Characteristics of two tsunamis generated by successive M_w 7.4 and M_w 8.1 earthquakes in Kermadec Islands on March 4, 2021

On March 4, 2021, two tsunamigenic earthquakes (Mw 7.4 and Mw 8.1) occurred successively within 2 h in Kermadec Islands. We examined sea level records at tide gauges located at ~100 km to ~2,000 km from the epicenters, conducted Fourier and Wavelet analyses as well as numerical modelling of both tsunamis. Fourier analyses indicated that the energy of the first tsunami is mainly distributed in the period range of 5–17 min, whereas it is 8–28 min for the second tsunami. Wavelet plots showed that the oscillation of the first tsunami continued even after the arrival of the second tsunami. As the epicenters of two earthquakes are close (~ 55 km), we reconstructed the source spectrum of the second tsunami by using the first tsunami as the empirical Green’s function. The main spectral peaks are 25.6 min, 16.0 min, and 9.8 min. The results are similar to those calculated using tsunami/background ratio method and also consistent with source models.

The Appropriate Acquisition Time Interval Following Injection of 99mTc-Sestamibi with Water Protocol in Single Photon Emission Computed Tomography Myocardial Perfusion Imaging: First Experience in Indonesia

BackgroundAccording to EANM/ESC guideline, image acquisitions in stress test should be begun at 30-60 minutes after tracer administration. Our center is a referral hospital for nuclear medicine imaging with many patients but limited number of gamma camera. The shorter time between injection of radiopharmaceutical and imaging acquisition will lead to more examination can be done.The aim of this study was to evaluate the appropriate acquisition time interval with water protocol in 99mTc-Sestamibi SPECT myocardial perfusion imaging.MethodsPatients who were referred to undergo stress MPI between October 2020 to December 2020 were included in this study. Cardiac stress procedure was performed using treadmill with modified Bruce Protocol. Subjects should drink a total of 330 mL water following 99mTc-Sestamibi injection. Image acquisitions were performed 10 and 30 minutes afterwards. Quantitative assessment was done by calculated target background ratio (TBR). Statistical analysis was performed using student t-test with Microsoft Excel version 2019. P-value < 0.05 was considered to be statistically significance.ResultsThirty out of 35 subjects were included in this study. Sixteen of them are male and 14 are female with mean of age was 48.7 years old (28 – 80). Mean target background uptake ratio (TBR) in 10- and 30-minutes images were 0.67 (0.44 – 1.11) and 0.76 (0.43 – 1.18) respectively (p-value = 0.15).ConclusionThere was no significant difference of target to background ratio between acquisition time 10- and 30-minutes following injection of 99mTc-Sestamibi with water protocol in myocardial perfusion imaging.Trial registrationNot applicable.

Head to head comparison of [99mTc]Tc(CO)3(NTA) and [99mTc]Tc-MAG3 in patients with suspected obstruction

Purpose 99mTc-tricarbonyl-nitrilotriacetic acid, [99mTc]Tc(CO)3(NTA), is a new 99mTc-renal radiopharmaceutical with a clearance equal to that of 131I-ortho-iodohippuran, [131I]I-OIH. Our purpose was to compare the performance of [99mTc]Tc(CO)3(NTA) and [99mTc]Tc-MAG3 in patients with suspected obstruction. Methods [99mTc]Tc(CO)3(NTA) was prepared with commercially available NTA ligand and CRS Isolink kit, and isolated by HPLC. Eighteen adult patients referred for diuretic renography received an intravenous injection of approximately 40 mg of furosemide 15 min prior to either [99mTc]Tc(CO)3(NTA) or [99mTc]Tc-MAG3 (mean activity of 47 ± 4.4 MBq). Data were acquired for 24 min followed by an anterior image of the liver and gall bladder and a measure of voided volume. Patients received a second furosemide injection equal to one third of the original dose followed fifteen minutes later by administration of the alternate tracer, mean activity of 320 ± 34 MBq. Clearances were measured using a camera-based technique. Results The clearance of NTA was greater than that of MAG3, 331 ± 146 versus 271 ± 105 mL/min/1.73 m2, respectively, p < 0.0001. The kidney to background ratio for NTA was greater than that of MAG3 for both left and right kidneys, p < 0.001; the 20 min/maximum count ratio was significantly less, p < 0.0001. There was no significant difference in the voiding volumes following NTA and MAG3 administration, 598 ± 237 mL versus 498 ± 170 mL, respectively, p = 0.07. Gall bladder activity was not observed with NTA but was present in 6/17 MAG3 studies. Images and renogram curves were comparable except for two patients where the NTA study excluded obstruction but the MAG3 study suggested an indeterminate or obstructed kidney. Conclusions Unlike MAG3, NTA is not eliminated via the hepatobiliary track. Moreover, NTA has a higher kidney to background ratio and more rapid clearance than MAG3. These advantages should allow more robust camera-based clearance measurements and may lead to better discrimination between obstructed and non-obstructed kidneys.

[11C]deschloroclozapine is an improved PET radioligand for quantifying a human muscarinic DREADD expressed in monkey brain

Previous work found that [11C]deschloroclozapine ([11C]DCZ) is superior to [11C]clozapine ([11C]CLZ) for imaging Designer Receptors Exclusively Activated by Designer Drugs (DREADDs). This study used PET to quantitatively and separately measure the signal from transfected receptors, endogenous receptors/targets, and non-displaceable binding in other brain regions to better understand this superiority. A genetically-modified muscarinic type-4 human receptor (hM4Di) was injected into the right amygdala of a male rhesus macaque. [11C]DCZ and [11C]CLZ PET scans were conducted 2–24 months later. Uptake was quantified relative to the concentration of parent radioligand in arterial plasma at baseline (n = 3 scans/radioligand) and after receptor blockade (n = 3 scans/radioligand). Both radioligands had greater uptake in the transfected region and displaceable uptake in other brain regions. Displaceable uptake was not uniformly distributed, perhaps representing off-target binding to endogenous receptor(s). After correction, [11C]DCZ signal was 19% of that for [11C]CLZ, and background uptake was 10% of that for [11C]CLZ. Despite stronger [11C]CLZ binding, the signal-to-background ratio for [11C]DCZ was almost two-fold greater than for [11C]CLZ. Both radioligands had comparable DREADD selectivity. All reference tissue models underestimated signal-to-background ratio in the transfected region by 40%–50% for both radioligands. Thus, the greater signal-to-background ratio of [11C]DCZ was due to its lower background uptake.

Head to Head Comparison of 99mTc(CO)3(NTA) and 99mTc-MAG3 in Patients with Suspected Obstruction

Purpose 99mTc-tricarbonyl-nitrilotriacetic acid, 99mTc(CO)3(NTA), is a new 99mTc-renal radiopharmaceutical with a clearance equal to that of 131I-ortho-iodohippuran. Our purpose was to compare the performance of 99mTc(CO)3(NTA) and 99mTc-MAG3 in patients with suspected obstruction.Methods 99mTc(CO)3(NTA) was prepared with commercially available NTA and CRS Isolink kit, and isolated by HPLC. Eighteen adult patients referred for diuretic renography received an intravenous injection of approximately 40 mg of furosemide 15 min prior to either 99mTc(CO)3(NTA) or 99mTc-MAG3 (mean activity of 47 ± 4.4 MBq). Data were acquired for 24 minutes followed by an anterior image of the liver and gall bladder and a measure of voided volume. Patients received a second furosemide injection equal to one third of the original dose followed fifteen minutes later by administration of the alternate tracer, mean activity of 320 ± 34 MBq. Clearances were measured using a camera-based technique.Results The clearance of 99mTc(CO)3(NTA) was greater than that of 99mTc-MAG3, 331 ± 146 vs 271 ± 105 mL/min/1.73 m2, respectively, p < 0.0001. The kidney to background ratio for 99mTc(CO)3(NTA) was greater than that of 99mTc-MAG3 for both left and right kidneys, p < 0.001; the 20 min/maximum count ratio was significantly less, p < 0.0001. There was no significant difference in the voiding volumes following 99mTc(CO)3(NTA) and 99mTc-MAG3 administration, 598 ± 237 mL vs 498 ± 170 mL, respectively, p = 0.07. Gall bladder activity was not observed with 99mTc(CO)3(NTA) but was present in 6/17 99mTc-MAG3 studies. Images and renogram curves were comparable except for two patients where the 99mTc(CO)3(NTA) study excluded obstruction but the 99mTc-MAG3 study suggested an indeterminate or obstructed kidney.Conclusions Unlike 99mTc-MAG3, 99mTc(CO)3(NTA) is not eliminated via the hepatobiliary track. Moreover, 99mTc(CO)3(NTA has a higher kidney to background ratio and more rapid clearance than 99mTc-MAG3. These advantages should allow more robust camera-based clearance measurements and may lead to better discrimination between obstructed and non-obstructed kidneys.

Imaging coronary plaques using 3D motion-compensated [18F]NaF PET/MR

Background Cardiac PET has recently found novel applications in coronary atherosclerosis imaging using [18F]NaF as a radiotracer, highlighting vulnerable plaques. However, the resulting uptakes are relatively small, and cardiac motion and respiration-induced movement of the heart can impair the reconstructed images due to motion blurring and attenuation correction mismatches. This study aimed to apply an MR-based motion compensation framework to [18F]NaF data yielding high-resolution motion-compensated PET and MR images. Methods Free-breathing 3-dimensional Dixon MR data were acquired, retrospectively binned into multiple respiratory and cardiac motion states, and split into fat and water fraction using a model-based reconstruction framework. From the dynamic MR reconstructions, both a non-rigid cardiorespiratory motion model and a motion-resolved attenuation map were generated and applied to the PET data to improve image quality. The approach was tested in 10 patients and focal tracer hotspots were evaluated concerning their target-to-background ratio, contrast-to-background ratio, and their diameter. Results MR-based motion models were successfully applied to compensate for physiological motion in both PET and MR. Target-to-background ratios of identified plaques improved by 7 ± 7%, contrast-to-background ratios by 26 ± 38%, and the plaque diameter decreased by −22 ± 18%. MR-based dynamic attenuation correction strongly reduced attenuation correction artefacts and was not affected by stent-related signal voids in the underlying MR reconstructions. Conclusions The MR-based motion correction framework presented here can improve the target-to-background, contrast-to-background, and width of focal tracer hotspots in the coronary system. The dynamic attenuation correction could effectively mitigate the risk of attenuation correction artefacts in the coronaries at the lung-soft tissue boundary. In combination, this could enable a more reproducible and reliable plaque localisation.

STUDI PENDAHULUAN PENGGUNAAN VOLUME OF INTEREST (VOI) DALAM MENGANALISIS BIODISTRIBUSI SENYAWA PENGONTRAS GD-DTPA-FOLAT DIBANDINGKAN DENGAN GD-DTPA PADA HEPAR DAN GINJAL TIKUS MENGGUNAKAN MRI

<p>Magnetic Resonance Imaging (MRI) merupakan modalitas pencitraan diagnostik yang sebagian besar menggunakan senyawa pengontras. Konsentrasi senyawa pengontras dapat diukur secara tidak langsung dari peningkatan instensitas sinyal yang merupakan bagian dari analisis tekstural ditampilkan dengan Region of Interest (ROI) ataupun Volume of Interest (VOI). Dua organ eliminasi dalam biodistribusi obat dalam tubuh yaitu hepar dan ginjal. VOI merupakan penilaian yang mencakup kuantifikasi tekstur seluruh jaringan, sehingga VOI dapat menilai biodistribusi pada hepar dan ginjal. Tujuan dari penelitian ini yaitu untuk menganalisis VOI senyawa pengontras Gd-DTPA-Folat dan Gd-DTPA dan membandingkannya dengan ROI dan target to background ratio. Studi pendahuluan yang merupakan penelitian observasional analitik menggunakan data prospektif. Analisis statistik menggunakan tes Mann-Whitney untuk membandingkan perbedaan intensitas sinyal senyawa pengontras Gd-DTPA-Folat dan Gd-DTPA pada konsentrasi 112 mg/0,5 ml dengan waktu pindai yang berbeda. Sampel dibagi menjadi 2 kelompok yang masing-masing terdiri dari 3 ekor tikus putih. Variabel independen adalah jenis kontras dan waktu pindai, variabel dependen adalah nilai ROI, target to background ratio, dan VOI. Variabel perancu dipengaruhi oleh perbedaan tempat dan ukuran. Bias dikurangi dengan pengukuran minimal 3 kali dengan ukuran 20 mm2. VOI digunakan sebagai modifikasi efek. Nilai rerata VOI Gd-DTPA-Folat dan Gd-DTPA memiliki nilai yang hampir sama pada hepar dan ginjal pada waktu yang berbeda serta menunjukkan waktu yang optimal pada 1 jam pertama. VOI memiliki keunggulan dalam menilai biodistribusi senyawa pengontras pada organ hepar dan ginjal dibandingkan dengan ROI dan target to background ratio.</p>