BackgroundInhaled saline may improve mucus transport in respiratory diseases, for example, cystic fibrosis. This randomised, placebo‐controlled, crossover study examined the effect of inhaled dry NaCl on mucociliary clearance in patients with chronic obstructive pulmonary disease (COPD).MethodsTwenty‐five patients with GOLD stage I‐III COPD (72% with excess mucus) were tested on two separate days after inhalation from a dry powder inhaler containing either 40 mg dry NaCl or placebo (empty). Pulmonary mucociliary clearance was assessed using inhalation of a radioactive 99mTc‐labelled nanocolloid tracer and gamma camera imaging. Clearance was measured for 2 h post‐intervention. Co‐primary outcomes were clearance after 1 and 2 h.ResultsThe study was terminated early due to COVID‐19 after enrolling 25 of 35 planned patients. No significant differences were observed in mucociliary clearance between NaCl and placebo after 1 h (11.3% ± 9.0% vs. 11.4% ± 7.0%, p = 0.97) or 2 h (15.3% ± 9.8% vs.16.1% ± 8.7%, p = 0.55). Normalised clearance based on initial radioaerosol deposition also showed no difference.ConclusionsInhalation of 40 mg dry NaCl was well tolerated without acute adverse effects in COPD patients. However, early termination left the study underpowered, increasing the risk of type II error. Non‐significant findings should not be interpreted as evidence of no effect. Larger, adequately powered trials are needed to clarify the impact of dry NaCl inhalation on mucociliary clearance in COPD.

Solid lipid nanoparticles (SLNs) are submicron colloidal systems widely investigated as drug carriers; however, their intrinsic biodistribution properties are also critical when SLNs are considered for diagnostic imaging. In the present proof-of-concept study, drug-free SLNs were evaluated exclusively as a radiolabeled imaging agent rather than as a drug delivery system. SLNs were radiolabeled with Technetium-99m (99mTc), and their in vivo biodistribution was investigated using gamma camera imaging, ex vivo organ counting, and confocal microscopy. SLNs were prepared by a microemulsion–low-temperature solidification method and characterized by dynamic light scattering (DLS), scanning electron microscopy (SEM), and differential scanning calorimetry (DSC). Radiolabeling efficiency was determined by instant thin-layer chromatography (ITLC) and exceeded 95%. Following intravenous administration in a rabbit model, dynamic scintigraphic imaging demonstrated predominant uptake in the liver and spleen. These findings were quantitatively confirmed by ex vivo biodistribution analysis at 4 h post-injection and qualitatively supported by confocal microscopy of liver and spleen tissues. The results indicate that 99mTc-labeled SLNs behave as RES-targeting radiocolloids and may serve as potential agents for liver–spleen scintigraphy.

The mucociliary clearance (MC) system clears mucus, pathogens, and toxins from the airways. Whole lung MC rate can be measured using gamma camera imaging after the inhalation of radiolabeled particulate. We sought a means to evaluate the therapeutic effect of clearance enhancing therapies in different airway size groups. We developed a mathematical model of mucus transport in the right lung that, when informed by imaging data, estimates MC rate and unclearable activity at points across the airway tree. We fit the model to imaging studies from 11 healthy controls (HC), resulting in a per-point mean absolute error (MAE) of 0.085 ± 0.016% of the total particulate deposition. Using principal component analysis and hierarchical clustering, we reduced the number of fitted clearance rate coefficients from 114 to 5 with only an 8.7% increase in MAE. These 5 cluster groups were closely associated with specific regions of the lung and likely with specific airway size groups. Comparing the HC group to a cystic fibrosis (CF) group we found only one cluster with significantly depressed MC rates in CF corresponding to the lower lobe. The inhalation of 7% hypertonic saline (HS) by the CF group increased MC rate in all clusters and decreased unclearable activity in 4/5 clusters. The computational model described provides detailed regional estimates of MC rate when applied to clearance imaging studies. If further informed, this model may provide a valuable tool for studying small airways obstructive disease and evaluating mucus clearance-enhancing therapies in the lung.

Radionuclide molecular imaging of epidermal growth factor receptor (EGFR) expression might permit the selection of patients for EGFR-targeting therapies. Designed ankyrin repeat protein (DARPin) E01 with a high affinity to the ectodomain III of the EGFR is a possible EGFR imaging probe. The goal of this study was to evaluate the potential of radiolabeled DARPin E01 for in vivo imaging of EGFR. DARPin E01 containing the (HE)3-tag was site-specifically labeled with a residualizing 99mTc (using 99mTc]Tc(CO)3). Two methods providing non-residualizing 123I labels, direct electrophilic radioiodination and indirect radioiodination using [123I]I-para-iodobenzoate (PIB), were tested. [99mTc]Tc-(HE)3-E01 and [123I]I-(HE)3-E01-PIB preserved specific binding to EGFR-expressing cells and affinity in the single-digit nanomolar range. Direct labeling with 123I resulted in a substantial loss of binding. In vitro cellular processing studies showed that both [99mTc]Tc-(HE)3-E01 and [123I]I-(HE)3-E01-PIB had rapid binding and relatively slow internalization. Evaluation of [99mTc]Tc-(HE)3-E01 biodistribution in normal CD1 mice showed that its hepatic uptake was non-saturable, suggesting that this tracer does not bind to murine EGFR. A side-by-side comparison of biodistribution and tumor targeting of [99mTc]Tc-(HE)3-E01 and [123I]I-(HE)3-E01-PIB was performed in Nu/j mice bearing EGFR-positive A-431 and EGFR-negative Ramos human cancer xenografts. Both radiolabeled DARPins demonstrated EGFR-specific tumor uptake. However, [123I]I-(HE)3-E01-PIB had appreciably lower uptake in normal organs compared to [99mTc]Tc-(HE)3-E01, which provided significantly (p < 0.05) higher tumor-to-organ ratios. Gamma-camera imaging confirmed that [123I]I-(HE)3-E01-PIB demonstrated a higher imaging contrast in preclinical models than [99mTc]Tc-(HE)3-E01. In conclusion, DARPin (HE)3-E01 labeled using a non-residualizing [123I]I-para-iodobenzoate (PIB) label is the preferred radiotracer for in vivo imaging of EGFR expression in cancer.

Background: Renal cortical scintigraphy using Tc-99m Dimercaptosuccinic acid (Tc-99m DMSA) is the detection of cortical abnormalities. In addition, relative renal function (RRF) is performed by DMSA scintigraphy and estimated from the radiopharmaceutical uptake in both kidneys with radiation attenuation correction. Generally, attenuation correction is calculated from mathematic methods with kidney depth correction for an accurate renal function value. Objective: The purpose of this research was to study the correlation of the RRF with radiation attenuation correction by geometric mean (GM) method and kidney depth correction by Beer-Lambert law equation. Methods: Researchers studied in the spherical phantom, kidney phantom and patient’s data using planar images from gamma camera imaging to evaluate the RRF. All study, the renal region of interest (ROI) is created from planar image for activity counts calculation. Results: The results are subtracted background and corrected the radiation attenuation using GM and kidney depth correction by Beer-Lambert law. Phantom studies, the RRF from GM radiation attenuation correction was consistent with kidney depth correction by Beer-Lambert law equation and true renal depth (ICC > 0.84). The patient’s study showed the RRF from GM method related to the other kidney depth correction methods (R2 > 0.95) and GM method was not significantly different from other renal depth correction methods (P > 0.05, ICC > 0.95). Conclusion: Finally, radiation attenuation is corrected by GM and kidney depth correction by Beer-Lambert law equation method can be used to estimate RRF appropriately in renal cortical scintigraphy.

Introduction/AimTerbium-161 (161Tb) has emerged as a promising therapeutic radionuclide, yet standardized imaging guidelines are lacking. This study aimed to characterize a SPECT/CT system, currently used in an ongoing clinical trial (BETA PLUS; NCT05359146), focusing on sensitivity, septal penetration, and dead-time effects.MethodsMeasurements were conducted on a Siemens Symbia Intevo system using two collimators: low-energy high-resolution (LEHR) and medium-energy low-penetration (MELP). Two energy windows were evaluated: 75 keV ± 10% and 48 keV ± 20%. Planar sensitivity and penetration were assessed using a 161Tb-filled Petri dish. Penetration fractions were determined as a function of distance for each collimator-window combination. Dead time was measured intrinsically for each detector using a set of 161Tb point sources. SPECT measurements of a homogenous cylinder phantom were performed to assess count rate performance and predict activity levels at which dead-time effects could occur. To evaluate the potential impact of dead time in patient imaging, SPECT projection data from patients treated with 1 GBq of [161Tb]Tb-DOTA-LM3 (n = 8) was analyzed.ResultsSensitivity was comparable for both collimators at 75 keV (LEHR: 15.7 cps/MBq, MELP: 18.5 cps/MBq) and increased at 48 keV (LEHR: 44.4 cps/MBq, MELP: 67.9 cps/MBq). Maximum penetration occurred at 75 keV with the LEHR collimator (7.5% at 10 cm). In acquired spectra, more than half of the detected counts (51.6%) appeared above the 75 keV window with LEHR, compared to only 12.2% with MELP. Dead-time analyses revealed non-linear detector responses at wide-spectrum count rates exceeding 93 kcps, corresponding to in-field activities of 1.4–2.0 GBq for LEHR and 1.7–2.2 GBq for MELP. The dead-time constant was determined to 0.42 µs for both detector heads, however, the maximum recorded count rate differed significantly (384 kcps vs. 546 kcps). The median and maximum wide-spectrum count rate for patients treated with [161Tb]Tb-DOTA-LM3 was estimated to ~ 20 and ~ 40 kcps per GBq 3 h p.i., respectively, when imaged with LEHR, corresponding to a maximum estimated dead-time loss of 1.7%.ConclusionsWhile high-quality 161Tb SPECT imaging is feasible, careful consideration is essential; the wide range of photons emitted will produce a higher wide-spectrum count rate as compared to 177Lu. The use of low-energy collimators increases penetration and scatter, impairing quantitative accuracy and elevating the wide-spectrum count rate, which may intensify dead-time effects. At therapeutic activity levels (e.g., 7.4 GBq), dead time should be closely monitored to ensure reliable quantification.Supplementary InformationThe online version contains supplementary material available at 10.1186/s40658-025-00792-x.

BackgroundNaI(Tl) scintillators used in most gamma cameras are hermetically sealed to prevent the absorption of water molecules from the surrounding environment. If this seal is compromised, crystal hydration, a localized defect resulting in non‐uniform attenuation of scintillation photons, may occur.PurposeThe purpose of this study was to evaluate the effects of crystal hydration across multiple radionuclides, characterizing the impact on spectral response and image uniformity.MethodsHydration was assessed using on‐peak and off‐peak imaging for several radionuclides. The progression of hydration was assessed by calculating the contrast‐to‐noise ratio in hydrated regions on monthly uniformity maps. Spectra were captured for both hydrated and non‐hydrated regions of the detector to determine photopeak energy and energy resolution.ResultsThe visual appearance of the hydration effect in off‐peak images was greatest for 133Xe. The effect was more substantial in the 10% low off‐peak image than in the 10% high off‐peak image. Hydration was not observed in on‐peak images for either 133Xe or 99mTc and was only barely visible for 131I. CNR measurements show a slow but notable progression of hydration in uniformity maps over time. The measured photopeak in hydrated regions was lower than that of non‐hydrated regions. Hydration also resulted in a degradation in energy resolution with the effect being more significant at lower energies.ConclusionsHydrated regions of the detector demonstrated an energy‐dependent degradation in energy resolution which corresponded to an energy dependence in the detectability of hydration in off‐peak images. Monthly updates to the uniformity correction maps were able to adequately account for hydration. When hydration has been identified, routine evaluation of its impact on uniformity maps may provide a convenient method of tracking progression.

Amino acid infusion (AAI) is a technique used in radiopharmaceutical therapy (RPT) to reduce toxicity in kidney and increase clearance rate of radiopharmaceuticals from body. In this study our aim is to evaluate its effect in personalized RPT considering kidney and salivary glands as dose limiting organs using a multiscale modeling framework. We developed a Physiologically-Based Pharmacokinetic (PBPK) model consisting of 19 compartments, personalized it for four prostate cancer patients using data derived from gamma camera imaging. This model was used to investigate the influence of AAI on the absorbed dose to tumors and organs at risk. We then computed the maximum safe injected activity based on the PBPK model. To address the effects of interstitial fluid pressure (IFP) and tumor heterogeneity, we coupled the PBPK model with convection-diffusion-reaction (CDR) equations. To compare the effectiveness of our modeling approaches, we calculated absorbed doses to the tumors with and without AAI, using both the standalone PBPK model and the coupled PBPK-CDR model. Our findings revealed a relative error (RE) of 9.6% ± 2.2% (mean ± SD) in total tumor absorbed dose calculation between PBPK and CDR equations, attributable to the consideration of IFP. Moreover, AAI proved beneficial for RPT when the kidney was designated as the organ-at-risk. It enabled an increase in radiopharmaceutical injection from 12.3 ± 6.32 MBq (mean ± SD) to 15.45 ± 6.95 MBq (RE: 28.5% ± 15.7%), resulting in a corresponding increase in tumor absorbed dose from 67.8 ± 47.45 Gy to 72.43 ± 51.03 Gy (RE: 8.6% ± 5.4%), while maintaining critical kidney absorbed dose limits. However, this was not observed when the salivary gland was considered the dose-limiting organ. Although, AAI allowed for increased therapeutic injection ranging from 4.22 ± 2.23 MBq to 5.25 ± 3.14 MBq (RE: 19.2% ± 9.9%), it results in a minimal increase in tumor absorbed dose of 0.22 ± 0.04 (RE: 1.4% ± 1.3%). Statistical analysis using the Wilcoxon Signed-Rank Test revealed significant effects of AAI on administered activity and tumor absorbed dose (p-value = 0.007 < 0.05). Finally, a local sensitivity analysis was performed on selected radiation and tumor transportation parameters individually to evaluate their impact on the tumor absorbed dose. In conclusion, selection of organ-at-risk in personalized RPT is critical, as it determines the injected activity amount and the efficacy of delivery-enhancing techniques.

Background203Pb and 212Pb show promise as theragnostic agents for targeted alpha therapy (TAT) because two chemically identical isotopes can be used for diagnostic imaging and treatment. In the 212Pb decay chain, in addition to alpha and beta particles, a large number of photons are emitted, those with an energy of 239 keV and the characteristic X-rays of 212Pb could be used for imaging. 203Pb decays by photon emission with an energy of 279 keV, which appears suitable for gamma camera imaging. The aim of this study was to investigate suitable imaging protocols and to characterize the scintigraphic imaging properties and their implications for the clinical feasibility as theragnostic isotopes.MethodsPlanar and SPECT/CT images were obtained with medium- and high-energy collimators on a Siemens Symbia Intevo 6 using a NEMA image quality phantom in various phantom setups and another body-shaped phantom with several inserts. Different energy windows were investigated and measurements were evaluated in terms of sensitivity, count rate performance, spatial resolution, contrast recovery, lesion detectability, and image quantification.ResultsEvaluation of image quality showed superior imaging characteristics for 203Pb compared to 212Pb regarding spatial resolution, contrast recovery, image noise, and quantification accuracy. Both medium- and high- energy collimators were suitable for 203Pb imaging, with the medium energy collimators showed slightly better imaging properties. Images obtained with the HE collimators in the 79 keV energy window showed the best visual image quality for 212Pb. Due to high-energy photon emissions from 212Pb daughter nuclides (e.g., 2.6 MeV from 208Tl), dead time related count losses occurred even at low activities (20% count loss at 20 MBq for MELP collimators).ConclusionsAccording to our results and first-in-human imaging studies, SPECT/CT imaging with the 203/212Pb theragnostic pair is clinically feasible. 203Pb is an appropriate imaging surrogate to investigate pharmacokinetics and perform predictive dosimetry. The less favorable imaging characteristics of 212Pb make image quantification and post-treatment dosimetry challenging and require further research.

Nuclear medicine in South Korea began in 1959 with the measurement of 131I uptake and excretion in patients with thyroid diseases and has achieved remarkable progress over the past 60 years. Diagnostic nuclear medicine imaging in South Korea, introduced in 1961, has evolved to include gamma camera imaging using gamma cameras and positron emission tomography (PET) combined with computed tomography (CT), which are now established as primary diagnostic modalities. The radionuclides used in gamma cameras and PET/CT are produced by generators and cyclotrons. These radionuclides are labeled to compounds that are selectively taken up by target organs, thereby forming radiopharmaceuticals. In South Korea, some of the commonly used radiopharmaceuticals for diagnostic nuclear medicine imaging in patients with pancreaticobiliary diseases include 99mTc-dicarboxypropane diphosphonate (DPD), 99mTc-methylene diphosphonate (MDP), 99mTc-hydroxymethylene diphosphonate (HMDP), 99mTc-bromotriethyl-iminodiacetic acid (BrIDA or mebrofenin), 18F-fluorodeoxyglucose (18F-FDG), 18F-2-fluoro-3,4-dihydroxyphenylalanine (18F-FDOPA), 111In-pentetreotide (octreotide), and 68Ga-1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid0-Tyr3-octreotide (68Ga-DOTA-TOC), which are widely used for the diagnosis and therapeutic planning of pancreaticobiliary neoplasms. The medical radiation exposure associated with diagnostic nuclear medicine imaging is considered to be at an acceptable level compared to radiation doses from natural background radiation. When clinicians understand the characteristics and advantages of nuclear medicine diagnostic imaging and effectively communicate this information to patients, this can contribute to building trust and improving the quality of medical care.

The mucociliary clearance (MC) system clears mucus, pathogens, and toxins from the airways. Whole lung MC rate can be measured using gamma camera imaging after the inhalation of radiolabeled particulate. We sought a means to evaluate the therapeutic effect of clearance enhancing therapies in different airway size groups. We developed a mathematical model of mucus transport in the right lung that, when informed by imaging data, estimates MC rate and unclearable activity at points across the airway tree. We fit the model to imaging studies from 11 healthy controls (HC), resulting in a per-point mean absolute error (MAE) of 0.085 ± 0.016% of the total particulate deposition. Using principal component analysis and hierarchical clustering, we reduced the number of fitted clearance rate coefficients from 114 to 5 with only an 8.7% increase in MAE. These 5 cluster groups were closely associated with specific regions of the lung and likely with specific airway size groups. Comparing the HC group to a cystic fibrosis (CF) group we found only one cluster with significantly depressed MC rates in CF corresponding to the lower lobe. The inhalation of 7% hypertonic saline (HS) by the CF group increased MC rate in all clusters and decreased unclearable activity in 4/5 clusters. The computational model described provides detailed regional estimates of MC rate when applied to clearance imaging studies. If further informed, this model may provide a valuable tool for studying small airways obstructive disease and evaluating mucus clearance-enhancing therapies in the lung.

Background[177Lu]Lu-EDTMP has emerged as a promising radiopharmaceutical for the palliation of pain caused by osseous metastases. This phase I/II study comprehensively evaluate the pharmacokinetics, biodistribution, clinical efficacy, and safety profile of [177Lu]Lu-EDTMP, in patients with skeletal metastases from breast and prostate cancer.MethodsA total of 27 patients with skeletal metastases were included in the study. Pharmacokinetics and biodistribution were analyzed in 17 patients through whole-body gamma camera imaging and quantification at multiple time points. Clinical efficacy and safety were evaluated in 18 patients receiving either low (1.3 GBq) or high (2.6 GBq) administered activity. Pain palliation was assessed using visual analog scale scores, analgesic usage (frequency and type), mobility scores, and Karnofsky performance status. The safety profile was determined through hematological and biochemical monitoring over 12 weeks.Results[177Lu]Lu-EDTMP demonstrated rapid blood clearance, with negligible residual activity at 24 h. Urinary excretion accounted for over 30% of administered activity at 24 h. Bone uptake increased progressively to over 70%.Scintigraphy revealed selective uptake in metastases, improving lesion-to-bone and lesion-to-soft tissue ratios. Both low (1.3 GBq) and high (2.6 GBq) activity groups showed significant pain relief, with faster, longer-lasting effects in the high-dose group, reducing opioid/NSAID use. No Grade III/IV myelotoxicity or major renal/hepatic events occurred.Conclusion[177Lu]Lu-EDTMP is a safe and effective bone pain palliation agent, with favorable pharmacokinetics, targeted skeletal uptake, and minimal toxicity. These findings support its potential use as an alternative radiopharmaceutical for pain palliation in patients with skeletal metastases.Clinical trial numberNot applicable.Supplementary InformationThe online version contains supplementary material available at 10.1007/s00259-025-07218-x.

Background: In a Gamma Camera Unit, bone scans are the most commonly performed imaging procedure. Diagnostic reference levels (DRLs) play a crucial role in optimizing radiation exposure for patients and staff, while maintaining high-quality diagnostic images.Objective: The objective of this study is to optimize the patient radiation dose by establishing a DRL for gamma camera imaging for bone scan performed at two hospitals in Colombo, Sri Lanka.Methods: A total of 134 imaging procedures were sourced and compiled from the hospital database for this study. 84 gamma camera imaging procedures were selected from Apeksha Hospital, Maharagama (Hospital No.1) and 50 procedures were selected from Asiri Surgical Hospital, Colombo (Hospital No.2), from September 2022 to November 2022. According to the recommendation of the International Commission of Radiological Protection (ICRP), the median value of the administered activity value was considered to develop DRL.Results: The median values of the administered activity for the two hospitals were 587 MBq for Hospital No.1and 586 MBq for Hospital No.2. The developed DRL values for bone scan in gamma camera imaging are 587 MBq (15.865 mCi) for Hospital No.1 and 586 MBq (15.839 mCi) for Hospital No.2. There is a 0.026 mCi difference in administered activity observed between two institutes.Conclusions: There were significant correlations observed between the administered activity and patient’s body mass index, and between the administered activity and patient’s clinical indication.

SUMMARYLymphedema is a chronic, progressive condition caused by impaired lymphatic transport, leading to edema in the lower and/or upper extremities, depending on the underlying cause. The diagnosis is based on clinical examination, ultrasound findings, and imaging tests. Treatment is mostly conservative, usually long-term, and often yielding unsatisfactory results. Recently, surgical options have also become available. Lymphoscintigraphy, a non-invasive and simple nuclear medicine imaging technique, is considered the method of choice in diagnostic workup. It consists of intracutaneous or subcutaneous application of colloidal particles labelled with radioactive technetium-99m and two-dimensional or three-dimensional gamma camera imaging. Lymphoscintigraphy helps differentiate lymphedema from edema of another origin, assess disease severity, and evaluate surgery outcome. However, the procedure is not fully standardized, especially in terms of semiquantitative methods, which are additionally used in disease staging; however, their implementation varies depending on local experience and expertise.

Purpose: Ruling out that healthy organs receive doses higher than those allowed in treatments with Iodo-131 (131I) for ablation of thyroid remnant is crucial for the radiological protection of the patient who also received the recombinant human thyroid-stimulating hormone (rhTSH). So, the investigation aimed to determine the changes in energy imparted by 131I in multiple organs due to the rhTSH in thyroid remnants and metastases of patients treated with high 131I activities (≥ 5,550 MBq). Materials and methods: Nine patients were divided into three groups (three per group); Group I included thyroid hormone withdrawal (THW) patients, while patients in groups II and III were stimulated with rhTSH. The activity and absorbed dose in regions of interest (ROIs) was quantified using the conjugated views method using gamma camera images. Results and discussion: Dosimetric variations of 131I produced by using rhTSH in the remnant thyroid (groups II and III) were observed, absorbed doses were minor for groups treated with rhTSH. Conclusion: The application of the high activities > 5,500 MBq administered together with the application of rhTSH is safe in dosimetric terms, also for 9250 MBq do not exceed established limits of absorbed dose in the bone marrow. Furthermore, these high activities provide more than three times the radiation dose to remaining thyroid tissue and approximately 1.5 times to metastases.

Abstract Targeted alpha (α) therapy (TAT) is an emerging therapeutic strategy for cancer treatment. To evaluate the safety and efficacy of targeted α‐therapy, the biodistribution and internal radiation dose of α‐emitting radionuclides should be determined. In vivo imaging of these radionuclides often involves the detection of gamma rays, X‐rays, and positrons generated during their complex decay processes. This review aims to classify the α‐emitting radionuclides (astatine‐211, actinium‐225, radium‐223, bismuth‐212, bismuth‐213, thorium‐227, and terbium‐149) according to their imageable signals. Additionally, this study summarizes various imaging modalities, including gamma camera imaging, single‐photon emission computed tomography, positron emission tomography, Compton imaging, bremsstrahlung imaging, and Cerenkov luminescence imaging, which hold potential for imaging α‐emitting radionuclides, to explore their biomedical applications in qualitative nuclide tracing and diagnosis, quantifying pharmacokinetics, and assessing prognosis and response to therapy.

Background: The diagnosis and treatment of pediatric lymphedema provide particular challenges. The defining feature of lymphedema is aberrant interstitial fluid collection, which can be caused by a variety of factors, including acquired illnesses and congenital defects. This study used lymphoscintigraphy to determine the source of lymphedema in children of various ages. Patients and Methods: In this retrospective analysis, 53 children were included, who were referred to National Institute of Nuclear Medicine and Allied Sciences (NINMAS) for lower limb lymphoscintigraphy in the years 2022.2023. All pertinent facts and data were taken from the medical records. An average dosage of 1+1 mCi of 99m Technetium- (99m Tc) labeled nanocolloid was injected into the web spaces of the first and second toes of each foot. Spot views and delayed whole-body sweep images were acquired on time. Dual head gamma camera images were collected anterior and posteriorly. The assessment of the injection site, primary lymphatic channels, collateral vessels, dermal backflow, and quantity and strength of radiotracer absorption of the lymph nodes were all included in the qualitative image interpretation process. Result: The mean age was 10.14 years ± 5.37 with age ranging from 0-17 years. In 48/53 cases (90.6%) of clinically positive leg swelling were found to be positive for lymphedema on lymphoscintigraphy, where 16 patients had unilateral and 33 patients had bilateral. Remaining 05/53 (9.4%) were scintigraphically normal. Among the positive patients, 48 cases (98%) were primary lymphedema and only one (2%) had secondary cause, who was a case of bilateral lymphedema, Grade-I in left lower limb (LLL) and Grade-III in right lower limb (RLL). Conclusion: Lymphoscintigraphy, a non-invasive, straightforward imaging modality, is very helpful in precisely documenting and grading lymphedema for finding the etiology and subsequent treatment plans in patients with leg swelling. It also serves as a means of functional evaluation of lymphatic channels. Additionally, it can be crucial for individuals undergoing surgical procedures to relieve clinical symptoms early on in their recovery. Bangladesh J. Nuclear Med. 27(1): 75-80, 2024

The development of molecular imaging agents targeting epidermal growth factor receptor (EGFR) with L858R mutation may help with the selection of non-small cell lung carcinoma (NSCLCL) patients who may benefit from EFGR tyrosine kinase inhibitor (TKI) therapy. In this study, we developed 99mTc STHHYYP-GHEG-ECGK-tetramethylrhodamine (STHHYYP-ECGK-TAMRA) to target EGFR with L858R mutation in NSCLC tumors and verified its probability as a molecular imaging agent. Fmoc solid-phase peptide synthesis was used to synthesize STHHYYP-ECGKTAMRA. 99mTc labelled STHHYYP-ECGK-TAMRA was prepared. Gamma imaging, fluorescent imaging and biodistribution were performed in murine models bearing NCI-H1975 and NCI-H1650 tumors. The binding affinity value (Kd) of 99mTc STHHYYP-ECGK-TAMRA was estimated to be 130.6 ± 29.2 nM in NCI-H1975 cells. The gamma camera images showed a substantial uptake of 99mTc STHHYYP-ECGK-TAMRA in the NCI-H1975 tumor. The % injected dose/gram of the NCI-H1975 tumor tissue was 2.77 ± 0.70 and 3.48 ± 1.01 at 1 and 3 h, respectively. Specific binding of 99mTc STHHYYP-ECGK-TAMRA to L858R-mutated EGFRpositive NCI-H1975 cells and tumors was demonstrated in in vivo and in vitro studies. The results suggest that 99mTc STHHYYP-ECGK-TAMRA is a good candidate agent for dualmodality imaging targeting EGFR with L858R mutation.

BackgroundThe administration of a 166Ho scout dose is available as an alternative to 99mTc particles for pre-treatment imaging in Selective Internal Radiation Therapy (SIRT). It has been reported that the 166Ho scout dose may be more accurate for the prediction of microsphere distribution and the associated therapy planning. The aim of the current study is to compare the scintigraphic imaging characteristics of both isotopes, considering the objectives of the pre-treatment imaging using clinically geared phantoms.MethodsPlanar and SPECT/CT images were obtained using a NEMA image quality phantom in different phantom setups and another body-shaped phantom with several inserts. The influence of collimator type, count statistics, dead time effects, isotope properties and patient obesity on spatial resolution, contrast recovery and the detectability of small activity accumulations was investigated. Furthermore, the effects of the imaging characteristics on personalized dosimetry are discussed.ResultsThe images with 99mTc showed up to 3 mm better spatial resolution, up to two times higher contrast recovery and significantly lower image noise than those with 166Ho. The contrast-to-noise ratio was up to five times higher for 99mTc than for 166Ho. Only when using 99mTc all activity-filled spheres could be distinguished from the activity-filled background. The measurements mimicking an obese patient resulted in a degraded image quality for both isotopes.ConclusionsOur measurements demonstrate better scintigraphic imaging properties for 99mTc compared to 166Ho in terms of spatial resolution, contrast recovery, image noise, and lesion detectability. While the 166Ho scout dose promises better prediction of the microsphere distribution, it is important to consider the inferior imaging characteristics of 166Ho, which may affect individualized treatment planning in SIRT.

Gamma camera imaging, including single photon emission computed tomography (SPECT), is crucial for research, diagnostics, and radionuclide therapy. Gamma cameras are predominantly based on arrays of photon multipliers tubes (PMTs) that read out NaI(Tl) scintillation crystals. In this way, standard gamma cameras can localize ɣ-rays with energies typically ranging from 30 to 360keV. In the last decade, there has been an increasing interest towards gamma imaging outside this conventional clinical energy range, for example, for theragnostic applications and preclinical multi-isotope positron emission tomography (PET) and PET-SPECT. However, standard gamma cameras are typically equipped with 9.5mm thick NaI(Tl) crystals which can result in limited sensitivity for these higher energies. Here we investigate to what extent thicker scintillators can improve the photopeak sensitivity for higher energy isotopes while attempting to maintain spatial resolution. Using Monte Carlo simulations, we analyzed multiple PMT-based configurations of gamma detectors with monolithic NaI (Tl) crystals of 20 and 40mm thickness. Optimized light guide thickness together with 2-inch round, 3-inch round, 60×60 mm2 square, and 76×76 mm2 square PMTs were tested. For each setup, we assessed photopeak sensitivity, energy resolution, spatial, and depth-of-interaction (DoI) resolution for conventional (140keV) and high (511keV) energy ɣ using a maximum-likelihood algorithm. These metrics were compared to those of a "standard" 9.5mm-thick crystal detector with 3-inch round PMTs. Estimated photopeak sensitivities for 511keV were 27% and 53% for 20 and 40mm thick scintillators, which is respectively, 2.2 and 4.4 times higher than for 9.5mm thickness. In most cases, energy resolution benefits from using square PMTs instead of round ones, regardless of their size. Lateral and DoI spatial resolution are best for smaller PMTs (2-inch round and 60×60 mm2 square) which outperform the more cost-effective larger PMT setups (3-inch round and 76×76 mm2 square), while PMT layout and shape have negligible (<10%) effect on resolution. Best spatial resolution was obtained with 60×60 mm2 PMTs; for 140keV, lateral resolution was 3.5mm irrespective of scintillator thickness, improving to 2.8 and 2.9mm for 511keV with 20 and 40mm thick crystals, respectively. Using the 3-inch round PMTs, lateral resolutions of 4.5 and 3.9mm for 140keV and of 3.5 and 3.7mm for 511keV were obtained with 20 and 40mm thick crystals respectively, indicating a moderate performance degradation compared to the 3.5 and 2.9mm resolution obtained by the standard detector for 140 and 511keV. Additionally, DoI resolution for 511keV was 7.0 and 5.6mm with 20 and 40mm crystals using 60×60 mm2 square PMTs, while with 3-inch round PMTs 12.1 and 5.9mm were obtained. Depending on PMT size and shape, the use of thicker scintillator crystals can substantially improve detector sensitivity at high gamma energies, while spatial resolution is slightly improved or mildly degraded compared to standard crystals.