bluuebunny/crossref_metadata_2025_split huggingface dataset:
Characterization of an in vivo diode dosimetry system for clinical use
Authors: Huang Kai , Bice William S. , Hidalgo‐Salvatierra Oscar 
Published: February 2007

An in vivo dosimetry system that uses p‐type semiconductor diodes with buildup caps was characterized for clinical use on accelerators ranging in energy from 4 to 18 MV. The dose per pulse dependence was investigated. This was done by altering the source‐surface distance, field size, and wedge for photons. The off‐axis correction and effect of changing repetition rate were also investigated. A model was developed to fit the measured two‐dimensional diode correction factors.PACS number(s): 87.66.–a, 87.52.–g
Radiation safety issues with high activities of liquid I‐125: Techniques and experience
Authors: de Guzman A. F. , Kearns W. T. , Shaw E. , Tatter S. , Stieber V. , Yates C. , Amadeo H. , Hinson W. H. 
Published: February 2007

The handling of a liquid radioactive source is a procedure that is uncommon for the average clinical medical physicist. A newly approved treatment device utilizes high activities of liquid I‐125 solution as the source of radiation. The radiation safety issues and our experience utilizing high activity liquid I‐125 sources are presented. To date we have treated 22 patients with infused activities ranging up to 26.8 GBq (724 mCi). The careful manipulation of such solutions is important to maintain a safe environment for the patients and the involved medical staff.PACS number(s): 87.53.‐j, 87.52.‐g
Stereotactic radiotherapy in the treatment of ocular melanoma: A noninvasive eye fixation aid and tracking system
Authors: Jaywant S. M. , Osei E. K. , Ladak S. 
Published: February 2007

Ocular melanoma is frequently treated using brachytherapy implants (such as and plaques or wire), surgery, or external beam radiotherapy using small beams, high energy x‐rays, or proton therapy. The last technique, though very expensive, provides improved dose distributions and dose localizations in the treatment of tumours adjacent to critical normal tissues. The technique of fractionated stereotactic radiotherapy is now being used at an increasingly large number of centers in the treatment of lesions in the brain, and the head and neck. This article describes the successful extension of the stereotactic technique to the treatment of ocular melanoma: an eye fixation aid is attached to a noninvasive, relocatable Gill‐Thomas‐Cosman head frame together with a simple eye‐movement tracking system.PACS number(s): 87.53.–j, 87.90.+y
Reimbursement versus effort in medical physics practice in radiation oncology
Authors: Herman Michael G. , Mills Michael D. , Gillin Michael T. 
Published: February 2007

The changes in health care reimbursement have the potential to affect the availability of quality medical physicist service in patient care. A survey was conducted by the AAPM Professional Council and the ACMP to collect cost information for special medical physics consultation, CPT4‐77370 and continuing medical physics, CPT4‐77336. The data collected from the survey was compared to current reimbursement schemes for a number of special procedures. Under varying reimbursement schemes, the costs of the medical physics services provided cannot be recaptured by the institution. It remains important for medical physicists to assess our utilization of resources and allocation to each of the services we provide and to understand the implications of policy changes at the federal and local levels.PACS number(s): 87.90.+y, 87.53.–j
Predictability of electron cone ratios with respect to linac make and model
Authors: Tailor R. C. , Followill D. S. , Hernandez N. , Ibbott G. S. , Hanson W. F. 
Published: February 2007

In the past, the Radiological Physics Center (RPC) has developed standard sets of photon depth‐dose and wedge‐factor data, specific to the make, model, and wedge design of the linear accelerator (linac). In this paper, the RPC extends the same concept to electron‐cone ratios. Since 1987, the RPC has measured and documented cone‐ratio (CR) values during on‐site dosimetry review visits to institutions participating in National Cancer Institute cooperative clinical trials. Data have been collected for approximately 500 electron beams from a wide spectrum of linac models. The analysis presented in this paper indicates that CR values are predictable to 2% to 3% (two standard deviations) for a given make and model of linac with a few exceptions. The analysis also revealed some other interesting systematics. For some models, such as the Varian Clinac 2500 and the Elekta/Philips SL18, SL20, and SL25, CR values were nearly identical for cone sizes (or ) and across the range of available energies. Certain models of the same make of linac, such as the Mevatron MD, KD, and 6700 series models or the Clinac 2100 and 2300 models, exhibited indistinguishable CRs. Irrespective of linac model, two consistent general trends were observed: namely, an increase in CR value with incident beam energy for cone sizes smaller than and a decrease with energy for cone sizes larger than . These data are valuable to the RPC as a quality assurance remote‐monitoring tool to identify potential dosimetry errors. The physics community will also find the data useful in several ways: as a redundant check for clinical values in use, to validate the values measured during commissioning of new machines or to ensure consistency of values measured during annual quality assurance procedures.PACS number(s): 87.54.–n, 87.53.–j
Dosimetric, mechanical, and geometric verification of conformal dynamic arc treatment
Authors: Malatesta T. , Landoni V. , delle Canne S. , Bufacchi A. , Marmiroli L. , Caspiani O. , Bonanni A. , Tortoreto F. , Leone M. V. , Capparella R. , Fragomeni R. , Begnozzi L. 
Published: February 2007

A conformal dynamic arc (CD‐arc) technique has been implemented at the S. Giovanni Calibita‐Fatebenefratelli Hospital Radiotherapy Center. This technique is performed by rotational beams and a dynamic multileaf collimator (DMLC): during the treatment delivery the gantry rotates and the field shape, formed by the DMLC changes continuously. The aim of this study was to perform dosimetric, mechanical, and geometric verification to ensure that the dose calculated by a commercial treatment planning system and administered to the patient was correct, before and during the clinical use of this technique. Absolute dose values, at the isocenter and at other points placed in dose heterogeneity zone, have been verified with an ionization chamber in a solid homogeneous phantom. In uniform dose regions measured dose values resulted in agreements with the calculated doses within 2%. Isodose distributions have also been determined by radiographic films and compared with those predicted by the planning system. Distance to agreement between calculated and measured isodoses in dose gradient zone was within 2 mm. In conclusion, our results demonstrated the feasibility and the accuracy of the CD‐arc technique for achieving highly conformal dose distributions. Up till now 20 patients have been treated with CD‐arc therapy.PACS number(s): 87.53.Kn, 87.53.Dq, 87.53.Oq, 87.53.St, 87.53.Tf
Comparison of ultrasound quality assurance phantom measurements from matched and mixed scanner‐transducer combinations
Authors: Tradup D. J. , Hangiandreou N. J. , Taubel J. P. 
Published: February 2007

Our goal in this work was to compare the results of common phantom tests made using matched and mixed ultrasound (US) scanner‐transducer combinations. Sets of common US quality assurance (QA) measurements were made using matched US scanner‐transducer combinations (i.e., transducers purchased for use with a particular scanner), as well as unmatched (mixed) combinations. Measurements of vertical and horizontal distance accuracy, and depth of penetration were performed using three common transducer types. Means, standard deviations, and differences between the mean mix and match measurements divided by the standard deviation (match‐mix difference, or MMD), and two‐sided, paired t‐tests were computed for the groups of mixed and matched measurements. MMDs for vertical and horizontal distance accuracy test results were less than 0.87 in all cases, well below our threshold value of 2.0, which indicates that a significant difference exists. MMDs for the depth of penetration measurements were less than 1.50, again below the threshold value. These results suggest that all of the mixed and matched data sets were very similar. The more sensitive t‐tests indicate statistically significant differences in only 2 of the 18 pairs of data sets. In conclusion, this study suggests that QA measurements generated by mixed or matched scanner‐transducer combinations are very comparable. The ability to obtain QA phantom test data from mixed scanner‐transducer combinations reduces the time required for US QA testing.PACS number(s): 87.57.–s, 87.62.+n
IMRT‐application with an add‐on MMLC
Authors: Tücking Thomas , Nill Simeon , Oelfke Uwe 
Published: February 2007

In order to provide automatic IMRT dose delivery with an add‐on MMLC a technical integration of a MMLC system with a linear accelerator was realized. The principle of this integration and the changes and enhancements of the existing hard‐and software are briefly described. The system was tested by the automatic delivery of an IMRT plan designed for a head and neck phantom. A verification of dose delivery was performed with film dosimetry. The plan consisting of 78 “step and shoot” segments could be delivered within 17 minutes. A high spatial accuracy of the fluence pattern at the isocentre was reached by a resolution of mm2. The measured dose profiles were within 3% of the maximum dose of the calculated profiles.PACS number(s): 87.53.–j, 87.90.+y
Using the frame averaging of aS500 EPID for IMRT verification
Authors: Chang J. , Ling C. C. 
Published: February 2007

In this study, we evaluated the use of aS500 EPID for the verification of IMRT beam delivery, using the synchronous, frame‐averaging acquisition. In this approach, an EPID continuously integrates frames while irradiated by an IMRT field; the averaged image is then converted to a dose profile using a linear calibration curve, and is compared with the planned profiles using a linear‐regression model, which returns an index σ (root mean squared error) for the goodness of fit. We identified several potential errors in this acquisition mode: missing data between the start of irradiation and imaging, and from the last (incomplete) frame, which we proved are insignificant for IMRT fields; and EPID dead time during irradiation stemming from data transfer, which we successfully corrected for clinical . We compared the measured relative profiles and central axis dose of 25 prostate fields with the planned ones. Applying our correction methods, very good agreement was obtained between the measured and planned profiles with a mean a of 1.9% and a standard deviation of 0.5%; for central‐axis dose the agreement was better than 2.0%. We conclude that the aS500 is an effective tool for verification of IM beam delivery in the range of clinical settings. Although the vender is developing an upgrade to fix similar problems, our results demonstrate that the current configuration with simple correction schemes can achieve satisfactory results.PACS number(s): 87.53.Oq, 87.53.Xd
A study of GafChromic XR Type R film response with reflective‐type densitometers and economical flatbed scanners
Authors: Thomas G. , Chu R. Y. L. , Rabe Frank 
Published: February 2007

The GafChromic XR Type R film is a relatively new product for recording high radiation dose in interventional radiological procedures. Means of measuring the film response were studied in this investigation. Two handheld reflective‐type densitometers of different models were compared in the range of 0–8 Gy. They were found to be in excellent agreement. Five reflective flatbed scanners of different models were compared by a simple preliminary test. Their widely differed performances suggest the need of testing a scanner before using it for dosimetry measurement. A selected scanner was further tested for its ability to measure radiation in the range of 0–8 Gy and for the development of a scanning protocol. This experiment suggested the inclusion of a calibration pattern with known exposures and a black reference step in the scanning of a film in RGB mode. Then the red component of this image should be used for dosimetry computation. This method was compared to the use of a red acetate filter. The latter was demonstrated to be a possible alternative for measurement below 5 Gy and when there is no software ability to split an image into color components.PACS number(s): 87.66.–a, 87.52.–g
Utilization of custom electron bolus in head and neck radiotherapy
Authors: Kudchadker R. J. , Antolak J. A. , Morrison W. H. , Wong P. F. , Hogstrom K. R. 
Published: February 2007

Conventional methods of treating superficial head and neck tumors, such as the wedge pair technique or the use of multiple electron fields of varying energies, can result in excellent tumor control. However, in some cases, these techniques irradiate healthy tissue unnecessarily and/or create hot and cold spots injunction regions, particularly in patients with complex surface contour modification or varying planning target volume (PTV) thickness. The objective of this work is to demonstrate how bolus electron conformal therapy can be used for these patients. Two patients treated using this technique are presented. The first patient was diagnosed with malignant fibrous histiocytoma involving the right ear concha and was treated with 12‐MeV electrons. The second patient was diagnosed with acinic cell carcinoma of the left parotid gland and was treated with 20‐MeV electrons after having undergone a complete parotidectomy. Each patient's bolus was designed using bolus design tools implemented in an in‐house treatment‐planning system (TPS). The bolus was fabricated using a computer‐controlled milling machine. As part of the quality assurance process to ensure proper fabrication and placement of the bolus, the patients underwent a second computed tomography (CT) scan with the bolus in place. Using that data, the final dose distribution was computed using the Philips Pinnacle3 TPS (Philips Medical Systems, Andover, MA). Results showed that the 90% isodose surface conformed well to the PTV and that the dose to critical structures such as cord, brain, and lung was well below tolerance limits. Both patients showed no evidence of disease six months post‐radiotherapy. In conclusion, electron bolus conformal therapy is a viable option for treating head and neck tumors, particularly patients having a variable thickness PTV or surface anatomy with surgical defects.PACS number(s): 87.53.Kn
Quality of coverage: Conformity measures for stereotactic radiosurgery
Authors: Wu Q.‐R. Jackie , Wessels B. W. , Einstein D. B. , Maciunas R. J. , Kim E. Y. , Kinsella T. J. 
Published: February 2007

In radiosurgery, conformity indices are often used to compare competing plans, evaluate treatment techniques, and assess clinical complications. Several different indices have been reported to measure the conformity of the prescription isodose to the target volume. The PITV recommended in the Radiation Therapy Oncology Group (RTOG) radiosurgery guidelines, defined as the ratio of the prescription isodose volume (PI) over the target volume (TV), is probably the most frequently quoted. However, these currently used conformity indices depend on target size and shape complexity. The objectives of this study are to systematically investigate the influence of target size and shape complexity on existing conformity indices, and to propose a different conformity index–the conformity distance index (CDI). The CDI is defined as the average distance between the target and the prescription isodose line. This study examines five case groups with volumes of 0.3, 1.0, 3.0, 10.0, and 30.0 cm3. Each case group includes four simulated shapes: a sphere, a moderate ellipsoid, an extreme ellipsoid, and a concave “C” shape. Prescription dose coverages are generated for three simplified clinical scenarios, i.e., the PI completely covers the TV with 1 and 2 mm margins, and the PI over‐covers one half of the TV with a 1 mm margin and under‐covers the other half with a 1 mm margin. Existing conformity indices and the CDI are calculated for these five case groups as well as seven clinical cases. When these values are compared, the RTOG PITV conformity index and other similar conformity measures have much higher values than the CDI for smaller and more complex shapes. With the same quality of prescription dose coverage, the CDI yields a consistent conformity measure. For the seven clinical cases, we also find that the same PITV values can be associated with very different conformity qualities while the CDI predicts the conformity quality accurately. In summary, the proposed CDI provides more consistent and accurate conformity measurements for all target sizes and shapes studied, and therefore will be a more useful conformity index for irregularly shaped targets.PACS number(s): 87.90.+y, 87.53.Ly
Book Review
Authors: III Walter H. Grant 
Published: February 2007

A Practical Guide to Intensity Modulated Radiation Therapy. Memorial Sloan‐Kettering Cancer Center (MSKCC) Staff, Medical Physics Publishing, Madison, WI, 2003. 450 pp. Price: $125.00. ISBN: 1‐30524‐13‐7.PACS number(s): 87.53.‐j, 87.53.Xd, 87.53.Kn
Book Review
Authors: Agazaryan Nzhde 
Published: February 2007

Proceedings of the 2003 AAPM Summer School, Intensity Modulated Radiation Therapy‐The State Of The Art. Colorado Springs, CO, 22–26 June 2003, edited by Jatinder R. Palta, Ph.D and T. Rockwell Mackie, Ph.D., Medical Physics Publishing, Madison, WI. Price: $100 (AAPM Members $80). ISBN: 1‐30524‐16‐1.PACS number(s): 87.53.Bn, 87.53.Kn
Technical note: The effect of the 4‐mm‐collimator output factor on gamma knife dose distributions
Authors: Gibbons John P. , Mihailidis Dimitris , Worthington Curtis , Alkhatib Hassaan , Boulware Raleigh , Clark Robert , Dial Burke , Neglia William 
Published: February 2007

We present results of investigations of the clinical significance of variations in the value of the 4‐mm‐collimator output factor, . Changes in treatment volume, dose‐volume histograms (DVHs), and isodose distributions were studied, by varying up to 20%. The variations were performed on a sample of clinical patient treatment plans for which the 4 mm collimator was used. Although smaller effects are noted for the prescription isodose line, greater dosimetric changes occur for higher dose regions within the target.PACS number(s): 87.53.–j, 87.52.–g
A dwell position verification method for high dose rate brachytherapy
Authors: Liu Lizhong , Prasad Satish C. , Bassano Daniel A. , Heavern Joel , Keshler Bonnie , Hahn Seung S. 
Published: February 2007

Misplacement of dwell positions is a potential source of misadministration in high dose rate (HDR) brachytherapy. In this work, we present a dwell position verification method using fluoroscopic images. A mobile C‐arm fluoroscopic machine is used to take a snapshot of the treatment machine's check cable as it reaches the most distal dwell position. This fluoroscopic image is displayed side‐by‐side with a treatment planning image on a dual monitor relay station at the HDR treatment console. Any discrepancy between the check cable's position on the verification image and the intended dwell position on the planning image can be identified, immediately, thus avoiding the possibility of treating the wrong target volume.PACS numbers: 87.53.Jw, 87.53.Xd, 87.59.Ci
Verification of inverse planning and treatment delivery for segmental IMRT
Authors: Bedford James L. , Childs Peter J. , Warrington Alan P. 
Published: February 2007

With intensity‐modulated radiotherapy (IMRT), it is important that the inverse planning process yields the most appropriate dose distribution for the patient and that the delivered dose then corresponds to the planned dose. This paper presents methods by which the inverse planning and delivery of segmental (step‐and‐shoot) IMRT can be verified, and gives results for a typical treatment planning system (Pinnacle3 v6.2b, Philips Radiation Oncology Systems, Milpitas, CA). Inverse planning was assessed by observing the reduction in objective function as fields were successively added to three‐field prostate, esophagus, and thyroid plans. The ability of the treatment planning system to calculate dose for a segmented field was examined by creating a stepped field with five successively narrowing segments. The complete planning process was then investigated by using two orthogonal IMRT fields to create a homogeneous dose distribution in a cubic water phantom. Finally, a clinical situation was simulated by creating a five‐field segmental IMRT plan for a lung target in an anthropomorphic phantom. A conformal plan was also compared for context. Addition of fields to inverse plans generally resulted in a reduction of objective function, indicating consistency of inverse planning solutions. Planned dose for fields with stepped intensity agreed with ionization chamber measurements to within 5%. For orthogonal fields, planned dose distributions agreed well with dose measured using film and agreed with ionization chamber measurements to within 3%. For the anthropomorphic phantom, the standard deviation of difference between planned and measured dose was 4%. Although no consensus has yet been reached on what constitutes an acceptable IMRT plan, these results indicate that step‐and‐shoot IMRT can be planned and delivered using the system described with comparable accuracy to a standard conformal treatment.PACS numbers: 87.53.Dq, 87.53.Kn, 87.53.Mr, 87.53.Tf, 87.53.Xd
Monte Carlo calculations of output factors for clinically shaped electron fields
Authors: Turian Julius V. , Smith Brett D. , Bernard Damian A. , Griem Katherine L. , Chu James C. 
Published: February 2007

We report on the use of the EGS4/BEAM Monte Carlo technique to predict the output factors for clinically relevant, irregularly shaped inserts as they intercept a linear accelerator's electron beams. The output factor for a particular combination—energy, cone, insert, and source‐to‐surface distance (SSD)—is defined in accordance with AAPM TG‐25 as the product of cone correction factor and insert correction factor, evaluated at the depth of maximum dose. Since cone correction factors are easily obtained, we focus our investigation on the insert correction factors (ICFs). An analysis of the inserts used in routine clinical practice resulted in the identification of a set of seven “idealized” shapes characterized by specific parameters. The ICFs for these shapes were calculated using a Monte Carlo method (EGS4/BEAM) and measured for a subset of them using an ion chamber and well‐established measurement methods. Analytical models were developed to predict the Monte Carlo–calculated ICF values for various electron energies, cone sizes, shapes, and SSDs. The goodness‐of‐fit between predicted and Monte Carlo–calculated ICF values was tested using the Kolmogorov–Smirnoff statistical test. Results show that Monte Carlo–calculated ICFs match the measured values within 2.0% for most of the shapes considered, except for few highly elongated fields, where deviations up to 4.0% were recorded. Predicted values based on analytical modeling agree with measured ICF values within 2% to 3% for all configurations. We conclude that the predicted ICF values based on modeling of Monte Carlo–calculated values could be introduced in clinical use.PACS numbers: 87.53.Wz, 87.53.Hv