Biomed Imaging Interv J
· 2007 Apr · PMID 21614278
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Selection of the appropriate radiation quality is an important aspect of optimisation for every clinical imaging task in radiology, since it affects both image quality and patient dose. Spreadsheet calculations of attenu...Selection of the appropriate radiation quality is an important aspect of optimisation for every clinical imaging task in radiology, since it affects both image quality and patient dose. Spreadsheet calculations of attenuation and absorption have been applied to basic imaging tasks to provide an assessment of imaging performance for a selection of phosphors used in radiology systems. Contrast, which is an important component of image quality affected by radiation quality, has been assessed in terms of the contrast to noise ratio (CNR) for a variety of X-ray beams. Both CNR and patient dose fall with tube potential, and selection of the best option is a compromise that will provide an adequate level of image quality with as low a radiation dose as practicable. It is important that systems are set up to match the response of the imaging phosphor, as there are significant differences between phosphors. For example, the sensitivity of barium fluorohalides used in computed radiography declines at higher tube potentials, whereas that of gadolinium oxysulphide used in rare earth screens increases. Addition of 0.2 mm copper filters, which can reduce patient entrance surface dose by 50%, may be advantageous for many applications in radiography and fluoroscopy. The disadvantage of adding copper is that tube output levels have to be increased. Application of simple calculations of the type employed here could prove useful for investigating and assessing the implications of potential changes in X-ray beam quality prior to implementation of new techniques.
Biomed Imaging Interv J
· 2007 Apr · PMID 21614277
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Positron emission tomography (PET) has become one of the major tools for the in vivo localisation of positron-emitting tracers and now is performed routinely using (18)F-fluorodeoxyglucose (FDG) to answer important clini...Positron emission tomography (PET) has become one of the major tools for the in vivo localisation of positron-emitting tracers and now is performed routinely using (18)F-fluorodeoxyglucose (FDG) to answer important clinical questions including those in cardiology, neurology, psychiatry, and oncology. The latter application contributed largely to the wide acceptance of this imaging modality and its use in clinical diagnosis, staging, restaging, and assessment of tumour response to treatment. Dual-modality PET/CT systems have been operational for almost a decade since their inception. The complementarity between anatomic (CT) and functional or metabolic (PET) information provided in a "one-stop shop" has been the driving force of this technology. Although combined anato-metabolic imaging is an obvious choice, the way to perform imaging is still an open issue. The tracers or combinations of tracers to be used, how the imaging should be done, when contrast-enhanced CT should be performed, what are the optimal acquisition and processing protocols, are all unanswered questions. Moreover, each data acquisition-processing combination may need to be independently optimised and validated. This paper briefly reviews the basic principles of dual-modality imaging and addresses some of the practical issues involved in optimising PET/CT scanning protocols in a clinical environment.
Spelic D, Kaczmarek R, Hilohi M
… +1 more, Belella S
Biomed Imaging Interv J
· 2007 Apr · PMID 21614276
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PURPOSE: The Mammography Quality Standards Act (MQSA) was enacted in 1992 to set national standards for high-quality mammography, including standards for mammographic X-ray equipment, patient dose, clinical image quality...PURPOSE: The Mammography Quality Standards Act (MQSA) was enacted in 1992 to set national standards for high-quality mammography, including standards for mammographic X-ray equipment, patient dose, clinical image quality, and related technical parameters. The MQSA also requires minimum qualifications for radiologic technologists, interpreting physicians and medical physicists, mandates acceptable practices for quality-control, quality-assurance, and requires processes to audit medical outcomes. This paper presents the findings of MQSA inspections of facilities, which characterize significant factors affecting mammography quality in the United States. MATERIALS AND METHODS: Trained inspectors collected data regarding X-ray technical factors, made exposure measurements for the determination of mean glandular dose (MGD), evaluated image quality, and inspected the quality of the film-processing environment. The average annual facility and total U.S. screening exam workloads were computed using workload data reported by facilities. RESULTS: Mammography facilities have made technical improvements as evidenced by a narrower distribution of doses, higher phantom-film background optical densities associated with higher phantom image-quality scores, and better film processing. It is estimated that approximately 36 million screening mammography exams were conducted in 2006, a rate that is almost triple the exam volume estimated for 1997. Digital mammography (DM) is now in use at approximately 14% (1,191 of 8,834) of MQSA-certified mammography facilities. The results indicate that DM can offer lower dose to the patient while providing comparable or better image quality.
Biomed Imaging Interv J
· 2007 Apr · PMID 21614275
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The International Atomic Energy Agency (IAEA) under its mandate of developing and applying standards of radiation safety has initiated a number of activities in recent years on radiation protection in interventional card...The International Atomic Energy Agency (IAEA) under its mandate of developing and applying standards of radiation safety has initiated a number of activities in recent years on radiation protection in interventional cardiology. These activities are implemented through four mechanisms, namely training, providing information through the website, research projects and assistance to Member States through Technical Cooperation (TC) projects. Major international initiatives have been taken in the area of training where more than half a dozen regional training courses have been conducted for cardiologists from over 50 countries. Additionally four national training events for over 300 medical and paramedical staff members involved in interventional procedures were held. The training material is freely available on CD from the IAEA. The newly established website provides information on radiation protection issues [1]. Two coordinated research projects have just been completed where peak skin doses to patients undergoing high dose interventional procedures were studied and factors to manage patient doses were identified. The technical cooperation projects involving protection in cardiac interventional procedures have 30 countries as participants.
Biomed Imaging Interv J
· 2007 Apr · PMID 21614274
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In order to prevent accidents in radiotherapy, it is important to learn from accidents that have occurred previously. Lessons learned from a number of accidents are summarised and underlying patterns are looked for in th...In order to prevent accidents in radiotherapy, it is important to learn from accidents that have occurred previously. Lessons learned from a number of accidents are summarised and underlying patterns are looked for in this paper. Accidents can be prevented by applying several safety layers of preventive actions. Categories of these preventive actions are discussed together with specific actions belonging to each category of safety layer.
Biomed Imaging Interv J
· 2007 Apr · PMID 21614273
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PURPOSE: To present the experience in patient dose management and the development of an online audit tool for digital radiography. MATERIALS AND METHODS: Several tools have been developed to extract the information conta...PURPOSE: To present the experience in patient dose management and the development of an online audit tool for digital radiography. MATERIALS AND METHODS: Several tools have been developed to extract the information contained in the DICOM header of digital images, collect radiographic parameters, calculate patient entrance doses and other related parameters, and audit image quality. RESULTS: The tool has been used for mammography, and includes images from over 25,000 patients, over 75,000 chest images, 100,000 computed radiography procedures and more than 1,000 interventional radiology procedures. Examples of calculation of skin dose distribution in interventional cardiology based upon information of DICOM header and the results of dosimetric parameters for cardiology procedures in 2006 are presented. CONCLUSION: Digital radiology has great advantages for imaging and patient dose management. Dose reports, QCONLINE systems and the MPPS DICOM service are good tools to optimise procedures and to manage patient dosimetry data. The implementation of the ongoing IEC-DICOM standard for patient dose structured reports will improve dose management in digital radiology.
Biomed Imaging Interv J
· 2007 Apr · PMID 21614272
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The desire to increase the precision in radiotherapy delivery has led to the development of advanced imaging systems such as amorphous silicon (a-Si)-based electronic portal imaging, and kV and MV cone beam CT. These are...The desire to increase the precision in radiotherapy delivery has led to the development of advanced imaging systems such as amorphous silicon (a-Si)-based electronic portal imaging, and kV and MV cone beam CT. These are used prior to the delivery of radiation to visualise the organ to be treated and to ensure that the patient setup and treatment delivery are accurate. However, little attention has been given to the dose received by adjacent normal tissues during these imaging procedures. Though these doses are very small compared to the dose delivered during radiotherapy, the involvement of normal tissues and the concern that these could increase the probability of stochastic effect, mainly the induction of secondary malignancy, cannot be ignored. This article reviews some work on the doses received during imaging in radiotherapy and the methods to optimise the same.
Biomed Imaging Interv J
· 2007 Apr · PMID 21614271
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Radiation-induced injury to skin is an infrequent but potentially serious complication to complex fluoroscopically-guided interventional procedures. Due to a lack of experience with such injuries, the medical community h...Radiation-induced injury to skin is an infrequent but potentially serious complication to complex fluoroscopically-guided interventional procedures. Due to a lack of experience with such injuries, the medical community has found fluoroscopically-induced injuries difficult to diagnose. Injuries have occurred globally in many countries. Serious injuries most frequently occur on the back but have also occurred on the neck, buttocks and anterior of the chest. Severities of injuries range from skin rashes and epilation to necrosis of the skin and its underlying structures. This article reviews the characteristics of these injuries and some actions that can be taken to reduce their likelihood or seriousness.
Biomed Imaging Interv J
· 2007 Apr · PMID 21614270
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Radiography using film has been an established method for imaging the internal organs of the body for over 100 years. Surveys carried out during the 1980s identified a wide range in patient doses showing that there was s...Radiography using film has been an established method for imaging the internal organs of the body for over 100 years. Surveys carried out during the 1980s identified a wide range in patient doses showing that there was scope for dosage reduction in many hospitals. This paper discusses factors that need to be considered in optimising the performance of radiographic equipment. The most important factor is choice of the screen/film combination, and the preparation of automatic exposure control devices to suit its characteristics. Tube potential determines the photon energies in the X-ray beam, with the selection involving a compromise between image contrast and the dose to the patient. Allied to this is the choice of anti-scatter grid, as a high grid ratio effectively removes the larger component of scatter when using higher tube potentials. However, a high grid ratio attenuates the X-ray beam more heavily. Decisions about grids and use of low attenuation components are particularly important for paediatric radiography, which uses lower energy X-ray beams. Another factor which can reduce patient dose is the use of copper filtration to remove more low-energy X-rays. Regular surveys of patient dose and comparisons with diagnostic reference levels that provide a guide representing good practice enable units for which doses are higher to be identified. Causes can then be investigated and changes implemented to address any shortfalls. Application of these methods has led to a gradual reduction in doses in many countries.
Biomed Imaging Interv J
· 2007 Jan · PMID 21614269
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MatLab(®) has often been considered an excellent environment for fast algorithm development but is generally perceived as slow and hence not fit for routine medical image processing, where large data sets are now availab...MatLab(®) has often been considered an excellent environment for fast algorithm development but is generally perceived as slow and hence not fit for routine medical image processing, where large data sets are now available e.g., high-resolution CT image sets with typically hundreds of 512x512 slices. Yet, with proper programming practices - vectorization, pre-allocation and specialization - applications in MatLab(®) can run as fast as in C language. In this article, this point is illustrated with fast implementations of bilinear interpolation, watershed segmentation and volume rendering.
Teh B, Bloch C, Galli-Guevara M
… +12 more, Doh L, Richardson S, Chiang S, Yeh P, Gonzalez M, Lunn W, Marco R, Jac J, Paulino A, Lu H, Butler E, Amato R
Biomed Imaging Interv J
· 2007 Jan · PMID 21614267
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PURPOSE: Brain metastases from renal cell carcinoma (RCC) have been successfully treated with stereotactic radiosurgery (SRS). Metastases to extra-cranial sites may be treated with similar success using stereotactic body...PURPOSE: Brain metastases from renal cell carcinoma (RCC) have been successfully treated with stereotactic radiosurgery (SRS). Metastases to extra-cranial sites may be treated with similar success using stereotactic body radiation therapy (SBRT), where image-guidance allows for the delivery of precise high-dose radiation in a few fractions. This paper reports the authors' initial experience with image-guided SBRT in treating primary and metastatic RCC. MATERIALS AND METHODS: The image-guided Brainlab Novalis stereotactic system was used. Fourteen patients with 23 extra-cranial metastatic RCC lesions (orbits, head and neck, lung, mediastinum, sternum, clavicle, scapula, humerus, rib, spine and abdominal wall) and two patients with biopsy-proven primary RCC (not surgical candidates) were treated with SBRT (24-40 Gy in 3-6 fractions over 1-2 weeks). All patients were immobilised in body cast or head and neck mask. Image-guidance was used for all fractions. PET/CT images were fused with simulation CT images to assist in target delineation and dose determination. SMART (simultaneous modulated accelerated radiation therapy) boost approach was adopted. 4D-CT was utilised to assess tumour/organ motion and assist in determining planning target volume margins. RESULTS: Median follow-up was nine months. Thirteen patients (93%) who received SBRT to extra-cranial metastases achieved symptomatic relief. Two patients had local progression, yielding a local control rate of 87%. In the two patients with primary RCC, tumour size remained unchanged but their pain improved, and their renal function was unchanged post SBRT. There were no significant treatment-related side effects. CONCLUSION: Image-guided SBRT provides excellent symptom palliation and local control without any significant toxicity. SBRT may represent a novel, non-invasive, nephron-sparing option for the treatment of primary RCC as well as extra-cranial metastatic RCC.
Saw CB, Brandner E, Selvaraj R
… +3 more, Chen H, Saiful Huq M, Heron DE
Biomed Imaging Interv J
· 2007 Jan · PMID 21614265
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Respiratory-gated treatment techniques have been introduced into the radiation oncology practice to manage target or organ motions. This paper will review the implementation of this type of gated treatment technique wher...Respiratory-gated treatment techniques have been introduced into the radiation oncology practice to manage target or organ motions. This paper will review the implementation of this type of gated treatment technique where the respiratory cycle is determined using an external marker. The external marker device is placed on the abdominal region between the xyphoid process and the umbilicus of the patient. An infrared camera tracks the motion of the marker to generate a surrogate for the respiratory cycle. The relationship, if any, between the respiratory cycle and the movement of the target can be complex. The four-dimensional computed tomography (4DCT) scanner is used to identify this motion for those patients that meet three requirements for the successful implementation of respiratory-gated treatment technique for radiation therapy. These requirements are (a) the respiratory cycle must be periodic and maintained during treatment, (b) the movement of the target must be related to the respiratory cycle, and (c) the gating window can be set sufficiently large to minimise the overall treatment time or increase the duty cycle and yet small enough to be within the gate. If the respiratory-gated treatment technique is employed, the end-expiration image set is typically used for treatment planning purposes because this image set represents the phase of the respiratory cycle where the anatomical movement is often the least for the longest time. Contouring should account for tumour residual motion, setup uncertainty, and also allow for deviation from the expected respiratory cycle during treatment. Respiratory-gated intensity-modulated radiation therapy (IMRT) treatment plans must also be validated prior to treatment. Quality assurance should be performed to check for positional changes and the output in association with the motion-gated technique. To avoid potential treatment errors, radiation therapist (radiographer) should be regularly in-serviced and made aware of the need to invoke the gating feature when prescribed for selected patients.
Biomed Imaging Interv J
· 2007 Jan · PMID 21614264
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PET scanning, because of its impressive sensitivity and accuracy, is being incorporated into the standard staging workup for many cancers. These include lung cancer, lymphomas, head and neck cancers, and oesophageal canc...PET scanning, because of its impressive sensitivity and accuracy, is being incorporated into the standard staging workup for many cancers. These include lung cancer, lymphomas, head and neck cancers, and oesophageal cancers. PET often provides incremental information about the patient's disease status, adding to the data obtained from structural imaging methods, such as, CT scan or MRI. PET commonly upstages patients into more advanced disease categories. Incorporation of PET information into the radiotherapy planning process has the potential to reduce the risks of geographic miss and can help minimise unnecessary irradiation of normal tissues. The best means of incorporating PET information into radiotherapy planning is uncertain, and considerable effort is being expended in this area of research.
Naiyanet N, Oonsiri S, Lertbutsayanukul C
… +1 more, Suriyapee S
Biomed Imaging Interv J
· 2007 Jan · PMID 21614263
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PURPOSE: To measure the interfraction setup variation of patient undergoing intensity-modulated radiation therapy (IMRT) of head and neck cancer. The data was used to define adequate treatment CTV-to-PTV margin. MATERIAL...PURPOSE: To measure the interfraction setup variation of patient undergoing intensity-modulated radiation therapy (IMRT) of head and neck cancer. The data was used to define adequate treatment CTV-to-PTV margin. MATERIALS AND METHODS: During March to September 2006, data was collected from 9 head and neck cancer patients treated with dynamic IMRT using 6 MV X-ray beam from Varian Clinac 23EX. Weekly portal images of setup fields which were anterior-posterior and lateral portal images were acquired for each patient with an amorphous silicon EPID, Varian aS500. These images were matched with the reference image from Varian Acuity simulator using the Varis vision software (Version 7.3.10). Six anatomical landmarks were selected for comparison. The displacement of portal image from the reference image was recorded in X (Left-Right, L-R), Y (Superior-Inferior, S-I) direction for anterior field and Z (Anterior-Posterior, A-P), Y (S-I) direction for lateral field. The systematic and random error for individual and population were calculated. Then the population-based margins were obtained. RESULTS: A total of 135 images (27 simulation images and 108 portal images) and 405 match points was evaluated. The systematic error ranged from 0 to 7.5 mm and the random error ranged from 0.3 to 4.8 mm for all directions. The population-based margin ranged from 2.3 to 4.5 mm (L-R), 3.5 to 4.9 mm (S-I) for anterior field and 3.4 to 4.7 mm (A-P), 2.6 to 3.7 mm (S-I) for the lateral field. These margins were comparable to the margin that was prescribed at the King Chulalongkorn Memorial Hospital (5-10 mm) for head and neck cancer. CONCLUSION: The population-based margin is less than 5 mm, thus the margin provides sufficient coverage for all of the patients.
Biomed Imaging Interv J
· 2007 Jan · PMID 21614262
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The successful integration of molecular imaging and radiation therapy has been shown to significantly impact the management of patients with non-small cell lung cancer (NSCLC). The collaboration of multidisciplinary team...The successful integration of molecular imaging and radiation therapy has been shown to significantly impact the management of patients with non-small cell lung cancer (NSCLC). The collaboration of multidisciplinary team members, including radiation oncologists, radiation therapists, nuclear medicine physicians and physicists, has enabled PET/CT to be utilised for routine use throughout the radiotherapy treatment trajectory. Applications include disease diagnosis and staging, target volume definition for radiation therapy and monitoring tumour response to treatment. Not only has the adoption of this technology demonstrated benefits for our current patients, it is also opening doors for significant research in the future.
Ray Nj, Kringelbach M, Jenkinson N
… +7 more, Owen S, Davies P, Wang S, De Pennington N, Hansen P, Stein J, Aziz T
Biomed Imaging Interv J
· 2007 Jan · PMID 21614261
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PURPOSE: Treatment-resistant cluster headache can be successfully alleviated with deep brain stimulation (DBS) of the posterior hypothalamus [1]. Magnetoencephalography (MEG) is a non-invasive functional imaging techniqu...PURPOSE: Treatment-resistant cluster headache can be successfully alleviated with deep brain stimulation (DBS) of the posterior hypothalamus [1]. Magnetoencephalography (MEG) is a non-invasive functional imaging technique with both high temporal and high spatial resolution. However, it is not known whether the inherent electromagnetic (EM) noise produced by high frequency DBS is compatible with MEG. MATERIALS AND METHODS: We used MEG to record brain activity in an asymptomatic cluster headache patient with a DBS implanted in the right posterior hypothalamus while he made small movements during periods of no stimulation, 7 Hz stimulation and 180 Hz stimulation. RESULTS: We were able to measure brain activity successfully both during low and high frequency stimulation. Analysis of the MEG recordings showed similar activation in motor areas in during the patient's movements as expected. We also observed similar activations in cortical and subcortical areas that have previously been reported to be associated with pain when the patient's stimulator was turned on or off [2,3]. CONCLUSION: These results show that MEG can be used to measure brain activity regardless of the presence of high frequency deep brain stimulation.
Yartsev S, Dar A, Woodford C
… +3 more, Wong E, Bauman G, Van Dyk J
Biomed Imaging Interv J
· 2007 Jan · PMID 21614260
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Helical tomotherapy is a new form of image-guided radiation therapy that combines features of a linear accelerator and a helical computed tomography (CT) scanner. Megavoltage CT (MVCT) data allow the verification and cor...Helical tomotherapy is a new form of image-guided radiation therapy that combines features of a linear accelerator and a helical computed tomography (CT) scanner. Megavoltage CT (MVCT) data allow the verification and correction of patient setup on the couch by comparison and image registration with the kilovoltage CT multi-slice images used for treatment planning. An 84-year-old male patient with Stage III bulky non-small cell lung cancer was treated on a Hi-ART II tomotherapy unit. Daily MVCT imaging was useful for setup corrections and signaled the need to adapt the delivery plan when the patient's anatomy changed significantly.