bluuebunny/crossref_metadata_2025 huggingface dataset:
Hepatic nodular hamartoma containing liver cysts, ductal plate malformations and peribiliary glands
Authors: Terada Tadashi
Published: December 2010

An 83‐year‐old man with hepatocellular carcinoma was found to have a low‐echoic and low‐density tumor measuring 7.2 cm × 5.6 cm. Caroli's disease was absent. Clinical diagnosis was intrahepatic cholangiocarcinoma. Three cores of liver biopsy were obtained from the tumor. Histologically, it consisted of liver cysts, ductal plate malformations, peribiliary glands, hepatocytes, portal tracts and mesenchymal tissue. Apparent features of cirrhosis were not found. The liver cysts were lined by a layer of cuboidal cells with multiple papillary protrusions. The ductal plate malformations resembled fetal ductal plates. The peribiliary glands were seromucous glands. Immunohistochemically, these abnormal ductal structures showed positive reaction to biliary type cytokeratins, namely, cytokeratin (CK)7, CK8, CK18 and CK19. Mucin gene expression showed that these biliary structures are positive for fetal antigen MUC1. MUC6 is also positive in them. Aberrant expression of CD10 was observed in these biliary structures. MUC2, MUC5AC and CDX2 were negative. The author thinks that this lesion is hepatic hamartoma with ductal plate malformations, liver cysts and peribiliary glands. To the best of the author's knowledge, this type of liver nodule has not been reported in the published work.
Carnosic acid prevents obesity and hepatic steatosis in ob/ob mice
Authors: Wang Ting , Takikawa Yasuhiro , Satoh Takumi , Yoshioka Yoshichika , Kosaka Kunio , Tatemichi Yoshinori , Suzuki Kazuyuki
Published: December 2010

Aim:  Carnosic acid (CA) inhibits adipogenesis in vitro. The present study evaluated the therapeutic effects of CA in ob/ob mice.

Methods:  The experimental animals were given a standard chow diet with or without CA for 5 weeks. Bodyweight gain and food intake were measured during this period. Magnetic resonance imaging analysis, histological examination, serum chemistry analysis and intraperitoneal glucose tolerance test (IPGTT) were all performed.

Results:  The mice fed CA experienced significant weight loss and reduced visceral adiposity, in addition to significantly reduced serum triglyceride (TG) and cholesterol levels. Importantly, CA had a dramatic effect on the liver by reducing the hepatic TG content, thus decreasing serum alanine aminotransferase levels. In addition, IPGTT revealed that CA significantly improved glucose tolerance.

Conclusion:  These data suggest that CA is a novel therapeutic agent for obesity‐related non‐alcoholic fatty liver disease.
Craniofacial parameters of Syrian children with β‐thalassemia major
Authors: Takriti Moutaz , Dashash Mayssoon
Published: January 2011

Abstract Aim:  To investigate cephalometric craniofacial parameters (skeletal and dental) of β‐thalassemic‐major patients and to compare findings with a group of healthy patients in the same age group.

Methods:  Fifty‐one Syrian thalassemic‐major patients aged 8–12 years were recruited. Lateral cephalometric radiographs were taken. Linear and angular cephalometric measurements were recorded and compared with Syrian controls (n = 50) in the same age group.

Results:  Thalassemic patients, when compared with controls, showed significant retrognathia in the mandible (reduced sella [mid‐point of sella turcica]–nasion [most anterior point on the frontonasal suture] B‐point [deepest point on the concavity of the mandibular profile between the alveolar crest and the point of the chin] angle, and decreased sella–nasion–pogonion [most anterior point on the bony chin] angle, P < 0.0001), a significant decrease in ramus height (articulare–gonian = 36.51 ± 3.87 mm, P < 0.0001). They also exhibited a significant class II skeletal pattern (P < 0.0001) and a convex facial profile as the nasion A‐point (deepest point on maxillary profile between the anterior nasal spine and the alveolar crest) pogonion angle and maxillomandibular A‐point–nasion P‐point angle increased. They also showed a highly‐significant decrease in the total posterior facial height (sella gonion [most posterior, inferior point on the angle of the mandible] = 64.24 ± 5.73 mm, P < 0.0001) and significant increase in the total anterior facial height (N–Me = 110.78 ± 6.66 mm, P = 0.009) when compared to controls.

Conclusion:  Thalassemic patients exhibited a skeletal class II malocclusion, retrognathia of the mandible, a short height of the ramus, an increase in anterior facial height, and a decrease in posterior facial height.
Subscales measuring symptoms of non‐specific depression, anhedonia, and anxiety in the Edinburgh Postnatal Depression Scale
Authors: Tuohy Alan. , McVey Cynthia.
Published: December 2010

Objectives

There has been considerable research and clinical interest in the comorbidity of anxiety and depression in the post‐partum period, and specifically in the possibility that the commonly used Edinburgh Postnatal Depression Scale (EPDS) incorporates an anxiety component. We hypothesized that the recommended version of factor analysis (Fabrigar, Wegener, MacCallum, & Strahan, 1999) would identify such covert dimensions more reliably than the commonly used principal components analysis with varimax rotation and eigenvalues greater than 1.

Design

Principal axis factor extraction with parallel analysis and oblique (direct quartimin) factor rotation was applied to the 10 EPDS items.

Method

The study used a sample of recent mothers recruited and assessed via e‐mail and the Internet (N = 440). In addition to the EPDS, the Hospital Anxiety and Depression Scale (HADS) and the Positive and Negative Affect Scales (PANAS) were also administered.

Results

Three factors were found, which were identified as ‘non‐specific depressive symptoms’, ‘anhedonia’, and ‘anxietal symptoms’ subscales, respectively. These subscales were regressed on the HADS anxiety and depression and the PANAS positive and negative affectivity scales, with results substantially consistent with current structural models of the taxonomy of the emotional disorders.

Limitations

The data were obtained from a self‐selected non‐clinical sample. In addition, it is known that the use of computer‐based assessment may tend to inflate self‐report scores.

Conclusions

It was concluded that there is now sufficient evidence that clinicians should not assume the EPDS to be unidimensional, but should assess all three subscales when screening for susceptibility to post‐partum depression and/or post‐partum anxiety.
Positive affect and psychosocial processes related to health
Authors: Steptoe Andrew , O'Donnell Katie , Marmot Michael , Wardle Jane
Published: December 2010

Positive affect is associated with longevity and favourable physiological function. We tested the hypothesis that positive affect is related to health‐protective psychosocial characteristics independently of negative affect and socio‐economic status. Both positive and negative affect were measured by aggregating momentary samples collected repeatedly over 1 day, and health‐related psychosocial factors were assessed by questionnaire in a sample of 716 men and women aged 58–72 years. Positive affect was associated with greater social connectedness, emotional and practical support, optimism and adaptive coping responses, and lower depression, independently of age, gender, household income, paid employment, smoking status, and negative affect. Negative affect was independently associated with negative relationships, greater exposure to chronic stress, depressed mood, pessimism, and avoidant coping. Positive affect may be beneficial for health outcomes in part because it is a component of a profile of protective psychosocial characteristics.
Chronic oral ingestion of l‐carnitine and carbohydrate increases muscle carnitine content and alters muscle fuel metabolism during exercise in humans
Authors: Wall Benjamin T. , Stephens Francis B. , Constantin‐Teodosiu Dumitru , Marimuthu Kanagaraj , Macdonald Ian A. , Greenhaff Paul L.
Published: January 2011

Non‐technical summary After 30 years of endeavour, this is the first study to show that muscle carnitine content can be increased in humans by dietary means and, perhaps more importantly, that carnitine plays a dual role in skeletal muscle fuel metabolism that is exercise intensity dependent. Specifically, we have shown that increasing muscle total carnitine content reduces muscle carbohydrate use during low intensity exercise, consistent with an increase in muscle lipid utilisation. However, during high intensity exercise muscle carnitine loading results in a better matching of glycolytic, pyruvate dehydrogenase complex and mitochondrial flux, thereby reducing muscle anaerobic energy generation. Collectively, these metabolic effects resulted in a reduced perception of effort and increased work output during a validated exercise performance test. These findings have significant implications for athletic performance and pathophysiological conditions where fat oxidation is impaired or anaerobic ATP production is increased during exercise.
‘Integrative Physiology 2.0’: integration of systems biology into physiology and its application to cardiovascular homeostasis
Authors: Kuster Diederik W. D. , Merkus Daphne , van der Velden Jolanda , Verhoeven Adrie J. M. , Duncker Dirk J.
Published: January 2011

Abstract  Since the completion of the Human Genome Project and the advent of the large scaled unbiased ‘‐omics’ techniques, the field of systems biology has emerged. Systems biology aims to move away from the traditional reductionist molecular approach, which focused on understanding the role of single genes or proteins, towards a more holistic approach by studying networks and interactions between individual components of networks. From a conceptual standpoint, systems biology elicits a ‘back to the future’ experience for any integrative physiologist. However, many of the new techniques and modalities employed by systems biologists yield tremendous potential for integrative physiologists to expand their tool arsenal to (quantitatively) study complex biological processes, such as cardiac remodelling and heart failure, in a truly holistic fashion. We therefore advocate that systems biology should not become/stay a separate discipline with ‘‐omics’ as its playing field, but should be integrated into physiology to create ‘Integrative Physiology 2.0’.
4D dose‐position verification in radiation therapy using the RADPOS system in a deformable lung phantom
Authors: Cherpak Amanda , Serban Monica , Seuntjens Jan , Cygler Joanna E.
Published: December 2010

Purpose:

A novel 4Din vivo dosimetry system (RADPOS), in conjunction with a deformable lung phantom, has been evaluated as a potential quality assurance tool for 4D radiotherapy.

Methods:

RADPOS detectors, which consist of a MOSFET dosimeter combined with an electromagnetic positioning probe, were placed inside the deformable lung phantom. One detector was positioned directly inside a tumor embedded in the lung phantom and another was positioned inside the lung portion of the phantom, outside the tumor. CT scans were taken with the phantom at three breathing phases, and for each phase, the detector position inside the phantom was read with the RADPOS software and compared to the position as determined from the CT data. These values were also compared to RADPOS measurements taken with the phantom on the couch of a Varian Clinac 6EX linac. The deformable phantom and the RADPOS system were also used in two radiation delivery scenarios: (1) A simulation of a free‐breathing delivery and (2) a simulation of an adaptive treatment.

Results:

Compared to CT imaging, the RADPOS positional accuracy was found to be better than 2.5 mm. The radial displacement measurements taken in the CT and linac rooms agreed to within an average of. Hence, the system can provide relative displacement measurements in the treatment room, consistent with measurements made in the CT room. For the free‐breathing delivery, the total dose reported by RADPOS agreed to within 4% and 5% of the treatment planning doses in the tumor and the lung portion of the phantom, respectively. The RADPOS‐measured dose values for the adaptive delivery were within 1.5% of the treatment plan values, which was well within the estimated experimental uncertainties.

Conclusions:

This work has shown that the deformable lung phantom‐RADPOS system can be an efficient quality assurance tool for 4D radiation therapy.
Patient‐specific radiation dose and cancer risk estimation in CT: Part I. Development and validation of a Monte Carlo program
Authors: Li Xiang , Samei Ehsan , Segars W. Paul , Sturgeon Gregory M. , Colsher James G. , Toncheva Greta , Yoshizumi Terry T. , Frush Donald P.
Published: December 2010

Purpose:

Radiation‐dose awareness and optimization in CT can greatly benefit from a dose‐reporting system that provides dose and risk estimates specific to each patient and each CT examination. As the first step toward patient‐specific dose and risk estimation, this article aimed to develop a method for accurately assessing radiation dose from CT examinations.

Methods:

A Monte Carlo program was developed to model a CT system (LightSpeed VCT, GE Healthcare). The geometry of the system, the energy spectra of the x‐ray source, the three‐dimensional geometry of the bowtie filters, and the trajectories of source motions during axial and helical scans were explicitly modeled. To validate the accuracy of the program, a cylindrical phantom was built to enable dose measurements at seven different radial distances from its central axis. Simulated radial dose distributions in the cylindrical phantom were validated against ion chamber measurements for single axial scans at all combinations of tube potential and bowtie filter settings. The accuracy of the program was further validated using two anthropomorphic phantoms (a pediatric one‐year‐old phantom and an adult female phantom). Computer models of the two phantoms were created based on their CT data and were voxelized for input into the Monte Carlo program. Simulated dose at various organ locations was compared against measurements made with thermoluminescent dosimetry chips for both single axial and helical scans.

Results:

For the cylindrical phantom, simulations differed from measurements by −4.8% to 2.2%. For the two anthropomorphic phantoms, the discrepancies between simulations and measurements ranged between (−8.1%, 8.1%) and (−17.2%, 13.0%) for the single axial scans and the helical scans, respectively.

Conclusions:

The authors developed an accurate Monte Carlo program for assessing radiation dose from CT examinations. When combined with computer models of actual patients, the program can provide accurate dose estimates for specific patients.
A new bias field correction method combining N3 and FCM for improved segmentation of breast density on MRI
Authors: Lin Muqing , Chan Siwa , Chen Jeon‐Hor , Chang Daniel , Nie Ke , Chen Shih‐Ting , Lin Cheng‐Ju , Shih Tzu‐Ching , Nalcioglu Orhan , Su Min‐Ying
Published: December 2010

Purpose:

Quantitative breast density is known as a strong risk factor associated with the development of breast cancer. Measurement of breast density based on three‐dimensional breast MRI may provide very useful information. One important step for quantitative analysis of breast density on MRI is the correction of field inhomogeneity to allow an accurate segmentation of the fibroglandular tissue (dense tissue). A new bias field correction method by combining the nonparametric nonuniformity normalization (N3) algorithm and fuzzy‐C‐means (FCM)‐based inhomogeneity correction algorithm is developed in this work.

Methods:

The analysis is performed on non‐fat‐sat T1‐weighted images acquired using a 1.5 T MRI scanner. A total of 60 breasts from 30 healthy volunteers was analyzed. N3 is known as a robust correction method, but it cannot correct a strong bias field on a large area. FCM‐based algorithm can correct the bias field on a large area, but it may change the tissue contrast and affect the segmentation quality. The proposed algorithm applies N3 first, followed by FCM, and then the generated bias field is smoothed using Gaussian kernal and B‐spline surface fitting to minimize the problem of mistakenly changed tissue contrast. The segmentation results based on the corrected images were compared to the N3 and FCM alone corrected images and another method, coherent local intensity clustering (CLIC), corrected images. The segmentation quality based on different correction methods were evaluated by a radiologist and ranked.

Results:

The authors demonstrated that the iterative correction method brightens the signal intensity of fatty tissues and that separates the histogram peaks between the fibroglandular and fatty tissues to allow an accurate segmentation between them. In the first reading session, the radiologist found ranking in 17 breasts, ranking in 7 breasts, in 32 breasts, in 2 breasts, and in 2 breasts. The results of the second reading session were similar. The performance in each pairwise Wilcoxon signed‐rank test is significant, showing superior to both N3 and FCM, and N3 superior to FCM. The performance of the new algorithm was comparable to that of CLIC, showing equivalent quality in 57/60 breasts.

Conclusions:

Choosing an appropriate bias field correction method is a very important preprocessing step to allow an accurate segmentation of fibroglandular tissues based on breast MRI for quantitative measurement of breast density. The proposed algorithm combining and CLIC both yield satisfactory results.
Comparison of scatter rejection and low‐contrast performance of scan equalization digital radiography (SEDR), slot‐scan digital radiography, and full‐field digital radiography systems for chest phantom imaging
Authors: Liu Xinming , Shaw Chris C. , Lai Chao‐Jen , Wang Tianpeng
Published: December 2010

Purpose:

To investigate and compare the scatter rejection properties and low‐contrast performance of the scan equalization digital radiography (SEDR) technique to the slot‐scan and conventional full‐field digital radiography techniques for chest imaging.

Methods:

A prototype SEDR system was designed and constructed with an a‐Se flat‐panel (FP) detector to improve image quality in heavily attenuating regions of an anthropomorphic chest phantom. Slot‐scanning geometry was used to reject scattered radiation without attenuating primary x rays. The readout scheme of the FP was modified to erase accumulated scatter signals prior to image readout. A 24‐segment beam width modulator was developed to regulate x‐ray exposures regionally and compensate for the low x‐ray flux in heavily attenuating regions. To measure the scatter‐to‐primary ratios (SPRs), a 2 mm thick lead plate with a 2‐D array of aperture holes was used to measure the primary signals, which were then subtracted from those obtained without the lead plate to determine scatter components. A 2‐D array of aluminum beads (3 mm in diameter) was used as the low‐contrast objects to measure the contrast ratios (CRs) and contrast‐to‐noise ratios (CNRs) for evaluating the low‐contrast performance in chest phantom images. A set of two images acquired with the same techniques were subtracted from each other to measure the noise levels. SPRs, CRs, and CNRs of the SEDR images were measured in four anatomical regions of chest phantom images and compared to those of slot‐scan images and full‐field images acquired with and without antiscatter grid.

Results:

The percentage reduction of SPR (percentage of SPRs reduced with scatter removal/rejection methods relative to that for nongrid full‐field imaging) averaged over four anatomical regions was measured to be 80%, 83%, and 71% for SEDR, slot‐scan, and full‐field with grid, respectively. The average CR over four regions was found to improve over that for nongrid full‐field imaging by 259%, 279%, and 145% for SEDR, slot‐scan, and full‐field with grid, respectively. The average CNR over four regions was found to improve over that for nongrid full‐field imaging by 201% for SEDR as compared to 133% for the slot‐scan technique and 14% for the antiscatter grid method.

Conclusions:

Both SEDR and slot‐scan techniques outperformed the antiscatter grid method used in standard full‐field radiography. For imaging with the same effective exposure, the SEDR technique offers no advantage over the slot‐scan method in terms of SPRs and CRs. However, it improves CNRs significantly, especially in heavily attenuating regions. The improvement of low‐contrast performance may help improve the detection of the lung nodules or other abnormalities and may offer SEDR the potential for dose reduction in chest radiography.
Neutron‐induced electronic failures around a high‐energy linear accelerator
Authors: Kry Stephen F. , Johnson Jennifer L. , White R. Allen , Howell Rebecca M. , Kudchadker Rajat J. , Gillin Michael T.
Published: December 2010

Purpose:

After a new in‐vault CT‐on‐rails system repeatedly malfunctioned following use of a high‐energy radiotherapy beam, we investigated the presence and impact of neutron radiation on this electronic system, as well as neutron shielding options.

Methods:

We first determined the CT scanner's failure rate as a function of the number of 18 MV monitor units (MUs) delivered. We then re‐examined the failure rate with both 2.7‐cm‐thick and 7.6‐cm‐thick borated polyethylene (BPE) covering the linac head for neutron shielding. To further examine shielding options, as well as to explore which neutrons were relevant to the scanner failure, Monte Carlo simulations were used to calculate the neutron fluence and spectrum in the bore of the CT scanner. Simulations included BPE covering the CT scanner itself as well as covering the linac head.

Results:

We found that the CT scanner had a 57% chance of failure after the delivery of 200 MUs. While the addition of neutron shielding to the accelerator head reduced this risk of failure, the benefit was minimal and even 7.6 cm of BPE was still associated with a 29% chance of failure after the delivery of 200 MU. This shielding benefit was achieved regardless of whether the linac head or CT scanner was shielded. Additionally, it was determined that fast neutrons were primarily responsible for the electronic failures.

Conclusions:

As illustrated by the CT‐on‐rails system in the current study, physicists should be aware that electronic systems may be highly sensitive to neutron radiation. Medical physicists should therefore monitor electronic systems that have not been evaluated for potential neutron sensitivity. This is particularly relevant as electronics are increasingly common in the therapy vault and newer electronic systems may exhibit increased sensitivity.
Beam commissioning and measurements validating the beam model in a new TPS that converts helical tomotherapy plans to step‐and‐shoot IMRT plans
Authors: Petersson Kristoffer , Ceberg Crister , Engström Per , Knöös Tommy
Published: December 2010

Purpose:

A new type of treatment planning system calledSHAREPLAN has been studied, which enables the transfer of treatment plans generated for helical tomotherapy delivery to plans that can be delivered on C‐arm linacs. The purpose is to ensure continuous patient treatment during periods of unscheduled downtime for the TomoTherapy unit, particularly in clinics without a backup unit. The purpose of this work was to verify that the plans generated in this novel planning system are deliverable and accurate. The work consists primarily of beam commissioning, verification of the beam model, and measurements verifying that generated plans are deliverable with sufficient accuracy.

Methods:

The beam commissioning process involves input of general geometric properties of the modeled linac, profiles and depth dose curves for a specific photon nominal energy (6 MV), and the automated modeling of other beam properties. Some manual tuning of the beam model is required. To evaluate its accuracy, the confidence limit concept [J. Venselaar et al., “Tolerances for the accuracy of photon beam dose calculations of treatment planning systems,” Radiother. Oncol. 60, 191–201 (2001)] was used, which is a method supported by ESTRO. Measurements were conducted with a 2D diode array at the commissioned linac as a final check of the beam model and to evaluate whether the generated plans were deliverable and accurate.

Results:

The comparison and evaluation of calculated data points and measured data according to the method applied confirmed the accuracy of the beam model. The profiles had a confidence limit of 1.1% and the depth dose curves had a confidence limit of 1.7%, both of which were well below the tolerance limit of 2%. Plan specific QC measurements and evaluation verified that different plans generated in the TPS were deliverable with sufficient accuracy at the commissioned linac, as none of the 160 beams for the 20 different plans evaluated had a fraction of approved data points below 90%, the local clinical approval criterion for delivery QA measurements.

Conclusions:

This study is a validation of the new TPS as it verifies that the generated plans are deliverable at a commissioned linac with adequate accuracy. A thorough investigation of the treatment plan quality will require a separate study. The TPS is proving to be a useful and time‐saving complement, especially for clinics having a single unit for helical delivery among its conventional linacs.
Technical Note: DIRART – A software suite for deformable image registration and adaptive radiotherapy research
Authors: Yang Deshan , Brame Scott , El Naqa Issam , Aditya Apte , Wu Yu , Murty Goddu S. , Mutic Sasa , Deasy Joseph O. , Low Daniel A.
Published: December 2010

Purpose:

Recent years have witnessed tremendous progress in image guide radiotherapy technology and a growing interest in the possibilities for adapting treatment planning and delivery over the course of treatment. One obstacle faced by the research community has been the lack of a comprehensive open‐source software toolkit dedicated for adaptive radiotherapy (ART). To address this need, the authors have developed a software suite called the Deformable Image Registration and Adaptive Radiotherapy Toolkit (DIRART).

Methods:

DIRART is an open‐source toolkit developed in MATLAB. It is designed in an object‐oriented style with focus on user‐friendliness, features, and flexibility. It contains four classes of DIR algorithms, including the newer inverse consistency algorithms to provide consistent displacement vector field in both directions. It also contains common ART functions, an integrated graphical user interface, a variety of visualization and image‐processing features, dose metric analysis functions, and interface routines. These interface routines make DIRART a powerful complement to the Computational Environment for Radiotherapy Research (CERR) and popular image‐processing toolkits such as ITK.

Results

:DIRART provides a set of image processing/registration algorithms and postprocessing functions to facilitate the development and testing of DIR algorithms. It also offers a good amount of options for DIR results visualization, evaluation, and validation.

Conclusions

: By exchanging data with treatment planning systems via DICOM‐RT files andCERR, and by bringing image registration algorithms closer to radiotherapy applications, DIRART is potentially a convenient and flexible platform that may facilitate ART and DIR research.
Prostate cancer characterization on MR images using fractal features
Authors: Lopes R. , Ayache A. , Makni N. , Puech P. , Villers A. , Mordon S. , Betrouni N.
Published: December 2010

Purpose:

Computerized detection of prostate cancer on T2‐weighted MR images.

Methods:

The authors combined fractal and multifractal features to perform textural analysis of the images. The fractal dimension was computed using the Variance method; the multifractal spectrum was estimated by an adaptation of a multifractional Brownian motion model. Voxels were labeled as tumor/nontumor via nonlinear supervised classification. Two classification algorithms were tested: Support vector machine (SVM) and AdaBoost.

Results:

Experiments were performed on images from 17 patients. Ground truth was available from histological images. Detection and classification results (sensitivity, specificity) were (83%, 91%) and (85%, 93%) for SVM and AdaBoost, respectively.

Conclusions

: Classification using the authors' model combining fractal and multifractal features was more accurate than classification using classical texture features (such as Haralick, wavelet, and Gabor filters). Moreover, the method was more robust against signal intensity variations. Although the method was only applied to T2 images, it could be extended to multispectral MR.
Verification of monitor unit calculations for non‐IMRT clinical radiotherapy: Report of AAPM Task Group 114
Authors: Stern Robin L. , Heaton Robert , Fraser Martin W. , Murty Goddu S. , Kirby Thomas H. , Lam Kwok Leung , Molineu Andrea , Zhu Timothy C.
Published: December 2010

The requirement of an independent verification of the monitor units (MU) or time calculated to deliver the prescribed dose to a patient has been a mainstay of radiation oncology quality assurance. The need for and value of such a verification was obvious when calculations were performed by hand using look‐up tables, and the verification was achieved by a second person independently repeating the calculation. However, in a modern clinic using CT/MR/PET simulation, computerized 3D treatment planning, heterogeneity corrections, and complex calculation algorithms such as convolution/superposition and Monte Carlo, the purpose of and methodology for the MU verification have come into question. In addition, since the verification is often performed using a simpler geometrical model and calculation algorithm than the primary calculation, exact or almost exact agreement between the two can no longer be expected. Guidelines are needed to help the physicist set clinically reasonable action levels for agreement. This report addresses the following charges of the task group: (1) To re‐evaluate the purpose and methods of the “independent second check” for monitor unit calculations for non‐IMRT radiation treatment in light of the complexities of modern‐day treatment planning. (2) To present recommendations on how to perform verification of monitor unit calculations in a modern clinic. (3) To provide recommendations on establishing action levels for agreement between primary calculations and verification, and to provide guidance in addressing discrepancies outside the action levels. These recommendations are to be used as guidelines only and shall not be interpreted as requirements.
Improving patient safety in radiation oncology
Authors: Hendee William R. , Herman Michael G.
Published: December 2010

Beginning in the 1990s, and emphasized in 2000 with the release of an Institute of Medicine report, healthcare providers and institutions have dedicated time and resources to reducing errors that impact the safety and well‐being of patients. But in January 2010 the first of a series of articles appeared in the New York Times that described errors in radiation oncology that grievously impacted patients. In response, the American Association of Physicists in Medicine and the American Society of Radiation Oncology sponsored a working meeting entitled “Safety in Radiation Therapy: A Call to Action.” The meeting attracted 400 attendees, including medical physicists, radiation oncologists, medical dosimetrists, radiation therapists, hospital administrators, regulators, and representatives of equipment manufacturers. The meeting was cohosted by 14 organizations in the United States and Canada. The meeting yielded 20 recommendations that provide a pathway to reducing errors and improving patient safety in radiation therapy facilities everywhere.
A novel respiratory tracking system for smart‐gated PET acquisition
Authors: Nehmeh S. A. , Haj‐Ali A. A. , Qing C. , Stearns C. , Kalaigian H. , Kohlmyer S. , Schoder H. , Ho A. Y. , Larson S. M. , Humm J. L.
Published: December 2010

Purpose:

In this study, the authors validated a novel respiratory tracking device, the multidimensional respiratory tracking (MDRT) system, that was designed to assist in correcting for respiratory motion in PET/CT images. The authors also investigated a novel PET acquisition technique, smart gating (SG), that enables to acquire motion‐free PET data prospectively, with minimum user interference and with no additional postprocessing of the PET data.

Methods:

MDRT uses visual tracking techniques to track simultaneously the two‐dimensional (in the vertical plane) motion of multiple fiducial markers using a standard video camera. A threshold window is set at the breathing amplitude of interest using the MDRT GUI. A trigger is generated at a rate of 250 Hz as long as the breathing signal is within the threshold window. The triggers are fed into the PET scanner to initialize one single bin of a gated acquisition every 4 ms. No triggers are delivered as the breathing signal drifts outside the threshold window. Consequently, PET data are acquired only whenever the breathing signal is confined within the amplitude threshold window, thus resulting into a motion‐free image set. The accuracy of MDRT in tracking the breathing signal was assessed (1) by comparing the period of an oscillating phantom, as measured by MDRT, to that measured with a photogate timer and (2) by comparing the MDRT output to that of the real‐time position management (RPM) in ten patients. The SG PET/CT acquisition was validated in phantoms and in two stereotactic body radiosurgery (SBRS) lung DIBH‐PET/CT patients.

Results:

MDRT was in agreement with the photogate timer in determining the period of motion to less than 2%. The percent errors between MDRT and RPM in the positions of the peaks and troughs of the ten patients' breathing signals were within 10%. In phantoms, SG technique enables to correct for motion‐induced artifacts in the PET images and improve the accuracy of PET quantitation. For the SBRS application, in one patient, the patient's CT lesion was not detected in the corresponding clinical PET images, while it exhibited an SUV of 1.8 in the DIBH image set. In the second patient, DIBH‐PET images showed an improved PET‐to‐CT spatial matching and a 52% increase in the lesion SUV.

Conclusions:

MDRT has been shown to be accurate in tracking breathing motion and assisted in implementing a smart‐gating PET acquisition technique that allowed to acquire prospectively motion‐free PET images.
Spectral optimization for dedicated breast CT
Authors: Weigel Michaela , Vollmar Sabrina V. , Kalender Willi A.
Published: December 2010

Purpose:

The authors investigated the choice of spectra for the optimization of the dose‐weighted contrast‐to‐noise ratio (CNRD) for a dedicated breast CT scanner. The objective is to provide the desired image quality level at minimal dose values. The CNRD was investigated as a function of energy or tube voltage and filtrations for various breast sizes and contrasts.

Methods:

The authors performed simulations of the pendant female breast as cylinders consisting of a homogeneous mixture of adipose and glandular tissue with diameters from 6 to 18 cm. The contrasts of adipose tissue, calcium hydroxyapatite, and iodine contrast agent relative to glandular tissue were analyzed using inserts of 9 mm in diameter. Simulations were conducted for monochromatic and polychromatic radiation with a 3 mm Al or a 0.3 mm Cu filter. Simulations and measurements on an experimental micro‐CT scanner were performed for validation purposes with a 6 cm water‐equivalent cylinder, with inserts representing a pure density difference of 10%, calcium hydroxyapatite, and iodine contrast agent. A breast tissue sample embedded in paraffin was investigated to confirm the simulation results.

Results:

Optimal tube voltages were found to be in the range of 30–55 kV for breast CT imaging. For example, with 3 mm Al or 0.3 mm Cu filtration, optimal tube voltages were about 53 and 48 kV, respectively, for the contrast iodine/glandular tissue for all diameters. With 3 mm Al filtration, optimal tube voltages increased from 30 to 37 kV and from 30 to 47 kV for the contrast calcium hydroxyapatite/glandular tissue and adipose/glandular tissue, respectively. Tube power requirements were estimated and the change in tube current relative to 80 kV was found to be between 4 and 14 and between 11 and 214 with 3 mm Al filtration or 0.3 mm Cu filtration, respectively. These numbers show that realizing the low optimal tube voltages may not be feasible in most cases due to power requirements.

Conclusions:

Depending on the filtration, the authors assume that a compromise solution has to be found between the highest potential dose reduction and a solution working with available x‐ray sources. In view of the tube power constraints, the authors recommend aiming for tube voltages in the range of 50 kV and higher.
Fast intensity‐modulated arc therapy based on 2‐step beam segmentation
Authors: Bratengeier Klaus , Gainey Mark , Sauer Otto A. , Richter Anne , Flentje Michael
Published: December 2010

Purpose:

Single or few arc intensity‐modulated arc therapy (IMAT) is intended to be a time saving irradiation method, potentially replacing classical intensity‐modulated radiotherapy (IMRT). The aim of this work was to evaluate the quality of different IMAT methods with the potential of fast delivery, which also has the possibility of adapting to the daily shape of the target volume.

Methods:

A planning study was performed. Novel double and triple IMAT techniques based on the geometrical analysis of the target organ at risk geometry (2‐step IMAT) were evaluated. They were compared to step and shoot IMRT reference plans generated using direct machine parameter optimization (DMPO®). Volumetric arc (VMAT) plans from commercial preclinical software (SMARTARC®) were used as an additional benchmark to classify the quality of the novel techniques. Four cases with concave planning target volumes (PTV) with one dominating organ at risk (OAR), viz., the PTV/OAR combination of the ESTRO Quasimodo phantom, breast/lung, spine metastasis/spinal cord, and prostate/rectum, were used for the study. The composite objective value (COV) and other parameters representing the plan quality were studied.

Results:

The novel 2‐step IMAT techniques with geometry based segment definition were as good as or better than DMPO® and were superior to the SMARTARC® VMAT techniques. For the spine metastasis, the quality measured by the COV differed only by 3%, whereas the COV of the 2‐step IMAT for the other three cases decreased by a factor of 1.4–2.4 with respect to the reference plans.

Conclusions:

Rotational techniques based on geometrical analysis of the optimization problem (2‐step IMAT) provide similar or better plan quality than DMPO® or the research version of SMARTARC® VMAT variants. The results justify pursuing the goal of fast IMAT adaptation based on 2‐step IMAT techniques.
Monitoring radiation use in cardiac fluoroscopy imaging procedures
Authors: Stevens Nathaniel T. , Steiner Stefan H. , Smith Ian R. , MacKay R. Jock
Published: December 2010

Purpose:

Timely identification of systematic changes in radiation delivery of an imaging system can lead to a reduction in risk for the patients involved. However, existing quality assurance programs involving the routine testing of equipment performance using phantoms are limited in their ability to effectively carry out this task. To address this issue, the authors propose the implementation of an ongoing monitoring process that utilizes procedural data to identify unexpected large or small radiation exposures for individual patients, as well as to detect persistent changes in the radiation output of imaging platforms.

Methods:

Data used in this study were obtained from records routinely collected during procedures performed in the cardiac catheterization imaging facility at St. Andrew's War Memorial Hospital, Brisbane, Australia, over the period January 2008–March 2010. A two stage monitoring process employing individual and exponentially weighted moving average (EWMA) control charts was developed and used to identify unexpectedly high or low radiation exposure levels for individual patients, as well as detect persistent changes in the radiation output delivered by the imaging systems. To increase sensitivity of the charts, we account for variation in dose area product (DAP) values due to other measured factors (patient weight, fluoroscopy time, and digital acquisition frame count) using multiple linear regression. Control charts are then constructed using the residual values from this linear regression. The proposed monitoring process was evaluated using simulation to model the performance of the process under known conditions.

Results:

Retrospective application of this technique to actual clinical data identified a number of cases in which the DAP result could be considered unexpected. Most of these, upon review, were attributed to data entry errors. The charts monitoring the overall system radiation output trends demonstrated changes in equipment performance associated with relocation of the equipment to a new department. When tested under simulated conditions, the EWMA chart was capable of detecting a sustained 15% increase in average radiation output within 60 cases ( of operation), while a 33% increase would be signaled within 20 cases.

Conclusions:

This technique offers a valuable enhancement to existing quality assurance programs in radiology that rely upon the testing of equipment radiation output at discrete time frames to ensure performance security.
Segmentation and quantification of materials with energy discriminating computed tomography: A phantom study
Authors: Le Huy Q. , Molloi Sabee
Published: December 2010

Purpose:

To experimentally investigate whether a computed tomography (CT) system based on CdZnTe (CZT) detectors in conjunction with a least‐squares parameter estimation technique can be used to decompose four different materials.

Methods:

The material decomposition process was divided into a segmentation task and a quantification task. A least‐squares minimization algorithm was used to decompose materials with five measurements of the energy dependent linear attenuation coefficients. A small field‐of‐view energy discriminating CT system was built. The CT system consisted of an x‐ray tube, a rotational stage, and an array of CZT detectors. The CZT array was composed of 64 pixels, each of which is. Images were acquired at 80 kVp in fluoroscopic mode at 50 ms per frame. The detector resolved the x‐ray spectrum into energy bins of 22–32, 33–39, 40–46, 47–56, and 57–80 keV. Four phantoms were constructed from polymethylmethacrylate (PMMA), polyethylene, polyoxymethylene, hydroxyapatite, and iodine. Three phantoms were composed of three materials with embedded hydroxyapatite (50, 150, 250, and 350 mg/ml) and iodine (4, 8, 12, and 16 mg/ml) contrast elements. One phantom was composed of four materials with embedded hydroxyapatite (150 and 350 mg/ml) and iodine (8 and 16 mg/ml). Calibrations consisted of PMMA phantoms with either hydroxyapatite (100, 200, 300, 400, and 500 mg/ml) or iodine (5, 15, 25, 35, and 45 mg/ml) embedded. Filtered backprojection and a ramp filter were used to reconstruct images from each energy bin. Material segmentation and quantification were performed and compared between different phantoms.

Results:

All phantoms were decomposed accurately, but some voxels in the base material regions were incorrectly identified. Average quantification errors of hydroxyapatite/iodine were 9.26/7.13%, 7.73/5.58%, and 12.93/8.23% for the three‐material PMMA, polyethylene, and polyoxymethylene phantoms, respectively. The average errors for the four‐material phantom were 15.62% and 2.76% for hydroxyapatite and iodine, respectively.

Conclusions:

The calibrated least‐squares minimization technique of decomposition performed well in breast imaging tasks with an energy resolving detector. This method can provide material basis images containing concentrations of the relevant materials that can potentially be valuable in the diagnostic process.
Computerized segmentation and measurement of malignant pleural mesothelioma
Authors: Sensakovic William F. , Armato Samuel G. , Straus Christopher , Roberts Rachael Y. , Caligiuri Philip , Starkey Adam , Kindler Hedy L.
Published: December 2010

Purpose:

The current linear method to track tumor progression and evaluate treatment efficacy is insufficient for malignant pleural mesothelioma (MPM). A volumetric method for tumor measurement could improve the evaluation of novel treatments, but a fully manual implementation of volume measurement is too tedious and time‐consuming. This manuscript presents a computerized method for the three‐dimensional segmentation and volumetric analysis of MPM.

Methods:

The computerized MPM segmentation method segments the lung parenchyma and hemithoracic cavities to define the pleural space. Nonlinear diffusion and a k‐means classifier are then implemented to identify MPM in the pleural space. A database of 31 computed tomography scans from 31 patients with pathologically confirmed MPM was retrospectively collected. Three observers independently outlined five randomly selected sections in each scan. The Jaccard similarity coefficient (J) between each of the observers and between the observer‐defined and computer‐defined segmentations was calculated. The computer‐defined and the observer‐defined segmentation areas (averaged over all observers) were both calculated for each axial section and compared using Bland–Altman plots.

Results:

The median J value among observers averaged over all sections was 0.517. The median J between the computer‐defined and manual segmentations was 0.484. The difference between these values was not statistically significant. The area delineated by the computerized method demonstrated variability and bias comparable to the tumor area calculated from manual delineations.

Conclusions:

A computerized method for segmentation and measurement of MPM was developed. This method requires minimal initialization by the user and demonstrated good agreement with manually drawn outlines and area measurements. This method will allow volumetric tracking of tumor progression and may improve the evaluation of novel MPM treatments.