Subtraction of single-photon emission computed tomography (SPECT) in radioembolization: a comparison of four methods

BACKGROUND: Subtraction of single-photon emission computed tomography (SPECT) images has a number of clinical applications in e.g. foci localization in ictal/inter-ictal SPECT and defect detection in rest/stress cardiac SPECT. In this work, we investigated the technical performance of SPECT subtraction for the purpose of quantifying the effect of a vasoconstricting drug (angiotensin-II, or AT2) on the Tc-99m-MAA liver distribution in hepatic radioembolization using an innovative interventional hybrid C-arm scanner. Given that subtraction of SPECT images is challenging due to high noise levels and poor resolution, we compared four methods to obtain a difference image in terms of image quality and quantitative accuracy. These methods included (i) image subtraction: subtraction of independently reconstructed SPECT images, (ii) projection subtraction: reconstruction of a SPECT image from subtracted projections, (iii) projection addition: reconstruction by addition of projections as a background term during the iterative reconstruction, and (iv) image addition: simultaneous reconstruction of the difference image and the subtracted image. RESULTS: Digital simulations (XCAT) and phantom studies (NEMA-IQ and anthropomorphic torso) showed that all four methods were able to generate difference images but their performance on specific metrics varied substantially. Image subtraction had the best quantitative performance (activity recovery coefficient) but had the worst visual quality (contrast-to-noise ratio) due to high noise levels. Projection subtraction showed a slightly better visual quality than image subtraction, but also a slightly worse quantitative accuracy. Projection addition had a substantial bias in its quantitative accuracy which increased with less counts in the projections. Image addition resulted in the best visual image quality but had a quantitative bias when the two images to subtract contained opposing features. CONCLUSION: All four investigated methods of SPECT subtraction demonstrated the capacity to generate a feasible difference image from two SPECT images. Image subtraction is recommended when the user is only interested in quantitative values, whereas image addition is recommended when the user requires the best visual image quality. Since quantitative accuracy is most important for the dosimetric investigation of AT2 in radioembolization, we recommend using the image subtraction method for this purpose

Long term effects of micro-surgical testicular sperm extraction on androgen status in patients with non obstructive azoospermia

BACKGROUND: The aim of our study was to review the results of microsurgically performed testicular sperm extraction (TESE) and to evaluate its possible long term effects on serum testosterone (T). METHODS: We operated on 48 men (35 +/- 8 years) with non-obstructive azoospermia (NOA). If no spermatozoa were found following a micro epididymal sperm extraction (Silber et al., 1994) and testicular biopsy, testicular microdissection was performed or multiple microsurgical testicular biopsies were taken. The mean follow-up of the serum T was 2.4 +/- 1.1 years. RESULTS: Sperm was retrieved in 17/48 (35%) of the men. The per couple take home baby rate if sperm was retrieved was 4/17 (24%). Serum T decreased significantly at follow-up (p < 0.05) and 5/31 (16%) de novo androgen deficiencies developed CONCLUSION: In patients with non-obstructive azoospermia in whom no spermatozoa were found following a micro epididymal sperm aspiration and a simple testicular biopsy, we were able to retrieve spermatozoa in 35% of the men. The take home baby rate was 24% among couples with spermatozoa present upon TESE. De novo androgen deficiency occurred in 16% of the male patients following TESE indicating that, in men with NOA, long term hormonal follow up is recommended after TESE

Een nederzetting uit de Midden en Late IJzertijd in het plangebied Tiliaans-Noord te Luyksgestel

Met lit. op

Opgraving van een grafkelder in de Nederlands Hervormde Kerk te Biervliet : archeologische begeleiding en definitief archeologisch onderzoek

Concept

Inventariserend veldonderzoek door middel van proefsleuven op de Noordesch te Anloo, gemeente Aa en Hunze

Met lit. op

Archeologische begeleiding Medel-NUON kabelsleuven, gemeente Tiel

Lit.opg. en verklarende woordenlijst

Een toekomstbestendig bedrijf in de biologische leghennenhouderij

In dit afstudeerwerkstuk is het onderwerp het samenstellen van een toekomstbestendig biologisch leghennenbedrijf. De eindconclusie kan een startend pluimvee-ondernemer gebruiken om zo zijn idee te ontwikkelen. Een aanleiding van het project zijn de huidige regels die steeds worden aangepast, om zo de sector optimaal te maken. Deze veranderingen zijn voor pluimveehouders moeilijk, omdat zij zo hun bedrijf om de aantal jaar moeten blijven aanpassen. Kan er geen mogelijkheid zijn, waardoor de ondernemer zijn bedrijf zo kan vormen, dat hij hier jaren mee voort kan zonder grote aanpassingen