Annals of Nuclear Medicine (v.29, #4)

Positron emission tomography-based evidence of low-amplitude respiratory motion in patients with chronic obstructive pulmonary disease by Joël Daouk; Pascal Bailly; Mitsuhiro Kamimura; David Sacksick; Vincent Jounieaux; Marc-Etienne Meyer (319-324).
Chronic obstructive pulmonary disease (COPD) is characterized by low vital capacity and tidal volume, which translate into smaller respiratory motions. We sought to demonstrate the limited respiratory motion in COPD by comparing respiratory-gated and free-breathing positron emission tomography (PET) images of lung nodules (“CT-based” and “Ungated” images) in patients with and without COPD.We studied 74 lung lesions (37 malignant) in 60 patients (23 patients with COPD; 37 without). An Ungated PET examination was followed by a CT-based acquisition. Maximum standard uptake value (SUVmax) for each lesion on PET images was measured. On CT images, we checked for the presence of emphysema and pleural adhesions or indentations associated with the nodules. Lastly, we used univariate and then multivariate analyses to determine the lung function parameters possibly affecting respiratory motion in patients with and without COPD.The mean “CT-based” vs. “Ungated” difference in SUVmax was 0.3 and 0.6 for patients with and without COPD, respectively. Statistical analysis revealed that lesion site, hyperinflation and pleural indentation were independently associated with a difference in SUVmax.PET lung lesion images in patients with COPD are barely influenced by respiratory motion. Thoracic hyperinflation in patients with COPD was found to be independently associated with an effect of respiratory motion on PET images. Moreover, pleural indentation limits the respiratory motion of lung nodules, regardless of the presence or absence of COPD.
Keywords: PET; 18F-fluorodeoxyglucose; Respiratory motion; Lung cancer

Radiosynthesis and in vivo evaluation of two imidazopyridineacetamides, [11C]CB184 and [11C]CB190, as a PET tracer for 18 kDa translocator protein: direct comparison with [11C](R)-PK11195 by Kentaro Hatano; Katsuhiko Sekimata; Takashi Yamada; Junichiro Abe; Kengo Ito; Mikako Ogawa; Yasuhiro Magata; Jun Toyohara; Kiichi Ishiwata; Giovanni Biggio; Mariangela Serra; Valentino Laquintana; Nunzio Denora; Andrea Latrofa; Giuseppe Trapani; Gaetano Liso; Hiromi Suzuki; Makoto Sawada; Masahiko Nomura; Hiroshi Toyama (325-335).
We report synthesis of two carbon-11 labeled imidazopyridines TSPO ligands, [11C]CB184 and [11C]CB190, for PET imaging of inflammatory process along with neurodegeneration, ischemia or brain tumor. Biodistribution of these compounds was compared with that of [11C]CB148 and [11C](R)-PK11195.Both [11C]CB184 and [11C]CB190 having 11C-methoxyl group on an aromatic ring were readily prepared using [11C]methyl triflate. Biodistribution and metabolism of the compounds were examined with normal mice. An animal PET study using 6-hydroxydopamine treated rats as a model of neurodegeneration was pursued for proper estimation of feasibility of the radioligands to determine neuroinflammation process.[11C]CB184 and [11C]CB190 were obtained via O-methylation of corresponding desmethyl precursor using [11C]methyl triflate in radiochemical yield of 73 % (decay-corrected). In vivo validation as a TSPO radioligand was carried out using normal mice and lesioned rats. In mice, [11C]CB184 showed more uptake and specific binding than [11C]CB190. Metabolism studies showed that 36 % and 25 % of radioactivity in plasma remained unchanged 30 min after intravenous injection of [11C]CB184 and [11C]CB190, respectively. In the PET study using rats, lesioned side of the brain showed significantly higher uptake than contralateral side after i.v. injection of either [11C]CB184 or [11C](R)-PK11195. Indirect Logan plot analysis revealed distribution volume ratio (DVR) between the two sides which might indicate lesion-related elevation of TSPO binding. The DVR was 1.15 ± 0.10 for [11C](R)-PK11195 and was 1.15 ± 0.09 for [11C]CB184.The sensitivity to detect neuroinflammation activity was similar for [11C]CB184 and [11C](R)-PK11195.
Keywords: Positron emission tomography; TSPO; PBR; Neuroinflammation; Alzheimer’s disease

High-uptake areas on positron emission tomography with the hypoxic radiotracer 18F-FRP170 in glioblastomas include regions retaining proliferative activity under hypoxia by Takaaki Beppu; Toshiaki Sasaki; Kazunori Terasaki; Hiroaki Saura; Hideki Mtsuura; Kuniaki Ogasawara; Makoto Sasaki; Shigeru Ehara; Ren Iwata; Yoshihiro Takai (336-341).
The aim was to evaluate the proliferative activity of high-uptake areas on positron emission tomography (PET) with the hypoxic cell radiotracer, 1-(2-[18F]fluoro-1-[hydroxymethyl]ethoxy)methyl-2-nitroimidazole (FRP170).Thirteen patients with glioblastoma underwent FRP170 PET before tumor resection. During surgery, tumor specimens were stereotaxically obtained from regions corresponding to high (high-uptake areas, HUAs) and relatively low (low-uptake areas, LUAs) accumulation of FRP170. We compared immunohistochemical staining for Ki-67 and hypoxia-inducible factor (HIF)-1α between HUA and LUA.HIF-1α index was significantly higher in HUAs than in LUAs. In contrast, mean Ki-67 indices did not differ significantly between HUAs and LUAs.Findings for HIF-1α index clearly indicated that HUAs on FRP170 PET represented hypoxic regions in glioblastoma. However, findings of Ki-67 index suggest that HUAs on FRP170 PET include regions retaining proliferative activity regardless of tissue hypoxia.
Keywords: Glioblastoma; FRP170; PET; Hypoxia; Proliferation

This study was aimed to compare the physical performances of cadmium–zinc–telluride (CZT) camera and conventional Anger camera. An anthropomorphic torso phantom and water bags to simulate breasts were used to evaluate artifacts arising from soft tissue attenuation.Linear source studies were performed to evaluate extrinsic resolution of CZT camera (Discovery NM 530c, GE) and conventional single-photon emission computed tomography (SPECT) Anger camera (Symbia T2, Siemens). Three sets of phantom experiments: cardiac phantom only (phantom H), anthropomorphic torso phantom added (phantom T), and torso phantom with water bags attached (phantom B), with Tc-99m were performed on both scanners. Imaging performances were evaluated through count sensitivity, contrast-to-noise ratio, quantitative sharpness profile, wall thickness, perfusion uniformity (measured by standard deviation of perfusion percentage of 20 segments using quantitative perfusion SPECT (QPS) software, Cedars-Sinai), and visual imaging quality (using 20-segment sum defect scores (SDS) of QPS) for CZT camera, conventional SPECT without and with computed tomography transmission attenuation correction (AC).CZT cameras had higher extrinsic resolution than conventional SPECT. Myocardium count sensitivity of CZT camera is about threefold of conventional SPECT. Contrast-to-noise ratios and sharpness profiles are higher on CZT camera but degraded while extracardiac soft tissue presented. Myocardial walls measured on CZT images were thicker. Images of CZT had lower SDS, while AC reduced the differences of SDS between CZT and CC. Perfusion images from CZT had the better uniformity than SPECT without or with AC. Breast attenuation was less prominent on CZT camera than conventional SPECT, while inferior and inferolateral segments still suffer marked soft tissue attenuation on CZT camera.CZT camera has better physical performance and image quality with less artificial perfusion defects than conventional SPECT. CZT camera also has less breast attenuation than conventional SPECT. However, extracardiac soft tissue may degrade the superior performance of CZT camera, and attenuation correction methods are still needed to solve the attenuation issues in inferior and inferolateral myocardium.
Keywords: Myocardial perfusion imaging; CZT camera; Conventional SPECT; Soft tissue attenuation

A novel respiratory gating method for oncologic positron emission tomography based on bioimpedance approach by Tuomas Koivumäki; Jarmo Teuho; Mika Teräs; Marko Vauhkonen; Mikko A. Hakulinen (351-358).
Respiratory motion causes loss of image quality and inaccuracy of quantification in oncologic positron emission tomography (PET) imaging. This study introduces a bioimpedance-based gating method for compensation of respiratory motion artefacts.The bioimpedance-based respiratory gating method was studied parallel to a clinically used respiratory gating method [Real-time Position Management by Varian Medical Systems] in 4D PET/CT acquisition of 9 oncologic patients. The quantitative analysis consisted of the evaluation of tumour SUVpeak, SUVmax and volume. Additionally, target-to-background ratios as well as motion in cranial–caudal and anterior–posterior directions were measured. The evaluation was performed with amplitude- and time-based gating using averaged attenuation correction maps.Bioimpedance gating resulted in 17.7–18.9 % increase in mean SUVpeak and 20.0–21.4 % decrease in mean volume compared to non-gated images. The maximum motion measured from the bioimpedance-gated images was 19 mm in cranial–caudal direction and 9 mm in anterior–posterior direction.Bioimpedance-based respiratory gating compensates the adverse effects of motion in oncologic PET imaging.
Keywords: Respiratory gating; Positron emission tomography; Motion artefacts; Bioimpedance; 4D PET/CT

This study was planned to determine the efficacies of single plasma sample methods (SPSMs) in indicating glomerular filtration rate (GFR) by taking two plasma sample method (TPSM) as reference in the determination of the GFR in cases with clinically stable renal transplantation.Ninety-six renal transplantation cases (33 female, 63 male; age interval 18–67, mean age 37.46 ± 11.81 years) progressing stably clinically and as laboratory, with minimum 6 months after transplantation were included in the study. The GFR values of the cases were measured with SPSM and TPSM.It is observed that all SPSMs have a strong correlation with TPSM. Highest correlation was observed between Groth&Aasted SPSM and TPSM GFR (intraclass correlation coefficient: 0.965). In the analyses performed by using the Bland–Altman analysis, GFR values calculated by all SPSMs were concordant to the TPSM which is the gold standard method in 95 % confidence interval (average ± 1.96 standard deviation) and were within the clinically acceptable limits. The narrowest concordance interval was obtained between Groth&Aasted Tc-99 m DTPA SPSM and Tc-99 m DTPA TPSM..Besides, we have obtained the minimum bias and precision value by the Groth&Aasted method.As a result; we can see that all the SPSMs give reliable results in measuring GFR in cases with renal transplantation; besides, we suggest Groth&Aasted method as the first option.
Keywords: Glomerular filtration rate; Renal transplantation; Single plasma sample method; Two plasma sample method

A myocardial perfusion imaging system using a multifocal collimator for detecting coronary artery disease: validation with invasive coronary angiography by Yutaka Ogino; Yoriko Horiguchi; Tomohiro Ueda; Tomofumi Shiomori; Masahiko Kanna; Tomoko Kawaminami; Naoki Iinuma; Yuta Sudo; Yukiko Morita (366-370).
Myocardial perfusion imaging (MPI) systems using a multifocal collimator can reduce scan time substantially compared with conventional MPI systems. In this study, we evaluated the diagnostic accuracy of multifocal collimator SPECT/CT in coronary artery disease (CAD) detection by comparing it with coronary artery angiography (CAG).We retrospectively analyzed 50 consecutive patients who had undergone CAG and stress 201Tl MPI multifocal collimator SPECT/CT within a 3-month period. A summed difference score (SDS) was calculated for each vascular territory from the MPI images. On CAG, a stenotic coronary artery was defined as one with luminal narrowing of ≥75 % with quantitative coronary angiography software.We analyzed the diagnostic accuracy of coronary artery stenosis detection using the definition that a coronary artery territory was ischemic when the SDS per vessel was ≥2. We generated receiver operating characteristic (ROC) curves to evaluate the usefulness of SDS per vascular territory to find coronary artery stenoses. The area under the ROC curve was 0.86 and cut-off value was 2. Sensitivity, specificity, positive predictive value, negative predictive value, and accuracy to detect stenoses were 85, 83, 66, 94 and 84 %, respectively.We confirmed the high accuracy of imaging with multifocal collimator SPECT/CT for detection of angiographically significant CAD.
Keywords: Coronary angiography; Coronary artery disease; IQ-SPECT; Multifocal collimator; Myocardial perfusion imaging

Parathyroid adenoma upstaging the lung cancer by Kursat Okuyucu; Kuthan Kavakli; Sukru Ozaydın; Serdar Karahatay; Okan Karatas; Deniz Doğan (371-374).
Mediastinal staging of NSCLC with noninvasive methods such as PET/CT can be misleading when a mediastinal disease accompany. Histopathologic confirmation should be made before any treatment plan. Herein, we presented a case of parathyroid adenoma upstaging the lung cancer.
Keywords: Lung cancer; Mediastinal staging; PET/CT; Parathyroid adenoma

Evaluation of various energy windows at different radionuclides for scatter and attenuation correction in nuclear medicine by Afrouz Asgari; Mansour Ashoor; Mostafa Sohrabpour; Parvaneh Shokrani; Ali Rezaei (375-383).
Improving signal to noise ratio (SNR) and qualified images by the various methods is very important for detecting the abnormalities at the body organs. Scatter and attenuation of photons by the organs lead to errors in radiopharmaceutical estimation as well as degradation of images. The choice of suitable energy window and the radionuclide have a key role in nuclear medicine which appearing the lowest scatter fraction as well as having a nearly constant linear attenuation coefficient as a function of phantom thickness.The energy windows of symmetrical window (SW), asymmetric window (ASW), high window (WH) and low window (WL) using Tc-99m and Sm-153 radionuclide with solid water slab phantom (RW3) and Teflon bone phantoms have been compared, and Matlab software and Monte Carlo N-Particle (MCNP4C) code were modified to simulate these methods and obtaining the amounts of FWHM and full width at tenth maximum (FWTM) using line spread functions (LSFs). The experimental data were obtained from the Orbiter Scintron gamma camera.Based on the results of the simulation as well as experimental work, the performance of WH and ASW display of the results, lowest scatter fraction as well as constant linear attenuation coefficient as a function of phantom thickness. WH and ASW were optimal windows in nuclear medicine imaging for Tc-99m in RW3 phantom and Sm-153 in Teflon bone phantom. Attenuation correction was done for WH and ASW optimal windows and for these radionuclides using filtered back projection algorithm. Results of simulation and experimental show that very good agreement between the set of experimental with simulation as well as theoretical values with simulation data were obtained which was nominally less than 7.07 % for Tc-99m and less than 8.00 % for Sm-153. Corrected counts were not affected by the thickness of scattering material. The Simulated results of Line Spread Function (LSF) for Sm-153 and Tc-99m in phantom based on four windows and TEW method were indicated that the FWHM and FWTM values were approximately the same in TEW method and WH and ASW, but the sensitivity at the optimal window was more than that of the other one.The suitable determination of energy window width on the energy spectra can be useful in optimal design to improve efficiency and contrast. It is found that the WH is preferred to the ASW and the ASW is preferred to the SW.
Keywords: Scatter fraction; Attenuation coefficient; Energy window; Sm-153; Tc-99m; Phantom; FWHM; MCNP4C

Effects of filtration on right ventricular function by the gated blood pool SPECT by Samane Mohseni; Alireza Kamali-Asl; Ahmad Bitarafan-Rajabi; Seyed Mohammad Entezarmahdi; Zohre Shahpouri; Nahid Yaghoobi (384-390).
Gated blood po ol single photon emission computed tomography (GBPS) offers the possibility of obtaining additional functional information from blood pool studies, including evaluation of left and right ventricular function simultaneously. The calculation of ventricular volumes based on the identification of the endocardial surface would be influenced by the spatial resolution in the reconstructed images. This study was performed to evaluate the effect of different filters on the right ventricular function.The normal four-dimensional (4-D) NURBS-based cardiac-torso (NCAT) phantom with known right ventricular volume and ejection fraction was generated. The SIMIND Monte Carlo program was used to create projections. The studies were reconstructed by FBP and post-processing filtration such as Butterworth, Hanning, Shepp-Logan, Metz and Wiener in different statuses (cutoff and order). Using the Cedars–Sinai QBS (quantitative blood pool SPECT) package, the ventricular functional parameters were computed. The calculated values were analyzed and compared with the normal NCAT results.The results implied that the calculated right ventricular end diastolic volume (RVEDV) by Butterworth filtration (cutoff frequency = 0.3) agreed more with the NCAT Phantom characteristics [relative difference percentage (RDP) = 1.2 %], while the maximum accordance in the calculation of the RV ejection fraction (EF) (RDP = 3 %) was observed by Metz filter (FWHM 20 pixel). Also, the results of this study demonstrate that the Butterworth filter provided the most stable values (cutoff frequency = 0.4–0.5) in the estimation of RVEDV (RDP = 7.5 %). The Hanning and Shepp-Logan filters produced a much larger RDP, particularly in low frequency (41.1 and 21.5 %, respectively) compared to other filters.This study demonstrated that the operation of different filters has a severe effect in computing right ventricular volume. The resolution recovery and Butterworth filters tend to give more comparable ventricular volumes with the actual normal NCAT value. Further evaluation using a large clinical database is underway to evaluate the optimum protocol in a clinical setting.
Keywords: GBPS; NCAT; Ventricular function; Filtration