Pradip Deb

Review on Production of 89Zr in a Medical Cyclotron for PET Radiopharmaceuticals

This article is intended to provide an overview of the production and application of 89Zr for the professional development of nuclear medicine technologists. It outlines the cyclotron targeting, separation and labeling options, and techniques for the preparation of the radionuclide 89Zr (half-life, 78.4 h [3.3 d]) used in PET. Unlike the commonly used 18F-FDG, with a 109.7-min half-life, the longer half-life of 89Zr makes it possible to use high-resolution PET/CT to localize and image tumors with monoclonal antibody radiopharmaceuticals and thus potentially expand the use of PET. Methods: This paper briefly reviews the cyclotron technique of 89Zr production and outlines the range and preparation techniques available for making 89Y targets as a starting material. It then discusses how cyclotron-produced 89Zr can be separated, purified, and labeled to monoclonal antibodies for PET/CT of specific tumors. Results: We argue that knowledge and understanding of this long-lived PET radionuclide should be part of the professional development of nuclear medicine technologists because it will lead to better patient outcomes and potentially increase the pool of collaborators in this field of research.

Bismuth oxide-coated fabrics for X-ray shielding

Lead aprons are widely used in medical imaging to protect radiographers and patients from harmful radiation. However, lead is not a desirable material for use in wearable radiation protection due to its heavy weight, inflexibility, poor durability, and toxicity. In this study, we explored the suitability of bismuth oxide (Bi2O3) coating for textiles as an alternative to lead. The intention was to demonstrate the concept and technology that will achieve a lead-equivalent lightweight X-ray protective textile material with improved wearability. The primary objective was to evaluate the X-ray shielding efficiency of two textile materials coated with Bi2O3. To do so, X-ray exposures were made at the system setting of 80 kVp, 12 mAs, and 80 SID (the distance from the X-ray beam source to the specimen). It is evident from this study that Bi2O3 in a suitable resin matrix can be coated on fabrics and is an effective method to produce flexible, wearable, and lead-free aprons. Coated polyester fabrics with over 50% Bi2O3 showed enhanced shielding ability for transmitted X-rays. This research has shown that microparticle size Bi2O3 can be effective for X-ray attenuation.

Radiobiological Model Comparison of 3D Conformal Radiotherapy and IMRT Plans for the Treatment of Prostate Cancer

The main aim of radiotherapy is to deliver a dose of radiation that is high enough to destroy the tumour cells while at the same time minimising the damage to normal healthy tissues. Clinically, this has been achieved by assigning a prescription dose to the tumour volume and a set of dose constraints on critical structures. Once an optimal treatment plan has been achieved the dosimetry is assessed using the physical parameters of dose and volume. There has been an interest in using radiobiological parameters to evaluate and predict the outcome of a treatment plan in terms of both a tumour control probability (TCP) and a normal tissue complication probability (NTCP). In this study, simple radiobiological models that are available in a commercial treatment planning system were used to compare three dimensional conformal radiotherapy treatments (3D-CRT) and intensity modulated radiotherapy (IMRT) treatments of the prostate. Initially both 3D-CRT and IMRT were planned for 2 Gy/fraction to a total dose of 60 Gy to the prostate. The sensitivity of the TCP and the NTCP to both conventional dose escalation and hypo-fractionation was investigated. The biological responses were calculated using the Källman S-model. The complication free tumour control probability (P+) is generated from the combined NTCP and TCP response values. It has been suggested that the α/β ratio for prostate carcinoma cells may be lower than for most other tumour cell types. The effect of this on the modelled biological response for the different fractionation schedules was also investigated.

A Review of Radiation Protection Solutions for the Staff in the Cardiac Catheterisation Laboratory.

Adverse health effects of radiation exposure to staff in cardiac catheterisation laboratories have been well documented in the literature. Examples include increased risk of cataracts as well as possible malignancies. These risks can be partly mitigated by reducing scatter radiation exposure to staff during diagnostic and interventional cardiac procedures. There are currently commercially available radiation protection tools, including radioprotective caps, gloves, eyewear, thyroid collars, aprons, mounted shields, table skirts and patient drapes to protect staff from excessive radiation exposure. Furthermore, real-time dose feedback could lead to procedural changes that reduce operator dose. The objective of this review is to examine the efficacy of these tools and provide practical recommendations to reduce occupational radiation exposure with the aim of minimising long-term adverse health outcomes.

An assessment of nursing staffs' knowledge of radiation protection and practice.

Although the exposure to nursing staff is generally lower than the allowable radiation worker dose limits, awareness and overcoming fears of radiation exposure is essential in order to perform routine activities in certain departments. Furthermore, the nursing staff, whether they are defined as radiation workers or not, must be able to respond to any radiological emergencies and provide care to any patient affected by radiation. This study aims to gauge the awareness of radiation safety among the nursing staff at a major hospital in different departments and recommend if further radiation safety training is required. A prospective multiple choice questionnaire was distributed to 200 nurses in 9 different departments. The questionnaire tested knowledge that would be taught at a basic radiation safety course. 147 nurses (74%) completed the survey with the average score of 40%. Furthermore, 85% of nurses surveyed felt there was a need for radiation safety training in their respective departments to assist with day to day work in the department. An increase in radiation safety materials that are specific to each department is recommended to assist with daily work involving radiation. Moreover, nursing staff that interact with radiation on a regular basis should undertake radiation safety courses before beginning employment and regular refresher courses should be made available thereafter.

An evaluation of the shielding effectiveness of lead aprons used in clinics for protection against ionising radiation from novel radioisotopes

The purpose of this study is to evaluate the effectiveness of personal radiation shields currently worn in hospital and other diagnostic environments. This study was performed with four different radioisotopes; (18)F, (99m)Tc, (124)I and (131)I. (18)F results showed a decrease in dose with 0.5-mm Pb shielding but the reduction provided does not warrant its use clinically. (124)I testing demonstrated that dose enhancement can occur in greater shield thicknesses. PET isotope (124)I can be adequately shielded using 0.25-mm Pb equivalent aprons but any higher thickness increase the wearers dose. As a result more shielding does not always equal more protection. The (131)I test showed that no dose reduction occurred, even when tested with up to 1.25-mm Pb equivalent shielding. Novel radioisotopes being used in the laboratory and clinic should be individually tested as each requires specific shielding testing.

Sensitivity of Electronic Portal Imaging Device (EPID) Based Transit Dosimetry to Detect Inter-fraction Patient Variations

The sensitivity of EPID-based transit dosimetry to detect patient variations between treatment fractions is examined using gamma analysis and a structural similarity (SSIM) index. EPID images were acquired for 3-dimensional conformal (3DCRT) and dynamic intensity modulated (dIMRT) radiation therapy fields in multiple fractions. Transit images were converted to doses, transit dose in the first fraction considered the reference dose. Variations in patient position or weight were then introduced in the subsequent fractions. Positional variations were examined using a lung and a head and neck phantoms. Anatomical variations were examined using a slab phantom in three scenarios, with solid water simulating tissue, medium-density fiberboard simulating fat, and Styrofoam simulating lung. The dose difference between the first and subsequent fractions was computed using various gamma criteria and the SSIM index. Using a criterion of 3%/3 mm, EPID can detect positional variations ≥ 4 mm, and tissue and fat variations ≥ 1 cm, whereas it cannot detect lung variations up to 4 cm. The sensitivity for 3DCRT is higher than for dIMRT. EPID can detect the most variations when using 3%/1 mm. With the SSIM index, EPID can detect a 2 mm positional variation and 1 cm of lung variation. The factor that optimized the sensitivity of EPID was a reduction in the distance to the agreement criteria. Our study introduces the SSIM as an alternative analysis with high sensitivity for minimal variations.

Radiation dose optimization in interventional cardiology: A teaching hospital experience

Radiological interventions play an increasingly relevant role in cardiology. Due to the inherent risks of ionizing radiation, proper care must be taken with monitoring and optimizing the dose delivered in angiograms to pose as low risk as possible to staff and patients. Dose optimization is particularly pertinent in teaching hospitals, where longer procedure times are at times necessary to accommodate the teaching needs of junior staff, and thus impart a more significant radiation dose. This study aims to analyze the effects of different protocol settings in routine coronary angiograms, from the perspective of a large tertiary center implementing a rapid dose reduction program. Routine coronary angiograms were chosen to compare baseline levels of radiation, and the dose imparted before and after dose optimization techniques was measured. Such methods included lowering dose per pulse, fluoroscopic pulse rates, and cine acquisition frame rates. The results showed up to 63% reduction in radiation dose without adverse impact on clinical or teaching outcomes. A 10 fps/low and 5 pps/low setting was found to achieve maximum dose optimization, with the caveat that settings require incremental changes to accommodate for patient complexities.

The influence of acquisition mode on the dosimetric performance of an amorphous silicon electronic portal imaging device

Aims: This study investigates the impact of cine acquisition mode on the dosimetric characteristics of a Varian aS500 amorphous silicon electronic portal imaging device (a-Si EPID). Materials and Methods: The performance of an a-Si EPID operated in cine mode was assessed and compared to its performance when operated in an integrated mode and dose measurements using an ionization chamber. This study was conducted at different photon energies and the EPID performance was assessed as function of the delivered dose, dose rate, multileaf collimator speed, field size, phantom thickness, and intensity-modulated radiation therapy fields. Results: The worst nonlinearity was observed at low monitor unit (MU) settings < 100 MU with the highest dose per frame. The nonlinearity of response at a low MU setting was attributed due to the loss of four cine images during each delivery. The EPID response with changing dose rate for 10 MU delivered had similar results to its performance in an integrated mode and ionization chamber. Despite the nonlinearity of response with low MU delivered, EPID performance operated in cine and integrated acquisition modes had comparable responses within 2%. Conclusions: For EPID dosimetry application using cine mode, this study recommends the calibration of the EPID images to be undertaken at a large MU. There were no additional corrections that were required when the EPID operated in cine acquisition mode as compared to calibration in integrated mode.

SU-F-T-263: Dosimetric Characteristics of the Cine Acquisition Mode of An A-Si EPID

PURPOSE To investigate the dosimetric characteristics of Varian a-Si-500 electronic portal imaging device (EPID) operated in cine mode particularly considering linearity with delivered dose, dose rate, field size, phantom thickness, MLC speed and common IMRT fields. METHODS The EPID that attached to a Varian Clinac 21iX linear accelerator, was irradiated with 6 and 18 MV using 600 MU/min. Image acquisition is controlled by the IAS3 software, Trigger delay was 6 ms, BeamOnDelay and FrameStartDelay were zero. Different frame rates were utilized. Cine mode response was calculated using MATLAB as summation of mean pixel values in a region of interest of the acquired images. The performance of cine mode was compared to integrated mode and dose measurements in water using CC13 ionization chamber. RESULTS Figure1 illustrates that cine mode has nonlinear response for small MU, when delivering 10 MU was about 0.5 and 0.64 for 6 and 18 MV respectively. This is because the missing acquired images that were calculated around four images missing in each delivery. With the increase MU the response became linear and comparable with integrated mode and ionization chamber within 2%. Figure 2 shows that cine mode has comparable response with integrated mode and ionization chamber within 2% with changing dose rate for 10 MU delivered. This indicates that the dose rate change has no effect on nonlinearity of cine mode response. Except nonlinearity, cine mode is well matched to integrated mode response within 2% for field size, phantom thickness, MLC speed dependences. CONCLUSION Cine mode has similar dosimetric characteristics to integrated mode with open and IMRT fields, and the main limitation with cine mode is missing images. Therefore, the calibration of EPID images with this mode should be run with large MU, and when IMRT verification field has low MU, the correction for missing images are required.