International Journal of Radiation Research
Year:2014 | Volume:12 | Issue:4|Papers Count:17

Background: In order to improve the evaluation of possible rectal toxicity based on the rectal normal tissue complication probability (NTCP), we consider the fractional dependence of the NTCP on the wall thickness (tW) and rectal displacement (RM).Materials and Methods: The two‐dimensional NTCP model (NTCP2D) was developed using radiotherapy plans of ten randomly selected patients with prostate cancer. The clinical rectal structures were substituted with rectal walls of cylindrical shape. To simulate full, partially‐full and empty state of the rectum, three tW were generated under the conditions of same length of the rectum and same volume of the rectal wall. A threshold iso‐line, NTCPTR, was used to split the NTCP2D field into areas: a lower risk area and a higher risk area for rectal toxicity. Two factors are introduced to help with the estimation of NTCP: a volume factor k1 which is the ratio between the volumes of the rectal wall and the intersection of the rectal wall with the planning target volume; and a probability factor k2, which is the ratio between the area of low risk to the entire area of the NTCP2D.Results: A correlation>0.9 between factors k1 and k2 was found.Conclusion: The NTCP2D field and the ratios k1 and k2 can be used as a patient‐specific parameters to evaluate the probability of rectal toxicity.

Background: It was intended to investigate the effect of physical wedge (PW) and enhanced dynamic wedges (EDW) on contralateral breast dose during primary breast irradiation in radiotherapy treatment, using high energy photon beams.Materials and Methods: The Varian’s Clinac dual mode linear accelerator model 2100 C/D and Siemen’s Primus accelerators were used for radiation doses with 6 MV and 15 MV. Doses were delivered using Tangential field techniques and asymmetric collimator jaws. Eclipse three‐dimensional Treatment Planning System (3DTPS) was used to measure contralateral breast dose for all fiend settings. Sixty five patients (with cancerous breast as well as chest wall) were taken and their contralateral breast doses were measured at a point 5 cm across, at 2 cm depth from the end of the medial field.Results: The contralateral breast dose mean difference was 0.25 cGy and 0.24 cGy during the comparison of PW and EDW on Varian’s Clinac and 0.19 cGy and 0.18 cGy were found for medial EDW and without medial EDW for the same machine in breast cases and chest wall cases respectively as per total prescribed dose. The mean difference for PW (Clinac) and PW (Primus) was found 0.08 cGy and 0.31 cGy and during the comparison of medial PW and without medial PW on primus machine this mean difference was 0.25 cGy and 0.51 cGy in breast cases and chest wall cases respectively as per total prescribed dose.Conclusion: The investigation demonstrates the significance that the EDW produces less scatiered dose, which can cause second breast malignancy, compared to PW. Furthermore, the medial wedge, too, can cause second breast malignancy and should be avoided in planning.

Background: For the purpose of individual clinical target volume assessment in radiotherapy of prostate cancer, MRSI was used as a molecular imaging modality with MRI and CT images. Materials and Methods: The images of 20 prostate cancer patients were used in this study. The MR and MRSI images were registered with CT ones using non‐rigid registration technique. The CT based planning (BP), CT/MRI BP and CT/MRSI BP was performed for each patient. For plan evaluation, Dose Volume Histograms (DVHs) data were used. A paired sample T‐test was used for the analysis of the obtained data.Results: The percentage of variation of CTVMRI to CTVCT and PTVMRI to PTVCT were 12.83% and 8.97%, respectively. CTVMRSI and PTVMRSI were 21% and 27.41% more than their corresponding values of CT volumes. The mean percentage of variation in rectum volume that received 60% of the prescribe dose (V60R) in MRSI/CT BP relative to CT BP was 14.66%.Conclusion: The use of MRSI in detecting of prostate adenocarcinoma could provide some decisive information to determine optimum volume and safe margin for target definition to improve adaptive radiotherapy in prostate cancer.

Background: Palliative whole brain radiotherapy (WBRT) has been the standard treatment for brain metastases. Ionizing radiation is known to be one of the most potent cataractogenic agents. We aimed to evaluate two different radiotherapy techniques with respect to the doses received by the organs at risk (OAR) in patients with brain metastasis who undergone WBRT.Materials and Methods: Ten consecutive patients with brain metastasis were included. For each patient, two different treatment plans were created for whole brain. Helmet‐field (HF) (anterior border was 2 cm posterior to lens, inferior border was the bottom of C2 vertebra) and classical technique with collimation (CT) (anterior border was defined as skin fall off, inferior border was the bottom of cranial base) were generated for all patients. Two techniques were compared with respect to the doses received by the OAR including bilateral lenses, optic nerves and eye‐balls, the dose homogeneity index (DHI), and the monitor unit counts (MU) required for the treatment.Student‐t test was used for statistical analysis.Results: There was no difference between two techniques in terms of both DHI (p: 0.182) and MU counts (p: 0.167). The maximum and mean doses received by the right lens, left lens and right eye‐ball were significantly reduced with CT (p values for maximum doses 0.007, 0.012 and 0.010; for median doses 0.027, 0.046 and 0.002 respectively).Conclusion: CT was found to be more advantageous, with respect to the lens doses in addition the dose received by the right eye‐ball during WBRT.

Background: The therapeutic administration of 131I for thyroid remnant ablation and for metastases comes up with some adverse effects. This study was conducted to investigate whether single high dose radioiodine therapy affects lacrimal gland functions or not. Materials and Methods: Seventy-eight eyes of 39 patients, who were diagnosed as differentiated thyroid carcinoma, were objectively tested with Schiermer’s test and tear film break-up time test; before and 1 and 6 months after high dose (³3700 MBq) 131I therapy.Results: The median values of pre‐treatment Schiermer’s test were 10.00 mm and 9.60 mm for right and left eyes, respectively. At the post‐treatment first and sixth months, no significant change was observed in the median values of Schiermer’s test in both eyes (p=0.189 and p=0.085, respectively, Friedman test). The median values of pre-treatment tear film break‐up time test were 9.15 sn and 9.20 sn for right and left eyes, respectively. The median values of post‐treatment tear film break-up times reduced at first and sixth months and the difference between the pre‐treatment and post-treatment values were significant in both eyes (p=0.020 and p=0.022 for right and left eyes, respectively, Friedman test).Conclusion: Impairment of goblet cell function occurs early after administration of single high dose 131I application. However, reduction in tear secretion from lacrimal gland is not observed.

Background: Making use of the orthovoltage machines in Radiotherapy, is one of the routine methods for the treatment of the superficial lesions. In this study, an important determinant of X‐ray quality, the HVL (Half Value Layer), has been evaluated. Materials and Methods: The HVLs of a orthovoltage X-ray machine in 120 and 180 kVp are measured, using an empirical method, in which the HVLs are derived from the absorption curves. The measured HVLs are compared with calculated (Monte Carlo simulation) HVLs. Using the BEAMDP code of simulation, the output spectra are obtained and employed for the measurement of the HVLs.Results: Comparing the calculated and measured HVL values, the results show that the highest and lowest differences between the two are 4.96% and 2.27%, respectively, which are, in fairly good agreement with those obtained in the former studies.Conclusion: This study shows that the EGSnrc simulation code is capable of being used for the extraction of the quality indices for the superficial X‐ray radiotherapy machines. It seems that, the mentioned code, with the mentioned experimental method, can be employed as a routine clinical test tool for every superficial radiotherapy department.

Background: Brain is the most important organ as it controls and co‐ ordinates all the activities of our body. Reports on neuroethological investigations in mice particularly associated with learning and memory after radiation exposure are very scanty. Hence, present investigation is an atiempt to examine the effects of low dose tritiated water (HTO) acute exposure on adult Swiss albino mice in the light of behavioral parameters. Materials and Methods: Swiss albino adult male mice were trained in a Hebb William’s Maze, model D. When the mice had learned the Maze, they were injected with tritiated water and then the same batch (pre learned mice) again tested for memory retention.Results: Our results clearly show that the adult mice learned the Maze in ten trials. On day ten of the experiment mice were injected with dose 111.0 kBq/gm. bd. wt. tritiated water. Immediately after the exposure, the mice started taking relatively more time to reach the goal which continued till trials 11, 12 and 13 of the experiment. However, after this, a reversal in the learned performance was observed in most of the experimental mice whereby the learned activity returned to a near normal on trials 14 and 15. From 16th trial onwards, the performance of the irradiated mouse was found to be even superior over the prelearned mice though, their pattern did not show the steady state as was evident just prior to HTO injection.Conclusion: The findings from our experiments signify that the possible alterations in behaviour in adult Swiss albino mice after low doses of acute tritiated water exposure cannot be safely ruled out.

Background: Hadron therapy for malignant tumor is becoming increasingly popular. There are many factors which effect on implementation of a proper treatment planning. The purpose of this work is to investigate the inhomogeneity effects as affecting factor on proton range, Full width at half maximum (FWHM) and 20% position of penumbra (P20) by MCNPX code.Materials and Methods: An inhomogeneous tissue (Bone or Adipose) with a variable thickness (0.1 cm, 0.5cm and 1.0 cm) was inserted into a phantom.Then this phantom was irradiated by 108.8 MeV proton beam located at 10 cm away from it. Particle energy deposition (PEDEP) in mesh tally card was used for simulation of Bragg curve and obtaining the proton range, FWHM and 20% position of penumbra (P20). Finally, the MCNPX results were compared with GEANT4.Results: The results of MCNPX for water phantom including 1cm adipose for range and P20 were 8.87 and 9.10 cm respectively, and for 1cm bone, range and P20 were 8.52 and 8.58 cm. By increasing the adipose thickness, range and P20 were reduced but it was vice versa for increasing the bone thickness. Also FWHM does not show a regular variation in both bone and adipose tissues.Conclusion: The results show that the location of the inhomogeneous tissues does not affect the variation of the whole shape of the Bragg curve, while it radically affects the dose in the Bragg curve. The comparison between MCNPX and GEANT4 results showed that the MCNPX results have the closer values than GEANT4 to references.

Background: Technetium‐99m radioisotope is the backbone of any nuclear medicine institute. This radioisotope is acquired by the elution of Molybdenum‐99/Technetium‐99m generator which emits 141 keV gamma ray and having 6.04 hour half‐life. Occasionally the contents of Molybdenum‐ 99 may mix up with elute, which may affect image quality and patients may receive higher doses than recommended. This study was initiated to check and evaluate the contamination of Molybdenum‐99 in Molybdenum‐99/ Technetium‐99m generators used at Nuclear Institute of Medicine and Radiotherapy (NIMRA) Jamshoro Pakistan before its administration to patients for diagnostic procedures.Materials and Methods: The Molybdenum‐99 impurity in Technetium‐99m elute for 50 generators was studied during the year 2012. The measurements were made using dose calibrator and a standard canister at the time of first elution of the generators. The dose calibrator displays result after executing various steps in a sequence. Due to some production process error or any mechanical fault high activity of Molybdenum‐99 was recorded and removed with decrease in Technetium‐99m yield.Results: The most of eluted generators (90%) contained 10% of molybdenum breakthrough of the permissible limit (P<0.05). The high activity of Molybdenum‐99 was recorded in only 6% of the generator and removed by using standard methods with some reduced Technetium‐99m activity.Conclusion: The molybdenum breakthrough was according to recommended standards in most of the generators. The removal of high contents of Molybdenum‐99 enabled the institute to continue routine imaging services by improved image quality and reduction in radiation dose to the patients.

Background: In this study the basic radiation properties of N‐isopropylacrylamaide polymer gel dosimeter were determined together with verification of its soti tissue equivalency. Materials and Methods: The NIPAM gel was prepared and irradiated approximately 2 h after manufacturing. The magnetic resonance (MR) images were made 24 h after irradiation. The nuclear magnetic resonance (NMR) response (R2) of the dosimeters was analyzed for conditions of varying dose, batch, dose rate, time post‐irradiation and energy. In order to verify tissue equivalence of NIPAM dosimeter, several parameters such as physical density, effective atomic number, relative electron density, CT (Computed Tomography) number and also elemental composition were determined and compared with those for soti tissue.Results: The response of the gel was found to be stable 24 hours after irradiation. The results showed that the dose response of the NIPAM polymer gel is reproducible in same and different batches of chemical and the gel response was linear up to 26 Gy with r2=0.995. In the measured range, the dose response of the NIPAM gel is independent of beam energy within less than ±0.02 and the dose rate had no effect on the gel response. This polymer gel has been found to be tissue equivalent.Conclusion: NIPAM gel dosimeter appears to be a promising dosimeter in all aspects of dosimetric properties which were assessed in this study, in addition to the advantage of reduced toxicity which it has over other polymer gels.

Background: In radiation therapy, peripheral dose or the dose outside the radiotherapy field, is important when anatomical structures with very low dose tolerances are involved. One of these critical organs in pelvic irradiation is testis. The amount of radiation delivered to the testes in radiotherapy must be kept as small as possible, consistent with the limit dose of this organ. The threshold doses for temporary and permanent sterility are 0.15 Gy and 6‐8 Gy, respectively. Therefore, in pelvic irradiation, protecting testis from these doses and also scatiered radiation which could escalate testis dose should be considered.Materials and Methods: In order to determine the possibility of using testicular shield for high and low energies, TLD dosimetry was done on phantom and 27 patients involved with bladder, rectum and prostate cancers.Results: Dosimetric results showed that the ability of testicular shield in reducing testes absorbed dose is approximately the same (about 7 cGy) for low and high energy photon beams.Conclusion: a testicular shield with a fixed thickness of 1.27cm can be used as testis protection for either high and low energies.

Background: The purpose of this work is to discover and analyze errors and incidents in some radiotherapy centers, and to introduce methods that could reduce their occurrences, especially those which had happened due to the use of improper and inadequate equipment. This work is a first step toward clarifying the role of education in a risk‐conscious culture, and changing the attitude of radiotherapy staff when they are working under encouraging conditions that remove barriers for reporting errors. Materials and Methods: For the present study clinical investigation, the data of 6000 patients were checked. They were treated at a few radiotherapy centers during one year.Patients were treated by linear accelerator or cobalt machine, photon or electron beams. A purposely designed check list was used for error data collection. Incidents were discovered by manual check at different steps of treatment. By highlighting frequency of occurrence, further investigation for preventing error repetition can be possible. Eighty five incidents were reported by Technologists, fifty four were reported by Physicists, and twenty six events were pointed out by Radiation Oncologists.Results: About fifty percent of total 165 detected events were classified as treatment field errors.Geometrical misses in treatment field have the highest probability for both photon and electron beams.Conclusion: Incident prevention considering likelihood of individual event can be possible when using facilities like record-and‐ verification (R& V) system and electronic‐portal‐image‐device (EPID), taking seriously QA, defining and implementing layers of defense in depth, and making an organized system for reporting and analyzing errors.

Background: In intracavitary brachytherapy for gynecological cancers, various techniques are used to locate the anterior rectal wall nearest to the sources but there is no consensus on the best method to do so. This study aimed to compare a technique used routinely in some centers that employs a wire marker to locate the position of the maximum rectal dose point, versus the method recommended by the ICRU Report 38.Materials and Methods: In a preliminary prospective study on 34 intracavitary insertions for patients with cervical or endometrial cancer, treated at our center based on the Manchester system, the dose distributions were obtained from a treatment planning system following the input of scanned orthogonal anteroposterior and lateral radiographs. For each case, an in‐house marked wire was inserted in the rectal lumen and the doses were calculated on several points along the wire seen on the radiographs, to obtain the maximum dose. For the same insertions, the ICRU method was also applied by considering the rectal wall hot spot as a point 0.5 cm posterior to the posterior vaginal wall (visualized on the radiographs by vaginal packing material containing contrast medium).Results: Averaged over all insertions, mean rectal wall hot spot dose calculated using the posivonal information obtained by the wire technique was lower by 28.6% than that given by the ICRU method (P<0.001).Conclusion: Our initial results add evidence to the suggestion that the wire technique underestimates the rectal wall hot spot dose significantly compared to the ICRU method.

Background: The present study aimed to evaluate the balance between training and demand for radiologists in the Iranian health care system between 2008 and 2027.Materials and Methods: A total number of 250 clusters were randomly selected from urban and rural areas of Iran, of which 168 were selected from urban areas and 82 were selected from rural areas. In order to collect basic medical data and to determine the number of radiology visits in the last two weeks, questionnaires were prepared and sent out to the subjects' houses. Information on the number of radiologists as well as statistics on the Iran's population were provided by the Medical Council of the Islamic Republic of Iran (IRI) and the Statistics Center of IRI, respectively.Results: Radiologists were visited 245 times during a two‐week time period, which resulted in an average referral to radiologists of 0.125 for each individual. Our results indicated a slight shortage of radiologists in 2008, which is expected to disappear till 2023. Afterwards, the training of radiologists is expected to slightly surpass the demands.Conclusion: Results from the present study suggested that an overall balance between training and demand for radiologists in Iran is likely to happen in near future.

Background: Hydrogen peroxide (H2O2), produced by gamma ray irradiation to watery solution, was used as an analytical parameter for dosimetry of cobalt-60 (60Co) radiation. Materials and Methods: Detection of the produced H2O2 was carried out using two methods: an amperometric biosensor fabricated by immobilization of anthraquinone 2-carboxylic acid modified horseradish peroxidase on glassy carbon electrode, and chemiluminescence technique using luminol as a fluorophore and diperiodatocuprate as a catalyst. Results: In the first method, at the applied potential of -550 mV (vs. Ag/AgCl) the biosensor showed the sensitivity of 74.46 nA/Gray and detection limit of 0.061 Gray (R.S.D=3.67% for N=3) towards H2O2 produced by 60Co. In the second method, the sensitivity and detection limit for 60Co gamma ray was determined to be 2.34 (luminescence intensity/Gray) and 0.069 Gray (R.S.D=4.16% for N=3), respectively. Conclusion: The obtained results revealed that both proposed techniques, with leaner range from 0.25 to 5 Grays are applicable for detection and dosimetry of gamma ray from 60Co.

Radiation induced sarcoma is a rare but recognized complication of radiotherapy and is associated with poor prognosis, frequently occurs 5 years after completion of treatment. We report radiation‐induced sarcoma in a 42 years old male, involving the left parietooccipital scalp region following treatment of brain tumor with craniotomy and post‐operative radiation with 60Co machine. Diagnosis of radiation induced sarcoma was confirmed by history, latency period and biopsy. This Radiation induced malignancy was diagnosed only 2 years after completion of Radiotherapy for primary lesion.

Background: Inflammatory myofibroblastic tumor (IMT) is a tumor composed of myofibroblasts and a mixed inflammatory infiltrate that rarely undergoes malignant transformation. The most common sites of involvement include the lung, liver and orbit, but it has been reported to occur in nearly every site of the body, including oral cavity and soti tissue. Although common in other sites, such a tumor in rarer location including inguinal region is likely to be missed/misdiagnosed and hence need to be reported.Case Report: We present an unusual case of a 50 year old male with bilateral inguinal swelling atiended our institute few days back with history of local excision twice, but still showing recurrence. He was treated by wide local excision with bilateral orchiectomy this time. Histopathological report revealed inflammatory myofibroblastic tumor with malignant transformation. Adjuvant radiotherapy was also given and patient taken in followup. At one year of serial follow‐ups, the patient is disease‐free both clinically and on investigations, indicating successful combined surgery and radiotherapy in the treatment of malignant IMT. Conclusion: IMT of the inguinal region is very rare. Its clinical presentation may resemble malignant tumor, so IMT should be kept as differential diagnosis. The recommended treatment is complete surgical resection with adjuvant corticosteroid. Adjuvant radiotherapy may be considered depending upon the location of the tumor.