Dynamic evaluation of the prognostic value of 18F-FDG PET/CT in extranodal NK/T-cell lymphoma, nasal type.

Extranodal natural killer/T-cell lymphoma, nasal-type (ENKTL) is a type of rare and distinct entity of non-Hodgkin lymphoma with poor prognosis. It is important to evaluate the early treatment response accurately to decide further treatment strategy. 18F-FDG PET/CT plays an important role in response evaluation and prognostic prediction in some kinds of lymphomas. However, data available regarding patients with ENKTL are limited. Thus, in this prospective study, we analyzed the prognostic value of 18F-FDG PET/CT in ENKTL. Thirty-four patients with newly diagnosed ENKTL were enrolled in this phase 2 study (NCT02825147, July 7, 2016). The patients received pre-, mid-, and end-treatment 18F-FDG PET/CT scans. Deauville score (DS), maximal standardized uptake values (SUVmax), and the change in SUVmax (ΔSUVmax) were recorded for response assessment. The median follow-up period was 42.2 months. The 2-year overall survival (OS) and progression-free survival (PFS) were 82.4% and 73.5%, respectively. Univariate analysis revealed that Ann Arbor stage (P < 0.002), mid-treatment DS (P = 0.005), mid-SUVmax (P = 0.001), mid-∆SUVmax (P = 0.004), end-treatment DS (P < 0.001), and end-SUVmax (P = 0.014) were prognostic factors for OS. Ann Arbor stage (P = 0.001), mid-treatment DS (P = 0.008), mid-SUVmax (P = 0.029), mid-∆SUVmax (P < 0.001), and end-treatment DS (P =0.021) were of prognostic significance for PFS. Multivariate analysis showed that mid-SUVmax (P = 0.042) and DS at the middle (P = 0.050) and end (P = 0.044) of treatment were significant independent predictors of PFS. 18F-FDG PET/CT is useful for predicting the prognosis of ENKTL.

Comparison of the recommendations of the AAPM TG-51 and TG-51 addendum reference dosimetry protocols.

This work quantified differences between recommendations of the TG-51 and TG-51 addendum reference dosimetry protocols. Reference dosimetry was performed for flattened photon beams with nominal energies of 6, 10, 15, and 23 MV, as well as flattening-filter free (FFF) beam energies of 6 and 10 MV, following the recommendations of both the TG-51 and TG-51 addendum protocols using both a Farmer® ionization chamber and a scanning ionization chamber with calibration coefficients traceable to absorbed dose-to-water (Dw ) standards. Differences in Dw determined by the two protocols were 0.1%-0.3% for beam energies with a flattening filter, and up to 0.2% and 0.8% for FFF beams measured with the scanning and Farmer® ionization chambers, respectively, due to kQ determination, volume-averaging correction, and collimator jaw setting. Combined uncertainty was between 0.91% and 1.2% (k = 1), varying by protocol and detector.

Unilateral and bilateral neck SIB for head and neck cancer patients : Intensity-modulated proton therapy, tomotherapy, and RapidArc.

AIM: To compare simultaneous integrated boost plans for intensity-modulated proton therapy (IMPT), helical tomotherapy (HT), and RapidArc therapy (RA) for patients with head and neck cancer. PATIENTS AND METHODS: A total of 20 patients with squamous cell carcinoma of the head and neck received definitive chemoradiation with bilateral (n = 14) or unilateral (n = 6) neck irradiation and were planned using IMPT, HT, and RA with 54.4, 60.8, and 70.4 GyE/Gy in 32 fractions. Dose distributions, coverage, conformity, homogeneity to planning target volumes (PTV)s and sparing of organs at risk and normal tissue were compared. RESULTS: All unilateral and bilateral plans showed excellent PTV coverage and acceptable dose conformity. For unilateral treatment, IMPT delivered substantially lower mean doses to contralateral salivary glands (< 0.001-1.1 Gy) than both rotational techniques did (parotid gland: 6-10 Gy; submandibular gland: 15-20 Gy). Regarding the sparing of classical organs at risk for bilateral treatment, IMPT and HT were similarly excellent and RA was satisfactory. CONCLUSION: For unilateral neck irradiation, IMPT may minimize the dry mouth risk in this subgroup but showed no advantage over HT for bilateral neck treatment regarding classical organ-at-risk sparing. All methods satisfied modern standards regarding toxicity and excellent target coverage for unilateral and bilateral treatment of head and neck cancer at the planning level.

Histopathologic and Histomorphometric Analysis of Irradiation Injury in Bone and the Surrounding Soft Tissues of the Jaws.

PURPOSE: Surgery of irradiated tissue has an increased complication rate because of the development of hypovascular, hypocellular, and hypoxic tissue. This study was undertaken to perform histopathologic and histomorphometric analyses of irradiation tissue injury in bone and the surrounding soft tissues. MATERIAL AND METHODS: The histopathologic findings of 40 human mandibular bones and the surrounding soft tissue specimens obtained from different patients who underwent surgical procedures for treatment of osteoradionecrosis of the jaws were reviewed. RESULTS: Histopathologic examination showed 7 processes in the following order of appearance: hyperemia, endarteritis, thrombosis, cell loss, hypovascularity, increase of fat in the bone marrow cavity, and fibrosis. Histomorphometric analysis showed significant hypocellularity (P = .007), hypovascularity (P < .001), and fibrosis (P < .001) in irradiated specimens compared with control specimens. CONCLUSION: These results showed that radiation injuries affect the bone and surrounding soft tissues. However, the irradiation-induced injuries, such as cellular loss (hypocellularity) and fibrosis, were more expressive in bone tissue than in the surrounding soft tissues.

Comparative Efficacy of Aloe vera and Benzydamine Mouthwashes on Radiation-induced Oral Mucositis: A Triple-blind, Randomised, Controlled Clinical Trial.

PURPOSE: To compare the efficacy of an Aloe vera mouthwash with a benzydamine mouthwash in the alleviation of radiation- induced mucositis in head and neck cancer patients using a triple-blind, randomised controlled trial. MATERIALS AND METHODS: Twenty-six eligible head and neck cancer patients who were to receive conventional radiation therapy at the radiation oncology department were randomised to receive an Aloe vera mouthwash or a benzydamine mouthwash. Mucositis severity was assessed during the course of radiation therapy using the WHO grading system. RESULTS: At baseline, there was no difference in the distribution of mucositis severity between the two groups. The mean interval between radiation therapy and onset of mucositis was similar for both groups (Aloe vera 15.69±7.77 days, benzydamine 15.85±12.96 days). The mean interval between the start of radiation therapy and the maximum severity of mucositis were was also similar in both the Aloe vera and benzydamine groups (Aloe vera 23.38±10.75 days, benzydamine 23.54±15.45 days). Mean changes of mucositis severity over time in both groups were statistically similar and the effect of both treatments did not change signficantly with time (p=0.09). CONCLUSION: Aloe vera mouthwash was as beneficial as benzydamine mouthwash in alleviating the severity of radiation-induced mucositis and showed no side effects. The Aloe vera mouthwash could be an alternative agent in the treatment of radiation-induced mucositis in patients with head and neck cancers.

Measurement and Monte Carlo simulation for energy- and intensity-modulated electron radiotherapy delivered by a computer-controlled electron multileaf collimator.

The dosimetric advantage of modulated electron radiotherapy (MERT) has been explored by many investigators and is considered to be an advanced radiation therapy technique in the utilization of electrons. A computer-controlled electron multileaf collimator (MLC) prototype, newly designed to be added onto a Varian linac to deliver MERT, was investigated both experimentally and by Monte Carlo simulations. Four different electron energies, 6, 9, 12, and 15 MeV, were employed for this investigation. To ensure that this device was capable of delivering the electron beams properly, measurements were performed to examine the electron MLC (eMLC) leaf leakage and to determine the appropriate jaw positioning for an eMLC-shaped field in order to eliminate a secondary radiation peak that could otherwise appear outside of an intended radiation field in the case of inappropriate jaw positioning due to insufficient radiation blockage from the jaws. Phase space data were obtained by Monte Carlo (MC) simulation and recorded at the plane just above the jaws for each of the energies (6, 9, 12, and 15 MeV). As an input source, phase space data were used in MC dose calculations for various sizes of the eMLC shaped field (10 × 10 cm2, 3.4 × 3.4 cm2, and 2 × 2 cm2) with respect to a water phantom at source-to-surface distance (SSD) = 94 cm, while the jaws, eMLC leaves, and some accessories associated with the eMLC assembly as well were modeled as modifiers in the calculations. The calculated results were then compared with measurements from a water scanning system. The results showed that jaw settings with 5 mm margins beyond the field shaped by the eMLC were appropriate to eliminate the secondary radiation peak while not widening the beam penumbra; the eMLC leaf leakage measurements ranged from 0.3% to 1.8% for different energies based on in-phantom measurements, which should be quite acceptable for MERT. Comparisons between MC dose calculations and measurements showed agreement within 1%/1 mm based on percentage depth doses (PDDs) and off-axis dose profiles for a range of field sizes for each of the electron energies. Our current work has demonstrated that the eMLC and other relevant components in the linac were correctly modeled and simulated via our in-house MC codes, and the eMLC is capable of accurately delivering electron beams for various eMLC-shaped field sizes with appropriate jaw settings. In the next stage, patient-specific verification with a full MERT plan should be performed.

Evaluation of the water-equivalent characteristics of the SP34 plastic phantom for film dosimetry in a clinical linear accelerator.

In this study, some confusing points about electron film dosimetry using white polystyrene suggested by international protocols were verified using a clinical linear accelerator (LINAC). According to international protocol recommendations, ionometric measurements and film dosimetry were performed on an SP34 slab phantom at various electron energies. Scaling factor analysis using ionometric measurements yielded a depth scaling factor of 0.923 and a fluence scaling factor of 1.019 at an electron beam energy of <10 MeV (i.e., R50 < 4.0 g/cm2). It was confirmed that the water-equivalent characteristics were similar because they have values similar to white polystyrene (i.e., depth scaling factor of 0.922 and fluence scaling factor of 1.019) presented in international protocols. Furthermore, percentage depth dose (PDD) curve analysis using film dosimetry showed that when the density thickness of the SP34 slab phantom was assumed to be water-equivalent, it was found to be most similar to the PDD curve measured using an ionization chamber in water as a reference medium. Therefore, we proved that the international protocol recommendation that no correction for measured depth dose is required means that no scaling factor correction for the plastic phantom is necessary. This study confirmed two confusing points that could occur while determining beam characteristics using electron film dosimetry, and it is expected to be used as basic data for future research on clinical LINACs.

Effect of different prosthetic materials on radiation dose distribution in an orbital defect: a clinical report.

It is challenging to treat and irradiate empty cavities with external-beam radiation therapy (EBRT) because body contour irregularities can result in dose heterogeneities. The use of compensator materials to fill the empty cavities can provide a more homogeneous radiation dose distribution. The purposes of this clinical report are to describe the use of 3 different materials (elastomeric material, water-filled balloon, and acrylic resin) in an orbital defect and compare the dosimetric parameters and photon-electron dose distribution during EBRT.

Empirical modeling of the percent depth dose for megavoltage photon beams.

INTRODUCTION: This study presents an empirical method to model the high-energy photon beam percent depth dose (PDD) curve by using the home-generated buildup function and tail function (buildup-tail function) in radiation therapy. The modeling parameters n and µ of buildup-tail function can be used to characterize the Collimator Scatter Factor (Sc) either in a square field or in the different individual upper jaw and lower jaw setting separately for individual monitor unit check. METHODS AND MATERIALS: The PDD curves for four high-energy photon beams were modeled by the buildup and tail function in this study. The buildup function was a quadratic function in the form of [Formula: see text] with the main parameter of d (depth in water) and n, while the tail function was in the form of e-µd and was composed by an exponential function with the main parameter of d and µ. The PDD was the product of buildup and tail function, PDD = [Formula: see text]. The PDD of four-photon energies was characterized by the buildup-tail function by adjusting the parameters n and µ. The Sc of 6 MV and 10 MV can then be expressed simply by the modeling parameters n and µ. RESULTS: The main parameters n increases in buildup-tail function when photon energy increased. The physical meaning of the parameter n expresses the beam hardening of photon energy in PDD. The fitting results of parameters n in the buildup function are 0.17, 0.208, 0.495, 1.2 of four-photon energies, 4 MV, 6 MV, 10 MV, 18 MV, respectively. The parameter µ can be treated as attenuation coefficient in tail function and decreases when photon energy increased. The fitting results of parameters µ in the tail function are 0.065, 0.0515, 0.0458, 0.0422 of four-photon energies, 4 MV, 6 MV, 10 MV, 18 MV, respectively. The values of n and µ obtained from the fitted buildup-tail function were applied into an analytical formula of Sc = nE(S)0.63µE to get the collimator to scatter factor Sc for 6 and 10 MV photon beam, while nE, µE, S denotes n, µ at photon energy E of field size S, respectively. The calculated Sc were compared with the measured data and showed agreement at different field sizes to within ±1.5%. CONCLUSIONS: We proposed a model incorporating a two-parameter formula which can improve the fitting accuracy to be better than 1.5% maximum error for describing the PDD in different photon energies used in clinical setting. This model can be used to parameterize the Sc factors for some clinical requirements. The modeling parameters n and µ can be used to predict the Sc in either square field or individual jaws opening asymmetrically for treatment monitor unit double-check in dose calculation. The technique developed in this study can also be used for systematic or random errors in the QA program, thus improves the clinical dose computation accuracy for patient treatment.

Fluence correction factors and stopping power ratios for clinical ion beams.

BACKGROUND: In radiation therapy, the principal dosimetric quantity of interest is the absorbed dose to water. Therefore, a dose conversion to dose to water is required for dose deposited by ion beams in other media. This is in particular necessary for dose measurements in plastic phantoms for increased positioning accuracy, graphite calorimetry being developed as a primary standard for dose to water dosimetry, but also for the comparison of dose distributions from Monte Carlo simulations with those of pencil beam algorithms. MATERIAL AND METHODS: In the conversion of absorbed dose to phantom material to absorbed dose to water the water-to-material stopping power ratios (STPR) and the fluence correction factors (FCF) for the full charged particle spectra are needed. We determined STPR as well as FCF for water to graphite, bone (compact), and PMMA as a function of water equivalent depth, z(w), with the Monte Carlo code SHIELD-HIT10A. Simulations considering all secondary ions were performed for primary protons as well as carbon, nitrogen and oxygen ions with a total range of 3 cm, 14.5 cm and 27 cm as well as for two spread-out Bragg-peaks (SOBP). STPR as a function of depth are also compared to a recently proposed analytical formula. RESULTS: The STPR are of the order of 1.022, 1.070, and 1.112 for PMMA, bone, and graphite, respectively. STPR vary only little with depth except close to the total range of the ion and they can be accurately approximated with an analytical formula. The amplitude of the FCF depends on the non-elastic nuclear interactions and it is unity if these interactions are turned off in the simulation. Fluence corrections are of the order of a percent becoming more pronounced for larger depths resulting in dose difference of the order of 5% around 25 cm. The same order of magnitude is observed for SOBP. CONCLUSIONS: We conclude that for ions with small total range (z(w-eq) ≤3 cm) dosimetry without applying FCF could in principle be performed in phantoms of materials other than water without a significant loss of accuracy. However, in clinical high-energy ion beams with penetration depths z(w-eq) ≥3 cm, where accurate positioning in water is not an issue, absorbed dose measurements should be directly performed in water or accurate values of FCF need to be established.

Effect of radiotherapy on the hardness and surface roughness of two composite resins.

The knowledge about the potential adverse effects of radiotherapy compared to dental composites is a useful information for the clinician's decision regarding adoption of repairs or replacement of dental restorations during oral cancer treatment. This study evaluated the effects of irradiation on microhardness and surface roughness of a microfilled and a packable composite resin. The microfilled composite resin demonstrated significantly lower microhardness and a smoother surface compared to the packable composite resin (p < 0.05). Although irradiation significantly reduced the microhardness for both composite resins (P < 0.05), increasing the x-ray doses did not cause an additional significant decrease in surface hardness (P > 0.05). Meanwhile, irradiation did not produce a significantly rougher surface (P > 0.05), but specimens submitted to abrasion exhibited a significant increase in surface roughness for both composite resins (P < 0.05). It was concluded that while irradiation can adversely affect the hardness of tested composite resins, it does not interfere with surface roughness.

Monte Carlo study of the energy and angular dependence of the response of plastic scintillation detectors in photon beams.

PURPOSE: By using Monte Carlo simulations, the authors investigated the energy and angular dependence of the response of plastic scintillation detectors (PSDs) in photon beams. METHODS: Three PSDs were modeled in this study: A plastic scintillator (BC-400) and a scintillating fiber (BCF-12), both attached by a plastic-core optical fiber stem, and a plastic scintillator (BC-400) attached by an air-core optical fiber stem with a silica tube coated with silver. The authors then calculated, with low statistical uncertainty, the energy and angular dependences of the PSDs' responses in a water phantom. For energy dependence, the response of the detectors is calculated as the detector dose per unit water dose. The perturbation caused by the optical fiber stem connected to the PSD to guide the optical light to a photodetector was studied in simulations using different optical fiber materials. RESULTS: For the energy dependence of the PSDs in photon beams, the PSDs with plastic-core fiber have excellent energy independence within about 0.5% at photon energies ranging from 300 keV (monoenergetic) to 18 MV (linac beam). The PSD with an air-core optical fiber with a silica tube also has good energy independence within 1% in the same photon energy range. For the angular dependence, the relative response of all the three modeled PSDs is within 2% for all the angles in a 6 MV photon beam. This is also true in a 300 keV monoenergetic photon beam for PSDs with plastic-core fiber. For the PSD with an air-core fiber with a silica tube in the 300 keV beam, the relative response varies within 1% for most of the angles, except in the case when the fiber stem is pointing right to the radiation source in which case the PSD may over-response by more than 10%. CONCLUSIONS: At +/- 1% level, no beam energy correction is necessary for the response of all three PSDs modeled in this study in the photon energy ranges from 200 keV (monoenergetic) to 18 MV (linac beam). The PSD would be even closer to water equivalent if there is a silica tube around the sensitive volume. The angular dependence of the response of the three PSDs in a 6 MV photon beam is not of concern at 2% level.

Radiation dose distribution in the external auditory canal with different prosthetic materials: a clinical report.

Radiotherapy (RT) is an essential component of cancer treatment and aims to deliver higher doses at target volumes and lower doses to surrounding organs to achieve higher tumor control with fewer side effects. Significant dose heterogeneities can occur during treatment of irregular surfaces with electron beams, especially in head, neck, and breast tissue. The external ear and external auditory canal have irregular surfaces, which may cause dose heterogeneity, primarily resulting in excessive doses in the normal tissues lining and adjacent to the ear canal. The purpose of this clinical report is to describe the use of an acrylic resin and an elastomeric material to fill the air cavities of the external auditory canal and compare the dosimetric parameters. The complications that occur after electron-beam therapy of the ear canal can be significantly reduced by filling the ear cavity with acrylic resin, which is a simple, feasible, and cost-effective method.

Comparison of two dedicated 'in beam' PET systems via simultaneous imaging of (12)C-induced beta(+)-activity.

The selective energy deposition of hadrontherapy has led to a growing interest in quality assurance techniques such as 'in-beam' PET. Due to the current lack of commercial solutions, dedicated detectors need to be developed. In this paper, we compare the performances of two different 'in-beam' PET systems which were simultaneously operated during and after low energy carbon ion irradiation of PMMA phantoms at GSI Darmstadt. The results highlight advantages and drawbacks of a novel in-beam PET prototype against a long-term clinically operated tomograph for ion therapy monitoring.

Temporomandibular disorder in head and neck cancer patients undergoing radiotherapy: Clinical findings and patient-reported symptoms.

BACKGROUND: The aim of this study was to investigate how common temporomandibular disorder (TMD) symptoms are among head and neck cancer (HNC) patients before and after oncological treatment. METHODS: Eighty-nine patients with HNC receiving radiotherapy were enrolled in the study. Patients were examined before radiotherapy and at 6 and 12 months after radiotherapy to evaluate the function and tenderness of the temporomandibular jaw and the muscles of mastication as well as the patient-reported symptoms. RESULTS: At 6 months after radiotherapy, there was a large increase in the number of patients reporting problems with opening their mouth, fatigue, stiffness, and pain of the jaw. Sixty-eight percent of the patients had symptoms of TMD before oncological treatment and 94% and 81% had symptoms at the 6- and 12-month follow-up, respectively. CONCLUSION: The signs and symptoms of TMD escalate after radiotherapy, with symptoms peaking at 6 months after radiotherapy. Most commonly, patients suffer from restricted mouth opening, stiffness, fatigue, and pain of the jaw.

Characterizing the response of miniature scintillation detectors when irradiated with proton beams.

Designing a plastic scintillation detector for proton radiation therapy requires careful consideration. Most of the plastic scintillators should not perturb a proton beam if they are sufficiently small but may exhibit some energy dependence due to the quenching effect. In this work, we studied the factors that would affect the performance of such scintillation detectors. We performed Monte Carlo simulations of proton beams with energies between 50 and 250 MeV to study signal amplitude, water equivalence, spatial resolution and quenching of light output. Implementation of the quenching effect in the Monte Carlo simulations was then compared with prior experimental data for validation. The signal amplitude of a plastic scintillating fiber detector was on the order of 300 photons per MeV of energy deposited in the detector, corresponding to a power of about 30 pW at a proton dose rate of 100 cGy min(-1). The signal amplitude could be increased by up to a factor of 2 with reflective coating. We also found that Cerenkov light was not a significant source of noise. Dose deposited in the plastic scintillator was within 2% of the dose deposited in a similar volume of water throughout the whole depth-dose curve for protons with energies higher than 50 MeV. A scintillation detector with a radius of 0.5 mm offers a sufficient spatial resolution for use with a proton beam of 100 MeV or more. The main disadvantage of plastic scintillators when irradiated by protons was the quenching effect, which reduced the amount of scintillation and resulted in dose underestimation by close to 30% at the Bragg peak for beams of 150 MeV or more. However, the level of quenching was nearly constant throughout the proximal half of the depth-dose curve for all proton energies considered. We therefore conclude that it is possible to construct an effective detector to overcome the problems traditionally encountered in proton dosimetry. Scintillation detectors could be used for surface or shallow measurements with a single calibration for specific beam energy. For deeper measurements, Monte Carlo simulations can be used to generate depth-dependent correction factors.

HDR brachytherapy irradiation of the jaw - as a new experimental model of radiogenic bone damage.

INTRODUCTION: Hitherto, no suitable experimental model exists to test new treatments for radiogenic bone damage, such as new step from knowledge about bone growth factors or angiogenesis factors. The goal of this investigation was to establish such a standardised experimental model. MATERIAL AND METHODS: Twenty-four rats were used in this study. In 12 rats a plastic tube was implanted along the right half of the mandible and treated with a single dose of 20 Gy at a high-dose-rate (HDR) using an afterloading machine, the remainder served as control (n=12). One hundred days after irradiation both sides of the mandible were examined using paraffin embedding and non-decalcified histology. RESULTS: All HDR irradiated rats developed localised alopecia within 2 weeks of radiotherapy. In the irradiated group, a clear growth reduction of the ipsilateral incisor was observed. Paraffin histology revealed minimal damage of the bone structure with slightly increased signs of regeneration. The bone apposition rate was significantly reduced on the irradiated right side, compared with the left side (p=0.028). The average diameter of the mandibular condyles on the irradiated right sides was significantly reduced when compared with the left sides (p=0.023). CONCLUSIONS: It is possible to induce radiogenic damage of the mandible by using HDR brachytherapy with a single dose of 20 Gy comparable to 45 x 2 Gy of conventional irradiation. This new model is easy and predictable and appears to be suitable for the testing of new treatment modalities. It is advantageous for the testing of bone growth and angiogenesis factors that the contralateral side exhibits completely normal bone apposition characteristics enabling a split-mouth design for future experiments.

BMP-2 and bFGF in an irradiated bone model.

INTRODUCTION: Basic fibroblast growth factor (bFGF) is considered to enhance angiogenesis and to support bone formation in the presence of vital bone cells. Bone morphogenetic protein-2 (rhBMP-2) is known to induce bone formation. The aim of this study was to analyze the effect of bFGF and rhBMP-2 in the irradiated mandible. MATERIAL AND METHODS: The right mandibles of 24 rats were irradiated with a single dose of 20 Gy at a high-dose-rate (HDR) after loading machine (bio effective equivalent dose to ca. 45 x 2 Gy). After 12 weeks 100 microg rhBMP-2 (n=6 animals, group 1), 100 microg bFGF (n=6 animals, group 2) and 100 microg rhBMP-2 plus 100 microg bFGF (n=6 animals, group 3) were injected along the right mandible (left mandible: no irradiation, no growth factor). Another 6 animals (group 4) remained untreated after the irradiation. After another 7 weeks the specimens were examined by non-decalcified histology. RESULTS: Bone apposition of the experimental versus control sides was not statistically significantly different when one of the growth factors was applied alone (rhBMP-2: p=0.917; bFGF: p=0.345). Average bone apposition was significantly decreased on the experimental sides of group 3 (rhBMP-2+bFGF: p=0.046) and group 4 (p=0.008). Average bone densities were unaffected in all settings (for all p>0.1). CONCLUSIONS: The application of bFGF and the application of rhBMP-2 alone did result in predictable bone generation in the irradiated mandible with the bone apposition being equal to that of the non-irradiated side. The application of both growth factors together or none at all after irradiation results in significantly reduced bone apposition.

Effect of a carbon fiber tabletop on the surface dose and attenuation for high-energy photon beams.

PURPOSE: The dose changes in the buildup region and beam attenuation by a carbon fiber tabletop were investigated for 6-and 18-MV photon beams. MATERIALS AND METHODS: Measurements were performed for 2 x 2 cm to 40 x 40 cm field sizes. The surface dose and percentage depth doses (PDD) were measured by a Markus parallel plate chamber. Attenuation measurements were made at the cylindrical phantom for 180 degrees rotation of the beam. RESULTS: A carbon fiber tabletop increases the surface dose from 7.5% to 63.0% and from 4% to 43% for small fields at 6 and 18 MV, respectively. The increase was nearly fivefold for the 10 x 10 cm field and nearly twofold for the 40 x 40 cm field. Beam attenuation of the tabletop varies from 3.0% to 5.6% for 180 degrees and 120 degrees gantry angles for 6 MV. CONCLUSION: The carbon fiber tabletop significantly decreases the skin-sparing effect. The dosimetric effect of the tabletop may be higher, especially for the intensity-modulated radiation therapy depending on the beam orientation. Attenuation should be considered and corrected such as any material under the patient at the treatment planning stage.

[Results of stage I and II tongue squamous cell carcinomas treated with different modalities].

OBJECTIVE: To analyze the results of stage I and II tongue squamous cell carcinomas treated with different treatment modalities. METHODS: The clinical data of 103 patients with stage I and II primary tongue squamous cell carcinoma treated with surgery or radiotherapy alone or combined modality therapy were reviewed retrospectively. The treatment results were compared by Log-rank test, Kaplan-Meier and Chi square test among three groups: surgery alone (S), radiotherapy alone (R) and combined modality therapy (surgery plus preoperative or postoperative radiotherapy, R + S/S + R), and the prognostic factors were also analyzed using Cox regression models. RESULTS: The overall 5-year survival rate (OS) was 82.4% for stage I and 80.0% for stage II disease (P = 0.361). The 5-year survival rates of S, R and R + S/S + R groups were 90.3%, 68.4%, and 84.0%, respectively (P = 0.104). The local recurrence rates of those three groups were 2.5%, 35.7% and 5.7%, respectively (P < 0.001). Occult lymph node metastasis rate was 23.8%, frequently metastasized to level II lymph nodes. The patients with poorly differentiated carcinoma were found to have the highest regional recurrence rate. Local and regional recurrence was revealed as an independent prognostic factor. CONCLUSION: Surgery alone can achieve good treatment result for stage I and II tongue squamous cell carcinomas, and lymph node dissection of level I to IV in the neck is recommended.