International Journal of Radiation Research
Volume:3 Issue: 2, Apr 2005

ABSTRACT Manual fusion (MF) is a readily available image registration technique that does not require matching algorithms. The operator performs rigid-body transformations interactively. The precision of MF (as implemented on the Philips Pinnacle treatment planning system) was required for cranial CT-MR images used in radiotherapy planning for typical centrally located planning target volumes (PTVs). A multi-stage MF procedure was developed which 11 observers followed to match the head contour, bones, soft tissues and contoured structures for 5 patient image-sets. Registration parameters were calculated by solving the transformation matrix following a consistent order of translations (T) and rotations (R). The mean position of centre of each PTV averaged over all observers was used as the reference. The effect of misregistration on the PTV co-ordinates and the volume increase resulting from application of a margin for registration uncertainty were calculated. Mean intra- and inter-observer T/R SDs were 0.5mm/0.4 and 1.1mm/1.0, respectively. Mean intra- and inter-observer registration error (3D distance of each PTV centre from the mean position for all observers) was 0.7  0.3 mm (1 SD) and 1.6  0.7 mm respectively, the latter reducing to 1.4  0.6 mm excluding the 3 least experienced operators. A subsequent 2 mm margin for misregistration on average increased the PTV volume by 27%. Moderately trained operators produced clinically acceptable results while experienced operators improved the precision. MF still has an important role in the registration of cranial CT and MR images for radiotherapy planning especially for under-resourced centers.

ABSTRACT Breast cancer is the most widespread cancer in women. Early detection of this disease has been identified as a major effective factor to save the lives of many women. The ability of small angle X-ray scattering to provide molecular in formations on live tissue has led to investigate the possibility of exploiting coherent scattered X-rays as a diagnostic tool in breast cancer. In this study an angular dispersive set up was used in Daresbury laboratory (UK). 84 human breast tissue biopsies including 50 cancerous and 34 normal tissues were studied. For this study a beam size of 0.5 mm2 at the sample and a wavelength of 1.54 Å were used. The other included conditions were, the sample to detector distance (SSD), 2000 m and exposure time of 200 sec. Data were recorded using the Daresbury 2-D multiwire proportional counter operated at 512 512 pixels. The region between the specimen and detector was evacuated to minimize air scatter. With exposure to the each sample, at first a two dimensional image was produced and then the corrected intensity versus momentum transfer (Q) was plotted by using PCDetpack software. It was found that there was a noticeable coherent intensity difference between tumor and normal breast tissues especially in the range of Q from 0.4-0.7 nm-1, that the coherent X-ray scattering intensity in the tumor breast tissue was significantly higher (P < 0.0001, CI= 95%) than in the normal breast tissue in the 0.4-0.7 nm –1 range. In this study, by using 2 m distance of camera collagen diffraction peaks were seen at 0.3 and 0.45 nm-1. Applying SAXS, it is possible to differentiate normal and tumoral breast tissues as separated groups (P < 0.0001, CI = 95%), on the base of integrated intensity, in the 0.4-0.7 nm –1 range. Since having collagen damge in tumors, is probable therefore, it is suggested to do some cytocellular examinations on tumoral tissues.

ABSTRACT Dual X-Ray energy Absorptiometry (DXA) is a method that can be used extensively for bone mineral densitometry (BMD). A newer method is called DXL, associates dual X ray absorptiometry assisted by laserX-ray absorptiometry to the measures of heel thickness with a laser beam. In this study the cut off points for DXL of calcaneus in the diagnosis of osteoporosis in different bone regions in postmenopausal women were determined. In 268 postmenopausal women, BMD of the spinal and femoral regions was measured by DXA and the value for the heel calcaneous was measured by DXL. The agreement of the two methods in diagnosis of osteoporosis and optimal cut-off point for DXL in defining osteoporosis was obtained. DXA showed osteoporosis in 40.7% of cases with 35.2% in L2-L4, 16.2% in the femoral neck, and 11.7% for the femoral total region. The DXL found osteoporosis, considering -2.5 SD as a threshold, in 26.1% of cases. According to WHO criteria, agreementAgreement of the two methods in the diagnosis of osteoporosis (Kappa score) was 0.443 for the lumbar region, 0.464 for the neck, and, 0.421 for total femur regions (all P values were significant). Using Receiver Operating Characteristic (ROC) curves, it was found that a T-score of -2.1, -2.6 and -2.4 as the optimal cut-off point of DXL in the diagnosis of osteoporosis in the lumbar spine, the neck and total region of femur, respectively. The results of this study showed a moderate agreement of the two methods in the diagnosis of osteoporosis. It seems that the DXL cannot be used as a substitute for the DXA method, but it can be used as a screening method for finding osteoporosis.

ABSTRACT A prototype stereotactic radiosurgery set was designed and constructed for a Neptun 10 PC linac that is currently being used at Imam Reza hospital in Mashhad. A complete quality assurance program was designed and performed for the constructed system including isocentric accuracy test, localization accuracy test, dose delivery accuracy test and leakage radiation test. Target simulator, control alignment device and plexiglass phantom which were parts of the developed hardware were used to fulfill quality assurance program. The average isocentric shift resulted from the gantry rotation and couch turning were respectively obtained to be 1.4 and 2 mm. The average localization error in the three coordinates was found to be 2.2 mm. The total treatment uncertainty due to all of the probable errors in the system was equal to 4.32 mm. The dose delivery accuracy test was carried out, the result indicated a 3-7% difference between the given and measured dose. The quality assurance tests showed consistent performance of the constructed system within the accepted limits; however, some inconsistency might exist in certain cases. The safety of SRS method is increased when the overall uncertainty is minimized and the treatment of the lesions adjacent to critical organs is avoided.

ABSTRACT Radon and its short-lived decay products in dwellings are recognized as the main sources of public exposure from the natural radioactivity. The tap water used for drinking and other household uses can make variable contributions to the indoor radon level. This study has provided data on radon concentrations in domestic water supplies in Tehran. Water samples were collected from various sources supplying domestic water in Tehran. Sample preparation for measuring waterborne radon by liquid scintillation counting was carried out in place. A modified sample preparation method providing higher measurement sensitivity was applied in this work. According to measurements, the mean 222Rn concentrations in groundwater and surface water supplies were 46.40±11.50 and 2.50±1.20 Bq.L-1, respectively. The mean radon concentration in tap water was 3.70±0.94 Bq.L-1. The annual total effective dose to adults due to waterborne radon in Tehran was estimated to be about 10 μSv. The radon concentrations in tap water actually used by people in Tehran are low enough and below the proposed limits in other countries.

ABSTRACT Natural radionuclides in soil constitute a significant component of the background exposure sources of the population. A meaningful contribution to the total dose from natural sources comes from terrestrial radionuclides such as 238U, 232Th and 40K. The concentrations of natural radionuclides of 238U, 232Th and 40K in surface soil (5 cm depth) of Tehran have been measured by gamma spectrometry. The samples were dried and homogenized and measured for 60k seconds after radionuclides secular equilibrium, using a high purity germanium (HPGe) gamma-ray spectrometer. The high energy resolution of this type of detector is particularly useful for activity measurements of uranium and thorium chain members due to their complex spectras. The absorbed dose rates in air were also measured by using ionization-chamber at the point where soil samples were collected which includes terrestrial and cosmic rays. The natural gamma emitting terrestrial radionuclides in soils are directly relevant to outdoor exposure. The average activity concentrations of 238U, 232Th and 40K in different districts of Tehran were found to be 24, 28 and 635 Bq kg-1, respectively. The average outdoor gamma absorbed dose rate in air at 1 meter above ground was calculated as 102 nGy h-1. By using the data obtained in this study the average annual effective dose equivalent for a person living in Tehran was found to be about 125 Sv. According to data of 66 soil samples measurement covering 22 districts in Tehran, the average outdoor gamma dose rate in air due to terrestrial and cosmic radiation was found to be about 102 nGy h-1 and the average annual effective dose equivalent for a person living in Tehran is about 125 Sv.

ABSTRACT Non-uniformity test is the most essential in daily quality control procedures of nuclear medicine equipments. However, the calculation of non-uniformity is hindered due to high level of noise in nuclear medicine data. Non-uniformity may be considered as a type of systematic error while noise is certainly a random error. The present methods of uniformity evaluation are not able to distinguish between systematic and random error and therefore produce incorrect results when noise is significant. In the present study, two hypothetical methods have been tested for evaluation of non-uniformity in nuclear medicine images. Using the Monte Carol method, uniform and non-uniform flood images of different matrix sizes and different counts were generated. The uniformity of the images was calculated using the conventional method and proposed methods. The results were compared with the known non-uniformity data of simulated images. It was observed that the value of integral uniformity never went below the recommended values except in small matrix size of high counts (more than 80 millions counts). The differential uniformity was quite insensitive to the degree of non-uniformity in large matrix size. Matrix size of 64×64 was only found to be suitable for the calculation of differential uniformity. It was observed that in uniform images, a small amount of non-uniformity changes the p-value of Kolmogorov-Smirnov test and noise amplitude of fast fouries transformation (FFT) test significantly while the conventional methods failed to detect the non-uniformity. The conventional methods do not distinguish noise, which is always present in the data and occasional non-uniformity at low count density. In a uniform intact flood image, the difference between maximum and minimum pixel count (the value of integral uniformity) is much more than the recommended values for non-uniformity. After filtration of image, this difference decreases, but remains high. Both proposed methods were more sensitive to the non-uniformity at a much lower count density.

ABSTRACT To assess the frequency and severity of myelosuppression due to cranio-spinal irradiation to identify patients at high risk of haematological toxicity who may require supportive therapy. Patients and Between 1998 and 2002, 45 patients received craniospinal axis radiotherapy as part of the treatment of primary CNS tumours at departement of radiotherapeutic oncology of cancer Institute. The dose to the whole brain ranged from 30 to 40 Gy in 1.5-1.85 Gy/f. The usual dose to the posterior fossa or to the site of primary disease was 50– 55 Gy in 6–8 weeks for adults and was reduced to 45–50 Gy in 6–7 weeks for children aged, 3 years. Complete blood counts (CBC) were obtained during radiation therapy. Any interruption in treatment due hematologic toxicity (G3-4) lasting 2 days was defined as a significant treatment interruption. In 45 patients who received craniospinal irradiation (CSI) 19 patients had treatment interruption more than 2 days. The median dose at interruption was 21.6± 8.7 Gy and the the frequency of grade 3,4 hematologic toxicity occurred with peack incidence in fourth week of CSI(median day of interruption was day 23,range 8-38). The median WBC count was 1900(range 100-2140).The mean of interruption period was 7±8 days (one patient died from neutropenic fever then he didn’t finish his treatment. In 19 patients who had treatment interruption, 13 of them were under 12 years while 5 patients were greater than 12 years. With Mann-Whitney U test the median age of patients with treatment interruption was lower; 10.2 years and 16.2 years respectively(P=.059).).In 24 patients with dose/fraction =<1.6 Gy 12 patients (50%) had treatment interruption but in 21 patients with dose/fraction >1.6 Gy 7 (33%) had treatment interruption(P=.2) but interruption period was longer in patients with dose/ fraction >1.6 Gy. From 12 patients who had dose/fraction <=1.6Gy, 7 patients had interruption period less than 5 days while in group with dose/fraction >1.6 Gy all patients had treatment interruption period more than 5 days(P=.016,CI 95% for interruption period difference =1.2-4.7). . In summary, in our study 42% of patients undergoing CSI had treatment interruption. The risk was higher in children and in patients who received higher spinal dose fraction the treatment interruption was longer, but the overall treatment-related morbidity was low. In a population at risk of hematological toxicity where further studies of HGFs should be targeted.