Physical characterization of single convergent beam device for teletherapy: theoretical and Monte Carlo approach.

The main purpose of this work is to determine the feasibility and physical characteristics of a new teletherapy device of radiation therapy based on the application of a convergent x-ray beam of energies like those used in radiotherapy providing highly concentrated dose delivery to the target. We have denominated it Convergent Beam Radio Therapy (CBRT). Analytical methods are developed first in order to determine the dosimetry characteristic of an ideal convergent photon beam in a hypothetical water phantom. Then, using the PENELOPE Monte Carlo code, a similar convergent beam that is applied to the water phantom is compared with that of the analytical method. The CBRT device (Converay(®)) is designed to adapt to the head of LINACs. The converging beam photon effect is achieved thanks to the perpendicular impact of LINAC electrons on a large thin spherical cap target where Bremsstrahlung is generated (high-energy x-rays). This way, the electrons impact upon various points of the cap (CBRT condition), aimed at the focal point. With the X radiation (Bremsstrahlung) directed forward, a system of movable collimators emits many beams from the output that make a virtually definitive convergent beam. Other Monte Carlo simulations are performed using realistic conditions. The simulations are performed for a thin target in the shape of a large, thin, spherical cap, with an r radius of around 10-30 cm and a curvature radius of approximately 70 to 100 cm, and a cubed water phantom centered in the focal point of the cap. All the interaction mechanisms of the Bremsstrahlung radiation with the phantom are taken into consideration for different energies and cap thicknesses. Also, the magnitudes of the electric and/or magnetic fields, which are necessary to divert clinical-use electron beams (0.1 to 20 MeV), are determined using electromagnetism equations with relativistic corrections. This way the above-mentioned beam is manipulated and guided for its perpendicular impact upon the spherical cap. The first results that were achieved show in-depth dose peaks, having shapes qualitatively similar to those from hadrontherapy techniques. The obtained results demonstrate that in-depth dose peaks are generated at the focus point or isocenter. These results are consistent with those obtained with Monte Carlo codes. The peak-focus is independent of the energy of the photon beam, though its intensity is not. The realistic results achieved with the Monte Carlo code show that the Bremsstrahlung generated on the thin cap is mainly directed towards the focus point. The aperture angle at each impact point depends primarily on the energy beam, the atomic number Z and the thickness of the target. There is also a poly-collimator coaxial to the cap or ring with many holes, permitting a clean convergent-exit x-ray beam with a dose distribution that is similar to the ideal case. The electric and magnetic fields needed to control the deflection of the electron beams in the CBRT geometry are highly feasible using specially designed electric and/or magnetic devices that, respectively, have voltage and current values that are technically achievable. However, it was found that magnetic devices represent a more suitable option for electron beam control, especially at high energies. The main conclusion is that the development of such a device is feasible. Due to its features, this technology might be considered a powerful new tool for external radiotherapy with photons.

Experimental dosimetry in conformal breast teletherapy compared with the planning system.

The objective of this study was to compare and analyse the absorbed dose profiles from the conformal radiotherapy planning and experimental dosimetry taken in a breast anthropomorphic and anthropometric phantom. Conformal radiotherapy planning was elaborated in the Treatment Planning System (TPS). EBT2 Gafchromic radiochromic films were applied as dosimeters, positioned internally and superficially in the breast phantom. The standard radiation protocol was applied in the breast phantom. The films were digitalised, and their responses were analysed in RGB. The optical densities were processed, reproducing the spatial dose distribution.

Secondary radiation dose during high-energy total body irradiation.

AIM: The goal of this work was to assess the additional dose from secondary neutrons and γ-rays generated during total body irradiation (TBI) using a medical linac X-ray beam. BACKGROUND: Nuclear reactions that occur in the accelerator construction during emission of high-energy beams in teleradiotherapy are the source of secondary radiation. Induced activity is dependent on the half-lives of the generated radionuclides, whereas neutron flux accompanies the treatment process only. MATERIALS AND METHODS: The TBI procedure using a 18 MV beam (Clinac 2100) was considered. Lateral and anterior-posterior/posterior-anterior fractions were investigated during delivery of 2 Gy of therapeutic dose. Neutron and photon flux densities were measured using neutron activation analysis (NAA) and semiconductor spectrometry. The secondary dose was estimated applying the fluence-to-dose conversion coefficients. RESULTS: The main contribution to the secondary dose is associated with fast neutrons. The main sources of γ-radiation are the following: (56)Mn in the stainless steel and (187)W of the collimation system as well as positron emitters, activated via (n,γ) and (γ,n) processes, respectively. In addition to 12 Gy of therapeutic dose, the patient could receive 57.43 mSv in the studied conditions, including 4.63 µSv from activated radionuclides. CONCLUSION: Neutron dose is mainly influenced by the time of beam emission. However, it is moderated by long source-surface distances (SSD) and application of plexiglass plates covering the patient body during treatment. Secondary radiation gives the whole body a dose, which should be taken into consideration especially when one fraction of irradiation does not cover the whole body at once.

Using fiducial markers in the prostate bed in postprostatectomy external beam radiation therapy improves accuracy over surgical clips.

BACKGROUND AND PURPOSE: The purpose of this work was to assess the stability of fiducial markers in the prostate bed and compared their use to surgical clips. PATIENTS AND METHODS: In this study, 3-4 gold fiducial markers were transrectally implanted in the prostate bed of 14 patients. The stability of the fiducial markers position (fiducial markers fixity) over an EBRT course was assessed. Furthermore, the advantages of the fiducial markers compared to the surgical clips were assessed and the interobserver variation between the two technologies was compared. RESULTS: The mean fiducial marker migration during a course of EBRT was small with 1.2 mm (SD ± 0.8 mm). Compared to fiducial markers, the matches with surgical clips were mismatched ≥ 2 mm in 68% of treatments. This discrepancy of > 2 mm was on average 3.7 ± 1.3 mm. There was less interobserver variability for matching of fiducial markers (0.8 ± 0.7 mm) than for surgical clips (2.0 ± 1.6 mm). CONCLUSION: Fiducial markers showed less interobserver variability in matching and less variation in position than surgical clips. Fiducial markers could ultimately help in reducing treatment margins.

Introduction to radiotherapy and standard teletherapy techniques.

Radiation was first discovered in the late 19th century by Wilhelm Roentgen and has since been used extensively to treat a variety of cancers. Over the last century, we have developed an extensive understanding of the physical properties of radiation as well as radiation biology. Technological advances in the last few decades in medical imaging and radiotherapy delivery have led to the development of highly complex radiation delivery systems such as intensity modulated radiotherapy, which can be utilized to conformally treat complex tumor shapes while minimizing radiation dose to the surrounding normal tissue. To completely appreciate the application of radiotherapy for ophthalmic cancers, it is important to have a basic understanding of radiation therapy. In this chapter, we will discuss the fundamentals of radiation and radioactive decay, the mechanism of tumor cell damage leading to tumor cell apoptosis, as well as radiation and treatment parameters that are relevant for an ophthalmic oncologist. We will also discuss the concept of tissue tolerance which is of critical importance when prescribing radiation treatment as well as introduce the principles of three-dimensional conformal radiotherapy and intensity modulated radiotherapy.

Teletherapy: advanced techniques.

Radiotherapy has been utilized as a treatment for ophthalmologic processes for more than one hundred years. Over this century, the field of ophthalmologic oncology has been revolutionized through medical discoveries, development of novel surgical interventions, and innovation of advanced radiotherapy techniques. In this chapter, novel radiotherapy techniques are considered. Material presented will build on basic radiation therapy principles, techniques, and treatment parameters established in the previous chapter through consideration of intensity modulated radiotherapy, stereotactic radiotherapy, and heavy ion therapy. Deliberation of matters common across advanced radiotherapy techniques including target delineation, treatment planning, and requisites for ensuring accurate, precise treatment delivery will precede discussion of advanced radiotherapy techniques as applied to the management ophthalmologic malignancies.

Radiation therapy: uveal tumors.

Among primary uveal tumors, uveal melanoma is the most frequently occurring malignant neoplasm, albeit much less common than skin melanoma and indeed most other cancers. Traditionally, uveal melanoma was treated by enucleation of the globe, but is now increasingly been managed by an eye-preserving option, which saves vision without compromising the life of patients. More than 90% of eyes now preserved have some form of radiotherapy; most often episcleral brachytherapy that is easily accessible at many ophthalmic centers. Conversely, teletherapy in the form of charged particle irradiation, stereotactic radiotherapy or radiosurgery is only available at a comparatively small number of centers. Radiotherapy for uveal melanoma causes significant side effects and complications, but the vast majority of patients can keep their eye with some remaining function. This is of significant benefit to the quality of life for many patients. The side effects of radiotherapy are intimately related to the size of the irradiated tumor, hence early detection and identification of tumors that need to be treated is critical to improve the functional outcome. Experience gained from treating uveal melanoma has been expanded to treat benign uveal tumors such as choroidal hemangioma and other malignant tumors such as uveal lymphoma and uveal metastasis.

First report of elective selective neck dissection in the management of squamous cell carcinoma of the maxillary sinus.

Controversy remains about management of the neck in squamous cell carcinoma (SCC) of the maxillary sinus and we know of no reports of the use of elective selective neck dissection for management in this site. We retrospectively reviewed 18 consecutive patients with SCC of the maxillary sinus who were managed by primary operation with curative intent. A total of 13 patients had an elective selective neck dissection, which was invaded in one case 8%. Four patients had regional metastases, two with positive nodal disease confirmed after elective selective neck dissection, and two who developed regional recurrence (both after elective selective neck dissections which were negative (pN0)). A review of other published articles in the English language showed no cases of elective selective neck dissections reported. The mean regional recurrence rate was 12% (range 0-26%) and total mean regional metastases rate 21% (range 5-36%). Elective selective neck dissection did not contribute to an improved rate of neck control with regional recurrence of 11% (2/18) compared with 12% in the review. There is no evidence in this report to indicate that elective selective neck dissections for maxillary sinus SCC will result in better disease control. Future research may indicate fewer radiotherapy fields for necks with pathologically clear nodes after elective selective neck dissection.

Adaptive off-line protocol for prostate external radiotherapy with cone beam computer tomography.

PURPOSE: The goal of this work was to prepare and to evaluate an off-line adaptive protocol for prostate teleradiotherapy with kilovoltage cone beam computer tomography (CBCT). PATIENTS AND METHODS: Ten patients with localized prostate carcinoma treated with external beams underwent image-guided radiotherapy. In total, 162 CBCT images were collected. Position of prostate and pubis symphysis (PS) with respect to the isocenter were measured off-line. Using the CBCT scans obtained in the first three fractions the average position of prostate in relation (AvPosPr) to PB was calculated. On each CBCT scan, the position of prostate with respect to AvPosPr was calculated and cumulative histogram of prostate displacement with respect to AvPosPr was prepared. Using this data, the adaptive protocol was prepared in which (1) based on the CBCT made in the first three fractions the AvPosPr to PS is obtained, (2) in all other fractions two orthogonal images are acquired and if for any direction set-up error exceeds 0.2 cm the patient's position is corrected, and (3) additionally, the patient's position is corrected if the AvPosPr exceeds 0.2 cm in any direction. To evaluate the adaptive protocol for 30 consecutive patients, the CBCT was also made in 10th and 21st fraction. RESULTS: For the first 10 patients, the results revealed that the prostate was displaced in relation to AvPosPr >0.7 cm in the vertical and longitudinal directions only on 4 and 5 images of 162 CBCT images, respectively. For the lateral direction, this displacement was >0.3 cm in one case. For the group of 30 patients, displacement was never >0.7, and 0.3 cm for the vertical and lateral directions. In two cases, displacements were >0.7 cm for the longitudinal direction. CONCLUSION: Implementation of the proposed adaptive procedure based on the on-line set-up error elimination followed by a reduction of systematic internal error enables reducing the CTV-PTV margin to 0.7, 0.7, and 0.4 cm for the vertical, longitudinal, and lateral directions, respectively.

Serum interleukin-16 and RANTES during treatment of Graves' orbitopathy with corticosteroids and teleradiotherapy.

INTRODUCTION: To assess the usefulness of circulating IL-16 and RANTES measurements as markers of Graves' orbitopathy (GO) activity and to estimate the role of these cytokines in GO pathogenesis. MATERIAL AND METHODS: 42 individuals were divided into four groups: Group 1 comprised 15 euthyroid patients with clinical symptoms of GO who underwent corticosteroid therapy consisting of intravenous infusions of methylprednisolone (MP) and teleradiotherapy (TR); Group 2 comprised ten patients with hyperthyroid GD (Gtx); Group 3 comprised ten patients with GD in euthyreosis (Geu); and Group 4 comprised seven healthy volunteers age- and sex-matched to Groups 1-3. Serum samples were collected 24 hours before the first dose of MP, 24 hours after the first dose of MP, before TR, and at the end of therapy. Serum IL-16 and RANTES were determined by ELISA and TSH-Rab by RIA. RESULTS: Serum IL-16 levels in patients with GO were significantly elevated at the end of therapy: 346 pg/mL (257-538) compared to IL-16 values before treatment: 250 ng/mL (211-337) and to the control group. RANTES serum concentrations did not significantly differ between studied groups, and immunosuppressive treatment did not influence its level. A negative correlation between TSH-Rab and RANTES was found in all studied groups (R = -0.32, p 〈 0.01). CONCLUSIONS: Our data suggests that IL-16 may exert an immunoregulatory effect in Graves' orbitopathy. Serum measurements of both IL-16 and RANTES may be clinically useful; however, establishing their place in the diagnostics and treatment monitoring of GO needs further research.

Aperture superposition dose model versus pencil beam superposition dose model for a finite size Cobalt-60 source for tomotherapy deliveries.

PURPOSE: The finite size pencil beam (FSPB) superposition method is a commonly used dose calculation method in intensity modulated radiation therapy (IMRT). The FSPB model assumes that dose for a broad intensity modulated beam can be calculated by superposition of dose from small, pencil-like beams. However, this model is limited to point-like radiation sources and is not valid for finite size sources, such as a Cobalt-60 (Co-60) source of 2 cm diameter. In this paper, the authors present results that show the limitation of this model and propose an alternative model, namely the aperture superposition (AS) model, to calculate photon dose for intensity modulated beams arising from finite size radiation sources. METHODS: The AS model is based on adding beam apertures rather than pencil beams. Each aperture is defined as a series of adjacently opened leaves of a multileaf collimator with no closed leaves in between them. The apertures are calculated using the EGSnrc Monte Carlo program. The accuracy of the AS model was tested for dose calculations of fan beams, as encountered in tomotherapy treatment plans. The results were compared with the FSPB model and GafChromic film measurements. The measurements and simulations were performed for a clinical Theratronics T780C Co-60 unit with MIMiC binary multileaf collimator mounted on it. RESULTS: The comparisons between the AS model and film measurements show agreement better than 1.5% in the high dose regions and 3.7% in the low dose regions. On the contrary, film measurement comparisons to the FSPB model show that the FSPB model underestimates the dose by up to 7% for small field sizes such as 2 × 2 cm(2) and 20% for larger field sizes such as 20 × 2 cm(2). CONCLUSIONS: The results presented in this paper indicate that the AS model provides better accuracy than the FSPB model when calculating dose for fan beams from large radiation sources. The implementation of this model to the current treatment planning systems has the scope of advancing Co-60 based IMRT and tomotherapy.

Pattern of oncologic emergencies seen in adult cancer patients attending the Radiotherapy and Oncology Centre, Ahmadu Bello University Teaching Hospital, Zaria - Nigeria.

AIMS AND OBJECTIVES: To evaluate the Pattern of Oncologic Emergencies seen in Adult cancer patients and the treatment modalities used. MATERIALS AND METHODS: Between January 2004 and December 2008, a total of 1824 (M:F = 1:1.8) new patients were seen. 196 (M:F = 1:1.4) consecutive patients with histologically confirmed malignancies presenting with or having oncologic emergencies were treated and have been reviewed. Patients' folders were reviewed retrospectively with a structured pro forma. Results were analysed using Epi Info soft ware Version 3.4.1; 2007 Edition. RESULTS: The median age was 49 years and mean age of 42 years (range, 15 - 82 years). M: F = 1:1.4. 162 patients had oncologic emergencies at presentation while 21 during treatments and 13 during follow up. At the time of diagnosis of oncologic emergency, 126 were not on any treatment, 42 patients on hormonal therapy and 28 patients were on diverse chemotherapy. All the patients presented late with 108 patients presenting with metastatic disease and 88 patients with locally advanced disease. Only 35 patients were treated within 1 week of onset of emergency. 59 patients had cervical cancer, 31 patients with breast cancer and 28 patients with prostate cancer. Tumour haemorrhage wass the commonest oncologic emergency seen in 107 patients followed by bone pain with imminent cord compression from bone metastases in 59 patients. Of 107 patients with tumour haemorrhage, 54 patients had cardiovascular collapse with 7 having acute renal failure. Similarly, of the 107 with tumour haemorrhage, 56 patients bled from cervical cancer, 12 patients from breast cancer and 8 patients from urinary bladder. 129 patients were treated with teletherapy, 31 patients had chemotherapy, 27 patients had emergency surgery and 5 patients had chemoradiation. Oncologic emergencies were corrected in 126 patients. CONCLUSION: Tumour haemorrhage is the commonest oncologic emergency in this environment and teletherapy is the commonest therapy used. More radiotherapy centres are needed for prompt treatment and their usefulness in managing emergencies should be made known. Oncologic emergencies are commonly seen in metastatic and locally advanced disease.

Estimation of inhomogenity correction factors for a Co-60 beam using Monte Carlo simulation.

AIM: The aim was to obtain inhomogenity correction factors (ICFs) for lung tissue inhomogenity for a Co-60 teletherapy beam using Monte Carlo simulation and to compare them with factors obtained from a commercially available treatment planning system. MATERIALS AND METHODS: The Monte Carlo simulation code of EGSnrc is used for the depth dose calculations. Two clinical like situations were simulated-dose calculation point beyond the lung tissue volume and dose calculation point within the lung tissue volume. The variation of ICF with lung thicknesses and positions was studied. ICF values were obtained for the similar situations from a commercially available treatment planning system, Theraplan Plus. RESULTS: Percentage depth dose data obtained from Monte Carlo simulation is well matching with the published measurement data. ICFs for lung tissue inhomogenity calculated using the Monte Carlo code are in good agreement with Theraplan Plus TPS values for small inhomogenity thicknesses. CONCLUSION: These results can be used for the verification of TPS calculation or manual treatment time calculation.

Radiotherapy of splenomegaly : a palliative treatment option for a benign phenomenon in malignant diseases.

PURPOSE: Since the 20(th) century, radiotherapy (RT) has been used for treatment of symptomatic splenomegaly (SM). SM occurs in association with hematologic disorders. The purpose of this analysis was to determine the indication, treatment concepts, and efficiency of RT. MATERIAL AND METHODS: Clinical features, treatment concepts, and outcome data during the past 20 years were analyzed. Endpoints were pain relief, symptomatic and hematological response, and treatment-related side effects. RESULTS: From 1989-2009, a total of 122 patients received 246 RT courses because of symptomatic SM. Overall 31 patients had chronic myelogenous leukemia (CML), 37 had chronic lymphocytic leukemia (CLL), 23 had osteomyelofibrosis (OMF), 17 had polycythemia vera (PV), 5 had acute myelogenous leukemia, 4 had idiopathic thrombocytopenic purpura (ITP), 3 had non-Hodgkin lymphoma (NHL), and 2 had multiple myeloma (MM). Patients were treated with (60)Co gamma rays or 5-15MV photons. The fraction size ranged from 10-200 cGy and the total dose per treatment course from 30-1600 cGy. Significant pain relief was achieved for 74.8% of the RT courses given for splenic pain. At least 50% regression was attained for 77% of the RT courses given for SM. 36 patients died within 2 months due to the terminal nature of their disease. Of the RT courses applied for cytopenia, 73.6% achieved a significant improvement of hematological parameters and reduction of transfusion need. Notable hematologic toxicities were reported < EORTC/RTOG II°. CONCLUSION: The present analysis documents the efficacy of RT. In addition, RT as a palliative treatment option for symptomatic SM should not be forgotten.

Dosimetric evaluation of high-dose-rate interstitial brachytherapy boost treatments for localized prostate cancer.

PURPOSE: To quantitatively evaluate the dose distributions of high-dose-rate (HDR) prostate implants regarding target coverage, dose homogeneity, and dose to organs at risk. MATERIAL AND METHODS: Treatment plans of 174 implants were evaluated using cumulative dose-volume histograms (DVHs). The planning was based on transrectal ultrasound (US) imaging, and the prescribed dose (100%) was 10 Gy. The tolerance doses to rectum and urethra were 80% and 120%, respectively. Dose-volume parameters for target (V90, V100, V150, V200, D90, D(min)) and quality indices (DNR [dose nonuniformity ratio], DHI [dose homogeneity index], CI [coverage index], COIN [conformal index]) were calculated. Maximum dose in reference points of rectum (D(r)) and urethra (D(u)), dose to volume of 2 cm(3) of the rectum (D(2ccm)), and 0.1 cm(3) and 1% of the urethra (D(0.1ccm) and D1) were determined. Nonparametric correlation analysis was performed between these parameters. RESULTS: The median number of needles was 16, the mean prostate volume (V(p)) was 27.1 cm(3). The mean V90, V100, V150, and V200 were 99%, 97%, 39%, and 13%, respectively. The mean D90 was 109%, and the D(min) was 87%. The mean doses in rectum and urethra reference points were 75% and 119%, respectively. The mean volumetric doses were D(2ccm) = 49% for the rectum, D(0.1ccm) = 126%, and D1 = 140% for the urethra. The mean DNR was 0.37, while the DHI was 0.60. The mean COIN was 0.66. The Spearman rank order correlation coefficients for volume doses to rectum and urethra were R(D(r),D(2ccm)) = 0.69, R(D(u),D0.(1ccm)) = 0.64, R(D(u),D1) = 0.23. CONCLUSION: US-based treatment plans for HDR prostate implants based on the real positions of catheters provided acceptable dose distributions. In the majority of the cases, the doses to urethra and rectum were kept below the defined tolerance levels. For rectum, the dose in reference points correlated well with dose-volume parameters. For urethra dose characterization, the use of D1 volumetric parameter is recommended.

[Concurrent chemoradiotherapy versus radiotherapy in advanced cervical carcinoma].

BACKGROUND & OBJECTIVE: Cisplatin-based concurrent chemoradiotherapy has become the standard treatment modality for locally advanced cervical cancer. However, the optimal chemotherapy regimen combined with radiotherapy remains controversial. This study was to compare the therapeutic efficacy and toxicity of concurrent chemoradiotherapy with those of radiotherapy, and those among different regimens of concurrent chemoradiotherapy for stage IIB-IIIB cervical cancer. METHODS: From Jan. 2003 to Dec. 2004, 285 patients with stage IIB-IIIB cervical cancer treated in Maternal and Child Health Hospital of Jiangxi Province were randomly assigned to receive radiotherapy alone or concurrent chemoradiotherapy. According to different chemotherapy regimens, patients in the concurrent chemoradiotheapy group were randomly chosen to receive radiotherapy with chemotherapy of bleomycin and cisplatin (RT+BP), radiotherapy with chemotherapy of taxol and carboplatin (RT+TP), and radiotherapy with chemotherapy of 5-fluorouracil and cisplatin (RT+FP). The 3-year survival rates and toxicity of different groups were compared. RESULTS: After a median follow-up of 42 months, the 3-year survival was higher in the concurrent chemoradiotheray group (75%) than in the radiotherapy group (65%) (P=0.042). Acute treatment-related toxicity (grade III and IV) was higher in the concurrent chemoradiotherapy group than in the radiotherapy group (P<0.001); while the delayed treatment-related toxicity was similar in the two groups (P=0.613). The 3-year survival rates of BP, TP and FP chemoradiotherapy groups were 74%, 80% and 71%, without significant differences (P=0.792). Acute toxicities (grade III and IV) and delayed toxicities were similar among the three groups. CONCLUSIONS: Concurrent chemoradiotherapy significantly improves the survival for patients with stage IIB-IIIB cervical cancer compared to radiotherapy alone. Among the three chemoradiotherapy regimens, radiotherapy combined with taxol and carboplatin exerts a slightly higher 3-year survival than the other two regimens with tolerable toxicity.

Radiotherapeutic management of laryngeal carcinoma.

Authors discuss laryngeal lesions, metastases, and relevant anatomy. Outcome of surgical and radiotherapy in terms of voice preservation is discussed. Radiation techniques and outcomes for laryngeal cancer are presented along with discussion of interdisciplinary treatment. Authors review studies and quality of life outcomes of surviving laryngeal cancer patients.