Accurate quantitation of activity provides the basis for internal dosimetry of targeted radionuclide therapies. This study investigated quantitative imaging capabilities at sites with a variety of experience and equipment and assessed levels of errors in activity quantitation in Single-Photon Emission Computed Tomography (SPECT) and planar imaging. Participants from 9 countries took part in a comparison in which planar, SPECT and SPECT with X ray computed tomography (SPECT-CT) imaging were used to quantify activities of four epoxy-filled cylinders containing 133Ba, which was chosen as a surrogate for 131I. The sources, with nominal volumes of 2, 4, 6 and 23 mL, were calibrated for 133Ba activity by the National Institute of Standards and Technology, but the activity was initially unknown to the participants. Imaging was performed in a cylindrical phantom filled with water. Two trials were carried out in which the participants first estimated the activities using their local standard protocols, and then repeated the measurements using a standardized acquisition and analysis protocol. Finally, processing of the imaging data from the second trial was repeated by a single centre using a fixed protocol. In the first trial, the activities were underestimated by about 15% with planar imaging. SPECT with Chang’s first order attenuation correction (Chang-AC) and SPECT-CT overestimated the activity by about 10%. The second trial showed moderate improvements in accuracy and variability. Planar imaging was subject to methodological errors, e.g., in the use of a transmission scan for attenuation correction. The use of Chang-AC was subject to variability from the definition of phantom contours. The project demonstrated the need for training and standardized protocols to achieve good levels of quantitative accuracy and precision in a multi-centre setting. Absolute quantification of simple objects with no background was possible with the strictest protocol to about 6% with planar imaging and SPECT (with Chang-AC) and within 2% for SPECT-CT.

not availableBangladesh J. Nuclear Med. 18(1): 73-84, January 2015

not availableBangladesh J. Nuclear Med. 18(1): 85-88, January 2015

Positron Emission Tomography-Computed Tomography (popularly known as PET-CT or PET/CT) is a nuclear medicine imaging technique. PET is called the emission technique where gamma rays created during the emission of positron are detected by the scanner. Positron emitting radionuclides tagged to specific tracers are injected intravenously into the patient. These are then taken up by various organs or tissues either physiologically or pathologically and gives an image map that is essentially functional.On the other hand, CT is called the transmission technique where X-ray passes through the body and at the same time from opposite direction, detection of attenuation of the body is carried out by the detectors and forms an anatomical image.PET and CT are fused on a single gantry into a hybrid technology for the ultimate combination of functional and anatomical image in single frame.Nuclear Medicine in Bangladeshis entering a new era with the inclusion of PET/CT. PET-CT has revolutionized cancer diagnosis and therapy. It is a stronger diagnostic tool for the early detection of cancer, to determine the staging of cancer, therapy planning and follow-up. One very important application of PET-CT is the treatment planning system (TPS) i.e. how much dose is required at the site of tumor for the treatment of a cancer patient before a patient undergoes a radiotherapy process. It can precisely determine the site where radiation needs to be focused.Since 2015 the National Institute of Nuclear Medicine and Allied Sciences started to perform PET-CT examination for the first time in public sector. So far PET-CT diagnostic facilities were only available in the private sector.The good news is that another PET-CT will be commissionedin 3 months in the public sector at nuclear medicine institute, Dhaka Medical campus, that will enhance the patients servicing capacity. We have to think about the optimal usage of this highly sophisticated and expensive technology. As mentioned above, PET-CT particularly has a very important role in oncology. It helps to differentiate malignant from benign lesions in many cases and is invaluable for image guided radiotherapy. In addition, it can give valuable information about the metabolism of the myocardium and is also useful in diagnosis of many non-malignant diseases.As before, this year too, a number of interesting papers on a very wide range of topics have been published. These will expand the horizon of the reader's knowledge. Therefore colleagues, good luck and keep it up! 7

A Hot-Lab is the major source of radiation exposure by medical technicians in a nuclear medicine set up. A table top bench shield is used to reduce this exposure which consists of a lead base and a lead wall in the bottom part while a viewing window is provided in the top part through the use of thick glass or leaded glass. In our laboratory, a home-made shield was used earlier which incorporated a 254mm ordinary glass window in the top and a thick lead wall at the bottom part. Recently a commercial bench shield was procured that uses a lighter lead glass window for better viewing. This lead glass gives an equivalent lead thickness of 2.2 mm. The present work was taken up to study the changes in the radiation exposure to nuclear medicine technicians due to this change in the bench shield. The effective doses received by two technicians were 0.937 mSv and 1.098 mSv respectively when they worked for two months using the old table top bench shield. This dose came down substantially to 0.292 mSv and 0.187 mSv respectively, when they used the new table top bench shield for the same period of time. Side by side, the radiation reaching the outer surfaces of the glass shield and the lead wall were measured due to a radiation source placed at 0mm, 10mm and 20mm from the respective inner surfaces. For the lead shield the dose rates were not much different between the two models, but for the glass window, the commercial one gave much reduced dose rate. Although the dosage was higher in the indigenously made device, the duty schedules of the technicians were rotated so that none received dosage greater than safe limits over a full year. DOI: http://dx.doi.org/10.3329/bjmp.v5i1.14669 Bangladesh Journal of Medical Physics Vol.5 No.1 2012 37-40