Population dynamics and growth of perch in a small, humic lake over a 20-year period — importance of abiotic and biotic factors

Peer reviewe

Food Web Responses to Artificial Mixing in a Small Boreal Lake

In order to simulate food web responses of small boreal lakes to changes in thermal stratification due to global warming, a 4 year whole-lake manipulation experiment was performed. Within that time, period lake mixing was intensified artificially during two successive summers. Complementary data from a nearby lake of similar size and basic water chemistry were used as a reference. Phytoplankton biomass and chlorophyll a did not respond to the greater mixing depth but an increase was observed in the proportional abundance of diatoms, and the proportional abundance of cryptophytes also increased immediately after the onset of mixing. Obligate anoxic green sulphur bacteria vanished at the onset of mixing but gradually recovered after re-establishment of hypolimnetic anoxic conditions. No major effect on crustacean zooplankton was found, but their diversity increased in the metalimnion. During the mixing, the density of rotifers declined but protozoan density increased in the hypolimnion. Littoral benthic invertebrate density increased during the mixing due to Ephemeroptera, Asellus aquaticus and Chironomidae, whereas the density of Chaoborus larvae declined during mixing and lower densities were still recorded one year after the treatment. No structural changes in fish community were found although gillnet catches increased after the onset of the study. The early growth of perch (Perca fluviatilis) increased compared to the years before the mixing and in comparison to the reference lake, suggesting improved food availability in the experimental lake. Although several food web responses to the greater mixing depth were found, their persistence and ecological significance were strongly dependent on the extent of the disturbance. To better understand the impacts of wind stress on small lakes, long term whole-lake experiments are needed.Peer reviewe

Comparison of standardized uptake values between Tc-99m-HDP SPECT/CT and F-18-NaF PET/CT in bone metastases of breast and prostate cancer

Background: Despite recent technological advances allowing for quantitative single-photon emission computed tomography (SPECT), quantitative SPECT has not been widely used in the clinical practice. The aim of this study is to evaluate the feasibility of quantitative SPECT for measuring metastatic bone uptake in breast and prostate cancer by comparing standard uptake values (SUVs) measured with Tc-99m-HDP SPECT/CT and F-18-NaF PET/CT.Methods: Twenty-six breast and 27 prostate cancer patients at high risk of bone metastases underwent both Tc-99m-HDP SPECT/CT and F-18-NaF PET/CT within 14days of each other. The SPECT and PET data were reconstructed using ordered-subset expectation-maximization algorithms achieving quantitative images. Metastatic and benign skeletal lesions visible in both data sets were identified, and their maximum, peak, and mean SUVs (SUVmax, SUVpeak, and SUVmean) were determined. SUV ratios (SUVRs) between the lesions and adjacent normal appearing bone were also calculated. Linear regression was used to evaluate the correlations between the SUVs of SPECT and PET and Bland-Altman plots to evaluate the differences between the SUVs and SUVRs of SPECT and PET.Results: A total of 231 skeletal lesions, 129 metastatic and 102 benign, were analyzed. All three SUV measures correlated very strongly between SPECT and PET (R(2)0.80, pConclusion: The strong correlation between SUVs and similar SUVRs of Tc-99m-HDP SPECT/CT and F-18-NaF PET/CT demonstrate that SPECT is an applicable tool for clinical quantification of bone metabolism in osseous metastases in breast and prostate cancer patients.</div

Valkea-Kotinen ‒ long-term results from a Finnish ICP Integrated Monitoring (IM) catchment

Part of the online report: Merilä, P. & Jortikka, S. (eds.). Forest Condition Monitoring in Finland – National report. The Finnish Forest Research Institute. http://urn.fi/URN:NBN:fi:metla-201305087568. Original webpages have been converted to a PDF file

Comparison of reprojected bone SPECT/CT and planar bone scintigraphy for the detection of bone metastases in breast and prostate cancer

Objective The aim of this study was to compare reprojected bone SPECT/CT (RBS) against planar bone scintigraphy (BS) in the detection of bone metastases in breast and prostate cancer patients. Methods Twenty-six breast and 105 prostate cancer patients with high risk for bone metastases underwent Tc-99m-HMDP BS and whole-body SPECT/CT, 1.5-T whole-body diffusion-weighted MRI and F-18-NaF or F-18-PSMA-1007 PET/CT within two prospective clinical trials (NCT01339780 and NCT03537391). Consensus reading of all imaging modalities and follow-up data were used to define the reference standard diagnosis. The SPECT/CT data were reprojected into anterior and posterior views to produce RBS images. Both BS and RBS images were independently double read by two pairs of experienced nuclear medicine physicians. The findings were validated against the reference standard diagnosis and compared between BS and RBS on the patient, region and lesion levels. Results All metastatic patients detected by BS were also detected by RBS. In addition, three metastatic patients were missed by BS but detected by RBS. The average patient-level sensitivity of two readers for metastases was 75% for BS and 87% for RBS, and the corresponding specificity was 79% for BS and 39% for RBS. The average region-level sensitivity of two readers was 64% for BS and 69% for RBS, and the corresponding specificity was 96% for BS and 87% for RBS. Conclusion Whole-body bone SPECT/CT can be reprojected into more familiar anterior and posterior planar images with excellent sensitivity for bone metastases, making additional acquisition of planar BS unnecessary.Peer reviewe

Kvantitatiivinen yksifotoniemissiotomografia ja sen soveltaminen luusto- ja sydäntutkimuksiin

Yksifotoniemissiotomografia (single photon emission computed tomography, SPECT) on kehon fysiologiaa kuvantava isotooppilääketieteen menetelmä, joka perustuu potilaan sisälle vietävästä säteilylähteestä emittoituvien gammafotonien havaitsemiseen potilaan ulkopuolella. Säteilylähteenä käytetään radiolääkeainetta eli radioaktiivisella isotoopilla leimattua kehon aineenvaihduntaan osallistuvaa biomolekyyliä, joka yleensä injisoidaan potilaaseen suonensisäisesti. SPECT on aikaisemmin ollut mittausmenetelmänä epäkvantitatiivinen, mutta tietokonetomografiaa (TT) hyödyntävien SPECT-TT-yhdistelmälaitteistojen ja rekonstruktio-ohjelmistojen kehitys on tehnyt kvantitatiivisen SPECTin mahdolliseksi. Kvantitatiivinen SPECT perustuu säteilyn vaimenemisesta ja sironnasta aiheutuvien vääristymien korjaamiseen. Korjauksiin voidaan käyttää mm. TT-kuvasta muodostettua vaimenemiskarttaa ja Monte Carlo -simulaatioita. Positroniemissiotomografia (PET) on samankaltainen, mutta tarkempi kuvantamismenetelmä kuin SPECT, ja PET on ollut kvantitatiivinen kehityksensä alusta alkaen. Tämän työn tarkoitus on verrata kvantitatiivisista SPECT- ja PET-kuvista määritettyjä standardoituja kertymäarvoja (standardized uptake value, SUV) toisiinsa. Työssä hyödynnettiin Turun yliopistollisessa keskussairaalassa aikaisemmin kuvattuja luusto- ja sydäntutkimuksia. SPECT-kuvat rekonstruoitiin käyttämällä kvantitatiivisia kuvia tuottavaa rekonstruktio-ohjelmistoa. Luustokuvista segmentoitiin selvät kudosvauriot eli leesiot ja sydänkuvista sydänlihas. Leesioiden keskiarvo- ja maksimi-SUVit sekä sydänlihasten keskiarvo-SUVit määritettiin. SUVien lineaarista riippuvuutta tutkittiin Pearsonin korrelaatiokertoimella. SPECTillä ja PETillä kuvattujen leesioiden keskiarvo- ja maksimi-SUVit korreloivat keskenään tilastollisesti merkittävästi (r > 0,80; p < 0,001). Myös SPECT- ja PET-sydänkuvista määritetyt keskiarvo-SUVit korreloivat tilastollisesti merkitsevästi. Sydänlihaksen lepo- ja rasituskuvien keskiarvo-SUVien suhteesta lasketut sepelvaltimon virtausreservit korreloivat SPECT- ja PET-kuvien välillä kohtalaisesti (r = 0,48; p = 0,006). Tulosten perusteella kvantitatiivinen SPECT toimii vastaavalla tarkkuudella kuin PET ainakin luustotutkimuksissa. Kvantitatiivisen SPECTin toimivuutta sydäntutkimuksissa ei voitu osoittaa, koska käytetyn merkkiaineen sydänlihaskertymän saturoituminen haittaa kvantitointia.Siirretty Doriast

Comparison of standardized uptake values between 99mTc-HDP SPECT/CT and 18F-NaF PET/CT in bone metastases of breast and prostate cancer

Abstract Background Despite recent technological advances allowing for quantitative single-photon emission computed tomography (SPECT), quantitative SPECT has not been widely used in the clinical practice. The aim of this study is to evaluate the feasibility of quantitative SPECT for measuring metastatic bone uptake in breast and prostate cancer by comparing standard uptake values (SUVs) measured with 99mTc-HDP SPECT/CT and 18F-NaF PET/CT. Methods Twenty-six breast and 27 prostate cancer patients at high risk of bone metastases underwent both 99mTc-HDP SPECT/CT and 18F-NaF PET/CT within 14 days of each other. The SPECT and PET data were reconstructed using ordered-subset expectation-maximization algorithms achieving quantitative images. Metastatic and benign skeletal lesions visible in both data sets were identified, and their maximum, peak, and mean SUVs (SUVmax, SUVpeak, and SUVmean) were determined. SUV ratios (SUVRs) between the lesions and adjacent normal appearing bone were also calculated. Linear regression was used to evaluate the correlations between the SUVs of SPECT and PET and Bland-Altman plots to evaluate the differences between the SUVs and SUVRs of SPECT and PET. Results A total of 231 skeletal lesions, 129 metastatic and 102 benign, were analyzed. All three SUV measures correlated very strongly between SPECT and PET (R 2  ≥ 0.80, p < 0.001) when all lesions were included, and the PET SUVs were significantly higher than SPECT SUVs (p < 0.001). The median differences were 21%, 12%, and 19% for SUVmax, SUVpeak, and SUVmean, respectively. On the other hand, the SUVRs were similar between SPECT and PET with median differences of 2%, − 9%, and 2% for SUVRmax, SUVRpeak, and SUVRmean, respectively. Conclusion The strong correlation between SUVs and similar SUVRs of 99mTc-HDP SPECT/CT and 18F-NaF PET/CT demonstrate that SPECT is an applicable tool for clinical quantification of bone metabolism in osseous metastases in breast and prostate cancer patients

Comparison of reprojected bone SPECT/CT and planar bone scintigraphy for the detection of bone metastases in breast and prostate cancer

Objective The aim of this study was to compare reprojected bone SPECT/CT (RBS) against planar bone scintigraphy (BS) in the detection of bone metastases in breast and prostate cancer patients. Methods Twenty-six breast and 105 prostate cancer patients with high risk for bone metastases underwent 99mTc-HMDP BS and whole-body SPECT/CT, 1.5-T whole-body diffusion-weighted MRI and 18F-NaF or 18F-PSMA-1007 PET/CT within two prospective clinical trials (NCT01339780 and NCT03537391). Consensus reading of all imaging modalities and follow-up data were used to define the reference standard diagnosis. The SPECT/CT data were reprojected into anterior and posterior views to produce RBS images. Both BS and RBS images were independently double read by two pairs of experienced nuclear medicine physicians. The findings were validated against the reference standard diagnosis and compared between BS and RBS on the patient, region and lesion levels. Results All metastatic patients detected by BS were also detected by RBS. In addition, three metastatic patients were missed by BS but detected by RBS. The average patient-level sensitivity of two readers for metastases was 75% for BS and 87% for RBS, and the corresponding specificity was 79% for BS and 39% for RBS. The average region-level sensitivity of two readers was 64% for BS and 69% for RBS, and the corresponding specificity was 96% for BS and 87% for RBS. Conclusion Whole-body bone SPECT/CT can be reprojected into more familiar anterior and posterior planar images with excellent sensitivity for bone metastases, making additional acquisition of planar BS unnecessary. </jats:sec