@article { author = {Tanomand, Asghar and Afshin khaki, Amir and Mehrad, Hossin and Montazam, Hassan and Kafshnochi, Maghasood}, title = {Study of Gentamicin Effect on Staphylococcus Aureus in the Presence of Electromagnetic Field}, journal = {Iranian Journal of Medical Physics}, volume = {5}, number = {Issue 1,2}, pages = {1-8}, year = {2008}, publisher = {Mashhad University of Medical Sciences}, issn = {2345-3672}, eissn = {2345-3672}, doi = {10.22038/ijmp.2008.7521}, abstract = {Introduction:  Nowadays  the  medical,  therapeutic  and  pharmacological  application  of  magnetic  fields  (MF)  and  its  biological  effect  has  raised  question  about  the  safety  of  MF.  This  study  aimed  at  scrutinizing the effect of static MF on the resistance of S. aureus to antibiotic.  Materials and Methods: This prospective, case–control study was conducted to evaluate the effect of  low intensity (0.5 mT) static MF on the growth rate and the antibiotic resistance of S. aureus sensitive to  gentamicin. The studied bacterium is a nosocomial type and the growth rate was calculated by colony  counting to understand the effect of MF on it. In the next stage, the rate of bacterial growth along with  the different concentration of antibiotic was studied and the Minimum Inhibitory Concentration (MIC)  and Minimum Bactericidal Concentration (MBC) were determined.  Results: It is concluded that the 0.5 mT MF didn't affect the growth rate of S. aureus after 24 and 48 hours.  The 0.5 mT MF induced a 50 percent decline of MIC and MBC of gentamicin after a 48 hour incubation (MIC  = 4 6g /cc, MBC = 8 6g /cc in the case group vs. MIC = 8 6g /cc, MBC = 16 6g /cc in the control group).  Conclusion: Low–intensity MF didn't affect the bacterial growth rate. However, the bactericidal effects  of gentamicin were greater in the presence of MF. It is possible to apply the static MF for enhancing the  effect of antibiotic on S. aureus.}, keywords = {Staphylococcus aureus,MIC,MBC,Gentamicin,Electromagnetic Field,Drug resistance}, url = {https://ijmp.mums.ac.ir/article_7521.html}, eprint = {https://ijmp.mums.ac.ir/article_7521_550e9a68c7f770dea0fc4d38127495da.pdf} } @article { author = {Raisali, Gholamreza and Sadeghi, Mahdi and Ataeinia, Vahideh and Shahvar, Arjang and Ghonchehnazi, Maryam Ghasemi}, title = {Determination of Dosimetric Parameters of the Second Model of Pd-103 Seed Manufactured at Agricultural, Medical and Industrial Research School}, journal = {Iranian Journal of Medical Physics}, volume = {5}, number = {Issue 1,2}, pages = {9-22}, year = {2008}, publisher = {Mashhad University of Medical Sciences}, issn = {2345-3672}, eissn = {2345-3672}, doi = {10.22038/ijmp.2008.7526}, abstract = {Introduction: The use of low energy isotopes such as  103 Pd in brachytherapy for the treatment of cancers  such as prostate, eye, head, neck, breast and cervix is increasing. In this regard, different models of Pd- 103  seeds  have  been  designed  and  manufactured  at  the  Agricultural,  Medical  and  Industrial  Research  School (AMIRS) of Atomic Energy Organization of Iran. In this research, the dosimetric parameters of  the second model of Pd-103 seed manufactured at AMIRS have been calculated and measured.   Materials and Methods: The dosimetric parameters of the second Pd-103 seed manufactured at AMIRS  were determined according to TG-43U1 protocol using Monte Carlo calculations (MCNP4C computer  code)  and  measurements  performed  using  TLD-GR200A  dosimeters  in  a  Perspex  phantom.  The  parameters  include  dose  rate  constant,  geometry  function,  radial  dose  function,  anisotropy  function,  anisotropy factor and anisotropy constant.  Results:  It  was  found  that  by  using  MCNP4C  code  the  calculated  dose  rate  constant  in  water  and  Perspex  was  0.706±0.001   and  0.501±0.001  cGyh -1 U -1 , respectively.  Using  the  calculated  geometry  function,  the  radial  dose  function  and  the  anisotropy  function  were  determined  by  experimental  and  theoretical methods in water and Perspex phantom. Also, the calculated value of anisotropy constant in  water was equal to 0.88.  Discussion and Conclusion: A discrepancy of less than 10% between the calculated and the measured  values indicates a reasonable agreement between the simulation and the measurement method. Also, the  dosimetric parameters of this seed have been compared to the dosimetric parameters of the first Pd-103  seed  manufactured  at  AMIRS  and  some  other  seeds.  The  obtained  results  indicate  that  the  seeds  manufactured at AMIRS have acceptable dosimetric parameters suitable for brachytherapy applications.   }, keywords = {Brachytherapy,Pd-103 Seed,TG-43U1 Protocol,Monte Carlo Simulation,Thermoluminescent Dosimetry}, url = {https://ijmp.mums.ac.ir/article_7526.html}, eprint = {https://ijmp.mums.ac.ir/article_7526_1a8c71d395704c29e7ea3f46bb927b5a.pdf} } @article { author = {Shirmohammad, Maryam and Ay, Mohammad Reza and Sarkar, Saeed and Rahmim, Arman}, title = {Comparing 511 keV Attenuation Maps Obtained from Different Energy Mapping Methods for CT Based Attenuation Correction of PET Data}, journal = {Iranian Journal of Medical Physics}, volume = {5}, number = {Issue 1,2}, pages = {23-34}, year = {2008}, publisher = {Mashhad University of Medical Sciences}, issn = {2345-3672}, eissn = {2345-3672}, doi = {10.22038/ijmp.2008.7527}, abstract = {Introduction:  The  advent  of  dual-modality  PET/CT  scanners  has  revolutionized  clinical  oncology  by  improving lesion localization and facilitating treatment planning for radiotherapy. In addition, the use of  CT images for CT-based attenuation correction (CTAC) decreases the overall scanning time and creates  a noise-free  attenuation  map  (6map).  CTAC  methods  include  scaling,  segmentation,  hybrid  scaling/segmentation, bilinear and dual energy methods. All CTAC methods require the transformation  of CT Hounsfield units (HU) to linear attenuation coefficients (LAC) at 511 keV. The aim of this study is  to compare the results of implementing different methods of energy mapping in PET/CT scanners.   Materials and Methods: This study was conducted in 2 phases, the first phase in a phantom and the  second  one  on  patient  data.  To  perform  the  first  phase,  a  cylindrical  phantom  with  different  concentrations of K2HPO4 inserts was CT scanned and energy mapping methods were implemented on  it. For performing the second phase, different energy  mapping  methods  were implemented on several  clinical studies and compared to the transmission (TX) image derived using Ga-68 radionuclide source  acquired on the GE Discovery LS PET/CT scanner.   Results: An ROI analysis was performed on different positions of the resultant 6maps and the average  6value of each ROI was compared to the reference value. The results of the 6maps obtained for 511 keV  compared to the theoretical  values showed that in the phantom for low  concentrations  of K 2 HPO 4 all  these  methods  produce  511  keV  attenuation  maps  with  small  relative  difference  compared  to  gold  standard. The relative difference for scaling, segmentation, hybrid, bilinear and dual energy methods was  4.92,  3.21,  4.43,  2.24  and  2.29%,  respectively.  Although  for  high  concentration  of  K 2 HPO 4 the  three  methods;   hybrid   scaling/segmentation, bilinear and dual energy produced the lowest relative difference of  10.91, 10.88 and 5%, respectively. For patients it was found that for soft tissues all the mentioned energy  mapping  methods  produce  acceptable  attenuation  map  at  511  keV.  The  relative  difference  of  scaling,  segmentation,  hybrid,  and  bilinear  methods  compared  to  TX  method  was  6.95,  4.51,  7,  and  6.45%  respectively.  For bony tissues, the quantitative analysis  showed that  scaling and segmentation  method  produce high relative difference of 26 and 23.2%, respectively and the relative difference of hybrid and  bilinear in comparison to TX method was 10.7 and 20%, respectively.   Discussion and Conclusion:  Based on the result obtained from these two studies it can be concluded  that for soft tissues all energy mapping methods yield acceptable results while for bony tissues all the  mentioned methods except the scaling and segmentation yield acceptable results. }, keywords = {PET/CT,XCOM,TX}, url = {https://ijmp.mums.ac.ir/article_7527.html}, eprint = {https://ijmp.mums.ac.ir/article_7527_7eec0987584a57fe9199b2823ce73a43.pdf} } @article { author = {ahmasebi, Mohammad Javad T and Behrooz, Mohammad Ali and Arvandi, Shole and khezerloo, Davood and karbalai, Mojtaba}, title = {Investigation of the Field Size Effect on Wedge Field Isodose Curves Angle for Two Energies; 6 & 18 MV, produced by VARIAN 2100C Linac}, journal = {Iranian Journal of Medical Physics}, volume = {5}, number = {Issue 1,2}, pages = {35-43}, year = {2008}, publisher = {Mashhad University of Medical Sciences}, issn = {2345-3672}, eissn = {2345-3672}, doi = {10.22038/ijmp.2008.7528}, abstract = {Introduction: Nowadays,  considerable developments  in  the field  of  radiotherapy have  been  achieved.  They  include  the  advances  made  in  the  equipments  and  treatment  planning  techniques  which  require  highly complex calculations. Such achievements have made it possible to treat cancer patients not only  with  higher  radiation  dose  but  also  with  higher  precision  and  consequently  increasing  the  chance  of  curing the cancer. However, the conventional techniques requiring physical wedge are still being used  but with a lesser frequency. One of the wedge parameters needed to be measured is the wedge angle. It is  the angle that the horizontal line creates with the tilted isodose curve at a specific depth and for a certain  field size.   In this study, the variation of wedge angle for different field sizes was evaluated using dosimetric and  mathematical method.  Material and Methods: For the wedge fields with a dimension of 6×6 to 20×20 cm 2 , the wedge angle  for  two  photon  energies  of  6  and  18  MV  was  measured  by  the  dosimetric  method.  For  these  measurements, the conventional wedges having the nominal wedge angle of 15, 30, 45 & 60 were used.  The theoretical method suggested by Saw et al. is also used to indirectly calculate the slope of isodose  curve  by  the  dose  profile  and  percent  depth  dose  data.  The  dose  profile,  percentage  depth  dose  and  isodose curves were drawn for all the field sizes and the tilt of isodose curve at 10 cm depth, according to  international definition, is considered as the wedge angle. The data were obtained using the theoretical  equation of wedge angle and it was compared to the dosimetric data.  Results: The result obtained in this work shows that the wedge angle increases with the field size. For a  6×6 cm 2 field size, the calculated wedge angle has the highest difference in comparison to the nominal  wedge angle. The difference is equal to 14.7 degree for a 45° wedge and a 6 MV photon. The highest  difference for a 45° wedge angle, a field size of 10×10 cm 2 and a 6 MV photon is 9.2 degree. Comparing  the calculated and measured wedge angles shows a maximum difference of 4 degree for 6 and 18 MV  photon beams.  Discussion  and  Conclusion:  The  wedge  angle  varies  with  field  size.  In  order  to  get  a  better  dose  distribution in the conventional radiotherapy, it is necessary to use the appropriate wedge angle which  generates the desired slope for the isodose line and for the specific field size.  }, keywords = {Profile Curve,PDD Curve,Isodose Curve,Wedge Angle}, url = {https://ijmp.mums.ac.ir/article_7528.html}, eprint = {https://ijmp.mums.ac.ir/article_7528_2cab9efd47d08c430b6cfc8bc9e736ca.pdf} } @article { author = {Kaviani Moghadam, Mehri and Pourmir Firoozabadi, , Seyed Mohammad Jafar and Lak, M. and Janahmadi, M.}, title = {The Measurement of Low Frequency Magnetic Field of Two Kinds of GSM900 Mobile Phone}, journal = {Iranian Journal of Medical Physics}, volume = {5}, number = {Issue 1,2}, pages = {43-53}, year = {2008}, publisher = {Mashhad University of Medical Sciences}, issn = {2345-3672}, eissn = {2345-3672}, doi = {10.22038/ijmp.2008.7529}, abstract = {Introduction:  The  use  of  mobile  communication  systems  has  dramatically  increased  over  the  past  decade. Although many studies have been performed to determine the effect of radio frequency (RF) but  less attention has been paid to the possible biological impact of exposure to extremely low frequency  (ELF) components.   The objective of this study is two folds. One is to design the equipments needed for the measurement of  the ELF fields of two types of GSM900 mobile phone. Secondly, use a protocol suitable for an accurate  assessment of the ELF fields.  Materials  and Methods:  First  a  home-made  search  coil  was  provided  and  calibrated precisely  under  several experiments. Using Fast Fourier Transform, the power spectrum density of the induced voltage in  the search coil was analyzed and the amplitudes of 217 Hz and its harmonics were extracted and then the  distribution of magnetic field in the back side of mobile phones was determined.  Results: The values of B-field on the back side of the two kinds of GSM mobile phone were different.  They  were  between  50  to  160  µT in  Nokia  3310  and  14  to  30  µT in  Nokia  8310.  Considering  the  difference between the amplitudes of frequency components at 217 Hz and its harmonics in the two kinds  of mobile phone, a range of magnetic flux density at different times in a five day period was measured.  Discussion and Conclusion: These findings emphasize the need for considering the distribution of low  frequency magnetic field from mobile phone when biological effects of magnetic fields are studied. To  determine  the  intensity  windowing  effect,  one  must  consider  the  physical  characteristics  of  the  fundamental  frequency  component  wave  (217  Hz)  and  its  harmonics  produced  by  the  mobile  phone  similar to the one generated under a real situation. }, keywords = {217 Hz,Magnetic Fields,Mobile Phones,GSM900}, url = {https://ijmp.mums.ac.ir/article_7529.html}, eprint = {https://ijmp.mums.ac.ir/article_7529_90d24046085275fb11ac4b7dd41e4a44.pdf} } @article { author = {Lakdashti, Abolfazl and Moin, Mohammad Shahram and Badie, Kambiz}, title = {Content Based Radiographic Images Indexing and Retrieval Using Pattern Orientation Histogram}, journal = {Iranian Journal of Medical Physics}, volume = {5}, number = {Issue 1,2}, pages = {55-66}, year = {2008}, publisher = {Mashhad University of Medical Sciences}, issn = {2345-3672}, eissn = {2345-3672}, doi = {10.22038/ijmp.2008.7530}, abstract = {Introduction: Content Based Image Retrieval (CBIR) is a method of image searching and retrieval in a  database. In medical applications, CBIR is a tool used by physicians to compare the previous and current  medical images associated with patients pathological conditions. As the volume of pictorial information  stored in medical image databases is in progress, efficient image indexing and retrieval is increasingly  becoming a necessity.  Materials and Methods: This paper presents a new content based radiographic image retrieval approach  based on histogram of pattern orientations, namely pattern orientation histogram (POH). POH represents  the  spatial  distribution  of  five  different  pattern  orientations:  vertical,  horizontal,  diagonal  down/left,  diagonal down/right and non-orientation. In this method, a given image is first divided into image-blocks  and  the  frequency  of  each  type  of  pattern  is  determined  in  each  image-block.  Then,  local  pattern  histograms for each of these image-blocks are computed.   Results: The method was compared to two well known texture-based image retrieval methods: Tamura  and  Edge  Histogram  Descriptors  (EHD)  in  MPEG-7  standard.  Experimental  results  based  on  10000  IRMA  radiography  image  dataset,  demonstrate  that  POH  provides  better  precision  and  recall  rates  compared to Tamura and EHD. For some images, the recall and precision rates obtained by POH are,  respectively, 48% and 18% better than the best of the two above mentioned methods.    Discussion and Conclusion: Since we exploit the absolute location of the pattern in the image as well as  its global composition, the proposed matching method can retrieve semantically similar medical images. }, keywords = {Radiographic Image Retrieval,Texture Feature,Pattern Orientation Histogram}, url = {https://ijmp.mums.ac.ir/article_7530.html}, eprint = {https://ijmp.mums.ac.ir/article_7530_9e7705aa8b772d3af05f12720cd326ae.pdf} } @article { author = {Mowlavi, Ali Asghar}, title = {Monte Carlo Dose Calculation of 90 Sr/ 90 Y Source in Water Phantom}, journal = {Iranian Journal of Medical Physics}, volume = {5}, number = {Issue 1,2}, pages = {67-72}, year = {2008}, publisher = {Mashhad University of Medical Sciences}, issn = {2345-3672}, eissn = {2345-3672}, doi = {10.22038/ijmp.2008.7531}, abstract = {Introduction:  90 Sr/ 90 Y source  has  been  used  for  the  intravascular  brachytherapy  to  prevent  coronary  restenosis in the patients who have undergone angioplasty. The aim of this research is to determine the  dose distribution of  90 Sr/ 90 Y source in a water phantom.  Materials  and  Methods:  In  the  present  work,  MCNP  code  has  been  applied  to  calculate  the  dose  distribution around a 3 cm length of  90 Sr/ 90 Y source in a 30×30×30 cm 3 water phantom. Also, the exact  geometry  of  the  source  has  been  used  in  this  simulation.  Tally  *F8:e  which  is  suitable  for  beta  ray  dosimetry has been evaluated with less than %5 relative error in a sphere having 0.2 mm radius.  Results:  The  isodose  curve  for  10,  20,  40,  and  90%  depth  dose  (PDD)  were  derived  based  on  the  calculated dose curves along the parallel and perpendicular axis to the source.  Discussion  and  Conclusion:  The  results  obtained  in  this  work  are  in  a  good  agreement  with  the  experimental  result  published  by  Buckley  et  al.  and  the  International  Atomic  Energy  Agency  (IAEA)  report  in  a  water  phantom.    Therefore,  the  result  of  this  research  can  be  used  in  the  intravascular  brachytherapy. }, keywords = {90 Sr/ 90 Y Source,Intravascular Brachytherapy,MCNP4C Code,Water Phantom,Isodose Curves}, url = {https://ijmp.mums.ac.ir/article_7531.html}, eprint = {https://ijmp.mums.ac.ir/article_7531_7964e672cff48cdf929509baa81665f5.pdf} }