International Commission On Radiation Units Research Articles

Longitudinally Heterogeneous Tumor Dose Optimizes Proton Broadbeam, Interlaced Minibeam, and FLASH Therapy.

Simple SummaryThe aim of any kind of external radiation therapy is to control a tumor with the highest possible probability of the lowest possible side effects. Here, we study further opportunities of reducing the side effects of proton therapy by applying longitudinally heterogeneous dose distributions in the tumor respecting the delivery of a minimum prescribed dose. In our simulations, the longitudinally heterogeneous dose distributions show a reduced dose in the healthy tissue already in the case of proton broadbeam irradiations, but a much higher (calculated) mean cell survival in the case of proton minibeam irradiation. This demonstrates its potential to substantially reduce side effects at a simultaneously higher tumor control probability, opening new opportunities of easier application when striving for high dose-rate applications of proton beams (>~10 Gy/s), in order to additionally profit from the so-called FLASH effects.The prerequisite of any radiation therapy modality (X-ray, electron, proton, and heavy ion) is meant to meet at least a minimum prescribed dose at any location in the tumor for the best tumor control. In addition, there is also an upper dose limit within the tumor according to the International Commission on Radiation Units (ICRU) recommendations in order to spare healthy tissue as well as possible. However, healthy tissue may profit from the lower side effects when waving this upper dose limit and allowing a larger heterogeneous dose deposition in the tumor, but maintaining the prescribed minimum dose level, particularly in proton minibeam therapy. Methods: Three different longitudinally heterogeneous proton irradiation modes and a standard spread-out Bragg peak (SOBP) irradiation mode are simulated for their depth-dose curves under the constraint of maintaining a minimum prescribed dose anywhere in the tumor region. Symmetric dose distributions of two opposing directions are overlaid in a 25 cm-thick water phantom containing a 5 cm-thick tumor region. Interlaced planar minibeam dose distributions are compared to those of a broadbeam using the same longitudinal dose profiles. Results and Conclusion: All longitudinally heterogeneous proton irradiation modes show a dose reduction in the healthy tissue compared to the common SOBP mode in the case of broad proton beams. The proton minibeam cases show eventually a much larger mean cell survival and thus a further reduced equivalent uniform dose (EUD) in the healthy tissue than any broadbeam case. In fact, the irradiation mode using only one proton energy from each side shows better sparing capabilities in the healthy tissue than the common spread-out Bragg peak irradiation mode with the option of a better dose fall-off at the tumor edges and an easier technical realization, particularly in view of proton minibeam irradiation at ultra-high dose rates larger than ~10 Gy/s (so-called FLASH irradiation modes).

Vaginal dose of radical radiotherapy for cervical cancer in China: a multicenter study

BackgroundThe posterior-inferior border of symphysis (PIBS) point system is a novel vaginal dose-reporting method and is a simple and reliable method proposed by the Medical University of Vienna proposed for both external-beam radiotherapy (EBRT) and brachytherapy (BT). In this multicenter study, we sought to first evaluate the vaginal radiation dose in Chinese cervical cancer patients according to the PIBS point system and then to analyze the factors influencing the dose distribution.MethodsWe collected data from the medical records of 936 cervical cancer patients who underwent concurrent radiochemotherapy at 13 different institutions in China. Radiation doses at points A, PIBS+ 2 cm, PIBS and PIBS-2 cm, International Commission on Radiation Units (ICRU)-R and ICRU-B were measured.ResultsThe median total doses in EQD2α/β = 3 at points PIBS+ 2 cm, PIBS and PIBS-2 cm were 82.5 (52.7–392.1) Gy, 56.2 (51.4–82.1) Gy and 2.6 (0.9–7.4) Gy, respectively. The median total doses in EQD2α/β = 3 at ICRU-R and ICRU-B were 77.5 (54.8–132.4) Gy and 79.9 (60.7–133.7) Gy, respectively. The mean vaginal reference length (VRL) was 4.6 ± 1.0 cm (median, 4.5 cm). In patients with VRL ≤4.5 cm, the mean total doses in EQD2α/β = 3 at points PIBS+ 2 cm, PIBS and PIBS-2 cm were 128.5, 60.7 and 0.8 Gy, respectively. In patients with VRL > 4.5 cm, the mean total doses at these three points were 68.9, 0.5 and 54.5 Gy, respectively. Classification of patients revealed significant differences (P < 0.05) between these two groups.ConclusionsWith the PIBS point system, Chinese patients with a shorter VRL of < 4.5 cm received higher radiation doses at the PIBS+ 2 cm, PIBS and PIBS-2 cm points than European and American patients. Further studies are required to establish the dose–effect relationships with these points as references.The study was registered as a clinical trial (NCT03257475) on August 22, 2017.

Do all the linear accelerators comply with the ICRU 91's constraints for stereotactic body radiation therapy treatments?

Recent technological developments in linear accelerators (linacs) and their imaging systems have made it possible to routinely perform stereotactic radiotherapy (SRT) treatments. To ensure the security and quality of the treatments, national and international recommendations have been written. This review focuses on the recommendations of the report 91 of the International Commission on Radiation Units (ICRU) on stereotactic treatments with small photon beams and proposes to answer the question of the eligibility of the commercially available accelerators for the treatment of extra-cranial SRT (SBRT). The ICRU 91 report outlines important features needed to respect the constraints, which are high intensity photon beam, integrated image-guidance, high mechanical accuracy of the linac, multileaf collimator with reduced leaf width, bundled motion management and bundled 6 Dimensional “robotic” couch tabletop. Most of the contemporary linacs meet these recommendations, in particular, stereotactic dedicated linacs, or modern gantry-based linacs equipped with 3 dimensional cone-beam CT imaging and 2D-stereoscopic planar imaging. Commercially available ring-based linacs have some limitations: they offer only coplanar treatments, and couch movements are limited to translations and, some have limited imaging equipment and no ability to manage intrafraction motion. However, for performing SBRT, non-coplanar irradiations are not mandatory, contrarily to intracranial stereotactic irradiations. Furthermore, patients’ rotations can be corrected, thanks to real-time adaptive radiotherapy available on MRI-linacs. Finally, significant improvements are expected in the short term to compensate the weaknesses of the current devices.

Liquid tissue surrogates for X-ray and CT phantom studies.

To develop a simple method for producing liquid-tissue-surrogate (LTS) materials that accurately represent human soft tissues in terms of density and X-ray attenuation coefficient. We evaluated hypothetical mixtures of water, glycerol, butanol, methanol, sodium chloride, and potassium nitrate; these mixtures were intended to emulate human adipose, blood, brain, kidney, liver, muscle, pancreas, and skin. We compared the hypothetical densities, effective atomic numbers (Zeff ), and calculated discrete-energy CT attenuation [Hounsfield Units (HU)] of the proposed materials with those of human tissue elemental composition as specified in International Commission on Radiation Units (ICRU) Report 46. We then physically produced the proposed LTS materials for adipose, liver, and pancreas tissue, and we measured the polyenergetic CT attenuation (also expressed as HU) of these materials within a 32cm phantom using a 64-slice clinical CT scanner at 80kVp, 100kVp, 120kVp, and 140kVp. The predicted densities, Zeff , and calculated discrete-energy CT attenuation of our proposed formulations generally agreed with those of ICRU within <1% or <10 HU. For example, the densities of our hypothetical materials agreed precisely with ICRU's reported values and were 0.95g/mL for adipose tissue, 1.04g/mL for pancreatic tissue, and 1.06g/mL for liver tissue; the discrete-energy CT attenuation at 60keV of our hypothetical materials (and ICRU-specified compositions) were -107HU (-113HU) for adipose #3, -89HU (-90HU) for adipose #2, 56HU (55HU) for liver tissue, and 31HU (31HU) for pancreatic tissue. The densities of our physically produced materials (compared to ICRU-specified compositions) were 0.947g/mL (0.0%) for adipose #2, 1.061g/mL (+2.0%) for pancreatic tissue, and 1.074g/mL (+1.3%) for liver tissue. The empirical polyenergetic CT attenuation measurements of our LTS materials (and the discrete-energy HU of the ICRU compositions at the mean energy of each spectrum) at 80kVp were -104HU (-113HU) for adipose #3, -87HU (-90HU) for adipose #2, 59HU (55HU) for liver tissue, and 33HU (31HU) for pancreatic tissue; at 120kVp, these were -83HU (-83HU) for adipose #3, -68HU (-63HU) for adipose #2, 55HU (52HU) for liver tissue, and 35HU (33HU) for pancreatic tissue. Our method for formulating tissue surrogates allowed straightforward production of solutions with CT attenuation that closely matched the target tissues' expected CT attenuation values and trends with kVp. The LTSs' inexpensive and widely available constituent chemicals, combined with their liquid state, should enable rapid production and versatile use among different phantom and experiment types. Further study is warranted, such as the inclusion of contrast agents. These liquid tissue surrogates may potentially accelerate development and testing of advanced CT imaging techniques and technologies.

Converting computed tomography images into photon interaction coefficients by using stoichiometric calibration and parametric fit models.

X ray and γ-ray are widely applied in radiology, radiotherapy, and nuclear medicine. Linear attenuation coefficients and linear energy absorption coefficients are essential for dose calculation and image correction. In this study, a method that entails combining the stoichiometric calibration and parametric physical models was developed to convert computed tomography (CT) images into the linear attenuation coefficients and linear energy absorption coefficients. A calibration scan was performed using standard tissue-equivalent materials to obtain the characteristics of the x-ray energy spectrum. Subsequently, relationships between CT numbers and tissue parameters were established using standard soft tissue and bone tissue data adopted from the literature. The linear attenuation coefficient and linear energy absorption coefficient were calculated using the parametric fit model. The results showed a linear relationship between CT numbers and tissue parameters. The tissue-equivalent materials differed from real human tissues, leading to considerable errors in estimation of mass attenuation coefficients when the photon energy was lower than 50keV. Mass attenuation coefficients and mass energy transfer coefficients of five tissues were calculated and validated using clinical CT images. The error was less than ±5% and ±8%, compared with the values of the International Commission on Radiation Units (ICRU) 46 report. The probability of photon interaction with tissues and physical characteristics of tissues can be accurately evaluated by using the proposed method and applied in various clinical applications.

SU-F-T-376: The Efficiency of Calculating Photonuclear Reaction On High-Energy Photon Therapy by Monte Carlo Method

Purpose: Secondary-neutrons having harmful influences to a human body are generated by photonuclear reaction on high-energy photon therapy. Their characteristics are not known in detail since the calculation to evaluate them takes very long time. PHITS(Particle and Heavy Ion Transport code System) Monte Carlo code since versions 2.80 has the new parameter “pnimul” raising the probability of occurring photonuclear reaction forcibly to make the efficiency of calculation. We investigated the optimum value of “pnimul” on high-energy photon therapy. Methods: The geometry of accelerator head based on the specification of a Varian Clinac 21EX was used for PHITS ver. 2.80. The phantom (30 cm * 30 cm * 30 cm) filled the composition defined by ICRU(International Commission on Radiation Units) was placed at source-surface distance 100 cm. We calculated the neutron energy spectra in the surface of ICRU phantom with “pnimal” setting 1, 10, 100, 1000, 10000 and compared the total calculation time and the behavior of photon using PDD(Percentage Depth Dose) and OCR(Off-Center Ratio). Next, the cutoff energy of photon, electron and positron were investigated for the calculation efficiency with 4, 5, 6 and 7 MeV. Results: The calculation total time until the errors of neutron fluence become within 1% decreased as increasing “pnimul”. PDD and OCR showed no differences by the parameter. The calculation time setting the cutoff energy like 4, 5, 6 and 7 MeV decreased as increasing the cutoff energy. However, the errors of photon become within 1% did not decrease by the cutoff energy. Conclusion: The optimum values of “pnimul” and the cutoff energy were investigated on high-energy photon therapy. It is suggest that using the optimum “pnimul” makes the calculation efficiency. The study of the cutoff energy need more investigation.

Safety of adjuvant intensity-modulated postoperative radiation therapy in endometrial cancer: Clinical data and dosimetric parameters according to the International Commission on Radiation Units (ICRU) 83 report

AimTo report a single-institution experience using postoperative pelvic Intensity Modulation Radiation Therapy (IMRT) using tomotherapy accelerators (TA) in postoperative endometrial cancer (EC) regarding ICRU 83 recommendations. BackgroundIMRT in gynecological malignancies provides excellent dosimetric data, lower rates of adverse events and clinical data similar to historical series. Material and methodsSeventy-six patients with EC were postoperatively treated with adjuvant IMRT using TA. The IMRT dose was 45Gy for patients without positive lymph nodes and Type I histology and 50.4Gy for patients with positive lymph nodes and/or type II histology. ResultsWith a median follow-up of 29 months, the 12- and 24-month Overall Survival (OS) and Disease-Free Survival (DFS) were 96%, 93%, 87%, and 74%, respectively. Age of less than 60 years was associated with better OS (HR: 8.9; CI: 1.1–68) and DFS (HR: 3.5; CI: 1.2–10.2). Patients with Type II and Type I Grade III histology had a worse OS (HR: 3.3; CI: 1.1–11). Five women (6.6%) presented in-field local vaginal recurrence, 2 (2.6%) presented non-in-field vaginal recurrence, 4 (5.2%) presented pelvic node and distant recurrence and 11 (14.4%) presented only distant metastases. One patient stopped radiation treatment due to Grade III acute diarrhea. No Grade III late toxicity was observed. Planning Target Volume (PTV) coverage showed mean D2, D50, D95, and D98 of 51.64–46.23Gy, 49.49–44.97Gy, 48.62–43.96Gy, and 48.47–43.58Gy for patients who received 45 and 50.4Gy, respectively. ConclusionsIMRT with TA in postoperative EC shows excellent conformity and homogeneity of PTV dose. Without Grade III late toxicity, data from this cohort demonstrated the utility of IMRT.

The Equivalent Dose Contribution from High-Dose-Rate Brachytherapy to Pelvic Positive Lymph Nodes in Locally Advanced Cervical Cancer Patients

Definitive radiation therapy for locally advanced cervical cancer involves both external beam radiation therapy (EBRT) and high-dose-rate (HDR) brachytherapy. There remains controversy and practice pattern variation for the optimal radiation prescription dose to metastatic pelvic lymph nodes. This study investigates the contribution of the pelvic lymph node dose from HDR brachytherapy. We also examine the variation of the lymph node prescribed dose and actual delivered dose as determined from the EBRT and brachytherapy plans. From September 2007 to October 2011, 68 patients were treated with curative intent. Of these, 17 patients with 36 positive pelvic lymph nodes were included in this retrospective analysis. All patients were treated with EBRT to the pelvis with a supplemental boost to the involved pelvic node, plus HDR brachytherapy. Pathologically involved lymph nodes were contoured on the planning EBRT image as well as the 4 to 5 brachytherapy planning images. The mean received dose of each lymph node from the EBRT and brachytherapy plans was recorded. The Equivalent Dose in 2-Gray Fractions (EQD2) was calculated using the equation EQD2 = D × [(d + α/β)/2 Gy + α/β] where D is total dose, d is dose per fraction and α/β-ratio is the dose at which the linear and quadratic components are equal. A student t-test was performed to determine if the mean received dose was significantly different from the mean intended prescribed dose and the mean intended EQD2. The average prescribed dose from the EBRT, including the initial pelvic fields and boost contribution, was 54.09Gy. The average prescribed HDR dose to International Commission on Radiation Units (ICRU) point A was 26.81Gy. The average dose delivered to the involved pelvic lymph nodes from EBRT and brachytherapy were 54.25Gy and 4.31Gy, respectively, with the corresponding EQD2 of 53.45Gy and 4.00Gy. Therefore, there was no statistically significant difference between the means of the received individual lymph node dose and intended prescribed pelvic lymph node dose for the EBRT and brachytherapy plans (p < 0.05). The similar results between the received dose and the EQD2 were observed. The equivalent dose contribution to the involved pelvic lymph nodes in locally advanced cervical cancer from HDR brachytherapy was 4.00Gy. Our study shows that is the HDR contribution is 7% of the total EQD2 (57.45Gy). The HDR contribution needs to be accounted for when prescribing the EBRT boost dose to pelvic lymph nodes for the optimal therapeutic dose.

Setup margins and geometric uncertainties in intensity-modulated radiation therapy in treating pituitary adenomas: the experience of Lyon Sud Hospital

The authors retrospectively evaluated the setup uncertainties in Intensity-Modulated Radiation Therapy (IMRT) for pituitary adenomas and verified the margins used in daily practice (3 mm). Craniocaudal (CC), anteroposterior (AP) and laterolateral (LL) displacements were measured during the first 3 days of treatment and then weekly by comparing two orthogonal images obtained by an electronic system of portal imaging with Digitally Reconstructed Radiographs (DRRs). Setup Margins (SM) were defined according to the International Commission on Radiation Units (ICRU)-62 formula, the Stroom equation and the van Herk equation. The systematic (Σ) and random (σ) errors of the population were calculated as standard deviation (SD) of the population mean and the mean of SDs for every patient, respectively. Twenty patients were treated by IMRT for pituitary adenomas, and a total of 231 measurements were obtained. Σ and σ were 0.6 and 1.3 mm, 0.8 and 1 mm, 1.2 and 1.5 mm in the AP, LL and CC direction, respectively. Larger setup margin was 2.4, 2.7 and 4 mm in the AP, LL and CC direction, respectively (van Herk formula). IMRT is a highly sophisticated treatment technique that requires precise definition and optimisation of local setup errors and, finally, of the irradiated volumes. The role of image-guided RT in these kinds of treatments should be prospectively evaluated.

MRI-based pre-planning in patients with cervical cancer treated with three-dimensional brachytherapy

The aim of this study was to analyse the feasibility and determine the benefits of MRI-based pre-planning with CT/MRI data fusion in patients with cervical cancer treated with radical radiotherapy. Patients underwent MRI examination prior to external beam radiotherapy and prior to the first and fourth fraction of brachytherapy with applicators in place. Insertion of applicators at the radiology department was performed under paracervical anaesthesia. The benefit of MRI pre-planning was determined by comparing conventional treatment planning with dose specification to "point A" and dose specification to 90% of the high-risk clinical target volume (HR-CTV D90). Tolerance of MRI evaluation with applicators, coverage of HR-CTV and dose-volume parameters for organs at risk (OAR) has been assessed in 42 brachytherapy procedures. Insertion of applicators at the radiology department was successful in all patients and there were no complications. The target dose was higher for MRI planning than for conventional planning (5.3 Gy vs 4.5 Gy). Maximum doses in the bladder and rectum were significantly lower (p<0.05) for MRI planning than for the conventional approach (6.49 Gy vs 7.45 Gy for bladder; 4.57 Gy vs 5.06 Gy for rectum). We found no correlation between the International Commission on Radiation Units (ICRU) point dose for OAR and the maximum dose in OAR. Nevertheless, a strong correlation between the maximum dose in OAR and the minimal dose in a volume of 2 cm(3) has been observed. MRI-based pre-planning with consecutive CT/MRI data fusion is feasible and safe, with the advantage of increasing the dose to the tumour and decreasing the dose to the organs at risk.

3. Quality and Performance Measures in Bone Densitometry

Introduction This is part 2 of a core chapter of the forthcoming Report on Bone Densitometry commissioned by the International Commission on Radiation Units (ICRU). It is written with the aim to review definitions of quantities and units used in bone densitometry research and to describe parameters and methods that can be used to compare and standardize densitometric equipment and measurements. Part 2 of this chapter contains the section on fracture risk.

Are Doses to ICRU Reference Points Valuable for Predicting Late Rectal and Bladder Morbidity after Definitive Radiotherapy in Uterine Cervix Cancer?

To evaluate whether doses or dose rates at International Commission on Radiation Units (ICRU) reference points are of value for predicting risks of late rectal and bladder morbidity in patients with uterine cervical cancer who have undergone external beam radiotherapy and intracavitary irradiation. Late rectal complications and late bladder complications were evaluated in 54 patients who were treated by external beam radiotherapy followed by intracavitary irradiation between January 1996 and December 1999. External beam radiotherapy was delivered in 1.8 Gy daily fractions to a whole pelvis dose of 50.4 Gy followed by intracavitary irradiation at total point A doses ranging from 75 Gy to 85 Gy. Intracavitary irradiation was performed with dose rates of 0.5-0.7 Gy/h to point A in most patients, but 8 patients were treated at a higher dose rate (0.83-1.15 Gy/h) to shorten the hospitalization period. Biologically effective doses for the reference points were calculated using a linear quadratic model. Grade 3 rectal and bladder morbidity by Radiation Therapy Oncology Group (RTOG) criteria developed in 4 patients (7.4%) and 1 (1.9%), respectively. An age of >60 years (P = 0.01) and a total dose to the rectal reference point of > or =80 Gy (P = 0.03) were found to be correlated with a higher rate of rectal morbidity. Total dose (> or =80 Gy), dose rate (> or = 0.75 Gy/h), and biologically effective doses (> or =135 Gy3) at the bladder reference point were found to be significant factors for the development of late bladder morbidity. By multivariate analysis, age was identified as the only significant factor of late rectal complications, and biologically effective doses at the bladder reference point was the only significant factor of late bladder complications. RTOG grade 3 late rectal and bladder morbidity developed in respectively 7.4% and 1.9% of the patients. The significant risk factors for late rectal and bladder morbidity were old age and biologically effective doses at the bladder reference point, respectively.

Modeling correlation indices between bladder and Foley′s catheter balloon dose with CT-based planning using limited CT slices in intracavitary brachytherapy for carcinoma of cervix

To derive and validate an index to correlate the bladder dose with the catheter balloon dose using limited computed tomography (CT) slices. Applicator geometry reconstructed from orthogonal radiographs were back-projected on CT images of the same patients for anatomy-based dosimetric evaluation. The correlation indices derived using power function of the catheter balloon dose and the bladder volume dose were validated in 31 patients with cervical cancer. There was significant correlation between International Commission on Radiation Units (ICRU)-38 balloon reference dose (Dr) and the dose received by 25% bladder volume (D(25)) (P< 0.0001). Significant correlation was also found between the reference dose of mid-balloon point (D(rm)) and the dose to D(25) (P < 0.0001). Average percentage difference [100 x (observed index - expected index)/ expected index] of observed value of I'25 (index for the dose to D25 bladder with respect to mid-balloon reference point) from that of expected value was 0.52%, when the index was modeled with reference dose alone. Similarly the average percentage difference for I'10cc (index for the dose to 10 cc volume of bladder with respect to mid balloon point) was 0.84%. When this index was modeled with absolute bladder volume and reference dose, standard deviation of the percentage difference between observed and expected index for D(rm) reduced by approximately 2% when compared to D(r). For clinical applications, correlation index modeled with reference dose and volume predicts dose to absolute volume of bladder. Correlation index modeled with reference dose gives a good estimate of dose to relative bladder volume. From our study, we found D(rm) to be a better indicator of bladder dose than D(r).

Quality and performance measures in bone densitometry

This is part 2 of a core chapter of the forthcoming Report on Bone Densitometry commissioned by the International Commission on Radiation Units (ICRU). It is written with the aim to review definitions of quantities and units used in bone densitometry research and to describe parameters and methods that can be used to compare and standardize densitometric equipment and measurements. Part 2 of this chapter contains the section on fracture risk. Building on concepts of risk assessment, including risk ratios and odds ratios, we review statistical concepts commonly used in cross-sectional and prospective fracture studies. Performance measures are defined that allow a comparison of the ability of densitometry techniques to assess fracture risk. The methods of discriminant analysis, logistic regression, Poisson regression models, and the Cox proportional hazard model are presented and compared. In addition, statistical concepts to characterize risk for the individual patient are reviewed.

Radiotherapy for solitary extramedullary plasmacytoma in the head-and-neck region: A dose greater than 45 Gy to the target volume improves the local control

Our aim was to determine the dose to the clinical target volume (CTV) required for solitary extramedullary plasmacytoma (EMP) in the head and neck (HN). Seventeen patients (15 Stage I and 2 Stage II) were treated for HN EMP at our institution between 1979 and 2003. The mean International Commission on Radiation Units (ICRU) dose prescribed to the CTV was 52.6 Gy (range, 40-65 Gy) over 24 fractions (range: 20-30). The Stage II patients received neck irradiation doses of 40 and 60 Gy. A mean dose of 36.4 Gy was used for 5 Stage I patients who received elective neck irradiation. Dose administrated to the CTV was evaluated from dosimetric data or from planning films when dosimetric data were not available. Two groups of patients were distinguished: CTV covered with a dose greater than 40 Gy and CTV covered with a dose greater than 45 Gy. The 5-year local control was 72.8%. It was 100% for patients who received dose to the CTV > or = [DOSAGE ERROR CORRECTED] 45 Gy vs. 50% for dose to the CTV <45 Gy (p = 0.034). The prognostic factor for 5-year disease-specific survival (81.6%) was local control (p = 0.058). The prognostic factors for disease-free survival (64.1%) were monoclonal immunoglobulin secretion (p = 0.008) and a CTV dose > or = 45 Gy (p = 0.056) Local control of EMP in the HN seems to be improved when the dose to the CTV is > or = [DOSAGE ERROR CORRECTED] 45 Gy. A minimum dose of 45 Gy should be recommended to the CTV.

SCULPTER: fast evidence-based 3D anatomy sculpting in radiotherapy by computerised topological self-mapping

International Commission on Radiation Units (ICRU)-50/62 recommendations encourage radiotherapy practice based on the location, shape and limits of disease targets and organs at risk. The inconsistency and variability of intra- and inter-expert delineation of these structures has been only marginally ameliorated by image processing, whilst the requirement for a defensible evidence basis has been entirely ignored. SCULPTER is a new tool for machine-assisted delineation of radiotherapy structures. It makes use of a limited number of clinically selected, evidence-based points to compute an inherently three-dimensional disease target or organ at risk. It does this by topological self-mapping using radial basis functions. Results show that a sparse cloud of evidence-based points can be used to eliminate the discontinuities inherent to iterated manual contouring of radiotherapy structures, volumes are highly correlated and that the SCULPTER process is three to four times faster than conventional contouring.

Reduction of the rectal dose in gynecological brachytherapy: Modification to the Fletcher-Suit applicator

The dose to the anterior rectal wall is a known limiting factor for the delivery of radical doses of radiation to the uterine cervix with brachytherapy. We developed a modification to the Fletcher-Suit afterloading applicator, consisting of two small inflatable balloons attached to the posterior end of each colpostat. The balloons are connected to catheters that emerge from the vagina attached to the colpostat's handles. The balloons were affixed to the colpostats with a plastic adaptor and are inserted empty. After an anterior radiograph is taken, the balloons are filled with radiological contrast material and a lateral orthogonal film is made. This lateral film taken with the balloons filled with contrast typically shows a significant posterior displacement of the anterior rectal wall away from the vaginal sources. The International Commission on Radiation Units (ICRU) rectal point is then determined 5 mm beyond the posterior boundary of the opacified balloons. We have performed 90 applications using this device, including brachytherapy applications for cervical cancer, as well as vaginal applications for endometrial carcinoma following TAH-BSO. On average, the ICRU rectal point was displaced 14 mm away from the colpostats, thus reducing the dose rate by 60% and resulting in an average dose sparing of about 1000 cGy to the anterior rectal wall.