Evaluation of effective dose for a patient under Ga-67 nuclear examination using TLD, water phantom and a simplified model

Data reconciliation connected to guard bands to set specification limits related to risk assessment for radiopharmaceutical activity

Radiopharmaceuticals have been used to diagnose several diseases, particularly because the procedure is non-invasive. However, it is important that the correct amount of radiopharmaceutical is used to avoid inaccurate diagnostic results and suboptimal therapeutic outcomes. The amount of the radiopharmaceutical is measured when produced (by the supplier) and a second time (by the receiver), before it's use. When measured at the receiver, the result is corrected for its normal radioactivity decay. Even then, it is possible that both measurements should be considered nominal different or even statistically different when compared through various statistical tools. This research combines two innovative techniques in the field of clinical metrology. The first technique is data reconciliation, which not only enhances measurement accuracy but also reduces measurement uncertainty. The second technique involves using uncertainty information to establish specification limits for compliance assessments. In this way, our proposal aimed to minimize the risk of making incorrect decisions regarding the conformity of the concentration of radiopharmaceutical activity, that is, rejecting an item or batch that is within specification or accepting an item or batch that is outside of specification. A spreadsheet, based on these metrology fundamentals, is available to help the user with the calculations, presenting numerical and graphical results for some common radioisotopes. Reliable specification limits can be calculated and used to determine if the radiopharmaceutical is in accordance with its proposed application.

Hypertrophic Pachymeningitis Presenting as “Eyebrows” Sign on 18F FDG PET/CT

Hypertrophic pachymeningitis refers to linear or nodular thickening of the dura mater covering the brain and spinal cord following various inflammatory/infective processes. Usually, magnetic resonance imaging brain shows uniform thickening with enhancement of involved meninges. Fluorodeoxyglucose positron emission tomography/computed tomography (PET/CT) findings of pachymeningitis are rarely reported in literature. We describe the PET/CT findings of a patient with hypertrophic pachymeningitis involving the bilateral supraorbital regions depicting as “eyebrows” on brain maximum intensity projection image.

ASSESSMENT OF TC-99M MDP ABSORBED DOSE AND RESIDENCE TIME AFTER BONE SCAN EXAMINATION: PERSONAL DOSIMETER MEASUREMENTS AND SEMI-EMPIRICAL FORMULA FOR 210 PATIENTS IN TAIWAN

Subject: This study assessed the absorbed dose for patients who underwent Tc-99m Methylene Diphosphonates (MDP) bone scan examination based on a series of personal dosimeter measurements and a derived semi-empirical formula. Material and methods: 210 volunteers among the patients, who were administrated 925 MBq Tc-99m MDP for the bone scan examination in the Department of Nuclear Medicine in the Dalin Tuzchi Hospital, Taiwan, underwent personal dosimeter measurements at 30, 120, and 180[Formula: see text]min after the injection. A personal dosimeter was held at a 30[Formula: see text]cm distance from the patient’s stomach. The acquired data were analyzed to derive the residence time of Tc-99m radionuclide in the patient’s body. Five biological parameters (gender, age, BMI, eGFR, and creatinine) of these 210 patients were collected and processed by the STATISTICA program, yielding a nonlinear 16-term first-order semi-empirical formula for the radionuclide residence time prediction. The respective four- and three-factor calculations, excluding creatinine and eGFR, provided poor correlation. Results and Conclusion: According to the phantom concept, treating a patient’s body as a homogenous spherical ball, a simplified formula was used to assess the absorbed dose rate and magnitude. Therefore, the derived residence time, dose rate, and absorbed dose were [Formula: see text][Formula: see text]min, [Formula: see text]Sv/min, and [Formula: see text]Sv, respectively. These results were lower than those obtained in previous studies, which can be attributed to accelerated radionuclide excretion of patients who drank 2000 cc of water after the procedure, yielding shorter residence times.

BIOKINETIC AND DOSIMETRIC ASSESSMENT OF FLUORINE 18 IN HEALTHY VOLUNTEERS SUBJECTED TO 18F–NaF PET/CT BONE SCANS VIA COMPARTMENTAL/MATLAB MODELS AND IN-VIVO STUDY

Objective: This study quantified the time-dependent concentration of [Formula: see text]F–NaF in critical organs according to a simplified compartmental biokinetic model with clinical verification. Methods: The eleven volunteers were given [Formula: see text][Formula: see text]MBq [Formula: see text]F–NaF administration, then scanned (with 15[Formula: see text]min-collection, every 20[Formula: see text]min, for 200 consecutive min) with a Philips Gemini GXL PET/CT. The empirical data were collected and normalized as the input dataset for MATLAB program. A six-compartmental model was created as a set of time-dependent differential equations and analyzed by the MATLAB to optimize the correlation between the in vivo data and calculated results. The six compartments were: body fluid, bone, kidney, liver, remainder and excretion, while kidney and liver compartments were conventionally split into two subunits with different half-lives to fit properly the empirical data. Results: The average biological half-lives of body fluid, bone, kidney-1, kidney-2, liver-1, liver-2 and the remainder (rest of body) were assessed as [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], and [Formula: see text][Formula: see text]min, respectively. A dimensionless AT index of disagreement between the empirical data and MATLAB optimal solutions was proposed of validating the applied acquisition system and analytical method feasibility. The body fluid and bone AT values did not exceed 20%. The proposed refined equation yielded the internal dose from both gamma- and beta-rays ([Formula: see text] cSv as [Formula: see text] cSv/MBq), which exhibited good correlation with literature (0.00168–0.00270 cSv/MBq). Conclusion: The proposed MATLAB-based fitting of in-vivo data with the theoretical results was instrumental for assessing the radiation dose received by the PET/CT bone scan participants.

A quantitative evaluation of multiple biokinetic models using an assembled water phantom: A feasibility study

This study examined the feasibility of quantitatively evaluating multiple biokinetic models and established the validity of the different compartment models using an assembled water phantom. Most commercialized phantoms are made to survey the imaging system since this is essential to increase the diagnostic accuracy for quality assurance. In contrast, few customized phantoms are specifically made to represent multi-compartment biokinetic models. This is because the complicated calculations as defined to solve the biokinetic models and the time-consuming verifications of the obtained solutions are impeded greatly the progress over the past decade. Nevertheless, in this work, five biokinetic models were separately defined by five groups of simultaneous differential equations to obtain the time-dependent radioactive concentration changes inside the water phantom. The water phantom was assembled by seven acrylic boxes in four different sizes, and the boxes were linked to varying combinations of hoses to signify the multiple biokinetic models from the biomedical perspective. The boxes that were connected by hoses were then regarded as a closed water loop with only one infusion and drain. 129.1±24.2 MBq of Tc-99m labeled methylene diphosphonate (MDP) solution was thoroughly infused into the water boxes before gamma scanning; then the water was replaced with de-ionized water to simulate the biological removal rate among the boxes. The water was driven by an automatic infusion pump at 6.7 c.c./min, while the biological half-life of the four different-sized boxes (64, 144, 252, and 612 c.c.) was 4.8, 10.7, 18.8, and 45.5 min, respectively. The five models of derived time-dependent concentrations for the boxes were estimated either by a self-developed program run in MATLAB or by scanning via a gamma camera facility. Either agreement or disagreement between the practical scanning and the theoretical prediction in five models was thoroughly discussed. The derived biokinetic model represented the metabolic mechanism in the human body and helped to solidify the internal circulatory system into concert with numerical verification.

Usefulness of 99mTc-dimercaptosuccinic acid renal scan in the diagnosis and follow-up of acute tubulointerstitial nephritis in children

BACKGROUND

Symptoms and signs of acute tubulointerstitial nephritis (ATIN) are nonspecific; therefore, renal biopsy is often necessary to clarify the diagnosis. The aim of this study was to evaluate the use of ^99mTc-dimercaptosuccinic acid (DMSA) scintigraphy in the diagnosis and follow-up of ATIN.

METHODS

We retrospectively reviewed the charts of five patients (nine renal units) with a median age of 14 years who underwent DMSA scan after a clinical and/or biopsy-proven diagnosis of ATIN. The exam was performed within 1 month after disease onset and repeated at a median time of 12 months after the acute phase.

RESULTS

DMSA renal scans performed during the acute phase allowed the discovery of suggestive findings, including diffuse reduction of the renal uptake of radionuclide and presence of multiple 'cold' focal lesions in a corticomedullary distribution. The follow-up scintigraphy resulted normal in two patients who were treated with steroids and in one patient who presented a mild renal dysfunction in the acute phase. By contrast, the control scan showed persistent renal damage in one patient who was further readmitted because of hypertension and in one renal transplanted patient who presented a Stage 3 acute kidney injury in the acute phase.

CONCLUSIONS

DMSA renal scan might be a reliable tool for an early non-invasive diagnosis of ATIN in children and might be particularly useful in those patients who are not candidates for a kidney biopsy. Moreover, DMSA scan gives accurate follow-up evaluation, as it allows monitoring of the evolution of acute renal parenchymal inflammation with potential risk of renal scar formation. Due to the small sample size, our findings warrant further validation in a larger study.

Radiation dose for normal organs by helical tomotherapy for lung cancer

This study derived a simple equation of effective dose (E) versus normal organ of patients with varying body weights undergoing lung cancer treatment of helical tomotherapy (TOMO). Five tissue-equivalent and Rando phantoms were used to simulate lung cancer patients. This study then measured E and equivalent dose of organ or tissues (DT) using thermoluminescent dosimetry (TLD-100H). The TLD-100H was calibrated using TOMO 6MV photons, then inserted into phantom positions that closely corresponded with the position of the represented organs and tissues. Both E and DT were evaluated by ICRP 103. Peripheral doses varied markedly at positions close to the tumor center. The maximum statistical and total errors were 16.7-22.3%. This analytical result indicates that E of Rando and tissue-equivalent phantoms was in the ranged of 9.44±1.70 (10kg) to 4.58±0.83 (90kg)mSv/Gy. Notably, E decreased exponentially as phantom weight increased. Peripheral doses were also evaluated by TLD as a function of distance from the tumor center. Finally, experimental results are compared with those in literature. These findings will prove useful to patients, physicians, radiologists, and the public.