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McKay T.A.,Monash University | Bishop S.,Illawarra Cancer Care Center | McKay M.J.,University of Sydney
Annals of Translational Medicine | Year: 2017

Malignant psoas syndrome (MPS) is an uncommon condition first described by Stevens et al. MPS is caused by malignant infiltration of the psoas muscle and adjacent nerves and is characterised by (fixed) flexion deformity of the ipsilateral hip and proximal lumbosacral plexopathy. It has previously been described in relation to metastatic carcinoma, melanoma and liposarcoma, as well as non-Hodgkins lymphoma. We present the case of a 68-year-old woman with a sarcoma arising in the left psoas muscle at the level of L4 who presented with symptoms of MPS. To the authors' knowledge this is the first case of MPS arising from a primary sarcoma of the iliopsoas compartment. The patient underwent presurgical radiotherapy, with a significant improvement in pain control without an increase in analgesic medications. We discuss the aetiology of MPS and the role of radiotherapy in the treatment of this rare syndrome. © Annals of Translational Medicine.

Yu P.,University of Wollongong | Gandhidasan S.,Wollongong Hospital | Miller A.A.,Illawarra Cancer Care Center
International Journal of Medical Informatics | Year: 2010

Background and purpose: The experience of clinicians at two public hospitals in Sydney, Australia, with the introduction and use of an oncology information system (OIS) was examined to extract lessons to guide the introduction of clinical information systems in public hospitals. Methods and materials: Semi-structured interviews were conducted with 12 of 15 radiation oncologists employed at the two hospitals. The personnel involved in the decision making process for the introduction of the system were contacted and their decision making process revisited. The transcribed data were analyzed using NVIVO software. Themes emerged included implementation strategies and practices, the radiation oncologists' current use and satisfaction with the OIS, project management and the impact of the OIS on clinical practice. Results: The hospitals had contrasting experiences in their introduction and use of the OIS. Hospital A used the OIS in all aspects of clinical documentation. Its implementation was associated with strong advocacy by the Head of Department, input by a designated project manager, and use and development of the system by all staff, with timely training and support.With no vision of developing a paperless information system, Hospital B used the OIS only for booking and patient tracking. A departmental policy that data entry for the OIS was centrally undertaken by administrative staff distanced clinicians from the system. All the clinicians considered that the OIS should continuously evolve to meet changing clinical needs and departmental quality improvement initiatives. Conclusions: This case study indicates that critical factors for the successful introduction of clinical information systems into hospital environment were an initial clear vision to be paperless, strong clinical leadership and management at the departmental level, committed project management, and involvement of all staff, with appropriate training. Clinician engagement is essential for post-adoption evolution of clinical information systems. © 2010 Elsevier Ireland Ltd.

Butson M.J.,City University of Hong Kong | Butson M.J.,Illawarra Cancer Care Center | Butson M.J.,University of Wollongong | Yu P.K.N.,City University of Hong Kong | And 2 more authors.
Radiation Measurements | Year: 2010

Gafchromic EBT2, Radiochromic film is assessed for its change in optical density response to x-ray radiation over a broad energy range, from low energy kilovoltage to megavoltage x-rays. A small energy dependence was found with variations in the change in optical density when scanned in the red component of a desktop scanner light source per unit dose of 6.5% from 50 kVp to 10 MV. This produces a slightly smaller and thus even more energy independent film than its predecessor, EBT film whose response varied by 7.7% over the same energy range. The energy response peaked at 100 kVp with a 5% over response compared to 6 MV x-rays and the minimum response found at both 50 kVp and 250 kVp being a 1.5% under response. It should be noted that the shape of the energy dependence response curve increases from 50 kVp up to 100 kVp followed by a decrease through to higher energies whilst the original EBT was found to increase in response from 50 kVp through to 10 MV. A reflected net optical density change of 0.215 ± 0.006 OD for the first Gray of radiation was found for EBT2 analysed in reflection mode at 6 MV x-ray energy. The minimal energy dependence of the EBT2 film provides further enhancement compared to EBT for its accuracy with respect to spectral changes in the beam to measure beams such as IMRT where complex field and multileaf collimator configurations exist causing small spectral changes to occur over the treatment field or at depth where spectral changes also occur. © 2010 Elsevier Ltd. All rights reserved.

Oborn B.M.,Illawarra Cancer Care Center | Metcalfe P.E.,Illawarra Cancer Care Center | Butson M.J.,University of Wollongong | Rosenfeld A.B.,Illawarra Cancer Care Center | Keall P.J.,University of Sydney
Medical Physics | Year: 2012

Purpose: In recent times, longitudinal field MRI-linac systems have been proposed for 6 MV MRI-guided radiotherapy (MRIgRT). The magnetic field is parallel with the beam axis and so will alter the transport properties of any electron contamination particles. The purpose of this work is to provide a first investigation into the potential effects of the MR and fringe magnetic fields on the electron contamination as it is transported toward a phantom, in turn, providing an estimate of the expected patient skin dose changes in such a modality. Methods: Geant4 Monte Carlo simulations of a water phantom exposed to a 6 MV x-ray beam were performed. Longitudinal magnetic fields of strengths between 0 and 3 T were applied to a 30 30 20 cm 3 phantom. Surrounding the phantom there is a region where the magnetic field is at full MRI strength, consistent with clinical MRI systems. Beyond this the fringe magnetic field entering the collimation system is also modeled. The MRI-coil thickness, fringe field properties, and isocentric distance are varied and investigated. Beam field sizes of 5 5, 10 10, 15 15 and 20 20 cm 2 were simulated. Central axis dose, 2D virtual entry skin dose films, and 70 m skin depth doses were calculated using high resolution scoring voxels. Results: In the presence of a longitudinal magnetic field, electron contamination from the linear accelerator is encouraged to travel almost directly toward the patient surface with minimal lateral spread. This results in a concentration of electron contamination within the x-ray beam outline. This concentration is particularly encouraged if the fringe field encompasses the collimation system. Skin dose increases of up to 1000 were observed for certain configurations and increases above Dmax were common. In nonmagnetically shielded cases, electron contamination generated from the jaw faces and air column is trapped and propagated almost directly to the phantom entry region, giving rise to intense dose hot spots inside the x-ray treatment field. These range up to 1000 or more of Dmax at the CAX, depending on field size, isocenter, and coil thickness. In the case of a fully magnetically shielded collimation system and the lowest MRI field of 0.25 T, the entry skin dose is expected to increase to at least 40, 50, 65, and 80 of Dmax for 5 5, 10 10, 15 15, and 20 20 cm 2, respectively. Conclusions: Electron contamination from the linac head and air column may cause considerable skin dose increases or hot spots at the beam central axis on the entry side of a phantom or patient in longitudinal field 6 MV MRIgRT. This depends heavily on the properties of the magnetic fringe field entering the linac beam collimation system. The skin dose increase is also related to the MRI-coil thickness, the fringe field, and the isocenter distance of the linac. The results of this work indicate that the properties of the MRI fringe field, electron contamination production, and transport must be considered carefully during the design stage of a longitudinal MRI-linac system. © 2012 American Association of Physicists in Medicine.

Oborn B.M.,Illawarra Cancer Care Center | Oborn B.M.,University of Wollongong | Metcalfe P.E.,University of Wollongong | Butson M.J.,Illawarra Cancer Care Center | Rosenfeld A.B.,University of Wollongong
Medical Physics | Year: 2010

Purpose: The main focus of this work is to continue investigations into the Monte Carlo predicted skin doses seen in MRI-guided radiotherapy. In particular, the authors aim to characterize the 70 μm skin doses over a larger range of magnetic field strength and x-ray field size than in the current literature. The effect of surface orientation on both the entry and exit sides is also studied. Finally, the use of exit bolus is also investigated for minimizing the negative effects of the electron return effect (ERE) on the exit skin dose. Methods: High resolution GEANT4 Monte Carlo simulations of a water phantom exposed to a 6 MV x-ray beam (Varian 2100C) have been performed. Transverse magnetic fields of strengths between 0 and 3 T have been applied to a 30×30×20 cm3 phantom. This phantom is also altered to have variable entry and exit surfaces with respect to the beam central axis and they range from -75° to +75°. The exit bolus simulated is a 1 cm thick (water equivalent) slab located on the beam exit side. Results: On the entry side, significant skin doses at the beam central axis are reported for large positive surface angles and strong magnetic fields. However, over the entry surface angle range of -30° to -60°, the entry skin dose is comparable to or less than the zero magnetic field skin dose, regardless of magnetic field strength and field size. On the exit side, moderate to high central axis skin dose increases are expected except at large positive surface angles. For exit bolus of 1 cm thickness, the central axis exit skin dose becomes an almost consistent value regardless of magnetic field strength or exit surface angle. This is due to the almost complete absorption of the ERE electrons by the bolus. Conclusions: There is an ideal entry angle range of -30° to -60° where entry skin dose is comparable to or less than the zero magnetic field skin dose. Other than this, the entry skin dose increases are significant, especially at higher magnetic fields. On the exit side there is mostly moderate to high skin dose increases for 0.2-3 T with the only exception being large positive angles. Exit bolus of 1 cm thickness will have a significant impact on lowering such exit skin dose increases that occur as a result of the ERE. © 2010 American Association of Physicists in Medicine.

Huang C.-Y.,University of New South Wales | Oborn B.M.,Illawarra Cancer Care Center | Oborn B.M.,University of Wollongong | Guatelli S.,University of Wollongong | Allen B.J.,University of New South Wales
Medical Physics | Year: 2012

Purpose: Metastatic melanoma lesions experienced marked regression after systemic targeted alpha therapy in a phase 1 clinical trial. This unexpected response was ascribed to tumor antivascular alpha therapy (TAVAT), in which effective tumor regression is achieved by killing endothelial cells (ECs) in tumor capillaries and, thus, depriving cancer cells of nutrition and oxygen. The purpose of this paper is to quantitatively analyze the therapeutic efficacy and safety of TAVAT by building up the testing Monte Carlo microdosimetric models. Methods: Geant4 was adapted to simulate the spatial nonuniform distribution of the alpha emitter 213Bi. The intraluminal model was designed to simulate the background dose to normal tissue capillary ECs from the nontargeted activity in the blood. The perivascular model calculates the EC dose from the activity bound to the perivascular cancer cells. The key parameters are the probability of an alpha particle traversing an EC nucleus, the energy deposition, the lineal energy transfer, and the specific energy. These results were then applied to interpret the clinical trial. Cell survival rate and therapeutic gain were determined. Results: The specific energy for an alpha particle hitting an EC nucleus in the intraluminal and perivascular models is 0.35 and 0.37 Gy, respectively. As the average probability of traversal in these models is 2.7% and 1.1%, the mean specific energy per decay drops to 1.0 cGy and 0.4 cGy, which demonstrates that the source distribution has a significant impact on the dose. Using the melanoma clinical trial activity of 25 mCi, the dose to tumor EC nucleus is found to be 3.2 Gy and to a normal capillary EC nucleus to be 1.8 cGy. These data give a maximum therapeutic gain of about 180 and validate the TAVAT concept. Conclusions: TAVAT can deliver a cytotoxic dose to tumor capillaries without being toxic to normal tissue capillaries. © 2012 American Association of Physicists in Medicine.

Oborn B.M.,Illawarra Cancer Care Center | Oborn B.M.,University of Wollongong | Kolling S.,University of Sydney | Metcalfe P.E.,University of Wollongong | And 5 more authors.
Medical Physics | Year: 2014

Purpose: A potential side effect of inline MRI-linac systems is electron contamination focusing causing a high skin dose. In this work, the authors reexamine this prediction for an open bore 1 T MRI system being constructed for the Australian MRI-Linac Program. The efficiency of an electron contamination deflector (ECD) in purging electron contamination from the linac head is modeled, as well as the impact of a helium gas region between the deflector and phantom surface for lowering the amount of air-generated contamination. Methods: Magnetic modeling of the 1 T MRI was used to generate 3D magnetic field maps both with and without the presence of an ECD located immediately below the MLC's. Forty-seven different ECD designs were modeled and for each the magnetic field map was imported into Geant4 Monte Carlo simulations including the linac head, ECD, and a 30 × 30 × 30 cm3 water phantom located at isocenter. For the first generation system, the x-ray source to isocenter distance (SID) will be 160 cm, resulting in an 81.2 cm long air gap from the base of the ECD to the phantom surface. The first 71.2 cm was modeled as air or helium gas, with the latter encased between two windows of 50 μm thick high density polyethlyene. 2D skin doses (at 70 μm depth) were calculated across the phantom surface at 1 × 1 mm2 resolution for 6 MV beams of field size of 5 × 5, 10 × 10, and 20 × 20 cm2. Results: The skin dose was predicted to be of similar magnitude as the generic systems modeled in previous work, 230% to 1400% of\documentclass[12pt]{minimal}\ begin{document}\rm D-{\rm max}\end{document}D max for 5 × 5 to 20 × 20 cm2, respectively. Inclusion of the ECD introduced a nonuniformity to the MRI imaging field that ranged from ∼20 to ∼140 ppm while the net force acting on the ECD ranged from ∼151 N to ∼1773 N. Various ECD designs were 100% efficient at purging the electron contamination into the ECD magnet banks; however, a small percentage were scattered back into the beam and continued to the phantom surface. Replacing a large portion of the extended air-column between the ECD and phantom surface with helium gas is a key element as it significantly minimized the air-generated contamination. When using an optimal ECD and helium gas region, the 70 μm skin dose is predicted to increase moderately inside a small hot spot over that of the case with no magnetic field present for the jaw defined square beams examined here. These increases include from 12% to 40% of \documentclass[12pt]{minimal}\ begin{document}\rm D-{\rm max}\end{document}D max for 5 × 5 cm 2, 18% to 55% of \documentclass[12pt]{minimal}\begin{document}\rm D-{\rm max}\end{document}D max for 10 × 10 cm2, and from 23% to 65% of \documentclass[12pt]{minimal}\begin{document}\rm D-{\rm max}\end{document}D max for 20 × 20 cm2. Conclusions: Coupling an efficient ECD and helium gas region below the MLCs in the 160 cm isocenter MRI-linac system is predicted to ameliorate the impact electron contamination focusing has on skin dose increases. An ECD is practical as its impact on the MRI imaging distortion is correctable, and the mechanical forces acting on it manageable from an engineering point of view. © 2014 American Association of Physicists in Medicine.

Kang S.,Illawarra Cancer Care Center | Koh E.-S.,Liverpool Hospital | Koh E.-S.,University of New South Wales | Vinod S.K.,Liverpool Hospital | And 3 more authors.
Journal of Medical Imaging and Radiation Oncology | Year: 2012

Introduction: Lung cancer is the leading cause of cancer mortality in Western nations, and associated health-care costs are escalating. The aim of this study was to describe the current pattern of resource use and direct medical costs associated in managing lung cancer in South Western Sydney, Australia. Methods: All new cases of primary lung carcinoma discussed at the Liverpool and Macarthur Cancer Therapy Centre (CTC) Lung Cancer Multidisciplinary Team meeting or seen at CTC between 1 December 2005 and 21 December 2006 were reviewed. Staging investigations, hospitalisation, treatment and follow-up investigations were documented from first consultation to last follow-up (31 October 2008 or death). Cost estimates were based on the Australian Medicare Benefits Schedule and reported in Australian dollars. Infrastructure, staff and non-medical costs were excluded. Results: There were 210 patients, median age 68.2 years (range 39-90) with median follow-up of 16.6 months. The pathology and stage distribution were: 3.8% limited stage small cell lung cancer (SCLC), 10.0% extensive stage SCLC, 13.4% stage I and II non-small cell lung cancer (NSCLC), 28.5% stage III NSCLC and 44.3% stage IV NSCLC. The estimated total cost for managing this patient cohort was A$2.91 million. The cost components were: staging investigations (10.1%), treatment 41.2% (2.8% surgery, 15.8% radiotherapy and 22.6% chemotherapy), hospitalisation (43.7%) and follow-up investigations (5%). The median costs for managing NSCLC and SCLC subgroups were A$10 675 (range A$669-612 789) and A$14 799 (range A$908-31 057), respectively. Conclusion: Hospitalisation and cancer treatment, particularly chemotherapy, accounted for the major components of direct medical costs in the management of lung cancer. © 2012 The Authors © 2012 The Royal Australian and New Zealand College of Radiologists.

PubMed | University of Sydney, Stanford University, Illawarra Cancer Care Center and Ingham Institute
Type: Journal Article | Journal: Medical physics | Year: 2016

To test the functionality of medical electron guns within the fringe field of a purpose built superconducting MRI magnet, and to test different recovery techniques for a variety of imaging field strengths and SIDs.Three different electron guns were simulated using Finite Element Modelling; a standard diode gun, a standard triode gun, and a novel diode gun designed to operate within parallel magnetic fields. The approximate working regime of each gun was established by assessing exit current in constant magnetic fields of varying strength and defining working as less than 10% change in injection current. Next, the 1.0T MRI magnet was simulated within Comsol Multiphysics. The coil currents in this model were also scaled to produce field strengths of .5, 1, 1.5 and 3T. Various magnetic shield configurations were simulated, varying the SID from 800 to 1300mm. The average magnetic field within the gun region was assessed together with the distortion in the imaging volume - greater than 150uT distortion was considered unacceptable.The conventional guns functioned in fields of less than 7.5mT. Conversely, the redesigned diode required fields greater than .1T to function correctly. Magnetic shielding was feasible for SIDS of greater than 1000mm for field strengths of .5T and 1T, and 1100mm for 1.5 and 3.0T. Beyond these limits shielding resulted in unacceptable MRI distortion. In contrast, the redesigned diode could perform acceptably for SIDs of less than 812, 896, 931, and 974mm for imaging strengths of 0.5, 1.0, 1.5, 3.0T.For in-line MRIlinac configurations where the electron gun is operating in low field regions, shielding is a straight forward option. However, as magnetic field strength increases and the SID is reduced, shielding results in too great a distortion in the MRI and redesigning the electron optics is the preferable solution. The authors would like to acknowledge funding from the National Health and Research Council (AUS), National Institute of Health (NIH), and Cancer Institute NSW.

Kolling S.,University of Sydney | Oborn B.,Illawarra Cancer Care Center | Keall P.,University of Sydney
Medical Physics | Year: 2013

Purpose: To cope with intrafraction tumor motion, integrated MRI-linac systems for real-time image guidance are currently under development. The multileaf collimator (MLC) is a key component in every state-of-the-art radiotherapy treatment system, allowing for accurate field shaping and tumor tracking. This work quantifies the magnetic impact of a widely used MLC on the MRI field homogeneity for such a modality. Methods: The finite element method was employed to model a MRI-linac assembly comprised of a 1.0T split-bore MRI magnet and the key ferromagnetic components of a Varian Millennium 120 MLC, namely, the leaves and motors. Full 3D magnetic field maps of the system were generated. From these field maps, the peak-to-peak distortion within the MRI imaging volume was evaluated over a 30cm diameter sphere volume (DSV) around the isocenter and compared to a maximum preshim inhomogeneity of 300μT. Five parametric studies were performed: (1) The source-to-isocenter distance (SID) was varied from 100 to 200cm, to span the range of a compact system to that with lower magnetic coupling. (2) The MLC model was changed from leaves only to leaves with motors, to determine the contribution to the total distortion caused by MLC leaves and motors separately. (3) The system was configured in the inline or perpendicular orientation, i.e., the linac treatment beam was oriented parallel or perpendicular to the magnetic field direction. (4) The treatment field size was varied from 0 × 0 to 20×20cm2, to span the range of clinical treatment fields. (5) The coil currents were scaled linearly to produce magnetic field strengths B0 of 0.5, 1.0, and 1.5T, to estimate how the MLC impact changes with B0. Results: (1) The MLC-induced MRI field distortion fell continuously with increasing SID. (2) MLC leaves and motors were found to contribute to the distortion in approximately equal measure. (3) Due to faster falloff of the fringe field, the field distortion was generally smaller in the perpendicular beam orientation. The peak-to-peak DSV distortion was below 300μT at SID≥130cm (perpendicular) and SID≥140cm (inline) for the 1.0T design. (4) The simulation of different treatment fields was identified to cause dynamic changes in the field distribution. However, the estimated residual distortion was below 1.2mm geometric distortion at SID≥120cm (perpendicular) and SID≥130cm (inline) for a 10mT/m frequency-encoding gradient. (5) Due to magnetic saturation of the MLC materials, the field distortion remained constant at 1.0\,\textnormal {T}$\end{document}]]>B 0>1.0T. Conclusions: This work shows that the MRI field distortions caused by the MLC cannot be ignored and must be thoroughly investigated for any MRI-linac system. The numeric distortion values obtained for our 1.0T magnet may vary for other magnet designs with substantially different fringe fields, however the concept of modest increases in the SID to reduce the distortion to a shimmable level is generally applicable. © 2013 © 2013 Author(s).

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