclusions:  In eyes with DMO, short‐term improvement in retinal sensitivity and fixation properties can be achieved by IVTA injection.
Reducing the incidence of early postoperative vitreous haemorrhage by preoperative intravitreal bevacizumab in vitrectomy for diabetic tractional retinal detachment
Authors: Yeung Ling , Liu Laura , Wu Wei‐Chi , Kuo Ya‐Hui , Chao An‐Ning , Chen Kuan‐Jen , Yang Ko‐Jen , Chen Tun‐Lu , Lai Chi‐Chun
Published: April 2009

Acta Ophthalmol. 2010: 88: 635–640

Purpose:  This study aimed to evaluate whether preoperative intravitreal injection of bevacizumab reduces early postoperative vitreous haemorrhage (VH) in vitrectomy for diabetic tractional retinal detachment.

Methods:  We conducted a retrospective chart review of a consecutive, interventional case series. This included 29 eyes (27 patients) in the bevacizumab group and 40 eyes (37 patients) in the non‐bevacizumab group. For statistical analysis, each patient was assigned to one of four groups according to the haemostatic modalities used (group 1, none; group 2, only long‐acting gas; group 3, only preoperative intravitreal bevacizumab; group 4, both long‐acting gas and preoperative intravitreal bevacizumab). The primary outcome measure was the incidence of early postoperative VH. The secondary outcome measure was visual acuity (VA) at 1 month.

Results:  The incidence of early postoperative VH was highest in group 1 (63%), followed by group 2 (21%), group 3 (20%) and group 4 (5%). Group 3 showed the best visual recovery in the first month. All eyes in group 3 reached VA ≥ 1/100 at 1 month after the operation, compared with 44%, 29% and 42% in groups 1, 2 and 4, respectively.

Conclusions:  Preoperative intravitreal injection of bevacizumab may be useful for reducing early postoperative VH in vitrectomy for diabetic tractional retinal detachment. Eyes receiving preoperative intravitreal bevacizumab without the use of long‐acting gas achieved the best visual recovery at 1 month after the operation.
Combined intravitreal bevacizumab and triamcinolone in exudative age‐related macular degeneration
Authors: Jonas Jost B. , Libondi Teodosio , Golubkina Lidia , Spandau Ulrich H. , Schlichtenbrede Frank , Rensch Florian
Published: April 2009

Acta Ophthalmol. 2010: 88: 630–634

Purpose:  We report on the combined application of intravitreal bevacizumab and triamcinolone acetonide for treatment of exudative age‐related macular degeneration (AMD).

Methods:  The clinical interventional case‐series study included 16 patients (16 eyes) with exudative AMD who had previously received 3.5 ± 1.8 mono‐injections of bevacizumab (1.5 mg) without significant improvement in visual acuity (VA) or reduction in macular exudation. All patients underwent a combined intravitreal injection of bevacizumab (1.5 mg) and triamcinolone acetonide (about 20 mg). Main outcome measures were VA and macular thickness as determined by optical coherence tomography. All patients were re‐examined at 2–3 months after the intervention.

Results:  Visual acuity improved significantly (p = 0.03) from 0.80 ± 0.40 logMAR prior to the combined injection to 0.65 ± 0.42 logMAR at 3 months after the injection. An improvement of ≥ 1 Snellen line was found in eight subjects, an increase of ≥ 2 lines in five subjects, and an improvement of ≥ 3 lines in two subjects. One patient lost 1 line and one patient lost 3 lines. Central retinal thickness decreased significantly from 272 ± 62 μm to 220 ± 47 μm (p = 0.03). At the 6‐month follow‐up examination, central retinal thickness had increased again to 319 ± 142 μm, which was not significantly (p = 0.30) different from baseline measurements.

Conclusions:  The combined intravitreal application of bevacizumab and triamcinolone may temporarily be helpful in the treatment of exudative AMD if previous intravitreal bevacizumab mono‐injections have failed to improve vision and reduce macular oedema.
Effects of 17β‐oestradiol on rat detrusor smooth muscle contractility
Authors: Valeri Aurora , Brain Keith L. , Young John S. , Sgaragli Giampietro , Pessina Federica
Published: April 2009

The aim of this study was to investigate the effect of 17β‐oestradiol (E2) on detrusor smooth muscle contractility and its possible neuroprotective role against ischaemic‐like condition, which could arise during overactive bladder disease. The effect of E2was investigated on rat detrusor muscle strips stimulated with carbachol, KCl and electrically, in the absence or presence of a selective oestrogen receptor antagonist (ICI 182,780) and, by using confocal Ca2+imaging technique, measuring the amplitude (ΔF/F0) and the frequency of spontaneous whole cell Ca2+flashes. Moreover, the effect of 1 and 2 h of anoxia–glucopenia and reperfusion (A‐G/R), in the absence or presence of the hormone, was evaluated in rat detrusor strips perfused with Krebs solution which underwent electrical field stimulation to stimulate intrinsic nerves; the amplitude and the frequency of Ca2+flashes were also measured. 17β‐Oestradiol exhibited antispasmogenic activity assessed on detrusor strips depolarized with 60 mmKCl at two different Ca2+concentrations. 17β‐Oestradiol at the highest concentration tested (30 μm) significantly decreased detrusor contractions induced by all the stimuli applied. In addition, the amplitude and the frequency of spontaneous Ca2+flashes were significantly decreased in the presence of E2(10 and 30 μm) compared with control detrusor strips. In strips subjected to A‐G/R, a significant increase in the amplitude of both spontaneous and evoked flashes was observed. 17β‐Oestradiol was found to increase the recovery of detrusor strips subjected to A‐G/R. The ability of E2to suppress contraction in control conditions may explain its ability to aid recovery following A‐G/R.
Effect of body posture on postexercise parasympathetic reactivation in men
Authors: Buchheit M. , Al Haddad H. , Laursen P. B. , Ahmaidi S.
Published: April 2009

The aim of the present study was to assess the influence of body posture on post‐submaximal exercise parasympathetic reactivation and to examine whether this influence was preserved under a heightened sympathetic background. On four occasions, eleven moderately trained subjects (22.1 ± 3.0 years old) performed, in random order, two consecutive submaximal running bouts (CTs), each followed by 5 min passive recovery in an upright (Up), sitting (Sit), supine (Sup) or supine with legs up position (SupLu). Between both CTs, participants performed 150 s of supramaximal intermittent running (SI). Parasympathetic reactivation was assessed from heart rate recovery (HRR) and variability (HRV; e.g. rMSSD30 s) indices calculated during the 5 min recovery periods [i.e. before (N) and after SI (post‐SI)]. In the N condition, Sup position was associated with a faster and greater increase in rMSSD30 s than Sit and SupLu (both P < 0.01), which were all higher compared with Up (P < 0.001). A ‘time’ effect was shown in Sit, Sup and SupLu (all P < 0.05), but not in Up (P= 0.99). All N values were higher than post‐SI values (P < 0.001), except for Up, where a trend was apparent (P= 0.06). In the post‐SI condition, a position effect was preserved for HRR (P < 0.001), but not for HRV indices (P= 0.99 for rMSSD30 s). In conclusion, the supine position accelerated and increased parasympathetic reactivation more than the other three positions, but the posture effect was less evident following supramaximal exercise. In the context of an accentuated sympathetic background (i.e. post‐SI), postexercise HRV indices are less gravity dependent than HRR, reflecting more the exercise‐related changes in parasympathetic activity.
Sinogram bow‐tie filtering in FBP PET reconstruction
Authors: Abella M. , Vaquero J. J. , Soto‐Montenegro M. L. , Lage E. , Desco M.
Published: April 2009

Low‐pass filtering of sinograms in the radial direction is the most common practice to limit noise amplification in filtered back projection (FBP) reconstruction of positron emission tomography studies. Other filtering strategies have been proposed to prevent the loss in resolution due to low‐pass radial filters, although results have been diverse. Using the well‐known properties of the Fourier transform of a sinogram, the authors defined a binary mask that matches the expected shape of the support region in the Fourier domain of the sinogram (“bow tie”). This mask was smoothed by a convolution with a ten‐point Gaussian kernel which not only avoids ringing but also introduces a pre‐emphasis at low frequencies. A new filtering scheme for FBP is proposed, comprising this smoothed bow‐tie filter combined with a standard radial filter and an axial filter. The authors compared the performance of the bow‐tie filtering scheme with that of other previously reported methods: Standard radial filtering, angular filtering, and stackgram‐domain filtering. All the quantitative data in the comparisons refer to a baseline reconstruction using a ramp filter only. When using the smallest size of the Gaussian kernel in the stackgram domain, the authors achieved a noise reduction of 33% at the cost of degrading radial and tangential resolutions (14.5% and 16%, respectively, for cubic interpolation). To reduce the noise by 30%, the angular filter produced a larger degradation of contrast (3%) and tangential resolution (46% at from the center of the field of view) and showed noticeable artifacts in the form of circular blurring dependent on the distance to the center of the field of view. For a similar noise reduction (33%), the proposed bow‐tie filtering scheme yielded optimum results in resolution (gain in radial resolution of 10%) and contrast (1% increase) when compared with any of the other filters alone. Experiments with rodent images showed noticeable image quality enhancement when using the proposed bow‐tie filtering scheme.
Assessment of the limiting spatial resolution of an MRI scanner by direct analysis of the edge spread function
Authors: Delakis Ioannis , Xanthis Christos , Kitney Richard Ian
Published: April 2009

Limiting spatial resolution is a key metric of the quality of magnetic resonance (MR) images, which can provide an indication of the smallest region that can effectively be imaged. In this paper a novel methodology for measuring the limiting spatial resolution of MR images is mathematically analyzed and successfully implemented on phantom images. The methodology presented in this paper is based on a direct fit of a mathematical expression of the edge spread function (ESF) profile to the ESF data acquired at the interface between different materials. The mathematical expression of ESF was determined by approximating the line spread function (LSF) of the system with a sinc function. The proposed methodology can be applied using signal data from magnitude MRI spin echo images and is not sensitive to noise amplification introduced by differentiating the ESF to produce the LSF, as performed in previous studies. In addition, the proposed methodology provides a quantitative, representative measurement of the limiting spatial resolution of MR images.
Ophthalmic applicators: An overview of calibrations following the change to SI units
Authors: Holmes Shannon M. , Micka John A. , DeWerd Larry A.
Published: April 2009

Since the NIST dose to water standard for ophthalmic applicators was introduced, numerous sources have undergone calibration either at NIST or at the University of Wisconsin Accredited Dosimetry Calibration Laboratory (UWADCL). From 1997 to 2008, 222 of these beta‐emitting sources were calibrated at the UWADCL, and prior reference source strength values were available for 149 of these sources. A survey of UWADCL ophthalmic applicator calibrations is presented here, demonstrating an average discrepancy of with a standard deviation of between prior reference values and the NIST‐traceable UWADCL absorbed dose to water calibrations. Values ranged from to .
Magnetic nanoparticle temperature estimation
Authors: Weaver John B. , Rauwerdink Adam M. , Hansen Eric W.
Published: April 2009

The authors present a method of measuring the temperature of magnetic nanoparticles that can be adapted to provide in vivo temperature maps. Many of the minimally invasive therapies that promise to reduce health care costs and improve patient outcomes heat tissue to very specific temperatures to be effective. Measurements are required because physiological cooling, primarily blood flow, makes the temperature difficult to predict a priori. The ratio of the fifth and third harmonics of the magnetization generated by magnetic nanoparticles in a sinusoidal field is used to generate a calibration curve and to subsequently estimate the temperature. The calibration curve is obtained by varying the amplitude of the sinusoidal field. The temperature can then be estimated from any subsequent measurement of the ratio. The accuracy was 0.3 °K between 20 and using the current apparatus and half‐second measurements. The method is independent of nanoparticle concentration and nanoparticle size distribution.
Fixed gantry tomosynthesis system for radiation therapy image guidance based on a multiple source x‐ray tube with carbon nanotube cathodes
Authors: Maltz Jonathan S. , Sprenger Frank , Fuerst Jens , Paidi Ajay , Fadler Franz , Bani‐Hashemi Ali R.
Published: April 2009

The authors present the design and simulation of an imaging system that employs a compact multiple source x‐ray tube to produce a tomosynthesis image from a set of projections obtained at a single tube position. The electron sources within the tube are realized using cold cathode carbon nanotube technology. The primary intended application is tomosynthesis‐based 3D image guidance during external beam radiation therapy. The tube, which is attached to the gantry of a medical linear accelerator (linac) immediately below the multileaf collimator, operates within the voltage range of and contains a total of 52 sources that are arranged in a rectilinear array. This configuration allows for the acquisition of tomographic projections from multiple angles without any need to rotate the linac gantry. The x‐ray images are captured by the same amorphous silicon flat panel detector employed for portal imaging on contemporary linacs. The field of view (FOV) of the system corresponds to that part of the volume that is sampled by rays from all sources. The present tube and detector configuration provides an FOV in the plane of the linac isocenter when the imaging detector is placed from the isocenter. Since this tomosynthesis application utilizes the extremities of the detector to record image detail relating to structures near the isocenter, simultaneous treatment and imaging is possible for most clinical cases, where the treated target is a small region close to the linac isocenter. The tomosynthesis images are reconstructed using the simultaneous iterative reconstruction technique, which is accelerated using a graphic processing unit. The authors present details of the system design as well as simulated performance of the imaging system based on reprojections of patient CT images.
Search for IMRT inverse plans with piecewise constant fluence maps using compressed sensing techniques
Authors: Zhu Lei , Xing Lei
Published: April 2009

An intensity‐modulated radiation therapy (IMRT) field is composed of a series of segmented beams. It is practically important to reduce the number of segments while maintaining the conformality of the final dose distribution. In this article, the authors quantify the complexity of an IMRT fluence map by introducing the concept of sparsity of fluence maps and formulate the inverse planning problem into a framework of compressing sensing. In this approach, the treatment planning is modeled as a multiobjective optimization problem, with one objective on the dose performance and the other on the sparsity of the resultant fluence maps. A Pareto frontier is calculated, and the achieved dose distributions associated with the Pareto efficient points are evaluated using clinical acceptance criteria. The clinically acceptable dose distribution with the smallest number of segments is chosen as the final solution. The method is demonstrated in the application of fixed‐gantry IMRT on a prostate patient. The result shows that the total number of segments is greatly reduced while a satisfactory dose distribution is still achieved. With the focus on the sparsity of the optimal solution, the proposed method is distinct from the existing beamlet‐ or segment‐based optimization algorithms.
The use of novel gradient directions with DTI to synthesize data with complicated diffusion behavior
Authors: Yanasak Nathan E. , Allison Jerry D. , Hu Tom C.‐C. , Zhao Qun
Published: April 2009

This study demonstrates a new technique for synthesizing diffusion tensor imaging (DTI) data sets that exhibit complex diffusion characteristics by performing operations on acquired DTI data of simple structures with anisotropic diffusive properties. The motivation behind this technique is to characterize the behavior of noise in complicated data using a phantom. Compared to simulations, an advantage to this approach is that the acquired data contain noise characteristic of the scanner and protocol. Using this technique, a simple capillary phantom is employed to infer the quality of data for more clinically realistic tissue structures (e.g., crossing fiber tracts). A water‐filled phantom containing capillary arrays was constructed to demonstrate this technique, which uses a DTI protocol with typical clinical parameters. Eigenvalues and fractional anisotropy were calculated for the initial prolate data. Data were adjusted to synthesize different apparent diffusion coefficient (ADC) spatial distributions, which were compared to theoretical and analytical models. RMS differences and volumetric overlap between expected and measured ADC distributions were quantified for all synthesized distributions. Differences between synthesized and actual distributions were discussed.
Electron beam quality control using an amorphous silicon EPID
Authors: Beck J. A. , Budgell G. J. , Roberts D. A. , Evans P. M.
Published: April 2009

An amorphous silicon EPID has been investigated to determine whether it is capable of quality control constancy measurements for linear accelerator electron beams. The EPID grayscale response was found to be extremely linear with dose over a wide dose range and, more specifically, for exposures of 95–100 MU. Small discrepancies of up to 0.8% in linearity were found at 6 MeV (8–15 MeV showed better agreement). The shape of the beam profile was found to be significantly altered by scatter in air over the approximately 60 cm gap between the end of the applicator and the EPID. Nevertheless, relative changes in EPID‐measured profile flatness and symmetry were linearly related to changes in these parameters at 95 cm focus to surface distance (FSD) measured using a 2D diode array. Similar results were obtained at 90° and 270° gantry angles. Six months of daily images were acquired and analyzed to determine whether the device is suitable as a constancy checker. EPID output measurements agreed well with daily ion chamber measurements, with a 0.8% standard deviation in the difference between the two measurement sets. When compared to weekly parallel plate chamber measurements, this figure dropped to 0.5%. A Monte Carlo (MC) model of the EPID was created and demonstrated excellent agreement between MC‐calculated profiles in water and the EPID at 95 and 157 cm FSD. Good agreement was also found with measured EPID profiles, demonstrating that the EPID provides an accurate measurement of electron profiles. The EPID was thus shown to be an effective method for performing electron beam daily constancy checks.
Investigation of lung nodule detectability in low‐dose 320‐slice computed tomography
Authors: Silverman J. D. , Paul N. S. , Siewerdsen J. H.
Published: April 2009

Low‐dose imaging protocols in chest CT are important in the screening and surveillance of suspicious and indeterminate lung nodules. Techniques that maintain nodule detectability yet permit dose reduction, particularly for large body habitus, were investigated. The objective of this study was to determine the extent to which radiation dose can be minimized while maintaining diagnostic performance through knowledgeable selection of reconstruction techniques. A 320‐slice volumetric CT scanner (Aquilion ONE™, Toshiba Medical Systems) was used to scan an anthropomorphic phantom at doses ranging from up to that typical of low‐dose CT (LDCT, ) and diagnostic CT . Radiation dose was measured via Farmer chamber and MOSFET dosimetry. The phantom presented simulated nodules of varying size and contrast within a heterogeneous background, and chest thickness was varied through addition of tissue‐equivalent bolus about the chest. Detectability of a small solid lung nodule (3.2 mm diameter, −37 HU, typically the smallest nodule of clinical significance in screening and surveillance) was evaluated as a function of dose, patient size, reconstruction filter, and slice thickness by means of nine‐alternative forced‐choice (9AFC) observer tests to quantify nodule detectability. For a given reconstruction filter, nodule detectability decreased sharply below a threshold dose level due to increased image noise, especially for large body size. However, nodule detectability could be maintained at lower doses through knowledgeable selection of (smoother) reconstruction filters. For large body habitus, optimal filter selection reduced the dose required for nodule detection by up to a factor of (from for sharp filters to for the optimal filter). The results indicate that radiation dose can be reduced below the current low‐dose (5 mGy) and ultralow‐dose (1 mGy) levels with knowledgeable selection of reconstruction parameters. Image noise, not spatial resolution, was found to be the limiting factor in detection of small lung nodules. Therefore, the use of smoother reconstruction filters may permit lower‐dose protocols without trade‐off in diagnostic performance.
On‐board SPECT for localizing functional targets: A simulation study
Authors: Roper Justin , Bowsher James , Yin Fang‐Fang
Published: April 2009

Single photon emission computed tomography (SPECT) was investigated for imaging on‐board radiation therapy machines in order to localize functional and molecular targets. A computer‐simulated female NCAT phantom was positioned supine on a flat‐top treatment couch. Twenty tumor locations were defined in the upper torso. The eight lung tumors were subject to the effects of respiratory motion. Tumor diameters of 10.8, 14.4, and 21.6 mm were simulated for tumor‐to‐background ratios of 3:1 and 6:1 that are characteristic of the radiotracer ‐sestamibi. Projection images representing scan times of 4, 8, and 20 min were simulated for an anterior, half‐circular trajectory. Images were reconstructed with attenuation correction by ordered‐subsets expectation maximization (OSEM) using six subsets and five iterations. Contrast‐to‐noise ratios (CNRs) were calculated from ensembles of 25 images. Cross correlation with a noise‐free tumor template was used to select the most suspicious tumor location within a 14.4‐mm‐radius search volume surrounding each tumor, with only that one tumor in each search volume. Localization accuracy was assessed by calculating average distances between measured and true tumor locations. Localization accuracy and CNRs were strongly affected by tumor location relative to the detector trajectory. For example, CNR values near the chest wall were greater by a factor of 3.5 than for tumors near the spine and posterior ribs, a much greater effect than the factor of 1.6 difference in CNR between 6:1 and 3:1 tumor uptakes. Typically, tumors of 6:1 uptake were localized as accurately with 4 min of scan time as tumors of 3:1 uptake that had been imaged for 20 min. Using 4 min scans, 14.4 and 21.6 mm anterior tumors of 6:1 uptake were localized within 2 mm. These results suggest that SPECT, on‐board radiation therapy machines, may be a viable modality for localizing certain functional and molecular targets using relatively short scan times.
Measurement of relative output factors for the 8 and 4 mm collimators of Leksell Gamma Knife Perfexion by film dosimetry
Authors: Novotny Josef , Bhatnagar Jagdish P. , Quader Mubina A. , Bednarz Greg , Lunsford L. Dade , Huq M. Saiful
Published: April 2009

Three types of films, Kodak EDR2, Gafchromic EBT, and Gafchromic MD‐V2‐55, were used to measure relative output factors of 4 and 8 mm collimators of the Leksell Gamma Knife Perfexion. The optical density to dose calibration curve for each of the film types was obtained by exposing the films to a range of known doses. Ten data points were acquired for each of the calibration curves in the dose ranges from 0 to 4 Gy, 0 to 8 Gy, and 0 to 80 Gy for Kodak EDR2, Gafchromic EBT, and Gafchromic MD‐V2‐55 films, respectively. For the measurement of relative output factors, five films of each film type were exposed to a known dose. All films were scanned using EPSON EXPRESSION 10000 XL scanner with 200 dpi resolution in 16 bit gray scale for EDR2 film and 48 bit color scale for Gafchromic films. The scanned images were imported in the red channel for both Gafchromic films. The background corrections from an unexposed film were applied to all films. The output factors obtained from film measurements were in a close agreement both with the Monte Carlo calculated values of 0.924 and 0.805 for 8 and 4 mm collimators, respectively. These values are provided by the vendor and used as default values in the vendor's treatment planning system. The largest differences were noted for the Kodak EDR 2 films (−2.1% and −4.5% for 8 and 4 mm collimators, respectively). The best agreement observed was for EBT Gafchromic film (−0.8% and differences for 8 and 4 mm collimators, respectively). Based on the present values, no changes in the default relative output factor values were made in the treatment planning system.
Closed bore XMR (CBXMR) systems for aortic valve replacement: Active magnetic shielding of x‐ray tubes
Authors: Bracken John A. , DeCrescenzo Giovanni , Komljenovic Philip , Lillaney Prasheel V. , Fahrig Rebecca , Rowlands J. A.
Published: April 2009

Hybrid closed bore x‐ray/MRI systems are being developed to improve the safety and efficacy of percutaneous aortic valve replacement procedures by harnessing the complementary strengths of the x‐ray and MRI modalities in a single interventional suite without requiring patient transfer between two rooms. These systems are composed of an x‐ray C‐arm in close proximity to an MRI scanner. The MRI magnetic fringe field can cause the electron beam in the x‐ray tube to deflect. The deflection causes the x‐ray field of view to shift position on the detector receptacle. This could result in unnecessary radiation exposure to the patient and the staff in the cardiac catheterization laboratory. Therefore, the electron beam deflection must be corrected. The authors developed an active magnetic shielding system that can correct for electron beam deflection to within an accuracy of 5% without truncating the field of view or increasing exposure to the patient. This system was able to automatically adjust to different field strengths as the external magnetic field acting on the x‐ray tube was changed. Although a small torque was observed on the shielding coils of the active shielding system when they were placed in a magnetic field, this torque will not impact their performance if they are securely mounted on the x‐ray tube and the C‐arm. The heating of the coils of the shielding system for use in the clinic caused by electric current was found to be slow enough not to require a dedicated cooling system for one percutaneous aortic valve replacement procedure. However, a cooling system will be required if multiple procedures are performed in one session.
Characterization of a mini‐multileaf collimator in a proton beamline
Authors: Daartz J. , Bangert M. , Bussière M. R. , Engelsman M. , Kooy H. M.
Published: April 2009

A mini‐multileaf collimator (MMLC) was mounted as a field shaping collimator in a proton beamline at the Massachusetts General Hospital. The purpose is to evaluate the device's dosimetric and mechanical properties for the use in a proton beamline. For this evaluation, the authors compared MMLC and brass aperture shaped dose distributions with regard to lateral and depth dose properties. The lateral fall off is generally broader with the MMLC, with difference varying with proton range from 0.2 to 1.2 mm. Central axis depth dose curves did not show a difference in peak‐to‐entrance ratio, peak width, distal fall off, or range. Two‐dimensional dose distributions to investigate the conformity of MMLC shaped doses show that the physical leaf width of does not have a significant impact. All differences seen in dose distribution shaped by the MMLC versus brass apertures were shown to be clinically insignificant. Measured neutron doses of 0.03–0.13 mSv/Gy for a closed brass beam block (depending on range) are very low compared to the previously published data. Irradiation of the tungsten MMLC, however, produced 1.5–1.8 times more neutrons than brass apertures. Exposure of the staff resulting from activation of the device is below regulatory limits. The measurements established an equivalency between aperture and MMLC shaped dose distributions.
Comparison of power spectra for tomosynthesis projections and reconstructed images
Authors: Engstrom Emma , Reiser Ingrid , Nishikawa Robert
Published: April 2009

Burgess et al. [Med. Phys. 28, 419–437 (2001)] showed that the power spectrum of mammographic breast background follows a power law and that lesion detectability is affected by the power‐law exponent which measures the amount of structure in the background. Following the study of Burgess et al., the authors measured and compared the power‐law exponent of mammographic backgrounds in tomosynthesis projections and reconstructed slices to investigate the effect of tomosynthesis imaging on background structure. Our data set consisted of 55 patient cases. For each case, regions of interest (ROIs) were extracted from both projection images and reconstructed slices. The periodogram of each ROI was computed by taking the squared modulus of the Fourier transform of the ROI. The power‐law exponent was determined for each periodogram and averaged across all ROIs extracted from all projections or reconstructed slices for each patient data set. For the projections, the mean averaged across the 55 cases was 3.06 (standard deviation of 0.21), while it was 2.87 (0.24) for the corresponding reconstructions. The difference in for a given patient between the projection ROIs and the reconstructed ROIs averaged across the 55 cases was 0.194, which was statistically significant . The 95% CI for the difference between the mean value of for the projections and reconstructions was [0.170, 0.218]. The results are consistent with the observation that the amount of breast structure in the tomosynthesis slice is reduced compared to projection mammography and that this may lead to improved lesion detectability.