Multidirectional lip-closing force in adult females after short-term lip training.

The purpose of this study was to investigate the multidirectional lip-closing force in adult females before and after short-term lip training. Sixty-six Japanese females participated in this study. The subjects performed lip training that involved maintaining 200 or 400 g of bottled water in the oral vestibule. The signals of directional lip-closing force were investigated in eight directions before training and 5 and 7 days after the lip training. The differences in the closing force between pre- and post-training were then analysed statistically. The lip-closing force increased in the following order: pre-training, 5 days post-training and 7 days post-training in every direction (P < 0·05). The patterns of the increase in the lip-closing force in the upper, lower, right and left directions as a result of the repetitions were similar. No significant differences were noted between the training effects with loads of 200 and 400 g. Our findings demonstrated that the lip-closing force was influenced by the short-term lip training.

Semi-automatic cone beam CT segmentation of in vivo pre-clinical subcutaneous tumours provides an efficient non-invasive alternative for tumour volume measurements.

OBJECTIVE: To evaluate the feasibility and accuracy of using cone beam CT (CBCT) scans obtained in radiation studies using the small-animal radiation research platform to perform semi-automatic tumour segmentation of pre-clinical tumour volumes. METHODS: Volume measurements were evaluated for different anatomical tumour sites, the flank, thigh and dorsum of the hind foot, for a variety of tumour cell lines. The estimated tumour volumes from CBCT and manual calliper measurements using different volume equations were compared with the "gold standard", measured by weighing the tumours following euthanasia and tumour resection. The correlation between tumour volumes estimated with the different methods, compared with the gold standard, was estimated by the Spearman's rank correlation coefficient, root-mean-square deviation and the coefficient of determination. RESULTS: The semi-automatic CBCT volume segmentation performed favourably compared with manual calliper measures for flank tumours ≤2 cm(3) and thigh tumours ≤1 cm(3). For tumours >2 cm(3) or foot tumours, the CBCT method was not able to accurately segment the tumour volumes and manual calliper measures were superior. CONCLUSION: We demonstrated that tumour volumes of flank and thigh tumours, obtained as a part of radiation studies using image-guided small-animal irradiators, can be estimated more efficiently and accurately using semi-automatic segmentation from CBCT scans. ADVANCES IN KNOWLEDGE: This is the first study evaluating tumour volume assessment of pre-clinical subcutaneous tumours in different anatomical sites using on-board CBCT imaging. We also compared the accuracy of the CBCT method to manual calliper measures, using various volume calculation equations.

Time series prediction of lung cancer patients' breathing pattern based on nonlinear dynamics.

This study focuses on predicting breathing pattern, which is crucial to deal with system latency in the treatments of moving lung tumors. Predicting respiratory motion in real-time is challenging, due to the inherent chaotic nature of breathing patterns, i.e. sensitive dependence on initial conditions. In this work, nonlinear prediction methods are used to predict the short-term evolution of the respiratory system for 62 patients, whose breathing time series was acquired using respiratory position management (RPM) system. Single step and N-point multi step prediction are performed for sampling rates of 5 Hz and 10 Hz. We compare the employed non-linear prediction methods with respect to prediction accuracy to Adaptive Infinite Impulse Response (IIR) prediction filters. A Local Average Model (LAM) and local linear models (LLMs) combined with a set of linear regularization techniques to solve ill-posed regression problems are implemented. For all sampling frequencies both single step and N-point multi step prediction results obtained using LAM and LLM with regularization methods perform better than IIR prediction filters for the selected sample patients. Moreover, since the simple LAM model performs as well as the more complicated LLM models in our patient sample, its use for non-linear prediction is recommended.

Multidisciplinary treatment for a patient with traumatically intruded permanent canine and premolar.

When selecting treatment for traumatically intruded teeth, various factors should be evaluated including the degree of intrusion, pulp vitality, patient's age and maturity of the tooth. Treatment options consist of surgical repositioning, orthodontic extrusion and spontaneous re-eruption. This study describes a case of a 22-year-old male with traumatically intruded maxillary canine and first premolar that was treated comprehensively by an orthodontist, endodontist and prosthodontist two months after injury.

The potential for an enhanced role for MRI in radiation-therapy treatment planning.

The exquisite soft-tissue contrast of magnetic resonance imaging (MRI) has meant that the technique is having an increasing role in contouring the gross tumor volume (GTV) and organs at risk (OAR) in radiation therapy treatment planning systems (TPS). MRI-planning scans from diagnostic MRI scanners are currently incorporated into the planning process by being registered to CT data. The soft-tissue data from the MRI provides target outline guidance and the CT provides a solid geometric and electron density map for accurate dose calculation on the TPS computer. There is increasing interest in MRI machine placement in radiotherapy clinics as an adjunct to CT simulators. Most vendors now offer 70 cm bores with flat couch inserts and specialised RF coil designs. We would refer to these devices as MR-simulators. There is also research into the future application of MR-simulators independent of CT and as in-room image-guidance devices. It is within the background of this increased interest in the utility of MRI in radiotherapy treatment planning that this paper is couched. The paper outlines publications that deal with standard MRI sequences used in current clinical practice. It then discusses the potential for using processed functional diffusion maps (fDM) derived from diffusion weighted image sequences in tracking tumor activity and tumor recurrence. Next, this paper reviews publications that describe the use of MRI in patient-management applications that may, in turn, be relevant to radiotherapy treatment planning. The review briefly discusses the concepts behind functional techniques such as dynamic contrast enhanced (DCE), diffusion-weighted (DW) MRI sequences and magnetic resonance spectroscopic imaging (MRSI). Significant applications of MR are discussed in terms of the following treatment sites: brain, head and neck, breast, lung, prostate and cervix. While not yet routine, the use of apparent diffusion coefficient (ADC) map analysis indicates an exciting future application for functional MRI. Although DW-MRI has not yet been routinely used in boost adaptive techniques, it is being assessed in cohort studies for sub-volume boosting in prostate tumors.

A dosimetric analysis of tomotherapy based intensity modulated radiation therapy with and without bone marrow sparing in gynecologic malignancies.

Whole pelvic radiotherapy with concurrent chemotherapy is the standard of care for locally advanced cervical carcinoma. Published literature reports that the pelvic bone marrow (BM) dosimetric parameters of V10 > 90% and V20 > 80% are associated with higher rates of hematologic toxicities using this approach. Here, we investigate the ability of Tomotherapy based intensity modulated radiation therapy (IMRT) to reduce dose to pelvic BM while evaluating dose distribution to critical structures and planning target volume (PTV) coverage. Ten patients were selected for analysis. Normal structures, whole pelvic BM, PTV contours, and IMRT objects were standardized. Two whole pelvis Tomotherapy plans were created for each patient, one standard plan, and one with the addition of a BM sparing (BMS) constraint (V10 <85%, V20 < 80%). Data were calculated from multiple points with regard to BM dose, normal structure dose, and PTV coverage. Differences in dose distributions between the two sets of plans were analyzed using a paired t-test. The addition of a BMS planning constraint resulted in significant decreases in pelvic BM dose at the following dosimetric points: V5, V10, V15, V20, V30, V40, V50, and mean dose (p < 0.05 for all points). There were no significant differences in dose to small bowel, bladder or rectum, with the exception of one data point (small bowel V30, p = 0.004) between the two sets of plans. There was no sacrifice of PTV coverage or loss of homogeneity with the addition of a BMS planning constraint. BMS-IMRT significantly reduces radiation dose to the pelvic BM while maintaining the ability to spare dose to the small bowel, bladder and rectum. The planning constraints were met without violation of study criteria, and without sacrifice of PTV coverage. Further investigation is warranted to determine if rates of hematologic toxicity improve with utilization of Tomotherapy based BMS-IMRT.

SU-E-J-144: Recurrence Quantification Analysis of Lung Cancer Patients' Breathing Pattern.

PURPOSE: To demonstrate that Recurrence quantification analysis (RQA) can be used as a quantitative decision making tool to classify patients breathing pattern and select treatment strategy for maneuvering the tumor motion : (a) MIP based treatment (b) 4D treatment using non-linear prediction only (c) 4D treatment non-linear control prediction and breathing control. METHOD AND MATERIALS: In our previous work we established that breathing patterns can be described as a 5-6 dimensional nonlinear, stationary and deterministic system that exhibits sensitive dependence on initial conditions. Recurrence plots enable one to investigate an m-dimensional state space trajectory through a two-dimensional representation of its recurrences where the value of a specific pixel is 1 if the distance between the two corresponding trajectory points is less than a threshold value ε. Important measures calculated are: Recurrence Rate (RR), %Determinism, Divergence, Shannon Entropy, LMean, and Renyi entropy (K2). Time Resolved RQA: By implementing a sliding window design, each of the above calculated parameters is computed multiple times. Alignment of those parameters with the time series reveals details not obvious in the 1 -dimensional time series data. The breathing pattern for seven randomly chosen volunteers were recorded using the RPM system for 15 minutes. Non-linear prediction was performed and the normalized root mean square error (NRMSE) was calculated for each of the volunteer data. RESULTS: The threshold value ε was chosen such that the Recurrence Rate was equal to 1%. There is a strong correlation of NRMSE with Entropy, Determinism and LMean. Time resolved RR locates strong Unstable Periodic Orbits(UPOs), i.e. patterns of uninterrupted equally spaced diagonal lines. CONCLUSIONS: RQAs could prove to be a very powerful tool for design of personalized treatment regimen. Entropy, Determinism in conjunction with strong UPOs can be used to determine if patients are suitable candidates for prediction and chaos control.

SU-E-J-146: Time Series Prediction of Lung Cancer Patients' Breathing Pattern Based on Nonlinear Dynamics.

PURPOSE: Prediction methods for breathing patterns, which are crucial to deal with system latency in treatments of moving lung tumors using state-space methodologies based on non-linear dynamics are contrasted to linear predictive methods. METHOD AND MATERIALS: In our previous work we established that breathing patterns can be described as a 5-6 dimensional nonlinear, stationary and deterministic system that exhibits sensitive dependence on initial conditions. In this work, nonlinear prediction methods are used to predict the short-term evolution of the respiratory system for 3 patients. Single step and N-point multi step prediction are performed for sampling rates of 5Hz, 10Hz, and 30Hz. We compare the employed nonlinear prediction methods with respect to prediction accuracy to Infinite Impulse Response (IIR) prediction filters. The simplest form of local prediction is finding similar segments of scalar time series data in a higher dimensional embedding space. Hence, we predict the future value x(t)of N-time steps ahead by simply finding the average of nearest neighbor points to the point x(t) in the past and using them to estimate x(t+N), yielding a local average model (LAM). Local linear models (LLM) which are linear autoregressive models that hold only for a region around the target point formed by the nearest neighbor points is combined with a set of linear regularization techniques to solve ill-posed regression problems are also implemented. RESULTS: For all sampling frequencies, both single step and N-point multi step prediction results obtained using LAM and LLM with regularization methods are better than IIR prediction filters for the selected sample patients. CONCLUSIONS: The use of non-linear prediction methods for predicting the breathing pattern of lung cancer patients may lead to improved, robust and accurate long-term prediction to account for system latencies.

EBT2 radiochromic film for quality assurance of complex IMRT treatments of the prostate: micro-collimated IMRT, RapidArc, and TomoTherapy.

In response to the clinical need for a dosimetry system with both high resolution and minimal angular dependence, this study demonstrates the utility of Gafchromic EBT2 radiochromic dosimetry film for the quality assurance of micro-collimated IMRT, RapidArc and TomoTherapy treatments. Firstly, preliminary measurements indicated that the dose response of EBT2 film does not appreciably vary with either the angle of incidence of the radiation beam or the depth in water at which the film is placed. Secondly, prostate treatment plans designed for delivery using static-beam IMRT (collimated using the BrainLab m3 microMLC), RapidArc and TomoTherapy were investigated by comparing dose planes obtained from treatment planning calculations with EBT2 film measurements. For all treatment plans, the proportion of dose points agreeing with the film measurements to within γ (3%,3 mm) was found to be above 95%, with all points agreeing within 5%. The film images provided sufficient information to verify that the treatments could be delivered with an acceptable level of accuracy, while also providing additional information on low-level dose variations that were not predicted by the treatment planning systems. This information included: the location and extent of dose from inter-leaf leakage (in the RapidArc plan) and helical field junctioning (in the TomoTherapy plan), as well as the existence of small regions where the treatment planning system under-predicted the dose from very small treatment segments (in the micro-collimated IMRT plan).

Distribution of brain metastases: implications for non-uniform dose prescriptions.

OBJECTIVES: The aim of this study was to determine the disease-specific distribution of brain metastases and, using radiobiological modelling, estimate how these anatomical tendencies might be exploited when delivering prophylactic whole-brain radiotherapy for small cell lung cancer in complete remission. METHODS: Disease-specific brain metastasis atlases were created by mapping brain metastases to a standard image set from a database of patients who were to receive external beam radiation therapy. The specific diseases investigated included lung (both small cell and non-small cell), breast, renal and gynaecological cancers as well as melanoma. Radiobiological modelling was used to estimate how much improvement, in terms of the metastasis-free rate at 3 years, might be possible with non-uniform dose distributions if there are spatial biases in the incidence of micrometastases from small cell lung cancer. RESULTS: For lung and breast cancer, there was an increased probability of cerebellar metastases compared with what would be predicted based solely on brain volume. This trend was not evident for renal cancer, gynaecological malignancies or melanoma. CONCLUSION: Radiobiological models suggest that if there is a non-uniform distribution of microscopic brain metastases in patients with small cell lung cancer, higher population-based metastasis-free rates might be achievable with non-uniform irradiation compared with the same integral whole-brain dose delivered as a uniform prescription.

Independent quality assurance of a helical tomotherapy machine using the dose magnifying glass.

PURPOSE: Helical tomotherapy is a complex delivery technique, integrating CT image guidance and intensity modulated radiotherapy in a single system. The integration of the CT detector ring on the gantry not only allows patient position verification but is also often used to perform various QA procedures. This convenience lacks the rigor of a machine-independent QA process. METHODS: In this article, a Si strip detector, known as the Dose Magnifying Glass (DMG), was used to perform machine-independent QA measurements of the multileaf collimator alignment, leaf open time threshold, and leaf fluence output factor (LFOF). RESULTS: The DMG measurements showed good agreements with EDR2 film for the MLC alignment test while the CT detector agrees well with DMG measurements for leaf open time threshold and LFOF measurements. The leaf open time threshold was found to be approximately 20 ms. The LFOF measured with the DMG agreed within error with the CT detector measured LFOF. CONCLUSIONS: The DMG with its 0.2 mm spatial resolution coupled to TERA ASIC allowed real-time high temporal resolution measurements of the tomotherapy leaf movement. In conclusion, DMG was shown to be a suitable tool for machine-independent QA of a tomotherapy unit.

Time series analyses of breathing patterns of lung cancer patients using nonlinear dynamical system theory.

The underlying requirements for successful implementation of any efficient tumour motion management strategy are regularity and reproducibility of a patient's breathing pattern. The physiological act of breathing is controlled by multiple nonlinear feedback and feed-forward couplings. It would therefore be appropriate to analyse the breathing pattern of lung cancer patients in the light of nonlinear dynamical system theory. The purpose of this paper is to analyse the one-dimensional respiratory time series of lung cancer patients based on nonlinear dynamics and delay coordinate state space embedding. It is very important to select a suitable pair of embedding dimension 'm' and time delay 'τ' when performing a state space reconstruction. Appropriate time delay and embedding dimension were obtained using well-established methods, namely mutual information and the false nearest neighbour method, respectively. Establishing stationarity and determinism in a given scalar time series is a prerequisite to demonstrating that the nonlinear dynamical system that gave rise to the scalar time series exhibits a sensitive dependence on initial conditions, i.e. is chaotic. Hence, once an appropriate state space embedding of the dynamical system has been reconstructed, we show that the time series of the nonlinear dynamical systems under study are both stationary and deterministic in nature. Once both criteria are established, we proceed to calculate the largest Lyapunov exponent (LLE), which is an invariant quantity under time delay embedding. The LLE for all 16 patients is positive, which along with stationarity and determinism establishes the fact that the time series of a lung cancer patient's breathing pattern is not random or irregular, but rather it is deterministic in nature albeit chaotic. These results indicate that chaotic characteristics exist in the respiratory waveform and techniques based on state space dynamics should be employed for tumour motion management.

Assessment of multiple task activation and reproducibility in patients with benign and low-grade neoplasm.

Twenty-four patients with proven benign and low-grade brain neoplasms each performed two iterations of four fMRI paradigms: language (word generation), primary and association auditory (text listening), upper limb fine motor control (alternating-limb bilateral finger tapping), and primary visual perception (reversing checkerboard). Activation clusters with varying thresholds were generated for each scan and used to calculate reproducibility parameters: Difference in the Center of Mass (COM) location, R(size), and R(overlap). The average difference in the COM, R(size), and R(overlap) values ranged from 1.70 +/- 0.53 mm -10.60 +/- 3.21 mm, 0.6 +/- 0.04-0.90 +/- 0.05 and 0.23 +/- 0.12 -1 +/- 0.16 respectively for all tasks. These values are within the range of, or higher than, previously published reports on fMRI test-retest precision. FMRI is indicated to be a noninvasive tool with acceptable reproducibility measures for assessing the localizations of multiple language and sensorimotor functions in patients scheduled for radiotherapy treatment.

Accurate accumulation of dose for improved understanding of radiation effects in normal tissue.

The actual distribution of radiation dose accumulated in normal tissues over the complete course of radiation therapy is, in general, poorly quantified. Differences in the patient anatomy between planning and treatment can occur gradually (e.g., tumor regression, resolution of edema) or relatively rapidly (e.g., bladder filling, breathing motion) and these undermine the accuracy of the planned dose distribution. Current efforts to maximize the therapeutic ratio require models that relate the true accumulated dose to clinical outcome. The needed accuracy can only be achieved through the development of robust methods that track the accumulation of dose within the various tissues in the body. Specific needs include the development of segmentation methods, tissue-mapping algorithms, uncertainty estimation, optimal schedules for image-based monitoring, and the development of informatics tools to support subsequent analysis. These developments will not only improve radiation outcomes modeling but will address the technical demands of the adaptive radiotherapy paradigm. The next 5 years need to see academia and industry bring these tools into the hands of the clinician and the clinical scientist.

On the impact of functional imaging accuracy on selective boosting IMRT.

In order to quantify the impact of loss of functional imaging sensitivity and specificity on tumor control and normal tissue toxicity for selective boosting IMRT four selective boosting scenarios were designed: SB91-81 (EUD=91Gy for the high-risk tumor subvolume and EUD=81Gy for a remaining low-risk PTV (rPTV)), SB80-74, SB90-70, and risk-adaptive optimization. For each sensitivity loss level the loss in tumor control probability (DeltaTCP) was calculated. For each specificity loss level, the increase in rectal and bladder toxicity was quantified using the radiobiological indices (equivalent uniform dose (EUD) and normal tissue complication probability (NTCP)) as well as %-volumes irradiated. The impact of loss in sensitivity on local tumor control was maximal when the prescription dose level for rPTV had the lowest value. The SB90-70 plan had a DeltaTCP=29.6%, the SB91-81 plan had a DeltaTCP=9.5%, while for risk-adaptive optimization a DeltaTCP=4.7% was found. Independent of planning technique loss in functional imaging specificity appears to have a minimal impact on the expected normal tissue toxicity, since an increase in rectal or bladder toxicity as a function of loss in specificity was not observed. Additionally, all plans fulfilled the rectum and the bladder sparing criteria found in the literature for late rectal bleeding and genitourinary complications. Our study shows that the choice of a low-risk classification for the rPTV in selective boosting IMRT may lead to a significant loss in TCP. Furthermore, for the example considered in which normal tissue complications can be limited through the use of a tissue expander it appears that the therapeutic ratio can be improved using a functional imaging technique with a high sensitivity and limited specificity; while for cases were this is not possible, an optimal balance between sensitivity and specificity has to be found.

Dose escalated, hypofractionated radiotherapy using helical tomotherapy for inoperable non-small cell lung cancer: preliminary results of a risk-stratified phase I dose escalation study.

To improve local control for inoperable non-small cell lung cancer (NSCLC), a phase I dose escalation study for locally advanced and medically inoperable patients was devised to escalate tumor dose while limiting the dose to organs at risk including the esophagus, spinal cord, and residual lung. Helical tomotherapy provided image-guided IMRT, delivered in a 5-week hypofractionated schedule to minimize the effect of accelerated repopulation. Forty-six patients judged not to be surgical candidates with Stage I-IV NSCLC were treated. Concurrent chemotherapy was not allowed. Radiotherapy was delivered via helical tomotherapy and limited to the primary site and clinically proven or suspicious nodal regions without elective nodal irradiation. Patients were placed in 1 of 5 dose bins, all treated for 25 fractions, with dose per fraction ranging from 2.28 to 3.22 Gy. The bin doses of 57 to 80.5 Gy result in 2 Gy/fraction normalized tissue dose (NTD) equivalents of 60 to 100 Gy. In each bin, the starting dose was determined by the relative normalized tissue mean dose modeled to cause < 20% Grade 2 pneumonitis. Dose constraints included spinal cord maximum NTD of 50 Gy, esophageal maximum NTD < 64 Gy to < or = 0.5 cc volume, and esophageal effective volume of 30%. No grade 3 RTOG acute pneumonitis (NCI-CTC v.3) or esophageal toxicities (CTCAE v.3.0 and RTOG) were observed at median follow-up of 8.1 months. Pneumonitis rates were 70% grade 1 and 13% grade 2. Multivariate analysis identified lung NTD(mean) (p=0.012) and administration of adjuvant chemotherapy following radiotherapy (p=0.015) to be independent risk factors for grade 2 pneumonitis. Only seven patients (15%) required narcotic analgesics (RTOG grade 2 toxicity) for esophagitis, with only 2.3% average weight loss during treatment. Best in-field gross response rates were 17% complete response, 43% partial response, 26% stable disease, and 6.5% in-field thoracic progression. The out-of-field thoracic failure rate was 13%, and distal failure rate was 28%. The median survival was 18 months with 2-year overall survival of 46.8% +/- 9.7% for this cohort, 50% of whom were stage IIIB and 30% stage IIIA. Dose escalation can be safely achieved in NSCLC with lower than expected rates of pneumonitis and esophagitis using hypofractionated image-guided IMRT. The maximum tolerated dose has yet to be reached.

On the possible increase in local tumour control probability for gliomas exhibiting low dose hyper-radiosensitivity using a pulsed schedule.

Using modelling, we have developed a treatment strategy for gliomas exhibiting low dose hyper-radiosensitivity (HRS) that employs both a reduced dose-rate and pulsed treatment dose delivery. The model exploits the low dose hypersensitivity observed in some glioma cell lines at low radiation doses. We show, based on in vitro data, that a pulsed delivery of external beam radiation therapy could yield significant increases in local control. We therefore propose a pulsed delivery scheme for the treatment of gliomas in which the daily treatment fraction is delivered using 0.20 Gy pulses, separated by three minutes for a time-averaged dose-rate of 0.0667 Gy/min. The dose per pulse of 0.2 Gy is near or below the transition dose observed in vitro for four of the five glioma cell lines we have studied. Using five established glioma cell lines our modelling demonstrates that our pulsed delivery scheme yields a substantial increase in tumour control probability (TCP).

Intensity-modulated radiation therapy: emerging cancer treatment technology.

The use of intensity-modulated radiation therapy (IMRT) is rapidly advancing in the field of radiation oncology. Intensity-modulated radiation therapy allows for improved dose conformality, thereby affording the potential to decrease the spectrum of normal tissue toxicities associated with IMRT. Preliminary results with IMRT are quite promising; however, the clinical data is relatively immature and overall patient numbers remain small. High-quality IMRT requires intensive physics support and detailed knowledge of three-dimensional anatomy and patterns of tumour spread. This review focuses on basic principles, and highlights the clinical implementation of IMRT in head and neck and prostate cancer.

Quality assurance of a helical tomotherapy machine.

Helical tomotherapy has been developed at the University of Wisconsin, and 'Hi-Art II' clinical machines are now commercially manufactured. At the core of each machine lies a ring-gantry-mounted short linear accelerator which generates x-rays that are collimated into a fan beam of intensity-modulated radiation by a binary multileaf, the modulation being variable with gantry angle. Patients are treated lying on a couch which is translated continuously through the bore of the machine as the gantry rotates. Highly conformal dose-distributions can be delivered using this technique, which is the therapy equivalent of spiral computed tomography. The approach requires synchrony of gantry rotation, couch translation, accelerator pulsing and the opening and closing of the leaves of the binary multileaf collimator used to modulate the radiation beam. In the course of clinically implementing helical tomotherapy, we have developed a quality assurance (QA) system for our machine. The system is analogous to that recommended for conventional clinical linear accelerator QA by AAPM Task Group 40 but contains some novel components, reflecting differences between the Hi-Art devices and conventional clinical accelerators. Here the design and dosimetric characteristics of Hi-Art machines are summarized and the QA system is set out along with experimental details of its implementation. Connections between this machine-based QA work, pre-treatment patient-specific delivery QA and fraction-by-fraction dose verification are discussed.