Effect of a High-Protein Energy-Restricted Diet Combined with Resistance Training on Metabolic Profile in Older Individuals with Metabolic Impairments.

Adequate protein intake and resistance training are effective strategies to maintain muscle mass, but the effect of their combination on metabolic profile during weight loss remains to be determined in older adults. The main objective of this study was to determine the effect of a 16-week high-protein caloric restriction combined with resistance training on chronic disease risk factors in obese older individuals with metabolic impairments. A total of 26 overweight adults aged between 60 and 75 years (BMI 32.4 ± 3.9 kg/m2) with at least 2 factors of the metabolic syndrome participated in this study and were randomized into two groups: 1) high-protein caloric restriction (HP; n= 12) and 2) high-protein caloric restriction combined with dynamic-resistance training (HP+RT; n=14). Caloric intake was reduced by 500 kcal/d in all participants and protein intake equated 25-30% of total calories (~1.4 g/kg/d). Exercise training consisted of 3 session/week of resistance training on pulley machines. Outcome measures included total and trunk fat mass (FM), total and appendicular lean body mass (LBM), fasting glucose level, lipid profile and blood pressure. Our results showed that total and trunk FM (all p<0.0001) as well as fasting glucose (p<0.0001), triglycerides (p=0.002) and total cholesterol (p=0.03) levels decreased similarly in both groups. However, total (p=0.04) and appendicular (p=0.02) LBM decreased in the HP group only. Our data show that high-protein energy restriction improves health profile of obese elderly at high risk of chronic disease but needs to be combined with resistance training to maintain LBM.

Dosimetric Comparison Between 3-Dimensional Conformal and Robotic SBRT Treatment Plans for Accelerated Partial Breast Radiotherapy.

Accelerated partial breast irradiation is an attractive alternative to conventional whole breast radiotherapy for selected patients. Recently, CyberKnife has emerged as a possible alternative to conventional techniques for accelerated partial breast irradiation. In this retrospective study, we present a dosimetric comparison between 3-dimensional conformal radiotherapy plans and CyberKnife plans using circular (Iris) and multi-leaf collimators. Nine patients who had undergone breast-conserving surgery followed by whole breast radiation were included in this retrospective study. The CyberKnife planning target volume (PTV) was defined as the lumpectomy cavity + 10 mm + 2 mm with prescription dose of 30 Gy in 5 fractions. Two sets of 3-dimensional conformal radiotherapy plans were created, one used the same definitions as described for CyberKnife and the second used the RTOG-0413 definition of the PTV: lumpectomy cavity + 15 mm + 10 mm with prescription dose of 38.5 Gy in 10 fractions. Using both PTV definitions allowed us to compare the dose delivery capabilities of each technology and to evaluate the advantage of CyberKnife tracking. For the dosimetric comparison using the same PTV margins, CyberKnife and 3-dimensional plans resulted in similar tumor coverage and dose to critical structures, with the exception of the lung V5%, which was significantly smaller for 3-dimensional conformal radiotherapy, 6.2% when compared to 39.4% for CyberKnife-Iris and 17.9% for CyberKnife-multi-leaf collimator. When the inability of 3-dimensional conformal radiotherapy to track motion is considered, the result increased to 25.6%. Both CyberKnife-Iris and CyberKnife-multi-leaf collimator plans demonstrated significantly lower average ipsilateral breast V50% (25.5% and 24.2%, respectively) than 3-dimensional conformal radiotherapy (56.2%). The CyberKnife plans were more conformal but less homogeneous than the 3-dimensional conformal radiotherapy plans. Approximately 50% shorter treatment times and 50% lower number of delivered monitor units (MU) were achievable with CyberKnife-multi-leaf collimator than with CyberKnife-Iris. The CyberKnife-multi-leaf collimator treatment times were comparable to 3-dimensional conformal radiotherapy, however, the number of MU delivered was approximately 2.5 times larger. The suitability of 10 + 2 mm margins warrants further investigation.

[Head and neck adaptive radiotherapy]. / Radiothérapie adaptative ORL.

Onboard volumetric imaging systems can provide accurate data of the patient's anatomy during a course of head and neck radiotherapy making it possible to assess the actual delivered dose and to evaluate the dosimetric impact of complex daily positioning variations and gradual anatomic changes such as geometric variations of tumors and normal tissues or shrinkage of external contours. Adaptive radiotherapy is defined as the correction of a patient's treatment planning to adapt for individual variations observed during treatment. Strategies are developed to selectively identify patients that require replanning because of an intolerable dosimetric drift. Automated tools are designed to limit time consumption. Deformable image registration algorithms are the cornerstones of these strategies, but a better understanding of their limits of validity is required before adaptive radiotherapy can be safely introduced to daily practice. Moreover, strict evaluation of the clinical benefits is yet to be proven.

Irradiation of the prostate and pelvic lymph nodes with an adaptive algorithm.

PURPOSE: The simultaneous treatment of pelvic lymph nodes and the prostate in radiotherapy for prostate cancer is complicated by the independent motion of these two target volumes. In this work, the authors study a method to adapt intensity modulated radiation therapy (IMRT) treatment plans so as to compensate for this motion by adaptively morphing the multileaf collimator apertures and adjusting the segment weights. METHODS: The study used CT images, tumor volumes, and normal tissue contours from patients treated in our institution. An IMRT treatment plan was then created using direct aperture optimization to deliver 45 Gy to the pelvic lymph nodes and 50 Gy to the prostate and seminal vesicles. The prostate target volume was then shifted in either the anterior-posterior direction or in the superior-inferior direction. The treatment plan was adapted by adjusting the aperture shapes with or without re-optimizing the segment weighting. The dose to the target volumes was then determined for the adapted plan. RESULTS: Without compensation for prostate motion, 1 cm shifts of the prostate resulted in an average decrease of 14% in D-95%. If the isocenter is simply shifted to match the prostate motion, the prostate receives the correct dose but the pelvic lymph nodes are underdosed by 14% ± 6%. The use of adaptive morphing (with or without segment weight optimization) reduces the average change in D-95% to less than 5% for both the pelvic lymph nodes and the prostate. CONCLUSIONS: Adaptive morphing with and without segment weight optimization can be used to compensate for the independent motion of the prostate and lymph nodes when combined with daily imaging or other methods to track the prostate motion. This method allows the delivery of the correct dose to both the prostate and lymph nodes with only small changes to the dose delivered to the target volumes.

SU-E-T-556: Integration of Lung Blocks in the Inverse Planning Process of Modulated Arc Total Body Irradiation Using Cone Beam CT.

PURPOSE: The sizing and placement of lung blocks for total-body irradiation (TBI) is critical to prevent lung toxicities and maintain effective treatments. During modulated-arc TBI (MATBI) treatment, the patient is stationary near the floor while open-field beams with varying exposures are delivered. The inverse planning process currently aims for a uniform dose to the body, without accounting for the presence of lung blocks. This study investigates the possibility of including the effect of these blocks in the MATBI optimization process. METHODS: Dosimetric comparisons were performed using a water tank and a simple stack of solid water slabs. Lungs blocks made of cerrobend were fabricated and imaged using on-board megavoltage CBCT (MVCBCT). The reconstructed MVCBCT images were precisely registered with the reference CT for inverse planning. The cerrobend blocks were contoured in the planning system and the density was overridden to 9.3 g/cm3 . Simulated doses in Pinnacle were compared to ion chamber, diode array and gaf-chromic film measurements obtained at 1.0, 5.0, 10.0 and 20.0 cm depths. Specific optimization objectives on the lungs were tested on 5 patients including a lung re-treatment. RESULTS: The maximum difference between ion chamber measurements and the treatment planning predictions was 2.4%. The measurements profiles with the diode array correlated reasonably well (<5%) with predictions. Gaf-chromic films demonstrated good accuracy at depth but large differences (>10%) on the surface. Lung blocks reconstructed with MVCBCT were structuraly accurate without significant metal artifacts. A comparison of MATBI plans on patients shows that inclusion of lung blocks during optimization can reduce hot and cold areas in the lungs and the sternum. CONCLUSION: Reasonable predictions of the lung block transmission can be obtained following the developed technique using megavoltage CBCT. Thus, lung blocks can be included in the MATBI inverse planning process, which can help prevent complications and local failure.

SU-E-J-94: Investigating the Use of Deformable Algorithms to Register MR Images Acquired with and Without an Endo-Rectal Coil.

PURPOSE: Magnetic resonance spectroscopic imaging (MRSI) can identify the dominant intraprostatic lesion, which can then be boosted using high-dose rate (HDR) brachytherapy. MRSI requires the use of an endo-rectal coil, which deforms the prostate. We investigate the performance of deformable registration algorithms to deform MR images acquired with an endo-rectal coil to images acquired without a coil for HDR brachytherapy planning. METHODS: This study utilized MR images of five HDR brachytherapy patients acquired with and without an endo-rectal coil during the same MRSI imaging study. The prostate was contoured on each set of 'Coil-In' and 'Coil-Out' MR images by an experienced radiation oncologist. The 'Coil-In' and 'Coil-Out' images were rigidly aligned such that the posterior margins of the prostate were as close as possible without deformation. Variations on a commercially available deformation algorithm using the B-spline method were applied to a volume of interest that surrounded the prostate and excluded as much of the coil and rectum as possible. The Dice similarity index (DSI) was calculated between rigidly registered contours (DSI1), and compared to the DSI calculated between the 'Coil-In' contour and the contour deformed from the 'Coil-Out' image to the 'Coil-In' image (DSI2). The difference was calculated between DSI2 and DSI1, where a positive change in DSI would indicate an improvement in contour agreement over rigid registration of the prostate in the 'Coil-Out' and 'Coil-In' images. RESULTS: The B-spline deformation algorithm designed specifically for MR images was most effective in deforming the 'Coil-Out' to the 'Coil-In' prostate contour with a mean change in DSI of 0.0124 with contrast correction, and 0.0004 without. CONCLUSIONS: Out of six algorithms tested, only the MR-specific algorithm produced positive changes in DSI. The accuracy of the deformation algorithm on mapping the internal structures of the prostate between 'Coil-Out' and 'Coil-In' images is under investigation. We acknowledge Velocity for providing the registration software.

SU-E-J-84: Investigating the Use of Deformable Algorithms to Register and Accumulate Dose to the Spinal Cord for Head-And-Neck Radiotherapy Patients.

PURPOSE: Mega-voltage cone-beam CT (MVCBCT) imaging can be used to monitor changes in neck flexion and calculate the true spinal cord dose during radiotherapy. To sum the dose over multiple fractions and compare with the planned dose requires deformable image registration. This study investigates the accuracy of deformable registration of the spine in kilovoltage CT (kVCT) to MVCBCT images for head-and-neck patients. METHODS: Head-and-neck kVCT and MVCBCT images were selected from five patients who exhibited large changes in neck flexion. The spinal canal was contoured in each image. MVCBCT images were rigidly registered to the kVCT image by aligning the C1-C2 vertebrae. Variations of a commercial deformable registration algorithm using the B-spline method were applied to a volume of interest surrounding the spine to deform the spinal cord structure from the kVCT to the MVCBCT. The Dice similarity index (DSI) was calculated between rigidly registered structures (DSI1), and compared against the DSI calculated between the MVCBCT structure and the structure deformed from kVCT to MVCBCT (DSI2). The difference between DSI2 and DSI1 was calculated to investigate the ability of the deformation algorithm to match the change in neck flexion. RESULTS: In this data set, a single-pass B-spline deformation algorithm was the most effective in deforming the kVCT spinal canal to the MVCBCT spinal canal, with a mean improvement in DSI (DSI2 - DSI1) of 0.134. The mean change in DSI for a single-pass algorithm with a contrast correction was 0.111; for a multiple-pass algorithm was 0.105; and for a multiple-pass algorithm with contrast correction was 0.075. CONCLUSIONS: Several versions of a commercially implemented B-spline deformation algorithm were found to improve the registration of the spinal canal in kVCT and MVCBCT head-and-neck images. The resulting accuracy in the calculation of the cumulative dose to the spinal cord is under investigation. We acknowledge Velocity for providing the registration software.

SU-E-J-96: Investigation into the Accuracy of Deformable Registration Algorithms for Use in Dose Summation: A Case Study in Combined Modalities.

PURPOSE: To better understand the accuracy and limitation of deformable registration algorithms for dose summation by studying the results produced through two different deformable registration techniques for a clinical case of combining a Cyberknife radiosurgery plan and an electron boost to the scar tissues. METHODS: A patient was treated with a Cyberknife plan with supine CT and an electron boost plan with prone CT concurrently. The CT, RT structures and dose grids were exported from the Cyberknife MultiPlan system and the Pinnacle system and imported into two commercial DICOM viewing systems equipped with deformable registration algorithms. One of the systems uses intensity-based free-form deformable registration while the other uses B-spline free-form deformable registration. The electron boost plan was first registered to the CK plan using rigid registration, then secondly using deformable registration in each system. The region of interest used for registration was chosen to encompass the whole CT volumes due to the supine vs. prone positions. RESULTS: The summation doses for the Cyberknife CTV and critical structures do not differ between rigid registration and deformable registration for both systems. The electron boost volume does show higher mean dose received for the deformable registration compared with rigid registration for both systems (12.90 Gy vs. 11.71 Gy and 12.39 Gy vs. 11.53 Gy). There are slight variations between the doses produced by the two systems for all the structures, with an averaged difference of approximately 0.02% to 2.63%. CONCLUSIONS: These results show that for cases like this one, where the two treatment volumes do not overlap, there will not be significant differences between rigid and deformable registration, and that the only significant difference in summation dose between the different deformable registration algorithms is where the volume is deformed the most, in this case, the electron boost volume.

WE-E-213CD-01: Best in Physics (Joint Imaging-Therapy) - Evaluation of Deformation Algorithm Accuracy with a Two-Dimensional Anatomical Pelvic Phantom.

PURPOSE: To objectively evaluate the accuracy of 11 different deformable registration techniques for bladder filling. METHODS: The phantom represents an axial plane of the pelvic anatomy. Urethane plastic serves as the bony anatomy and urethane rubber with three levels of Hounsfield units (HU) is used to represent fat and organs, including the prostate. A plastic insert is placed into the phantom to simulate bladder filling. Nonradiopaque markers reside on the phantom surface. Optical camera images of these markers are used to measure the positions and determine the deformation from the bladder insert. Eleven different deformable registration techniques are applied to the full- and empty-bladder computed tomography images of the phantom to calculate the deformation. The applied algorithms include those from MIMVista Software and Velocity Medical Solutions and 9 different implementations from the Deformable Image Registration and Adaptive Radiotherapy Toolbox for Matlab. The distance to agreement between the measured and calculated deformations is used to evaluate algorithm error. Deformable registration warps one image to make it similar to another. The root-mean-square (RMS) difference between the HUs at the marker locations on the empty-bladder phantom and those at the calculated marker locations on the full-bladder phantom is used as a metric for image similarity. RESULTS: The percentage of the markers with an error larger than 3 mm ranges from 3.1% to 28.2% with the different registration techniques. This range is 1.1% to 3.7% for a 7 mm error. The least accurate algorithm at 3 mm is also the most accurate at 7 mm. Also, the least accurate algorithm at 7 mm produces the lowest RMS difference. CONCLUSIONS: Different deformation algorithms generate very different results and the outcome of any one algorithm can be misleading. Thus, these algorithms require quality assurance. The two-dimensional phantom is an objective tool for this purpose.

Sci-Sat AM: Brachy - 10: Adaptation of the CVT algorithm for catheter optimization in high dose rate brachytherapy.

INTRODUCTION: In interstitial high dose rate (HDR) brachytherapy, the number and positions of the catheter are usually fixed by the use of a template, without considering tumor size and shape. In this work, we present a simple and fast method to optimize both the number and position of catheters, using a modified version of the Centroidal Voronoi Tessellations (CVT) algorithm. METHODS: 8 prostate HDR clinical cases were chosen randomly to test our method. The treatment plan was obtained from a research version of IPSA. Clinically relevant dosimetric parameters were computed to evaluate our method and help optimizing the CVT algorithm parameters. Plans were generated with a specified number of catheters ranging from 9 to 18 and compared to the clinical cases with 17 catheters. RESULTS: The computation time to optimize the positions of a specific number of catheters was 1.5 s. The prostate V100 was better than the clinical case up to 12 catheters. Plans with 9 or less catheters would not be clinically acceptable in terms of prostate V100 and D90. High conformity is achieved whether the number of catheters used. The V75 of the bladder seems slightly higher, but not significant clinically. All other dosimetric indices are as good as the clinical plan. CONCLUSION: We have devised a simple, fast and efficient method to optimize the number and position of catheters in HDR brachytherapy. Ultimately, this catheter optimization algorithm could be coupled with a 3D ultrasound system to allow real-time guidance and planning for any interstitial brachytherapy sites.

SU-E-T-123: Understanding the Meaning of IMRT QA Passing Rates with a 2D Diode Array.

PURPOSE: A lower than ideal tolerance limit is used in intensity-modulated radiation therapy quality assurance (IMRT QA) with a 2D diode array due to passing rate fluctuations. The objective is to identify patterns in the passing rates to predict sources of uncertainty that can affect treatment delivery, for example, the need to re-calibrate the multileaf collimator when the passing rates start to decrease. METHODS: Five complex clinical prostate IMRT plans were evaluated with a 2D diode array. The QA for each plan was repeated five times during one and a half month period. One of the plans was randomly selected and repeated the same day five consecutive times. The planar doses calculated by the treatment planning system were compared to the measurements of the 2D diode array. The individual passing rates per beam per plan were compared. RESULTS: The average passing rate for each plan ranged from 94% to 97%. While the average percent difference of this ranged between -7.67% to 17.61%. Additionally, the minimum and maximum standard deviation among all beams was 0.13% and 9.63% respectively. We also compared the standard deviation of a plan QA repeated during different days versus a plan QA repeated during the same day. For the former the highest standard deviation was 6.05 % while for the later 0.21%. We noticed that the largest discrepancy between the passing rates was for angles at around 155° and 205°. CONCLUSION: These results show some inconsistency in the IMRT QA passing rates from one day to the next. Moreover, lower passing rates for a specific angle like the ones shown here can represent possible mechanical or tuning problems with the linear accelerator at these specific locations. Early identification of these sources of uncertainty can greatly improve the precision of the treatment delivery.

SU-D-211-04: Sector Intensity Modulated (SIM) Gamma Knife Stereotactic Radiosurgery.

PURPOSE: The latest Gamma Knife (GK) system, Perfexion, consists of 192 Co-60 sources divided into eight sectors. Treatment delivery includes multiple shots placed at different positions. For every shot, each sector can be either blocked or open with four different aperture sizes. However, the beam-on time is designed to be fixed. We proposed an innovative concept, Sector Intensity Modulated (SIM) Gamma Knife by dynamically varying the beam-on time for each individual sector to improve stereotactic radiosurgery planning quality. METHODS: The anatomic structures and dose matrices from each sector for every shot were obtained from the GK workstation. The beam-on time for each sector was decomposed with various discrete levels and brute-force algorithm was used to get the optimal solution. The resulting SIM plan was then re-entered into the GK workstation. Six indices were used to benchmark the plan quality: Coverage, Conformality, Gradient, Maximum Dose(s) to critical structure(s), Volume receiving over 8 and 12 Gy. All the SIM plans in comparison with the original plans were further reviewed by an experienced oncologist. RESULTS: The simulations were tested on various pituitary adenoma cases. Results consistently showed that SIM yielded better plans with all quantitative indices improved compared to original plan. It provides better conformality, quicker drop off of the isodose line outside the tumor, lower doses to the critical structures as optical- nerve/chiasm while maintaining at least 99% coverage of the tumor. Results were more favorable according to oncologist's view. In particular, up to 20% or 0.6 cc volume decrease in healthy tissue receiving 8 Gy was observed. This may translate into clinically observable reduction in acute/late toxicities. CONCLUSIONS: Our preliminary results show that Sector Intensity Modulated Gamma Knife offers superior treatment plans compared to the originally delivered plans. Further works as adding dynamic shot location and dynamic shot shaping will be discussed.

Dosimetric equivalence of nonstandard HDR brachytherapy catheter patterns.

PURPOSE: To determine whether alternative high dose rate prostate brachytherapy catheter patterns can result in similar or improved dose distributions while providing better access and reducing trauma. MATERIALS AND METHODS: Standard prostate cancer high dose rate brachytherapy uses a regular grid of parallel needle positions to guide the catheter insertion. This geometry does not easily allow the physician to avoid piercing the critical structures near the penile bulb nor does it provide position flexibility in the case of pubic arch interference. This study used CT datasets with 3 mm slice spacing from ten previously treated patients and digitized new catheters following three hypothetical catheter patterns: conical, bi-conical, and fireworks. The conical patterns were used to accommodate a robotic delivery using a single entry point. The bi-conical and fireworks patterns were specifically designed to avoid the critical structures near the penile bulb. For each catheter distribution, a plan was optimized with the inverse planning algorithm, IPSA, and compared with the plan used for treatment. Irrelevant of catheter geometry, a plan must fulfill the RTOG-0321 dose criteria for target dose coverage (V100(Prostate) > 90%) and organ-at-risk dose sparing (V75(Bladder) < 1 cc, V75(Rectum) < 1 cc, V125(Urethra) << 1cc). RESULTS: The three nonstandard catheter patterns used 16 nonparallel, straight divergent catheters, with entry points in the perineum. Thirty plans from ten patients with prostate sizes ranging from 26 to 89 cc were optimized. All nonstandard patterns fulfilled the RTOG criteria when the clinical plan did. In some cases, the dose distribution was improved by better sparing the organs-at-risk. CONCLUSION: Alternative catheter patterns can provide the physician with additional ways to treat patients previously considered unsuited for brachytherapy treatment (pubic arch interference) and facilitate robotic guidance of catheter insertion. In addition, alternative catheter patterns may decrease toxicity by avoidance of the critical structures near the penile bulb while still fulfilling the RTOG criteria.

Characteristics of megavoltage cone-beam digital tomosynthesis.

This article reports on the image characteristics of megavoltage cone-beam digital tomosynthesis (MVCB DT). MVCB DT is an in-room imaging technique, which enables the reconstruction of several two-dimensional slices from a set of projection images acquired over an arc of 20 degrees-40 degrees. The limited angular range reduces the acquisition time and the dose delivered to the patient, but affects the image quality of the reconstructed tomograms. Image characteristics (slice thickness, shape distortion, and contrast-to-noise ratio) are studied as a function of the angular range. Potential clinical applications include patient setup and the development of breath holding techniques for gated imaging.

Health management program: factors influencing completion of therapy with high-dose interferon alfa-2b for high-risk melanoma.

The goal of the 1-year observational, multicentre, open-label study reported here was to identify factors influencing adherence to high-dose interferon alfa-2b adjuvant therapy in patients at high risk of recurrence following surgical excision of malignant melanoma. The study was carried out in 23 tertiary-care centres across Canada.The 225 patients enrolled in the study all had malignant melanoma that was surgically excised and that required adjuvant treatment with interferon alfa-2b. Of these patients, 64% were men. Mean age was 51.7 years. All patients received interferon alfa-2b treatment during a 4-week induction phase (20 MU/m(2) intravenously 5 days per week) followed by a 48-week maintenance phase (10 MU/m(2) subcutaneously 3 days per week).Oncology nurses reviewed side-effect management with the patients before the induction and maintenance phases. Patients were provided with daily diaries, comprehensive educational materials, and ongoing nursing support. Data on side effects and discontinuations were obtained from patient interviews and diaries. THE MAIN OUTCOME MEASUREMENTS WERE RELATED TO TREATMENT DISCONTINUATION: rate, timing, reason, and prevention. Of the 225 patients, 75 (33.3%) discontinued interferon during the induction phase, and 58 (25.8%) discontinued during the maintenance phase. The main reasons for discontinuation were adverse events (58%) and disease progression (26%). Patients with a daily fluid intake greater than 1.5 L were more likely to complete therapy than were those with an intake less than 1.5 L (64% vs. 36%, p < 0.0001).Of 225 patients enrolled in the interferon alfa-2b health management program, 41% completed the 1-year treatment course. Higher fluid intake (>1.5 L daily) was associated with increased adherence to therapy.

Sci-Thurs PM: Delivery-12: Correction and calibration of megavoltage cone-beam CT images for the calculation of the dose of the day.

PURPOSE: To show that accurate dose calculations can be achieved with megavoltage cone-beam CT (MVCBCT) images of head-and-neck (H&N) and prostate sites, allowing the verification of the daily dose distribution received by these patients. METHOD AND MATERIALS: Corrections for the cupping and missing data artifacts seen on MVCBCT images were developed for both H&N and pelvic imaging. MVCBCT images of six H&N and two prostate patients were acquired weekly during the course of their treatment. Several regions of interest were contoured including: the prostate and rectum and the spinal cord and parotids. Dose calculation was performed with the MVCBCT images using the plan beams. Variations from treatment plan dosimetric endpoints were analyzed. RESULTS: Dose calculations with kVCT and corrected MVCBCT images of the H&N (pelvic) regions show standard deviations of 1.9% (0.6%). The mean dose to the right parotid of H&N patients had an average increase of 18% during treatment. The maximum dose to 1% of the spinal cord went up by 2% on average. For prostate patients on one fraction the dose received by 95% of the prostate diminished by 3%. One patient had an average increase of 3.6% of the maximum dose received by 1% of the rectum. CONCLUSION: MVCBCT can be used to verify daily dose distributions for H&N and prostate patients. An increase in the mean dose to normal tissues was observed during H&N treatment. Underdosage of the prostate and the dosimetric consequences of volume changes in rectum and bladder were observed. Research supported by Siemens.

Effectiveness of a nursing support program for patients with recurrent ovarian cancer receiving pegylated liposomal doxorubicin (Caelyx/Doxil).

Pegylated liposomal doxorubicin (PLD) has become the preferred alternative for ovarian cancer patients who have failed platinum-based therapy, but side effects, such as palmar-plantar erythrodysesthesia (PPE), may lead to sub-optimal drug exposure and treatment discontinuation. A prospective Canadian multicentre open-label study evaluated the effects of a nurse-administered education and support program on treatment adherence and tolerability in 112 women with recurrent ovarian cancer. Subjects received an average of four four-week PLD cycles, the recommended number of courses required to evaluate the efficacy from PLD. Side effects were common, but 75% of patients were able to complete > 3 cycles and 59% completed > 4 cycles of PLD chemotherapy. With proactive nursing intervention, the incidence of PLD-associated grade three-four toxicities such as PPE and mucositis was substantially decreased. Nursing intervention may allow more patients to receive chemotherapy on schedule, thus reproducing the conditions of the clinical study in which the efficacy of the drug has been established.

Dose-guided radiation therapy with megavoltage cone-beam CT.

Recent advances in fractionated external beam radiation therapy have increased our ability to deliver radiation doses that conform more tightly to the tumour volume. The steeper dose gradients delivered in these treatments make it increasingly important to set precisely the positions of the patient and the internal organs. For this reason, considerable research now focuses on methods using three-dimensional images of the patient on the treatment table to adapt either the patient position or the treatment plan, to account for variable organ locations. In this article, we briefly review the different adaptive methods being explored and discuss a proposed dose-guided radiation therapy strategy that adapts the treatment for future fractions to compensate for dosimetric errors from past fractions. The main component of this strategy is a procedure to reconstruct the dose delivered to the patient based on treatment-time portal images and pre-treatment megavoltage cone-beam computed tomography (MV CBCT) images of the patient. We describe the work to date performed to develop our dose reconstruction procedure, including the implementation of a MV CBCT system for clinical use, experiments performed to calibrate MV CBCT for electron density and to use the calibrated MV CBCT for dose calculations, and the dosimetric calibration of the portal imager. We also present an example of a reconstructed patient dose using a preliminary reconstruction program and discuss the technical challenges that remain to full implementation of dose reconstruction and dose-guided therapy.

The use of megavoltage cone-beam CT to complement CT for target definition in pelvic radiotherapy in the presence of hip replacement.

In Europe and the USA combined, over half a million people had a hip joint replaced in 2005, contributing to the increasing number of radiotherapy patients with metallic hip prostheses. The treatment plan for external beam radiation therapy is based on the delineation of the anatomy in the planning CT scan. When implanted objects of high atomic number (Z) material are present, however, severe image artefacts are generated in conventional CT, strongly hindering the ability to delineate some organs. This is particularly the case for the planning of prostate patients with hip prostheses. This short communication presents the use of a new imaging modality, megavoltage cone-beam CT, to complement the regular CT for target definition of prostate cancer treatment of patients with hip replacements.

[Megavoltage cone-beam CT: Recent developments and clinical applications]. / Mégavoltage cone-beam CT: récents développements et applications cliniques pour la radiothérapie conformationnelle avec modulation d'intensité.

The Megavoltage cone-beam (MV CBCT) system consists of a new a-Si flat panel adapted for MV imaging and an integrated workflow application allowing the automatic acquisition of projection images, cone-beam CT image reconstruction, CT to CBCT image registration and couch position adjustment. This provides a 3D patient anatomy volume in the actual treatment position, relative to the treatment isocenter, moments before the dose delivery, that can be tightly aligned to the planning CT, allowing verification and correction of the patient position, detection of anatomical changes and dose calculation. In this paper, we present the main advantages and performance of this MV CBCT system and summarize the different clinical applications. Examples of the image-guided treatment process from the acquisition of the MV CBCT scan to the correction of the couch position and dose delivery will be presented for spinal and lung lesions and for head and neck, and prostate cancers.