Distributions of perfusion and lung water

We investigated the feasibility of using ¹²³I-iodoantipyrine (¹²³I-IAP) and ^99mTc-labeled macroaggregated albumin (^99mTc-MAA) to describe and compare the distributions of perfusion and water content in lung injuries. These radiopharmaceuticals were administered to 9 rabbits, 5 control and 4 with lung injuries. Isolated lungs were imaged by a scintillation γ camera. The distribution of ¹²³I-IAP outlined the entire lung mass whereas perfusion defect in the distribution of ^99mTc-MAA was seen clearly in the case of severe lung injury.     

Biological distribution of 99mTc-labeled YIGSR and IKVAV laminin peptides in rodents: 99mTc-IKVAV peptide localizes to the lung

Two laminin-derived peptides containing either YIGSR or IKVAV (single amino acid code) sequences were radiolabeled with ^99mTc and their biological distribution evaluated in rodents. Both ^99mTC-peptides cleared rapidly from the circulation though the kidney, and to a lesser extent, through the liver. ^99mTC-YIGSR peptide did not accumulate in any organ examined in normal, tumored, and emphysemic mice. The ^99mTc-IKVAV peptide localized within 10 min to the lung of normal animals, resulting in lung-to-blood ratios of approximately 23:1. The ^99mTc-IKVAV peptide localized to lung after submicron filtration and after intraperitoneal injection, suggesting that particulates do not play a major role in localization. Pre-incubation of ^99mTc-IKVAV peptide in whole blood decreased lung localization, suggesting that margination of radiolabeled blood cells does not play a major role in the lung localization. When ^99mTc-IKVAV was injected into mice with tumored lungs (melanoma), the lung uptake was markedly increased (up to 20% injected dose higher than control lungs) at all time points examined (10, 30, and 120 min). When ^99mTc-IKVAV was injected into mice with genetic emphysema, the lung uptake was markedly decreased at all time points. The localization of the ^99mTc-IKVAV-containing peptide to the lung is consistent with a receptor-based mechanism.     

Comparison of relative renal functions calculated with 99mTc-DTPA and 99mTc-DMSA for kidney patients of wide age ranges

Renal scintigraphy is an imaging method that uses small amount of radioactive materials called radiotracers, a Gamma camera and a computer to evaluate kidney functions and its anatomy. The present work reports the comparison of the relative renal functions (RRF) calculated with technetium-99m dimercaptosuccinic acid (^99mTc‑DMSA) and technetium-99m diethylenetriaminepentaacetic acid (^99mTc‑DTPA) for kidney patients of ages between 5 months and 71 years. A total of 50 patients including 29 male and 21 female has been selected and studied for renography. The mean RRFs have been found to be 52.68 ± 23.63% and 47.32 ± 23.63% respectively for the left and right kidneys with ^99mTc-DMSA measurement. With ^99mTc-DTPA the values are 52.74 ± 23.54% and 47.26 ± 23.54% for the same. In bivariate correlation analysis, a significant positive correlation (r = 0.996, P < .001) has been found between the RRFs calculated with the two methods. Following the patients’ diagnosis, in ANOVA test, no difference has been found between the RRFs calculated for the left and right kidneys. In Bland-Altman plots, the mean difference between the two methods has been found to be 0.1 and the correlation limit lies between −4.3 and 4.2. According to the result obtained in the present work, both the ^99mTc-DMSA and ^99mTc-DTPA scanning methods provide almost the same RRF values. It is, therefore, always not necessary to calculate the RRFs with both the methods. This study suggests that ^99mTc-DMSA may be the primary choice for the evaluation of RRF, but if the glomerular filtration rate (GFR) and renogram curve are required, ^99mTc-DTPA can be the obvious selection.     

Synthesis, characterization, conformational analysis of a cyclic conjugated octreotate peptide and biological evaluation of 99mTc-HYNIC-His3-Octreotate as novel tracer for the imaging of somatostatin receptor-positive tumors

Peptides are attracting increasing interest in nuclear oncology for targeted tumor diagnosis and therapy. We therefore synthesized new cyclic octapeptides conjugated with HYNIC by Fmoc solid-phase peptide synthesis. These were purified and analyzed by RP-HPLC, MALDI mass, ¹H NMR, ¹³C NMR, HSQC, HMBC, COSY and IR spectroscopy. Conformational analysis of the peptides was performed by circular dichroism spectroscopy, in pure water and trifluoroethanol–water (1:1), revealed the presence of strong secondary structural features like β-sheet and random coils. Labeling was performed with ^99mTc using Tricine and EDDA as coligands by SnCl₂ method to get products with excellent radiochemical purity >99.5 %. Metabolic stability analysis did not show any evidence of breaking of the labeled compounds and formation of free ^99mTc. Internalization studies were done and IC₅₀ values were determined in somatostatin receptor-expressing C6 glioma cell line and rat brain cortex membrane, and the results compared with HYNIC-TOC as standard. The IC₅₀ values of ^99mTc-HYNIC-His³-Octreotate (21 ± 0.93 nM) and ^99mTc-HYNIC-TOC (2.87 ± 0.41 nM) proved to be comparable. Biodistribution and image study on normal rat under gamma camera showed very high uptake in kidney and urine, indicating kidney as primary organ for metabolism and route of excretion. Biodistribution and image study on rats bearing C6 glioma tumor found high uptake in tumor (1.27 ± 0.15) and pancreas (1.71 ± 0.03). Using these findings, new derivatives can be prepared to develop ^99mTc radiopharmaceuticals for imaging somatostatin receptor-positive tumors.     

Metastatic melanoma imaging using a novel Tc-99m-labeled lactam-cyclized alpha-MSH peptide

The purpose of this study was to determine the metastatic melanoma imaging property of ^99mTc(EDDA)-HYNIC-Aoc-Nle-CycMSH_hex {hydrazinonicotinamide-8-aminooctanoic acid-Nle-c[Asp-His-DPhe-Arg-Trp-Lys]-CONH₂}. HYNIC-Aoc-Nle-CycMSH_hex was synthesized using fluorenylmethyloxy carbonyl (Fmoc) chemistry. The IC₅₀ value of HYNIC-Aoc-Nle-CycMSH_hex was 0.78?±?0.13?nM for B16/F10 melanoma cells. ^99mTc(EDDA)-HYNIC-Aoc-Nle-CycMSH_hex displayed significantly higher uptake (14.26?±?2.74 and 10.45?±?2.31%?ID/g) in B16/F10 metastatic melanoma-bearing lung than that in normal lung (0.90?±?0.15 and 0.53?±?0.14%?ID/g) at 2 and 4?h post-injection, respectively. B16/F10 pulmonary metastatic melanoma lesions were clearly visualized by SPECT/CT using ^99mTc(EDDA)-HYNIC-Aoc-Nle-CycMSH_hex as an imaging probe at 2?h post-injection, underscoring its potential as an imaging probe for metastatic melanoma detection.     

Technetium-99m labeled monoclonal antibodies: Evaluation of reducing agents

We have evaluated five compounds, stannous chloride (SnCl₂), 2-mercaptoethanol (2-ME), dithiothreitol (DTT), dithioerythritol (DTE), and ascorbic acid (AA) to reduce monoclonal antibody MoAb (disulfide groups and compared their efficacy for labeling MoAbs with ^99mTc. The reduction of ^99mTc with dithionite at pH 11 was nearly quantitative. The use of AA, at a molar ratio of 3500:1, for three IgG and three IgM antibodies examined, gave a labeling efficiency greater than 95%. Hence no purification was needed. The immunospecificity of AA preparations determined by specific antigen assay was 84 ± 1% for an IgM and 82.6 ± 1.1% for an IgG, highest among all agents tested. The stability of the tracer was evaluated by challenging the product with such ^99mTc avid agents as cysteine, DTPA, and human serum albumin. By HPLC analysis, no ^99mTc was transchelated using chelating agent to protein molar ratios as high as 500:1. In two separate groups of five mice each, the liver uptake at 4 h post injection averaged 6.8 ± 2.9% per gram for ¹²⁵I-TNT-1 (IgG) and 6 ± 5.1% per gram for the same MoAb labeled with ^99mTc using AA. The AA technique promises to label antibodies with ^99mTc and perhaps with ¹⁸⁶Re, by a simple “kit” procedure.     

Technetium-99m-labeled platelets: Comparison of labeling with a new lipid-soluble Sn(II)-mercaptopyridine-N-oxide and 99mTc-HMPAO

Platelets pretinned with a neutral Sn(II)-2-mercaptopyridme-N-oxide (SN-MPO) were labeled with ^99mTc and compared to those labeled with ^99mTc-HMPAO. The conditions of labeling platelets, e.g. concentrations of platelets and Sn(II)-MPO, ^99mTc in ACD-saline or ACD-plasma media, pH and incubation time, were optimized using canine platelets. Moderate labeling efficiency was obtained with 20 μg of tin(II) chloride and 30 min incubation with Sn-MPO and pertechnetate. The viability of labeled platelets was determined by platelet recovery and platelet survival times in Beagle dogs. The labeling efficiency with platelets from 43 mL of blood was 62.8 ± 7.6%. The platelet recovery was 35.7 ± 5.0% and exponential survival time was 34.6 ± 3.1 h compared to 43.3 ± 12.0% and 29.5 ± 3.3 h for ^99mTc-HMPAO-labeled platelets. These values were significantly (P < 0.01) lower than ¹¹¹In-labeled platelets. Biodistribution in dogs indicates lower retention in blood, spleen and liver after some initial ^99mTc excretion in urine. The platelet deposition with ^99mTc platelets (Sn-MPO method) on polyurethane angio-catheters was similar to ^99mTc-HMPAO-labeled platelets. This study indicates that the platelets could be successfully labeled with pertechnetate in a cost-effective manner for the evaluation of thromboembolic complications.     

Labelling of leukocytes with 99mTc-HMPAO for scintigraphy of inflammatory lesions and abscesses

A simplified and efficient procedure for ^99mTc-HMPAO-labelling of leukocytes is described. For this purpose, the pH and concentration of the ^99mTc-HMPAO preparation was modified. Leukocytes were isolated from a 20 mL mixture of patient blood, 5 mL ACD and 0.8 mL methylcellulose after 1 h sedimentation of erythrocytes and centrifugation (at 400 g) of the obtained plasma layer. Simultaneously, ^99mTc-HMPAO was prepared (one single-dose kit for two patients) by adding 2.2 mL ^99mTc-generator eluate and, after 10 min, 0.3 mL of phosphate buffer to lower the pH to 7. The isolated WBCs were then labelled by the addition of 1-1.2 mL of ^99mTc-HMPAO solution and incubated for 20 min. The unbound tracer was then discarded, the labelled WBC washed and finally resuspended in autologous cell-free plasma. Leukocytes labelled by this procedure were used for scintigraphic localization of inflammatory lesions and abscesses in the gastro-intestinal tract.The labelling efficiency was 60 ± 9%, with a separation yield of 55 ± 11%.     

Distribution of intrapleural and intravenous Corynebacterium parvum in humans; 99mTc−, and 131I-labeled bacteria

Summary The distribution of Corynebacterium parvum labeled with ¹³¹iodine or ^99mtechnetium was studied in 17 patients with bronchogenic carcinoma. The labeled bacteria were given intravenously or intrapleurally and monitored by whole-body gamma tracking and samples of blood and urine. Even though the rate of physical decay is quite different for ¹³¹iodine and ^99mtechnetium, the tracking time of labeled bacteria was limited to 24 h after injection for both radioactive isotopes. Technetium labeling was preferred because of greater imaging resolution and less radiation dose to the patient. Following intravenous administration, labeled C. parvum was found predominantly in the liver and spleen, and in a lesser amount in the lung. Radioactivity was confined to the pleural cavity after intrapleural injection. These results suggest the combined intravenous and intrapleural route of adjuvant immunosupportive agents such as C. parvum for operable lung cancer patients.     

Technetium-99m-labeled proteins for imaging inflammatory foci

Polyclonal human IgG (IgG), antinuclear antibody (TNT-1), and human serum albumin (HSA), were labeled with ^99mTc by a method recently developed in our laboratory, and administered i.v., each to a separate group of five mice, bearing inflammatory foci induced by an i.m. injection of 40μL turpentine or 5 × 10⁸E. coli and 5 × 10⁸ Entercocci. TNT-1 labeled with ¹²⁵I served as a control and ⁶⁷Ga-citrate as a “gold standard”. At 4 or 24 h post injection, animals were imaged and sacrificed for tissue distribution studies. At 4 h in the turpentine group, the abscess-to-muscle ratios were: ⁶⁷Ga, 4.8 ± 2.1, ¹²⁵I-TNT-1, 4.3 ± 1; ^99mTc-TNT-1, 3.5 ± 1.8; ^99mTc-IgG, 3.9 ± 0.6; and ^99mTc-HSA, 4.3± 1. In the microorganism group, these ratios were 2.6 ± 0.6, 3.3 ± 0.5, 3.4 ± 0.08, 3± 1.1 and 4.1 ± 0.6, respectively. Autoradiographic examination of infected tissues indicated that leakage of labeled proteins into interstitial space due to increased capillary permeability may be one of the major mechanisms of uptake.     

Comparative studies of radiocitrates in oncological models—I. 99mTc citrate and 67Ga citrate uptake by EMT-6 tumors in mice

⁶⁷Ga citrate and ^99mTc citrate (Solcocitran) were injected sequentially, with an interval of 48 h, into Balb/c mice bearing transplanted EMT-6 tumors. Tissue distributions of ⁶⁷Ga and ^99mTe were measured simultaneously at intervals of 1, 3, 5 and 8 h after injection of the ^99mTc citrate (49, 51, 53 and 56 h after ⁶⁷Ga citrate). Maximal tumor:blood ratios for ^99mGa and ^99mTc were 13.8 ± 3.2 and 4.0 ± 1.0 respectively, both occurring at the final period. The maximum tumor index (T.I. = T:B x % dose/g) for ⁶⁷Ga was 71 ± 23% 56 h after injection, and for Tc was 13 ± 12% 1 h after injection. Liver, kidney and spleen had equal or higher concentrations of radioactivity than tumor for either radiotracer. The somewhat higher tumor:blood ratio for ⁶⁷Ga citrate was offset by the time required for this optimum to be reached. Alternatively, the best ^99mTc citrate tumor:blood ratios were attained within 8 h, with less liver and gut radioactivity. These data fall within the range of results from other clinical and animal model studies of ⁶⁷Ga citrate and Tc citrate. In view of the radiation dose, the inconvenience of the 48–72 h wait, and the cost of ⁶⁷Ga, and because neither radiopharmaceutical is tumor specific, ^99mTc citrate may have a place in early oncological screening. The results are discussed as part of a comprehensive review of the ^99mTc citrate literature.     

Technetium-99m monoclonal antibody fragment (FAb) scintigraphy in the evaluation of small cell lung cancer: a preliminary report

Small cell lung cancer (SCC) has the most rapid growth rate of the four cell types and metastasizes early. Present imaging modalities for staging include chest x-ray, CT, MRI and bone scans. In this preliminary study, we assessed the clinical role of ^99mTc-monoclonal antibody (MOAB) scintigraphy in five patients with histologically proven SCC. Each patient was infused with 20–30 mCi of ^99mTc labeled Fab fragment of MOAB (NR-LU-10, NeoRx, Seattle, Wash.). Total body simultaneous anterior and posterior images were obtained 14–16 h post injection. SPECT images of the chest were obtained through a 360 ° rotation of the gamma camera and recorded on a 62 × 64 × 16 matrix. Images (1.2cm thick) were generated in transaxial, sagittal and coronal views.Fourteen of fifteen chest lesions detected by CT were confirmed by ^99mTc MOAB scintigraphy. Scintigraphy detected one additional chest lesion not seen by CT. Scintigraphy failed to detect a brain lesion (2 cm), a chest lesion, and two adrenal lesions, all of which were seen by CT. In one patient with multiple (more than 10) lesions in the liver, both scintigraphy and CT detected all lesions. Three spine lesions seen on ^99mTc MDP scan and positive for metastasis on MRI concentrated ^99mTc MOAB, but two rib lesions seen on ^99mTc MDP bone scan did not concentrate ^99mTc MOAB. It is concluded from these preliminary results that the potential usefulness of ^99mTc MOAB scintigraphy as a complementary imaging modality in the staging of small cell lung cancer should be investigated further.     

The glomerular filtration rate,effective renal plasma flow,and renal blood flow in the adult male chacma baboon (Papio ursinus)

Abstract: The radionuclide determination of glomerular filtration rate (GFR) and effective renal plasma flow (ERPF) has been validated in man, but not in the primate. GFR, ERPF, and renal blood flow (RBF) were measured in a group of 12 adult male chacma baboons using radiopharmaceuticals. GFR was determined using ^99mtechnetium-labelled diethylenetriamine-pentacetic acid. ERPF was measured with ¹³¹iodine-labelled hippuran. RBF, body surface area, and kidney weights were calculated using standard formulae. GFR was 49 ± 11 ml/min and ERPF was 237.9 ± 54.2 ml/min. Calculated RBF was 430.7 ± 111.9 ml/min and 507.4 ± 138.4 ml/min/100g of renal tissue. The results are in agreement with those obtained using more laborious nonradioisotopic techniques such as para-aminohippurate (PAH) and creatinine clearance and could serve as baseline normal values in the adult male chacma baboon.     

Synthesis of 99mTc-labeled 2-Mercaptobenzimidazole as a novel radiotracer to diagnose tumor hypoxia

Discovery of ^99mTc-labeled imidazole derivatives as a potential radiotracer for hypoxic tumor imaging is considered to be of great interest because of non-invasive detection capabilities. 2-Mercaptobenzimidazole (2-MBI) was successfully synthesized, characterized and radiolabeled with [^99mTc (CO)₃(H₂O)₃]⁺ intermediate to form ^99mTc-2-MBI complex with radiochemical purity of ≥95% yield as observed by instant-thin layer chromatography (ITLC) and radio-high performance liquid chromatography (radio-HPLC). The ^99mTc-2-MBI complex was observed to be stable in saline and serum with no noticeable decomposition at room temperature and 37 °C, respectively, over a time period of 24 h. Biodistribution results in Balb/c mice bearing S180 tumor show that ^99mTc-2-MBI highly internalized in tumor tissue, also possess preferably high tumor/muscle and tumor/blood ratios 4.14 ± 0.77 and 3.91 ± 0.63, respectively at 24 h incubation. Scintigraphic imaging study shows ^99mTc-2-MBI is visibly accumulated in hypoxic tumor tissue, suggesting it would be a promising radiotracer for early stage diagnosis of tumor hypoxia.     

Tissue distribution of 131I radiolabeled transferrin in the athymic nude mouse: Localization of a human colon adenocarcinoma HT-29 xenograft

The tissue distribution of ¹³¹I-transferrin (¹³¹I-Tf) was studied in athymic nude mice having s.c. human colonic adenocarcinoma HT-29 xenografts. Four days after ¹³¹I-Tf injection, the ¹³¹I specific activity measured in the HT-29 tumor, i.e. amount of radioactivity per gram of fresh tissue, represented 0.31 ± 0.09% of the injected radioactivity and was 1.90 fold more than that measured in the murine colon (P < 0.05). After correction for intravascular ¹³¹I-Tf as estimated by means of ^99mTc-Sn in vivo labeling of red blood cells, the ¹³¹I specific activity observed in the HT-29 tumor was 7.21 fold more than that observed in the murine colon. This subtracting method enabled us to localize a HT-29 tumor xenograft by γ scintigraphy of the entire animal and demonstrated that ¹³¹I-Tf could be a non-specific but potent marker for human colon cancer.     

Treatment of human lung carcinoma xenografts with a combination of 131I-labelled monoclonal antibody Po66 and doxorubicin

 Po66, a mouse monoclonal antibody, is directed against an intracytoplasmic antigen present in human lung squamous cell carcinoma cells. In previous work it was found that the co-administration of ¹²⁵I-radiolabelled Po66 and doxorubicin strongly enhanced the uptake of radioactivity by the tumour. The present-work was designed to evaluate, in a tumour-bearing mouse model of lung carcinoma, the ability of ¹³¹I-labelled Po66 to retard tumour growth when injected alone, or in combination with doxorubicin (8 mg kg ^– 1 at 1-week intervals). A single dose of 550 μCi ¹³¹I-Po66 alone had no effect on tumour growth, whereas three fractionated doses of 250 μCi ¹³¹I-Po66 decreased it over two doubling times from 14.5±1.5 days for untreated control mice to 24.8±2.7 days. Mice treated with doxorubicin alone had a double tumour doubling time of 22.6±4.9 days, compared to 35.2±2.9 days (1.55-fold increase) in mice treated with doxorubicin and a single dose of 550 μ Ci ¹³¹I-Po66. Doxorubicin combined with three fractionated doses of 250 μCi ¹³¹I-Po66 provoked a twofold decrease in tumour growth compared to mice treated with doxorubicin alone. The administration of fractionated doses of ¹³¹I-Po66 simultaneously with doxorubicin resulted in a highly delayed mortality, which was not observed when ¹³¹I-Po66 was administered after doxorubicin. Thus, in a non-small-cell lung tumour model, a ¹³¹I-radiolabelled monoclonal antibody, directed against an intracellular antigen, significantly potentiated the effect of chemotherapy. Such a therapeutic approach could be used as an adjuvant therapy and improve the effect of chemotherapy on distant small metastases. Received: 20 June 1996 / Accepted: 3 October 1996     

Die Verteilung von Technetium-99m und Jod-131 in der Magenschleimhaut

Zusammenfassung Es wird eine Methode zur Mikrohistoautoradiographie wasserlöslicher Isotope beschrieben und an der Verteilung von ¹³¹J sowie ^99mTc in der Magenschleimhaut demonstriert.Auf Grund mikrohistoautoradiographischer Untersuchungen wird gezeigt, daß Technetium-99m selektiv durch die Belegzellen der Magenschleimhaut ausgeschieden wird. Jod-131 wird demgegenüber von den Hauptzellen des Oberflächenepithels der Magenschleimhaut sezerniert. Die selektive Anreicherung von Technetium-99m in den Belegzellen macht wahrscheinlich, daß Technetium in den Belegzellen eine unmittelbare metabolisch gesteuerte Ausscheidung erfährt. Autoradiographisch wird somit in den Schleimhautzellen nach Gabe von Technetium fast die gesamte Aktivität im Fundus und nur wenig im Antrum gesehen. Die Aktivitätsverteilung in den Lymphgefäßen und Kapillaren der Submucosa ist in Antrum und Fundus gleich.Die Ergebnisse der quantitativen Bestimmung der Aktivitätsverteilung in den verschiedenen Magenabschnitten in Abhängigkeit von der Zeit geben eine gute Bestätigung der mikrohistoautoradiographischen Befunde.

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Distribution of Technetium-99m and Jodine-131 in the gastric mucosaA technique to determine microhistoautoradiographical distribution of water soluble isotopes

Summary A method for microhistoautoradiographic examination of water soluble radioactive isotopes and its use in studying the distribution of ¹³¹J and ^99mTc in the gastric mucosa is described.It is shown that technetium is selectively secreted by the parietal cells of the gastric mucosa. In contrast ¹³¹J is secreted by the chief and mucosal cells. The selective accumulation of ^99mTc in the parietal cells suggests that technetium is secreted via a metabolic pathway. The main activity of ^99mTc is observed in the gastric fundus. The distribution of both isotopes within the submucous lymphoid and capillary vessels of the antrum and fundus is equal.The microhistoautoradiographic results in the different parts of the stomach are confirmed by quantitative scintillation counting.

     

3D image-based dosimetry for Yttrium-90 radioembolization of hepatocellular carcinoma: Impact of imaging method on absorbed dose estimates

BackgroundTo improve therapy outcome of Yttrium-90 selective internal radiation therapy (⁹⁰Y SIRT), patient-specific post-therapeutic dosimetry is required. For this purpose, various dosimetric approaches based on different available imaging data have been reported. The aim of this work was to compare post-therapeutic 3D absorbed dose images using Technetium-99m (^99mTc) MAA SPECT/CT, Yttrium-90 (⁹⁰Y) bremsstrahlung (BRS) SPECT/CT, and ⁹⁰Y PET/CT.MethodsTen SIRTs of nine patients with unresectable hepatocellular carcinoma (HCC) were investigated. The ^99mTc SPECT/CT data, obtained from ^99mTc-MAA-based treatment simulation prior to ⁹⁰Y SIRT, were scaled with the administered ⁹⁰Y therapy activity. 3D absorbed dose images were generated by dose kernel convolution with scaled ^99mTc/⁹⁰Y SPECT/CT, ⁹⁰Y BRS SPECT/CT, and ⁹⁰Y PET/CT data of each patient. Absorbed dose estimates in tumor and healthy liver tissue obtained using the two SPECT/CT methods were compared against ⁹⁰Y PET/CT.ResultsThe percentage deviation of tumor absorbed dose estimates from ⁹⁰Y PET/CT values was on average −2 ± 18% for scaled ^99mTc/⁹⁰Y SPECT/CT, whereas estimates from ⁹⁰Y BRS SPECT/CT differed on average by −50 ± 13%. For healthy liver absorbed dose estimates, all three imaging methods revealed comparable values.ConclusionThe quantification capabilities of the imaging data influence ⁹⁰Y SIRT tumor dosimetry, while healthy liver absorbed dose values were comparable for all investigated imaging data. When no ⁹⁰Y PET/CT image data are available, the proposed scaled ^99mTc/⁹⁰Y SPECT/CT dosimetry method was found to be more appropriate for HCC tumor dosimetry than ⁹⁰Y BRS SPECT/CT based dosimetry.     

Comparing carbon sequestration in temperate freshwater wetland communities

High productivity and waterlogged conditions make many freshwater wetlands significant carbon sinks. Most wetland carbon studies focus on boreal peatlands, however, with less attention paid to other climates and to the effects of hydrogeomorphic settings and the importance of wetland vegetation communities on carbon sequestration. This study compares six temperate wetland communities in Ohio that belong to two distinct hydrogeomorphic types: an isolated depressional wetland site connected to the groundwater table, and a riverine flow‐through wetland site that receives water from an agricultural watershed. Three cores were extracted in each community and analyzed for total carbon content to determine the soil carbon pool. Sequestration rates were determined by radiometric dating with ¹³⁷Cs and ²¹⁰Pb on a set of composite cores extracted in each of the six communities. Cores were also extracted in uplands adjacent to the wetlands at each site. Wetland communities had accretion rates ranging from 3.0 to 6.2 mm yr^?1. The depressional wetland sites had higher (P < 0.001) organic content (146 ± 4.2 gC kg^?1) and lower (P < 0.001) bulk density (0.55 ± 0.01 Mg m^?3) than the riverine ones (50.1 ± 6.9 gC kg^?1 and 0.74 ± 0.06 Mg m^?3). The soil carbon was 98–99% organic in the isolated depressional wetland communities and 85–98% organic in the riverine ones. The depressional wetland communities sequestered 317 ± 93 gC m^?2 yr^?1, more (P < 0.01) than the riverine communities that sequestered 140 ± 16 gC m^?2 yr^?1. The highest sequestration rate was found in the Quercus palustris forested wetland community (473 gC m^?2 yr^?1), while the wetland community dominated by water lotus (Nelumbo lutea) was the most efficient of the riverine communities, sequestering 160 gC m^?2 yr^?1. These differences in sequestration suggest the importance of addressing wetland types and communities in more detail when assessing the role of wetlands as carbon sequestering systems in global carbon budgets.     

Bioimpedance for severe obesity: comparing research methods for total body water and resting energy expenditure

Objective: As the acceptance of surgical procedures for weight loss in morbid obesity is increasing, clinically useful baseline and follow‐up measures of total body water (TBW) and resting energy expenditure (REE) are important. Research methods such as deuterium (D²O) dilution and metabolic carts are problematic in the clinical setting. We compared bioimpedance analysis (BIA) predicted (Tanita TBF‐310) and measured TBW and REE. Methods and Procedures: Forty‐two paired presurgery studies were completed using BIA and D²O in patients with BMI (mean ± s.d.) 50.2 ± 8.8 kg/m² for TBW, and 30 patients with BMI 51.0 ± 13 kg/m² completed paired determinations of REE with metabolic carts and the Tanita balance with weight, height, sex, and age modifiers. Regression analysis and Bland‐Altman plots were applied. Results: When regression analysis was completed for TBW, regression line was consistent with the identity line “y = x.” The intercept was not different from 0 (95% confidence interval ?2.5 ± 7.0). The slope of the line was not different from 1.0 ± 0.1. The measured TBW 51.2 ± 10.1 l had a correlation with the predicted 49.5 ± 11.27 l of 0.92. There also was no significant difference (P = 0.33) between predicted (2,316 ± 559 kcal/day) and measured REE (2,383 ± 576 kcal/day);δ 66.7 ± 273 kcal/day. The two measures were highly correlated (r = 0.88) with no bias detected. Discussion: These observations support the use of the BIA system calibration in subjects with severe obesity. Without the use of complex, costly equipment and invasive procedures, BIA measurements can easily be obtained in clinical practice to monitor patient responses to treatment.