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Annals of Nuclear Medicine (v.24, #9)

Nuclear neuroimaging in acute and subacute ischemic stroke by Naohiko Oku; Toru Kashiwagi; Jun Hatazawa (pp. 629-638).

Neuroimaging in ischemic stroke continues to be one of the most developing fields in nuclear medicine. Many studies have established the efficacy of blood flow and metabolism measurements in acute ischemic stroke. Although the release of recombinant tissue plasminogen activator in clinical practice has minimized the use of SPECT or PET in the first few hours of ischemic stroke onset, implementing these techniques into a set of initial examinations is still beneficial to exclude risky patients for reperfusion therapy beyond several hours after onset. Rescuing of viable tissue suffering ischemic penumbra is an important target of early therapeutic strategy. Ischemic penumbra can be visualized by means of perfusion imaging, central type benzodiazepine receptor imaging, and hypoxy imaging. In the later phase of subacute ischemic stroke, inflammation and apoptosis can be visualized by means of peripheral-type benzodiazepine receptor imaging and annexin V imaging, respectively. Imaging of the penumbra and cellular responses will help evaluate the effects of drugs and interventions for ischemic stroke, suggesting its potential as a marker of the efficacy of future therapeutic regimens.

Keywords: Neuroimaging; Stroke; Penumbra; SPECT; PET

Technetium-99m depreotide imaging by single photon emission tomography/low resolution computed tomography in malignant lymphomas: comparison with gallium-67 citrate by Dimitris J. Apostolopoulos; Nikolaos I. Papandrianos; Argiris Symeonidis; Tryfon Spyridonidis; Sotiria Alexiou; Petros Zampakis; Christos Savvopoulos; Pavlos J. Vassilakos; Panagiota Matsouka (pp. 639-647).

Previous studies have demonstrated the feasibility of targeting lymphoma lesions with somatostatin receptor binding agents, mainly with In-111-pentetreotide. In the present work another somatostatin analog, Tc-99m depreotide, is investigated.One-hundred and six patients, 47 with Hodgkin’s (HL) and 59 with various types of non-Hodgkin’s lymphoma (NHL), were imaged with both Tc-99m depreotide and Ga-67 citrate. Planar whole-body and single photon emission tomography/low resolution computerized tomography (SPECT/CT) images were obtained. A total of 142 examinations were undertaken at different phases of the disease. Depreotide and gallium findings were compared visually and semi-quantitatively, with reference to the results of conventional work-up and the patients’ follow-up data.In most HL, intermediate- and low-grade B-cell, as well as in T-cell NHL, depreotide depicted more lesions than Ga-67 and/or exhibited higher tumor uptake. The opposite was true in aggressive B-cell NHL. However, there were notable exceptions in all lymphoma subtypes. During initial staging, 93.3% of affected lymph nodes above the diaphragm, 100% of inguinal nodes and all cases with splenic infiltration were detected by depreotide. On the basis of depreotide findings, 32% of patients with early-stage HL were upstaged. However, advanced HL and NHL cases were frequently downstaged, due to low sensitivity for abdominal lymph node (22.7%), liver (45.5%) and bone marrow involvement (36.4%). Post-therapy, depreotide detected 94.7% of cases with refractory disease or recurrence. Its overall specificity was moderate (57.1%). Rebound thymic hyperplasia, various inflammatory processes and sites of unspecific uptake were the commonest causes of false positive findings. The combination of depreotide and gallium enhanced sensitivity (100%), while various false positive results of either agent could be avoided.Except perhaps for early-stage HL, Tc-99m depreotide as a stand-alone imaging modality has limited value for the initial staging of lymphomas. Post-therapy, however, depreotide scintigraphy seems useful in the evaluation of certain anatomic areas, particularly in non-aggressive lymphoma types. The combination with Ga-67 potentially enhances sensitivity and specificity. If fluorodeoxyglucose positron emission tomography is not available or in case of certain indolent lymphoma types, Tc-99m depreotide may have a role as an adjunct to conventional imaging procedures.

Keywords: Lymphoma imaging; SPECT/CT; Tc-99m depreotide; Ga-67 citrate; Comparison

The management of pyothorax-associated lymphoma using ¹⁸F-FDG PET/CT by Kimiteru Ito; Yoshitaka Shida; Kazuo Kubota; Miyako Morooka; Takashi Aruga; Jun Itami; Hiroshi Matsuda (pp. 649-654).

Pyothorax-associated lymphoma (PAL) is a rare form of lymphoma and its management on ¹⁸F-fluorodeoxyglucose (FDG) positron emission tomography (PET) combined computed tomography (CT) has not been well reported. The purpose of this study was to evaluate the usefulness of FDG PET/CT in patients with PAL.Twenty-four PET/CT images in seven patients (5 men and 2 women) with PAL were studied retrospectively. Five of the 24 PET/CT scans were done for diagnosis and staging, 6 for restaging, 3 for follow-up, and 10 to evaluate the treatment response. PET/CT scan interpretations were performed visually and using the maximum standardized uptake values (SUVmax). Additionally, the efficacy of the enhanced CT findings in pre- and post-treatments was described.Six of the 7 patients with PAL received radiotherapy, and the efficacy of treatment was observed in their lesions. The percentage decrease of SUVmax in PAL was useful in providing complementary information. Enhanced CT findings showed decreasing enhancement of PAL after treatment; however, in five cases, residual masses were confirmed after treatment.FDG PET/CT may be an ideal modality for reducing the false-positive interpretation of residual masses occurring after treatment for PAL. The SUVmax provides complementary information for the management of PAL.

Keywords: Pyothorax-associated lymphoma (PAL); PET/CT; FDG; Empyema

A practical method of determining cross-calibration factors of PET scanners by moving a point-like ²²Na radioactive source by Tomoyuki Hasegawa; Keiichi Oda; Yasuhiro Wada; Yasushi Sato; Takahiro Yamada; Eiji Yoshida; Hideo Murayama; Kyoko Saito; Tohoru Takeda; Kei Kikuchi (pp. 655-661).

Thus far, cylindrical phantoms with ¹⁸F or ⁶⁸Ge/⁶⁸Ga have been used in the standard techniques for determining the cross-calibration factors (CCFs) of PET scanners. This paper describes a new practical method that uses a point-like ²²Na radioactive source for determining CCFs.A point-like ²²Na radioactive source (about 700 kBq) was equipped with a spherical aluminium absorber capsule to ensure the symmetry of the emitted photons. During measurements, the source was moved in the axial direction to cover the whole axial field of view (FOV) of a clinical PET scanner, SET-2400 W. The region-of-interest (ROI) values obtained in reconstructed images without scatter and attenuation corrections were used to calculate the CCFs of the PET scanner.The CCFs obtained by the proposed method agreed with those obtained by the standard cross-calibration (CC) method within a precision of 1.5% (σ). The temporal variations in the CCFs by the standard CC method were reproduced by the proposed method with a precision better than 1%.The CC method with a moving ²²Na point-like radioactive source is practically useful for determining the CCFs of PET scanners and monitoring their variations.

Keywords: PET; Calibration; Point-like source; ²²Na; Traceability

Imaging of a rat osteoarthritis model using ¹⁸F-fluoride positron emission tomography by Yusuke Umemoto; Takushi Oka; Tomio Inoue; Tomoyuki Saito (pp. 663-669).

Currently, conventional radiography is the standard method for the diagnosis and evaluation of the severity of osteoarthritis (OA), but it takes a couple of years to detect cartilage loss. Magnetic resonance imaging can delineate articular cartilage and accurately assess cartilage volume and thickness, but its reliability for very early diagnosis of OA is still controversial. The purpose of this study was to confirm the potential of ¹⁸F-fluoride PET for the early diagnosis of OA by using a surgically induced rat OA model.Seventeen 16-week-old male Sprague-Dawley rats underwent anterior cruciate ligament transection (ACLT) in the right knee to induce OA. The left knee underwent sham operation. At 2, 4, and 8 weeks after operation, the rats were injected with 2.5 MBq/kg of ¹⁸F-fluoride, and 30 min after injection, each rat was killed and the bilateral knees were resected. The femur and tibia were cut horizontally, approximately 2 mm from the joint surface excluding the growth plate, and were cut into the medial and lateral condyles. The patella was also resected and blood samples were collected. The radioactivity of each sample was measured by gamma counting. Assays for serum cartilage oligomeric matrix protein and serum C-telopeptide of type II collagen were performed. Histopathological grading was performed according to a modified Mankin’s scoring system. Two rats underwent PET scans at 2, 4, and 8 weeks after operation. The rats were injected with 30 MBq of ¹⁸F-fluoride, and 30 min after injection, bilateral knee images with a 30-min acquisition time were obtained with an animal PET system.The uptake of ¹⁸F-fluoride was significantly higher in ACLT knees than sham-operated knees in the medial femur and medial tibia at 2 weeks after operation. At 4 weeks after operation, the medial femur, medial tibia, and lateral tibia of OA knees showed significantly higher uptake of ¹⁸F-fluoride compared with sham-operated knees. At 8 weeks, all sections showed significant differences. The uptake of ¹⁸F-fluoride significantly increased as time elapsed in all sections. Uptake showed a significant correlation with histological scores.Our results suggest that ¹⁸F-fluoride is potentially useful for the early detection of osteoarthritic changes.

Keywords: Positron emission tomography; ¹⁸F-fluoride; Osteoarthritis; Knee; Rat model

Positron emission tomography inter-scanner differences in dopamine D₂ receptor binding measured with [¹¹C]FLB457 by Fumitoshi Kodaka; Hiroshi Ito; Miho Shidahara; Harumasa Takano; Hidehiko Takahashi; Ryosuke Arakawa; Kazuhiko Nakayama; Tetsuya Suhara (pp. 671-677).

It is well known that the positron emission tomography (PET) system is subject to inter-scanner differences of regional radioactivity distribution. In the present study, the effect of inter-scanner difference of regional radioactivity on estimated binding potential (BP_ND) of [¹¹C]FLB457 using the simplified reference tissue model (SRTM) was investigated.Each of the 11 subjects was given two PET scans using [¹¹C]FLB457, one each with both SET-3000 GCT/X (Shimadzu) and with ECAT EXACT HR+ (Siemens/CTI). In order to assess regional differences between the two scanners, estimated BP_ND values in six volumes of interest (VOIs) by SRTM method were compared in both individual PET space and anatomical template space after anatomical normalization. Statistical voxel-by-voxel paired t test of BP_ND images between SET-3000 GCT/X and ECAT EXACT HR+ was also performed.Shapes of time–activity curves of the two PET scanners were slightly different in each VOI, with estimated BP_ND values from ECAT EXACT HR+ appearing greater in the cerebral cortical regions and thalamus than that of SET-3000 GCT/X in both individual PET space and anatomical template space after anatomical normalization. Statistical voxel-by-voxel analysis showed similar tendency to BP_ND value estimation, with greater BP_ND values from ECAT EXACT HR+ than from SET-3000 GCT/X.We demonstrated the inter-scanner differences in dopamine D₂ receptor binding measured with [¹¹C]FLB457. In particular, statistically significant differences of BP_ND in certain regions were observed between two PET scanners, despite the subject groups being the same. Our results suggest that we reconsider the effect of the scanner model on the measurement of receptor binding.

Keywords: Brain PET; [¹¹C]FLB457; Inter-scanner difference; Binding potential; Simplified reference tissue model

Iodine-123-metaiodobenzylguanidine imaging can predict future cardiac events in heart failure patients with preserved ejection fraction by Shigehiko Katoh; Tetsuro Shishido; Daisuke Kutsuzawa; Takanori Arimoto; Shunsuke Netsu; Akira Funayama; Mitsunori Ishino; Takeshi Niizeki; Satoshi Nishiyama; Hiroki Takahashi; Takehiko Miyashita; Takuya Miyamoto; Joji Nitobe; Tetsu Watanabe; Isao Kubota (pp. 679-686).

Iodine-123-metaiodobenzylguanidine (¹²³I-MIBG) has been used to assess the function of the cardiac sympathetic nervous system in patients with chronic heart failure (HF). The usefulness of ¹²³I-MIBG imaging for evaluating patients with heart failure with preserved ejection fraction (HFPEF) has not been established.We performed ¹²³I-MIBG scintigraphy and echocardiography and measured the plasma brain natriuretic peptide (BNP) levels of 117 consecutive HF patients (64 men, mean age 66 ± 14 years) with a left ventricular ejection fraction (LVEF) of ≥50% who were admitted to our hospital. Patients were divided into 2 groups according to the New York Heart Association (NYHA) functional class.The ¹²³I-MIBG delayed heart-to-mediastinum (H/M) ratio was significantly lower, and the washout rate (WR) was higher in patients with HFPEF with advanced NYHA functional class (NYHA functional class I and II vs. III: 1.90 ± 0.34 vs. 1.49 ± 0.32, p < 0.0001; 25.9 ± 13.4 vs. 46.9 ± 16.3%, p < 0.0001, respectively). On the other hand, the ¹²³I-MIBG WR was not correlated with LVEF and had a weak correlation with plasma BNP levels (R = 0.207, p = 0.0346). Moreover, patients with a high ¹²³I-MIBG WR showed a poor clinical outcome (p = 0.0033). ¹²³I-MIBG imaging provides independent prognostic information in patients with HFPEF.

Keywords: Cardiac imaging; Sympathetic nervous system; Washout rate; Preserved ejection fraction

F-18 FDG PET/CT in relapsing polychondritis by Motohiro Sato; Takashi Hiyama; Takashi Abe; Yuta Ito; Syoujiro Yamaguchi; Keiko Uchiumi; Ikuta Hashimoto; Takayuki Kaburagi (pp. 687-690).

We report a case of relapsing polychondritis for which fluorodeoxyglucose (FDG) positron-emission tomography/computed tomography (PET/CT) showed increased FDG accumulation in all rib cartilages, as well as in the larynx, trachea, and major bronchi. Contrast-enhanced CT during PET/CT showed smooth tracheal and bronchial wall thickening with calcification and airway narrowing. After steroid therapy, clinical symptoms and laboratory data were improved and cartilaginous FDG accumulation had completely disappeared. FDG PET/CT is considered to be a powerful radiological tool to assess the disease activity of relapsing polychondritis.

Keywords: Relapsing polychondritis; F-18 FDG; PET/CT

Relative renal function with MAG-3 and DMSA in children with unilateral hydronephrosis by Gül Ege Aktaş; Sabahat Inanir (pp. 691-695).

Tc-99m DMSA renal cortical scan is a reference method for determining relative renal function (RRF). Tc-99m MAG-3 is also recommended for the estimation of RRF, particularly in young children. The aims of this study were to compare MAG-3 and DMSA RRF estimations and to assess the reproducibility of these estimations in children with unilateral hydronephrosis.We reviewed MAG-3 and DMSA scans of 19 children with unilateral hydronephrosis and a normal contralateral unit. All were imaged with 2 agents within 3 months. MAG-3 RRF was calculated using 2 different time intervals (1–2 and 2–3 min) and perirenal C-type region of background activity. No background correction method was used in the calculation of DMSA RRF. All data were processed twice by two independent operators.In the repeated estimates of MAG-3 RRF, the maximum mean intra-observer and inter-observer differences were 0.9% (SD 1.7%) and 1.4% (SD 3.3%), respectively. Intra-method analysis showed statistically significant agreement between repeated measures of RRF for two agents as well as for two operators (intra-class cross-correlation coefficients of early and later phase of MAG-3 and DMSA RRF values were 0.979, 0.993 and 0.996 for operator 1, and 0.986, 0.973 and 0.995 for operator 2, respectively; p < 0.001). There were statistically significant correlations between the MAG-3 and DMSA RRF estimations (r = 0.763/0.766 at 1–2 min, 0.835/0.825 at 2–3 min for the repeated measures of RRF for operator 1, and 0.812/0.793 and 0.83/0.89 for operator 2, respectively; p < 0.01, Pearson). Each scan classified as normal or abnormal according to RRF values inter-method analysis showed statistically significant agreement between MAG-3 and DMSA RRF estimations (Kappa statistics). However, there was a slight disagreement between the methods especially in infants and cases with higher grade of hydronephrosis, when 5% difference in estimations and supranormal estimates of RRF were taken into consideration.Although DMSA and MAG-3 RRF estimations demonstrated a statistically significant correlation with good reproducibility in children with unilateral hydronephrosis, overall the finding of surprising estimates of kidney function with MAG-3 calls attention to the existence of some problems especially in infants and in those with higher grades of hydronephrotic kidneys.

Keywords: Hydronephrosis; DMSA; MAG-3; RRF

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Annals of Nuclear Medicine (v.24, #9)

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Annals of Nuclear Medicine (v.24, #9)