Comparison of shortened gated myocardial perfusion imaging processed with „Myovation Evolution” with full time study

Background: The work compares results of shortened gated myocardial perfusion imaging (MPI), processed with „Myovation Evolution” software, with a study performed in a standard way.Material and methods: A retrospective study was conducted in a group of 95 patients (56 males and 39 females, age 62±9 years, BMI 28±4) with known or suspected CAD, without clinical history or any signs of a previous myocardial infarction. All patients underwent coronary angiography (CA) within 3 months of MPI. CA was used as a reference for diagnostic performance of MPI. Patients underwent a stress/rest 2-day MPI. Both studies were performed twice, with normal (25s) and shortened (13s) time per projection. Studies were processed using Myovation protocol (OSEM with 2 iterations and 10 subsets) for full time (FT) studies and a Myovation Evolution protocol dedicated to half time (HT) studies (OSEM with 12 iterations, 10 subsets). Reconstructed images, with and without attenuation correction (AC), were evaluated by 2 experienced nuclear medicine specialists (a consensus), with regard to image quality and perfusion, evaluated using a visual semi-quantitative method, applying a standard division of myocardium into 17 segments. Perfusion was assessed in every segment using a standard 5 grade scale. Summed stress scores were calculated for every patient and threshold values for detection of CAD were selected based on ROC analysis with CA treated as a reference method. After at least 2 months FT images were interpreted again by the same specialists.Results: Quality of images obtained from shortened and normal studies was equally good. All correlation coefficients between segmental scorings of FT and HT studies were high and statistically significant. Correlation coefficients between corresponding segments in FTAC and HTAC (i.e. with AC) studies were systematically higher than without AC. Agreement between FT and HT study results was equal to 81% for FT and HT studies and to 86% for FTAC and HTAC studies (p=0.40). Repeatability of FTAC study assessments was equal to 94%. 95-per cent confidence intervals calculated for agreement between FTAC and HTAC studies and repeatability of FTAC study overlapped considerably. Correlation coefficients for EDV, ESV and EF values between FT and HT were high: 0.93, 0.96 and 0.88, respectively. Conclusion: Myovation Evolution protocol used for reconstruction of myocardial perfusion studies with reduced number of counts requires AC. Disagreements observed during visual assessment of normal and reduced count studies are statistically not significantly larger than between dual assessment of a full count study.BACKGROUND: The work compares the results of shortened gated myocardial perfusion imaging (MPI), processed with „Myovation Evolution” software, with a study performed in a standard way. MATERIAL AND METHODS: A retrospective study was conducted in a group of 95 patients (56 males and 39 females, age 62 ± 9 years, BMI 28 ± 4) with known or suspected CAD, without clinical history or any signs of a previous myocardial infarction. All patients underwent coronary angiography (CA) within 3 months of MPI. CA was used as a reference for diagnostic performance of MPI. Patients underwent a stress/rest 2-day MPI. Both studies were performed twice, with normal (25s) and shortened (13s) time per projection. Studies were processed using Myovation protocol (OSEM with 2 iterations and 10 subsets) for full time (FT) studies and a Myovation Evolution protocol dedicated to half time (HT) studies (OSEM with 12 iterations, 10 subsets). Reconstructed images, with and without attenuation correction (AC), were evaluated by 2 experienced nuclear medicine specialists (a consensus), with regard to image quality and perfusion, evaluated using a visual semi-quantitative method, applying a standard division of myocardium into 17 segments. Perfusion was assessed in every segment using a standard 5 grade scale. Summed stress scores were calculated for every patient and threshold values for detection of CAD were selected based on ROC analysis with CA treated as a reference method. After 2 months FT images were interpreted again by the same specialists. RESULTS: The quality of images obtained from shortened and normal studies was equally good. All correlation coefficients between segmental scorings of FT and HT studies were high and statistically significant. Correlation coefficients between corresponding segments in FTAC and HTAC (i.e. with AC) studies were systematically higher than without AC. The agreement between FT and HT study results was equal to 81% for FT and HT studies and to 86% for FTAC and HTAC studies (p = 0.40). The repeatability of FTAC study assessments was equal to 94%. 95-percent confidence intervals calculated for agreement between FTAC and HTAC studies and the repeatability of FTAC study overlapped considerably. Correlation coefficients for EDV, ESV and EF values between FT and HT were high: 0.93, 0.96 and 0.88, respectively. CONCLUSION: Myovation Evolution protocol used for reconstruction of myocardial perfusion studies with reduced number of counts requires AC. The agreement between the results of visual assessment of normal and reduced count studies is high and not worse than the agreement between repeat assessment of a full time study

Effect of CT misalignment on attenuation — corrected myocardial perfusion SPECT

BACKGROUND: Use of CT based attenuation correction (AC) for myocardial perfusion SPECT (MPS) is growing fast due to a rapid development of hybrid SPECT/CT systems. SPECT and CT studies are performed in a sequential way extending total study acquisition and making a patient movement more likely. The present work aims at answering the question how large misalignment between SPECT and CT studies should be considered significant and how often those misregistrations are observed. MATERIAL AND METHODS: A retrospective study applying AC was performed in 107 patients who had coronary angiography (CA) performed within 3 months. Patients underwent a stress/rest Tc-99m MIBI 2 day SPECT/CT myocardial perfusion study. In case of SPECT and CT misalignment CT slices were shifted manually; shifts along 3 axes were recorded and after realignment a repeat reconstruction was performed. Euclidean distance of misalignment was also calculated. Images were analyzed by two experienced nuclear medicine specialists (consensus) applying visual semiquantitative method. Perfusion of three arteries was scored using a 5 grade scale. CA results were used as a reference for MPS findings. RESULTS: In 47 patients (44%) CT realignment was necessary. CT was shifted mostly along x and y axes, and less often along z axis. Euclidean distance S exceeded 2 pixels in 3 stress and 2 rest studies. Only in 7 patients changes of scores assigned to coronary vessels were noted as a result of CT realignment. These changes concerned 9 vessel areas. In 7 out of 9 cases changes were noted toward a better agreement with results of CA. Only in one patient, with stress S > 3 pixels and negative result of CA, CT realignment changed vessel area score significantly, from probably abnormal to normal. CONCLUSIONS: Only misalignments large enough, exceeding 2–3 pixels, have negative impact on attenuation corrected images. Such misalignments are rare, in our material were observed in 3 stress and 2 rest studies (3% and 2% of all studies, respectively). Only in one patient (below 1% of all studied patients) CT misalignment caused a significant study misinterpretation. Although alignment of SPECT and CT studies should be checked in every patient, small misalignments do not affect study interpretation

Reduced-time myocardial perfusion study processed with “Myovation Evolution” — assessment of diagnostic efficacy

BACKGROUND: While assessing images using standard segmental method, we felt that some defects were either underscored or missed. So this work is intended to compare results of low count myocardial perfusion studies (MPS) processed with „Myovation Evolution”, applying complete evaluation of all available slices, with full count studies and assess impact of reduction of counts on diagnostic efficacy of the study. MATERIAL AND METHODS: A retrospective study was conducted in a group of 95 patients (56 males, age 62 ± 9 years, BMI 28 ± 4) with known or suspected CAD, without clinical history or any signs of a previous myocardial infarction. All patients underwent coronary angiography (CA) within 3 months of MPS. CA was used as a reference method for diagnostic performance of MPS. Patients underwent a stress/rest 2-day MPS. Both studies were performed twice, with normal (25 s) and shortened (13 s) time/projection. Studies were processed using Myovation protocol (OSEM, 2 iterations, 10 subsets) for full time (FT) studies and a Myovation Evolution protocol for half time (HT) studies (OSEM, 12 iterations, 10 subsets, Resolution Recovery). Reconstructed images, with and without attenuation correction (AC), were evaluated by 2 experienced nuclear medicine specialists (a consensus) visually, taking into account all available slices, in a 5-grade scale (normal, probably normal, equivocal, probably abnormal and abnormal). Study results were additionally dichotomized as normal or abnormal. Perfusion defects were assigned to coronary arteries. RESULTS: An exact agreement between FT and HT study assessment, without AC, amounted to 66%, with AC it grew to 79%, p = 0.05. In studies without AC 10 perfusion defects were found only in HT studies in RCA area in male patients. A higher percentage of studies with perfusion defects in RCA area visible only in HT studies was found among discordant (7/25, 28%) than concordant results (3/70, 4%), p = 0.003. AC reduced this difference. HT study provided lower accuracy in detection of CAD than FT study (58% vs. 68%, p = 0.034). AC reduced this difference considerably. Dichotomized assessment agreed in 81% of studies without AC and in 87% with AC. CONCLUSIONS: Myovation Evolution protocol requires application of AC otherwise perfusion defects in RCA area in male patients are falsely detected. Shortened studies reconstructed with „Myovation Evolution” package without AC reveal a tendency toward reduction of accuracy of the study in detection of CAD. AC makes up for this reduction

Wartość prognostyczna scyntygrafii perfuzyjnej mięśnia sercowego metodą SPECT z użyciem 99mTc-MIBI w grupie pacjentów po przebytym w przeszłości zawale serca

Introduction. Data describing prognostic utility of SPECT (single-photon emission computed tomography) among patients with history of myocardial infarction (MI) is scarce. We aimed to compare prognostic value of SPECT scans in patients with vs. without history of myocardial infarction (MI) prior to perfusion imaging. Material and methods. 151 consecutive patients with history of myocardial infarction, who underwent exercise 99mTc-MIBI SPECT examination were enrolled in the study (group 1). Next, based on clinical and demographic baseline characteristics, SPECT result and duration of follow-up period, a matching control subgroup (group 2) of 151 patients without history of MI was formed. During a mean follow-up of 60 ± 15 months in group 1 and a mean follow-up of 60 ± 13.5 months in group 2, we analyzed prevalence of cardiovascular events rates (cardiac deaths, myocardial infarctions and cardiac revascularizations). Results. We observed the following rates of cardiac deaths, myocardial infarctions and cardiac revascularizations: 4%, 15% and 26%, respectively in group 1 and 1%, 13% and 17%, respectively in group 2. In patients without history of MI (group 2) presence of mixed perfusion defects on SPECT was associated with significantly higher rate of myocardial infarctions (p = 0.05), hospitalizatons (p = 0.0001) and revascularizations (p = 0.0002). Fixed perfusion defects were associated with significantly higher occurrence of deaths (p = 0.012) and hospitalizations (p = 0.02), but not myocardial infarctions (p = 0.52) or cardiac revascularizations (p = 0.10). In contrast, among patients with history of MI (group 1) there was no statistically significant relationship between any type of perfusion defects and cardiovascular events. Conclusions. Long term follow-up demonstrates that prognostic value of 99mTc-MIBI SPECT is different in patients with and without history of MI.Wstęp. W dostępnej literaturze brakuje badań służących ocenie przydatności prognostycznej scyntygrafii perfuzyjnej mięśnia sercowego SPECT (tomografia emisyjna pojedynczego fotonu) w grupie chorych z wywiadem przebytego zawału serca. Celem opisanego badania jest porównanie wartości prognostycznej SPECT w grupie pacjentów z wywiadem zawału serca przed badaniem SPECT oraz bez takiego wywiadu. Materiał i metody. Do badania włączono 151 kolejnych pacjentów z wywiadem zawału serca, u których wykonano badanie SPECT z użyciem 99mTc-MIBI. Następnie, na podstawie charakterystyki klinicznej i demograficznej oraz długości okresu obserwacji dobrano, grupę kontrolną 151 pacjentów poddanych badaniu SPECT, bez wywiadu wcześniejszego zawału serca. Wyniki. Po średnim okresie obserwacji 60 ± 15 miesięcy (grupa 1) i 60 ± 13,5 miesiąca (grupa 2) częstość wystąpienia punktów końcowych, takich jak zgon z przyczyn sercowo-naczyniowych, zawał serca, rewaskularyzacja, wyniosła odpowiednio 4%, 15% i 26% w grupie 1 oraz 1%, 13%, 17% w grupie 2. Wśród pacjentów bez wywiadu zawału serca (grupa 2) obecność mieszanych zaburzeń perfuzji w badaniu SPECT wiązała się z istotnie większą częstością zawałów serca (p =0,05), hospitalizacji (p = 0,0001) oraz rewaskularyzacji (p = 0,0002). Utrwalone zaburzenia perfuzji wiązały się z istotnie większą liczbą zgonów z przyczyn sercowo-naczyniowych, liczbą hospitalizacji (p=0,02), ale nie zawałów serca (p = 0,52) ani rewaskularyzacji (p = 0,10). Natomiast wśród pacjentów bez wywiadu zawału serca (grupa 1) nie zaobserwowano istotnej statystycznie zależności między typem zaburzeń perfuzji a występowaniem powyższych punktów końcowych. Wnioski. W długoterminowej obserwacji wykazano różnicę w zakresie wartości rokowniczej badania SPECT między pacjentami po przebytym zawale serca oraz bez wywiadu zawału

Neighbouring bases in template influence base-pairing of isoguanine.

Assuming that the efficiency of the incorporation of 5-methyl-2'-deoxyisocytosine-5' triphosphate (dMiCTP) and dTTP opposite isoguanine (iG) is a measure of the proportion of the keto and enol tautomers of iG in the Thermus aquaticus DNA polymerase active centre, we studied the influence of temperature and iG-neighbouring bases in the template on base-pairing of iG. On the basis of experiments with four sequences (3'-TXT-5', 3'-GXG-5', 3'-CXC-5', 3'-CXT-5', where X=iG) at 37, 50, 65 and 80 degrees C, we found that 3'-neighbours decrease the fraction of the keto tautomer in the order C>G>or=T, whereas temperature apparently does not influence the tautomeric equilibrium of iG. The variability of the ratio of incorporation of dMiCTP versus dTTP (5-20) primarily reflects the variability of K (m) values, since V (max) values are roughly similar, which indicates that the iG.MiC and iG.T pairs fit the polymerase active centre equally well. The altering of the base-pairing of iG by sequence context is discussed in relation to tautomerism and miscoding of this oxidized adenine derivative. A key derivative for preparation oligodeoxynucleotides, O (2)-diphenylcarbamoyl- N (6)-[(dimethylamino)ethylidene]-2'-deoxyisoguanosine, is extremely labile (t (1/2)=3.5 min) in 3% trichloroacetic acid/dichloromethane, i.e. under the conditions of automated DNA synthesis, which results in low yield and length heterogeneity of templates

Skuteczność diagnostyczna scyntygrafii perfuzyjnej mięśnia sercowego z zastosowaniem korekty osłabiania promieniowania

Background: Myocardial perfusion single-photon emission computed tomography (SPECT) is one of the basic tools used for the purpose of diagnosis of coronary artery disease (CAD), prognosis of its unfavourable consequences, and evaluation of therapy effectiveness. However, its efficacy is compromised by a relatively low specificity of detection of perfusion defects, which is attributed to attenuation of gamma rays inside the patient’s body, causing artefacts erroneously taken for perfusion defects. It is expected that attenuation correction (AC) could eliminate such artefacts. Aim: To evaluate whether visual, semi-quantitative analysis of attenuation-corrected myocardial perfusion imaging provides an advantage over a non-corrected study. Methods: A retrospective study applying AC was performed in 107 patients who had coronary angiography within three months. Patients underwent a stress/rest Tc-99m methoxyisobutylisonitrile (MIBI, POLATOM) double day SPECT/CT myocardial perfusion imaging. Images were analysed by two experienced nuclear medicine specialists (a consensus) applying a visual semiquantitative method. Coronary angiography findings were used as a reference for the analysis of diagnostic performance of myocardial perfusion study protocols. Results: AC increased the specificity of detection of CAD in the whole group of patients from 63% to 86% (p = 0.0005), with a slight reduction in sensitivity (from 83% to 79%). The improved specificity was also noted in subgroups of male and female patients. Accuracy in the whole group of patients increased from 71% to 83% (p = 0.01). AC improved the specificity and accuracy of the method in the detection of perfusion defects in the right coronary artery (RCA) area from 73% to 88% (p = 0.005) and from 74% to 83% (p = 0.04), respectively, and the accuracy of the method in the left anterior descending (LAD) artery area from 79% to 87% (p = 0.043). It also reduced the number of ambiguous results of the study. Conclusions: AC improved the diagnostic performance of myocardial perfusion study in the detection of CAD and identification of critically stenosed LAD and RCA vessels, with enhanced comfort of study interpretation.Wstęp: Scyntygrafia perfuzyjna mięśnia sercowego techniką SPECT stanowi cenne narządzie diagnostyczne służące przede wszystkim wykrywaniu choroby wieńcowej (CAD), prognozowaniu jej niekorzystnych następstw oraz ocenie skuteczności terapii. Jednak skuteczność diagnostyczna tej metody wykazuje ograniczenia w postaci suboptymalnej swoistości, wynikającej z osłabiania promieniowania gamma w ciele pacjenta, co skutkuje powstawaniem artefaktów, omyłkowo branych za ubytki perfuzji. Uważa się, że zastosowanie korekty osłabiania powinno poprawić skuteczność diagnostyczną tej metody. Cel: Celem pracy było zbadanie, czy wizualna, półilościowa metoda oceny zastosowana do scyntygramów z korekcją osłabiania promieniowania poprawia skuteczność diagnostyczną metody w wykrywaniu CAD. Metody: Badaniem retrospektywnym objęto pacjentów, u których scyntygrafie przeprowadzono w sposób umożliwiający zastosowanie korekty osłabiania promieniowania. Badana grupa składała się ze 107 pacjentów (65 mężczyzn i 42 kobiet), u których w odstępie czasu nie dłuższym niż 3 miesiące wykonano koronarografię. Badanie perfuzji mięśnia sercowego (wysiłkowe i spoczynkowe) przeprowadzono techniką SPECT/CT, wg protokołu 2-dniowego, po podaniu radiofarmaceutyku Tc-99m-metoksyizobutylizonitrylu (MIBI, POLATOM). Obrazy oceniało dwóch doświadczonych specjalistów medycyny nuklearnej, metodą konsensusu. Wyniki koronarografii traktowano jako weryfikację wyników scyntygrafii perfuzyjnej. Wyniki: Korekta osłabiania promieniowania poprawiła swoistość wykrywania CAD w całej grupie pacjentów, z 63% do 86% (p = 0,0005), przy nieznacznym obniżeniu czułości metody (z 83% do 79%), także w badanych podgrupach mężczyzn i kobiet. Dokładność metody wzrosła w całej grupie pacjentów z 71% do 83% (p = 0,01). Korekta osłabiania poprawiła swoistość i dokładność metody w wykrywaniu ubytków ukrwienia zlokalizowanych w prawej tętnicy wieńcowej, odpowiednio z 73% do 88% (p = 0,005) oraz z 74% do 83% (p = 0,04), a także w gałęzi przedniej zstępującej lewej tętnicy wieńcowej — z 79% do 87% (p = 0,043). Korekta ta zmniejszyła także liczbę wyników wątpliwych. Wnioski: Zastosowanie korekty osłabiania promieniowania poprawiło skuteczność diagnostyczną scyntygrafii perfuzyjnej mięśnia sercowego techniką SPECT w wykrywaniu CAD oraz krytycznie zwężonych naczyń: prawej tętnicy wieńcowej oraz gałęzi przedniej zstępującej lewej tętnicy wieńcowej. Dzięki zmniejszeniu udziału wyników wątpliwych korekta ta poprawiła także komfort interpretacji scyntygramów