Do Current Radiation Safety Guidelines allow the Safe Release of a Thyroid Cancer Patient after High-dose Radioiodine Therapy? An Indian Perspective.

AIM: Radionuclide therapy may produce a significant radiation exposure risk to the patient's caregivers. The study aims to assess the radiation exposure rate to caregivers after the patient's discharge from the isolation ward. MATERIALS AND METHODS: Patients of the well-Differentiated thyroid cancer (DTC)were given high-dose radioiodine therapy as an inpatient. Their radiation exposure was measured daily, and they were discharged once the exposure rate falls as per standard guidelines. Detail counseling of the patient and caregiver about radiation safety was done before admission and at the time of discharge. Caregivers were given thermoluminescence dosimeter (TLD) to wear as a locket for 7 days. Radiation exposure received by the caregiver was measure after that. RESULTS: A total of 22 patients (8 male and 14 female) of DTC were recruited in the study. The mean age was 39.0 ± 14.5 years. Patients were treated with 3.79 ± 1.07 (102.4 ± 28.9 mCi) (1.85-5.55 (50-150 mCi) GBq of radioiodine. They were discharged from the isolation ward at a radiation level of 0.028 ± 0.015 mSv/h (3.193 ± 1.71 mR). The mean effective dose received by the caregiver was 14.60 ± 3.43 mSv (1460 ± 343 mR) (9.73-24.25 (973-2765 mR) mSv. CONCLUSION: Our study denotes that the caregivers of DTC patients receive a significant radiation dose. It was well above the caregiver's annual dose-limit constraints regarding the rationales well as international guidelines of 5 mSv/yr. These could be related to the long travel in public transport and housing conditions. There is a need for patient-specific discharge criteria rather than following standard guidelines to minimize radiation exposure to caregivers.

Assessment of Radiation Dose Delivered and Volume Measurement By Low- and High-Dose Diagnostic Computed Tomography: Anthropomorphic Liver Phantom Study.

AIM: Liver volume measurement is a mandatory test before measure liver surgeries and transplantation. We aimed a study on the difference in volume measurement and radiation dose to an anthropomorphic liver phantom using high-dose and low-dose diagnostic computed tomography (CT). MATERIALS AND METHODS: Several measurements of the manual total volume measurement done on an anthropomorphic liver phantom mounted with thermoluminescent dosimeter. We exposed the phantom with diagnostic CT, low-dose CT, and a low-dose CT with copper filter. RESULTS: Phantom underwent ten scanning for each exposure. There was no significant difference in the total volume measurement in comparison to the phantom volume. The volume of phantom measured by low-dose CT, low-dose CT with copper phantom, and high-dose CT were 1869 ± 18 cm3, 1852 ± 24 cm3, and 1908 ± 12 cm3, (P = 0.3), respectively. However, the radiation dose delivered was significantly different (1.54 mGy, 0.77 mGy, and 5.84 mGy [P = 0.001], respectively). CONCLUSION: Total liver volume measurement provides essential clinical information in several clinical conditions. We recommended that the volume measured by a low-dose CT has an excellent correlation with the diagnostic quality CT and should be a routine in the routine clinical practice. CT volumetry achieves the same result while using very less radiation exposure. It may also be used with functional imaging to give complete information.

Assessment of Radiation Exposure and Radioactivity from the Liquid Discharge in a Nuclear Medicine Facility.

AIM: Radionuclide imaging and therapies produce radioactive liquid waste that may lead to significant radiation exposure to the general public. The study aims to assess the radiation exposure rate to public sewerage from a modified delay tank facility. We shall also evaluate the exposure rates and overall radioactivity at several points. MATERIALS AND METHODS: After having appropriate permission from the AERB, we measured the radiation exposure from the radionuclide therapy ward. Ward has three isolation beds and a single delay and decay tank of a capacity of 7500 liters. Effluents from the delay tank are processed at the filtration plant of the institute and subsequently released in the public sewerage. We obtained samples from several sites to determine discharged radioactivity. RESULTS: A total of 38 patients received 129.4 ± 42 mCi (Range 40- 200) radioiodine therapy during the study. Discharge of the tanks was done two times during the study. The radioactivity discharges into aeration plant were 89.2 and 71.2 mCi that correspond to 440.05 and 351 MBq/m3, respectively. This was diluted by the aeration tank (6 million liters). Finally, at the discharge time, the radioactivity in the discharge was 1.6 and 1.5 MBq/m3, respectively. The highest exposure rates were 14 µSv/h near the delay tank, which rapidly decreased on moving to the surrounding. CONCLUSION: Our study indicates that the addition of the dilution method and close monitoring may significantly reduce the radiation exposure and overall radioactivity release from the facility. Old facilities that do not have space to add up the tank capacity may get a benefit from it. A small change in the practice, such as admitting patients alternate months or providing extra decay time for radioactive waste, may lead to a cost-effective alternative.

Gallbladder Visualization on Tc-99m-labeled Red Cell Scintigraphy: A Rare Finding with an Emphasis on Role of Single-photon Emission Computed Tomography/Computed Tomography.

Tc-99m labeled red blood cell (RBC) scintigraphy is one of the most sensitive tests to diagnose occult gastrointestinal (GI) bleed. Visualization of gallbladder is a rare finding in this study. Most of the previously reported cases with similar false-positive finding were associated chronic renal failure, anemia, and received multiple blood transfusions. Thus, while interpreting GI bleed scan, a thorough clinical history is of utmost importance to avoid any false-positive findings. Here, we report a case of gallbladder visualization in 99mTc-RBC scintigraphy confirmed by single-photon emission computed tomography/computed tomography in a patient with chronic renal failure and anemia with failed renal transplant within 3 months.

Hypothyroidism in McCune-Albright Syndrome and Role of Bone Scan in Management of Fibrous Dysplasia: An Unusual Case Scenario with Review of Literature.

The McCune-Albright syndrome (MAS) is a triad of café-au-lait skin pigmentation, precocious puberty (PP), and polyostotic fibrous dysplasia of bone (FD). In general, FD seems to be the most common component of MAS but very rarely precocious puberty can be found in association with café-au-lait skin pigmentation in the absence of FD (about 1% of the cases). Therefore, a more clinically relevant definition of MAS is fibrous dysplasia of bone (FD) and at least one of the typical hyperfunctioning endocrinopathy and/or café-au-lait spots, with almost any combination possible. Bone scan can be the modality of choice to look for bone disease burden of fibrous dysplasia in most patients of MAS and may change the management accordingly. Most of the cases of MAS reported worldwide are associated with hyperthyroidism, up to best of our knowledge on the basis of literature search in pubmed and Google; no case was reported with hypothyroidism. Herein, we report a 12-year-old girl diagnosed with MAS and associated hypothyroidism. We have also reviewed the MAS related literature.

Extraosseous 99mTc-methylene diphosphonate uptake on bone scan: Unusual scenario.

In nuclear medicine, 99mTc-methylene diphosphonate. (MDP) bone scan is one of the most commonly performed procedures. MDP uptake in nonosseous tissues is occasionally found in bone scan, and the knowledge of these kinds of extraosseous uptakes is of much clinical relevance. We report here two cases where bone scan showed extraosseous MDP uptake either hepatic or splenic apart from the physiological skeletal uptake.

Evaluation of single-photon emission computed tomography images obtained with and without copper filter by segmentation.

BACKGROUND: Measurement of accurate attenuation of photon flux in tissue is important to obtain reconstructed images using single-photon emission computed tomography (SPECT). Computed tomography (CT) scanner provides attenuation correction data for SPECT as well as anatomic information for diagnostic purposes. Segmentation is a process of dividing an image into regions having similar properties such as gray level, color, texture, brightness, and contrast. Image segmentation is an important tool for evaluation of medical images. X-ray beam used in CT scan is poly-energetic; therefore, we have used a copper filter to remove the low energy X-rays for obtaining correct attenuation factor. Images obtained with and without filters were quantitatively evaluated by segmentation method to avoid human error. MATERIALS AND METHODS: Axial images of AAPM CT phantom were acquired with 3 mm copper filter (low intensity) and without copper filter (high intensity) using low-dose CT (140 kvp and 2.5 mA) of SPECT/CT system (Hawkeye, GE Healthcare). For segmentation Simulated Annealing Based Fuzzy c-means, algorithm is applied. Quantitative measurement of quality is done based on universal image quality index. Further, for the validation of attenuation correction map of filtered CT images, Jaszczak SPECT phantom was filled with 500 MBq of (99m)Tc and SPECT study was acquired. Low dose CT images were acquired for attenuation correction to be used for reconstruction of SPECT images. Another set of CT images were acquired after applying additional 3 mm copper filter. Two sets of axial SPECT images were reconstructed using attenuation map from both the CT images obtained without and with a filter. RESULTS AND CONCLUSIONS: When we applied Simulated Annealing Based Fuzzy c-means segmentation on both the CT images, the CT images with filter shows remarkable improvement and all the six section of the spheres in the Jaszczak SPECT phantom were clearly visualized.

Benefits of adopting good radiation practices in reducing the whole body radiation dose to the nuclear medicine personnel during (18)F-fluorodeoxyglucose positron emission tomography/computed tomography imaging.

INTRODUCTION: Positron emission tomography has been established as an important imaging modality in the management of patients, especially in oncology. The higher gamma radiation energy of positron-emitting isotopes poses an additional radiation safety problem. Those working with this modality may likely to receive higher whole body doses than those working only in conventional nuclear medicine. The radiation exposure to the personnel occurs in dispensing the dose, administration of activity, patient positioning, and while removing the intravenous (i.v.) cannula. The estimation of radiation dose to Nuclear Medicine Physician (NMP) involved during administration of activity to the patient and technical staff assisting in these procedures in a positron emission tomography/computed tomography (PET/CT) facility was carried out. MATERIALS AND METHODS: An i.v access was secured for the patient by putting the cannula and blood sugar was monitored. The activity was then dispensed and measured in the dose calibrator and administered to the patient by NMP. Personnel doses received by NMP and technical staff were measured using electronic pocket dosimeter. The radiation exposure levels at various working locations were assessed with the help of gamma survey meter. RESULTS AND DISCUSSION: The radiation level at working distance while administering the radioactivity was found to be 106-170 µSv/h with a mean value of 126.5 ± 14.88 µSv/h which was reduced to 4.2-14.2 µSv/h with a mean value of 7.16 ± 2.29 µSv/h with introduction of L-bench for administration of radioactivity. This shows a mean exposure level reduction of 94.45 ± 1.03%. The radiation level at working distance, while removing the i.v. cannula postscanning was found to be 25-70 µSv/h with a mean value of 37.4 ± 13.16 µSv/h which was reduced to 1.0-5.0 µSv/h with a mean value of 2.77 ± 1.3 µSv/h with introduction of L-bench for removal of i.v cannula. This shows a mean exposure level reduction of 92.85 ± 1.78%. CONCLUSION: This study shows that good radiation practices are very helpful in reducing the personnel radiation doses. Use of radiation protection devices such as L-bench reduces exposure significantly. PET/CT staff members must use their personnel monitors diligently and should do so in a consistent manner so that comparisons of their doses are meaningful from one monitoring period to the next.

Polylactide-co-glycolide nanoparticles of antitubercular drugs: formulation, characterization and biodistribution studies.

BACKGROUND: The present study was designed to prepare and characterize poly lactide-co-glycolide nanoparticles of antitubercular drugs (ATDs) for delivery through oral route to alveolar macrophages. METHODS: Nanoparticles were prepared by double emulsification solvent evaporation method. Ex vivo and in vivo drug accumulation studies were performed in alveolar macrophages, harvested by broncheoalveolar lavaging. Internalization of nanoparticles was studied by confocal laser scanning microscopy. γ-scintigraphy imaging using technetium-99m was done to study the biodistribution pattern of nanoparticles. RESULTS: High intracellular concentrations of ATDs were observed in macrophages within 30 min of administration of nanoparticles. Intense radioactivity recorded in liver, spleen and lungs revealed uptake of nanoparticles in macrophages, abundantly present in mononuclear phagocyte system present in these organs. CONCLUSION: Targeted delivery of ATDs will help reduce dose and associated side effects including hepatotoxicity of ATDs. Further studies are required to assess the potential therapeutic advantages for treatment of TB.

A new method to correct the attenuation map in simultaneous transmission/emission tomography using Gd/Ga radioisotopes.

Reconstruction of the tomographic images without attenuation correction can cause erroneously high count densities and reduced image contrast in low attenuation regions. In order to solve the problem of photon attenuation, one needs to know the attenuation coefficient for the individual patient being studied. Therefore, we made an attempt to correct the attenuation map in simultaneous transmission/emission tomography with (153)Gd/(67)Ga using maximum likelihood method using the expectation maximization (ML-EM) algorithm to correct the transmission window for both the spillover and downscatter. Spillover fraction, scatter fraction and parameters for the scatter function (A, b and c) were determined experimentally and optimized using the optimization program written in IDL based on simplex theory. All measurements were performed on a Vertex gamma camera using the anthropomorphic thorax phantom for validation of data obtained by the proposed method. It was observed that without spillover and downscatter correction, the mean counts were 19.29 in liver and 26.90 in lung, whereas after after applying the corrections, the mean counts were reduced to 3.80 and 15.10 in liver and lung, respectively, which were close to true mean counts (liver 2.15 and lung 14.89). In this proposed method, we introduced the set of F(t)(spillover) and K(t)(downscatter) to account for the variations in projection pixels (f(t) and k(t)) with the density and thickness. The F(t) and K(t) were determined using the transmission data by an iterative process. The quantitative error was reduced by 98.0% for lung and 90.0% for liver when the corrected transmission images were obtained after the subtraction of spillover and downscatter fraction.

An investigation of a sinogram discontinuity artifact on myocardial perfusion imaging.

UNLABELLED: Our purpose was to find out the cause of an unusual distinct break seen on a patient's sinogram despite within-tolerance results on all quality assurance tests during myocardial perfusion imaging (MPI) and corrective measures. METHODS: SPECT quality control is a prerequisite to obtaining high-quality diagnostic images. Daily uniformity and energy-peaking tests and weekly center-of-rotation (COR) tests are run to check the performance of the SPECT system. A distinct break in the sinogram of an MPI study was noticed for 1 patient, despite routine quality control tests that showed the system to be well within tolerance limits. Critical inspection of the γ-camera revealed that the 2 detector heads did not make complete contact with each other at a 90° position and that a gap of as much as 10.0 mm was left between the 2 edges of the detectors even though COR testing showed the system to be within tolerance limits. After this gap had been minimized (-10-mm position), the MPI study of this patient was repeated. RESULTS: Reduction of the gap between detectors corrected the sinogram discontinuity. On the MPI study, the break in the sinogram existed because the 2 detectors were not acquiring the data at the same position in their useful fields of view. When one of the detectors was tilted to exactly 45°, the gap was reduced and the data were acquired at the same useful field of view for both detectors. CONCLUSION: The sinogram artifact may arise even after perfect COR calibration, and in the reported case, the discontinuity in the sinogram was rectified by correcting the angle of the detectors. Meticulous investigation for artifacts must be performed to minimize the probability of false results.

Utility of single photon emission computed tomography perfusion scans in radiation treatment planning of locally advanced lung cancers.

PURPOSE: Lung perfusion scan provides a map of the spatial distribution of lung perfusion. This can be used to design radiation portals to spare functional lung (FL), potentially reducing lung toxicity. The purpose of this study was to assess the utility of lung perfusion single photon emission computed tomography (SPECT) in treatment planning for lung cancer patients. MATERIALS AND METHODS: Radiotherapy treatment planning computed tomography (CT) scans and SPECT scans of 11 patients of lung cancer suitable for external radiotherapy were co-registered. Conventional treatment plans (anatomic plan) and plans with FL information (functional plan) was generated. The difference in dose volume parameters (V20, V30 and mean lung doses) due to these two plans were compared using Bland-Altman plots. RESULTS: Functional plans produced a more favorable plan compared with anatomic plan in all except three cases. FL V20 values and FL mean lung dose were reduced for all patients by an average of 5.45 Gy and 7.72 Gy respectively which were statistically significant. CONCLUSIONS: Lung perfusion scans provide functional information which is not provided by CT scans. SPECT-guidance aids in reducing the dose delivered to highly perfused regions which could reduce the incidence of pneumonitis.

Do reconstruction filters really effect the volume and ejection fraction calculation with 99Tc-sestamibigated myocardial SPECT?

BACKGROUND: ECG -gated myocardial perfusion imaging is a sensitive test for diagnosis of ischemia as well as scarred myocardium. It provides additional information on global and regional myocardial contractile function. A number of methods are available to calculate left ventricular volumes and ejection fractions, which depends on various technical and patients specific factor. OBJECTIVE: This study was carried out to measure effect of reconstruction filter in calculations of left ventricularend diastolic volume (EDV) and end systolic volume (ESV) and left ventricular ejection fraction (LVEF) from 99mTc-sestamibi myocardial perfusion imaging. MATERIALS AND METHODS: 99mTc-sestamibi-gated SPECT myocardial perfusion imaging was performed in 90 patients. Studies were reconstructed with Butterworth and Metz filters. RESULTS: Mean ejection fraction with Butterworth and Metz filter are 64.3 and 64.2, respectively. Mean EDV is for Butterworth and Metz filters are 77.3 and 78.5 ml, respectively. While ESV was 36.49 and 36.63 ml, stroke volume calculated was 41.54 and 42 ml for Butterworth and Metz filters, respectively. Pearsons's correlation coefficients between results calculated with Metz and Butterworth filters were 0.994 for ESV, 0.996 for EDV, 0.966 for LVEF and 0.925 for SV. Student 't' test was applied on the data and no significant difference was noted between parameter estimated by Butterworth or Metz filter. CONCLUSION: This study shows that difference of filter application has no significant effect in computing left ventricular function parameters.