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Objective: Compared with radiation therapy using photon beams, particle therapies, especially those using carbons, show a high relative biological effectiveness and low oxygen enhancement ratio. Using cells cultured under normoxic conditions, our group reported a greater suppressive effect on cell growth by carbon beams than X-rays, and the subsequent therapeutic effect can be predicted by the cell uptake amount of 3'-deoxy-3'-[ 18 F]fluorothymidine ( 18 F-FLT) the day after treatment. On the other hand, a hypoxic environment forms locally around solid tumors, influencing the therapeutic effect of radiotherapy. In this study, the influence of tumor hypoxia on particle therapies and the ability to predict the therapeutic effect using 18 F-FLT were evaluated., Methods: Using a murine colon carcinoma cell line (colon 26) cultured under hypoxic conditions (1.0% O 2 and 5.0% CO 2 ), the suppressive effect on cell growth by X-ray, proton, and carbon irradiation was evaluated. In addition, the correlation between decreased 18 F-FLT uptake after irradiation and subsequent suppression of cell proliferation was investigated., Results: Tumor cell growth was suppressed most efficiently by carbon-beam irradiation. 18 F-FLT uptake temporarily increased the day after irradiation, especially in the low-dose irradiation groups, but then decreased from 50 h after irradiation, which is well correlated with the subsequent suppression on tumor cell growth., Conclusions: Carbon beam treatment shows a strong therapeutic effect against cells under hypoxia. Unlike normoxic tumors, it is desirable to perform 18 F-FLT positron emission tomography 2-3 days after irradiation for early prediction of the treatment effect., (© 2023. The Author(s).)

Cord blood is an important donor source for allogeneic hematopoietic stem cell transplantation (allo-HSCT), with its unique composition and quality of hematopoietic cells. The proliferation site and potency of infused hematopoietic stem cells in humans may vary between stem cell sources. We investigated this possibility in a prospective, exploratory study to assess hematopoietic dynamics using the radiopharmaceutical 3'-deoxy-3'- 18 F-fluorothymidine ( 18 F-FLT), a thymidine analog used in positron emission tomography imaging, before allo-HSCT and on days 50 and 180 after allo-HSCT. We evaluated 11 patients with hematological malignancies who underwent allo-HSCT [five with peripheral blood stem cell transplantation (PBSCT) and six with unrelated cord blood transplantation (UCBT)]. Before allo-HSCT, 18 F-FLT uptake did not differ between the two groups. At day 50, 18 F-FLT uptake in the spleen was significantly greater in the UCBT group than in the PBSCT group (p = 0.0043), with no difference in whole-body bone marrow. At day 180, the differences in spleen uptake had diminished, and there were no differences between groups in whole-body bone marrow or the spleen, except for the sternum. The persistence of splenic hematopoiesis after engraftment in the UCBT group may reflect the complex systemic homing and proliferation mechanisms of cord blood hematopoietic cells., (© 2023. The Author(s).)

Objective: In the [ 123 I]FP-CIT single-photon emission computed tomography (SPECT) examination, the specific binding ratio (SBR), calculated from the ratio of the striatal specific to extra-striatal background non-specific binding in the brain, is now commonly used as a quantitative index of parkinsonian syndrome. The purpose of this study was to examine the influence of count reduction on the SBR and to clarify the reliability of SBR values in patients with shorter scan times., Methods: A striatum phantom was used in a phantom study, with the radioactivity concentration adjusted so that the right striatum:left striatum:brain parenchyma ratio was 8:4:1. Changes in SBR values and image quality, expressed as the % coefficient of variation (%CV) and normalized mean squared error (NMSE), with decreasing acquisition counts were evaluated. In the clinical study, 106 patients (73.1 ± 9.6 years) with suspected parkinsonian syndrome underwent [ 123 I]FP-CIT SPECT, and SBR values from normal 30 min acquisitions ( full SBR) and half-count acquisitions ( half SBR) were compared. SBR values were calculated using the Tossici-Bolt (SBR TB ) and a fully automatic count-based (SBR cb ) methods., Results: In the phantom study, image quality decreased with a reduction of acquisition counts. The %CV and NMSE decreased by up to 52.5% and 81.5%, respectively. SBR values decreased slightly as acquisition counts decreased. In the clinical study, the mean values of half SBR were lower than those of full SBR, and they were significantly different except for SBR TB without attenuation correction. half SBR and full SBR values correlated well, with half SBR values 1-8% lower than full SBR. The accuracy of diagnosis did not decrease even after acquisition counts were reduced by half., Conclusion: This study demonstrated that SBR values decrease as a function of reduced acquisition counts. Since half SBR and full SBR showed excellent correlation, it is suggested that full SBR can be estimated from half SBR using a calibration formula when scan times are reduced., (© 2021. The Japanese Society of Nuclear Medicine.)

Objective: Integrated PET/MRI with [ 18 F]FDG is advantageous in that it enables simultaneous PET and MR imaging with higher soft-tissue contrast, multiplanar image acquisition, and functional imaging capability without using fat suppression and gadolinium-based contrast agents (GBCAs). The aims of this study were to demonstrate the feasibility of [ 18 F]FDG PET/MRI for assessing the extent of the primary tumor (T) in oral tongue cancer (OTC) based on the 8th edition of American Joint Committee on Cancer (AJCC) cancer staging system, and to compare the diagnostic accuracy between [ 18 F]FDG PET/MRI and contrast-enhanced MRI (ceMRI)., Methods: 18 patients with biopsy-proven operable OTC underwent preoperative regional [ 18 F]FDG PET/MRI and ceMRI within 2 weeks. For [ 18 F]FDG PET/MRI, rainbow-colored PET images were overlaid on the corresponding MR images. Tumor size and the depth of invasion (DOI) were visually measured on [ 18 F]FDG PET/MRI and ceMRI. The size, DOI, and clinical T stage were evaluated using the final surgical pathology as the reference., Results: Of the 18 OTCs, one was not detected by ceMRI due to metal artifacts from an artificial denture, and another due to superficial type (pathological DOI = 0 mm). Tumor sizes measured by ceMRI and [ 18 F]FDG PET/MRI had significant positive correlations with the pathological size (r = 0.80 and r = 0.90, respectively), and DOIs measured by ceMRI and [ 18 F]FDG PET/MRI had significant positive correlations with the pathological DOI (r = 0.74 and r = 0.64, respectively). The means ± SD of size (mm) were 20.4 ± 9.1, 22.9 ± 10.9, and 26.2 ± 10.0, and those of DOI (mm) were 7.1 ± 2.5, 6.9 ± 2.2, and 5.8 ± 3.2 for ceMRI, [ 18 F]FDG PET/MRI, and pathology, respectively. A significant difference was observed in tumor size between ceMRI and pathology (p < 0.05), whereas no significant differences were observed between any other sizes, DOIs, or T stages. The accuracy for T status was 72% (13/18 including 2 undetectable cases) for ceMRI and 89% (16/18) for [ 18 F]FDG PET/MRI., Conclusions: Although shallow DOIs are often overestimated, regional [ 18 F]FDG PET/MRI without fat suppression and gadolinium enhancement is comparable to and may be substituted for ceMRI in preoperative T staging for OTC patients, reducing metal artifacts and avoiding the adverse effects of GBCAs.

Objective: This pharmacovigilance-based survey was aimed at determining the prevalence of, and association between, radiopharmaceuticals and adverse reactions to radiopharmaceuticals from 1975 to 2017 in Japan., Methods: The Subcommittee for Safety Issues of Radiopharmaceuticals of the Japan Radioisotope Association's Medical Science and Pharmaceutical Committee mailed a form for reporting adverse reactions to radiopharmaceuticals to all institutes performing nuclear medicine examinations in Japan. This investigation included adverse reactions to diagnostic radiopharmaceuticals labeled with both single-photon- and positron-emitting radionuclides and therapeutic sodium iodide labeled with 131 I. Each institute returned the reporting form to the subcommittee each time an adverse reaction occurred., Results: Replies were obtained from 75% of the institutions. In total, 1099 adverse reactions were reported from 46,645,580 radiopharmaceutical administrations, giving a prevalence of 2.4 adverse reactions per 100,000 administrations (95% confidence interval 2.2-2.5). Adverse reactions were most frequently observed for 131 I-iodomethylnorcholesterol (230.1/10 5 administrations), followed by 131 I-HSA (76.3/10 5 administrations), 131 I-sodium iodohippurate (31.2/10 5 administrations), and 99m Tc-DTPA (12.0/10 5 administrations). Comparison of adverse reactions between before and after 1997 revealed that prevalence dropped from 3.7/10 5 administrations (95% confidence interval 3.5-4.1) to 1.5/10 5 administrations (95% confidence interval 1.4-1.6). During the study period, vasovagal reactions accounted for 50.3% of adverse reactions, fever for 7.5%, allergic reactions for 25.7%, and other for 16.5%; 3.7% of all adverse reactions were considered severe but none were lethal. A definite, probable, possible, less likely, and uncertain causal relationship with radiopharmaceuticals was observed in 13.1%, 33.7%, 39.9%, 6.2%, and 7.1% of adverse reactions, respectively., Conclusions: These results suggest that nuclear medicine staff must be aware of the possibility of adverse reactions from radiopharmaceuticals, despite their rarity.

Objective: To calculate the specific binding ratio (SBR) appropriately in dopamine transporter (DAT) imaging, a method for extracting the striatal volume of interest (VOI) was developed., Methods: This study included 200 patients (72 ± 10 years) who were suspected of parkinsonian syndromes (PS) or dementia with Lewy body (DLB). The patients were divided into three groups of PS with dopaminergic degeneration, DLB and non-PS after [ 123 I]ioflupane (FP-CIT) SPECT and clinical follow-up. The image data were reconstructed with CT attenuation correction and scatter correction, and with only CT attenuation correction (CTAC). The new method extracted striatal VOI according to the high-level counts and the average striatum volume, and calculated SBR using the reference occipital counts. The SBR values for each patient were obtained using the Tossici-Bolt method (SBR Bolt ) and our method. Reproducibility of SBR calculation using our method was compared by two operators., Results: The mean SBR values for the PS and DLB groups were significantly different from that of the non-PS group with both methods. The coefficients of variation of the SBR were significantly smaller with the proposed method compared with those of SBR Bolt (p < 0.001), except for the CTAC images. There were no differences in SBR between the two operators using our method. The diagnostic accuracies with our method for the PS and DLB groups were 98.4 and 96.0%, respectively., Conclusion: Our new method for SBR calculation in the FP-CIT SPECT showed less coefficients of variation with high reproducibility, which would be useful for clinical diagnosis and in assessing the severity of diseases in follow-up studies.

Objective: Statistical image analysis of brain SPECT images has improved diagnostic accuracy for brain disorders. However, the results of statistical analysis vary depending on the institution even when they use a common normal database (NDB), due to different intrinsic spatial resolutions or correction methods. The present study aimed to evaluate the correction of spatial resolution differences between equipment and examine the differences in skull bone attenuation to construct a common NDB for use in multicenter settings., Methods: The proposed acquisition and processing protocols were those routinely used at each participating center with additional triple energy window (TEW) scatter correction (SC) and computed tomography (CT) based attenuation correction (CTAC). A multicenter phantom study was conducted on six imaging systems in five centers, with either single photon emission computed tomography (SPECT) or SPECT/CT, and two brain phantoms. The gray/white matter I-123 activity ratio in the brain phantoms was 4, and they were enclosed in either an artificial adult male skull, 1300 Hounsfield units (HU), a female skull, 850 HU, or an acrylic cover. The cut-off frequency of the Butterworth filters was adjusted so that the spatial resolution was unified to a 17.9 mm full width at half maximum (FWHM), that of the lowest resolution system. The gray-to-white matter count ratios were measured from SPECT images and compared with the actual activity ratio. In addition, mean, standard deviation and coefficient of variation images were calculated after normalization and anatomical standardization to evaluate the variability of the NDB., Results: The gray-to-white matter count ratio error without SC and attenuation correction (AC) was significantly larger for higher bone densities (p < 0.05). The count ratio error with TEW and CTAC was approximately 5% regardless of bone density. After adjustment of the spatial resolution in the SPECT images, the variability of the NDB decreased and was comparable to that of the NDB without correction., Conclusion: The proposed protocol showed potential for constructing an appropriate common NDB from SPECT images with SC, AC and spatial resolution compensation.

The American Joint Committee on Cancer (AJCC) released the 8th edition of the AJCC cancer staging manual in 2017 that includes significant modifications from the 7th edition in the sections on oral cavity cancer (OCC) and oropharyngeal cancer (OPC). These highlights comprise the incorporation of the depth of invasion and exclusion of extrinsic tongue muscle involvement in the T staging of OCC, the separation of OPC staging based on the high-risk human papilloma virus status, and the inclusion of extranodal extension in N staging. The recent introduction of integrated positron emission tomography and magnetic resonance imaging (PET/MRI) with 2-[ 18 F]-fluoro-2-deoxy-D-glucose ( 18 F-FDG) has demonstrated the advantages of simultaneous PET and MR imaging with higher soft-tissue contrast, multiplanar image acquisition, and functional imaging capability. This pictorial essay discusses the role of 18 F-FDG PET/MRI in the diagnosis of OCC and OPC based on the new cancer staging system.

Objective: The aim of this study was to retrospectively evaluate the clinical significance of 18 F-FDG PET/CT textural features for discriminating uterine sarcoma from leiomyoma., Methods: Fifty-five patients with suspected uterine sarcoma based on ultrasound and MRI findings who underwent pretreatment 18 F-FDG PET/CT were included. Fifteen patients were histopathologically proven to have uterine sarcoma, 14 patients by surgical operation and one by biopsy, and 40 patients were diagnosed with leiomyoma by surgical operation or in a follow-up for at least 2 years. A texture analysis was performed on PET/CT images from which second- and higher order textural features were extracted in addition to standardized uptake values (SUVs) and other first-order features. The accuracy of PET features for differentiating between uterine sarcoma and leiomyoma was evaluated using a receiver-operating-characteristic (ROC) analysis., Results: The intratumor distribution of 18 F-FDG was more heterogeneous in uterine sarcoma than in leiomyoma. Entropy, correlation, and uniformity calculated from normalized gray-level co-occurrence matrices and SUV standard deviation derived from histogram statistics showed greater area under the ROC curves (AUCs) than did maximum SUV for differentiating between sarcoma and leiomyoma. Entropy, as a single feature, yielded the greatest AUC of 0.974 and the optimal cut-off value of 2.85 for entropy provided 93% sensitivity, 90% specificity, and 92% accuracy. When combining conventional features with textural ones, maximum SUV (cutoff: 6.0) combined with entropy (2.85) and correlation (0.73) provided the best diagnostic performance (100% sensitivity, 94% specificity, and 95% accuracy)., Conclusions: In combination with the conventional histogram statistics and/or volumetric parameters, 18 F-FDG PET/CT textural features reflecting intratumor metabolic heterogeneity are useful for differentiating between uterine sarcoma and leiomyoma.

Objectives: The aims of our study were to find the textural features on 18 F-FDG PET/CT which reflect the different histological architectures between cervical cancer subtypes and to make a visual assessment of the association between 18 F-FDG PET textural features in cervical cancer., Methods: Eighty-three cervical cancer patients [62 squamous cell carcinomas (SCCs) and 21 non-SCCs (NSCCs)] who had undergone pretreatment 18 F-FDG PET/CT were enrolled. A texture analysis was performed on PET/CT images, from which 18 PET radiomics features were extracted including first-order features such as standardized uptake value (SUV), metabolic tumor volume (MTV) and total lesion glycolysis (TLG), second- and high-order textural features using SUV histogram, normalized gray-level co-occurrence matrix (NGLCM), and neighborhood gray-tone difference matrix, respectively. These features were compared between SCC and NSCC using a Bonferroni adjusted P value threshold of 0.0028 (0.05/18). To assess the association between PET features, a heat map analysis with hierarchical clustering, one of the radiomics approaches, was performed., Results: Among 18 PET features, correlation, a second-order textural feature derived from NGLCM, was a stable parameter and it was the only feature which showed a robust trend toward significant difference between SCC and NSCC. Cervical SCC showed a higher correlation (0.70 ± 0.07) than NSCC (0.64 ± 0.07, P = 0.0030). The other PET features did not show any significant differences between SCC and NSCC. A higher correlation in SCC might reflect higher structural integrity and stronger spatial/linear relationship of cancer cells compared with NSCC. A heat map with a PET feature dendrogram clearly showed 5 distinct clusters, where correlation belonged to a cluster including MTV and TLG. However, the association between correlation and MTV/TLG was not strong. Correlation was a relatively independent PET feature in cervical cancer., Conclusions: 18 F-FDG PET textural features might reflect the differences in histological architecture between cervical cancer subtypes. PET radiomics approaches reveal the association between PET features and will be useful for finding a single feature or a combination of features leading to precise diagnoses, potential prognostic models, and effective therapeutic strategies.

Objective: A new method of delay time estimation was proposed to measure precise cerebral blood flow (CBF) and arterial-to-capillary blood volume (V 0 ) using 15 O-water PET., Methods: Nineteen patients with unilateral arterial stenoocclusive lesions were studied to evaluate hemodynamic status before treatment. The delay time of each pixel was calculated using least squares fitting with an arterial blood input curve adjusted to the internal carotid artery counts at the skull base. Pixel-by-pixel delay estimation provided a delay map image that could be used for precise calculation of CBF and V 0 using a one-tissue compartment model, and the values from this method were compared with those from the slice-by-slice correction method., Results: The affected side showed a longer delay time than the contralateral cerebral hemisphere. Although the mean cortical CBF values were not different between the two methods, the slice-by-slice delay correction overestimated CBF in the hypo perfused area. The scatter plot of V 0 pixel values showed significant difference between the two correction methods where the slice-by-slice delay correction significantly overestimated V 0 in the whole brain (P < 0.05)., Conclusion: Pixel-by-pixel delay correction provides delay images as well as better estimation of CBF and V 0 , thus offering useful and beneficial information for the treatment of cerebrovascular disease.

A 64-year-old, right-handed man underwent endovascular treatment for internal carotid artery stenosis after experiencing a left-hemispheric transient ischemic attack. 15 O-gas and H 2 O positron emission tomography revealed slightly reduced cerebral blood flow (CBF), elevated cerebral blood volume, and severely reduced cerebral vasoreactivity in the ipsilateral hemisphere as determined by an acetazolamide challenge test. The patient underwent left carotid artery stenting (CAS) via a prefemoral approach under local anesthesia without any complications. Follow-up examinations performed 20 h postoperatively showed subarachnoid hemorrhage (SAH) and cerebral hyperperfusion syndrome (CHS) in the left frontal lobe. Although it is a relatively rare phenomenon, SAH resulting from CHS was determined to be specifically caused by CAS. In this case, the causes of SAH may have been related to multiple factors including increased regional CBF, loss of cerebrovascular autoregulation, contrast agent-mediated disruption of major cerebral vessels, and strong antiplatelet therapy.15 O positron emission tomography revealed slightly reduced cerebral blood flow (CBF), elevated cerebral blood volume, and severely reduced cerebral vasoreactivity in the ipsilateral hemisphere as determined by an acetazolamide challenge test. The patient underwent left carotid artery stenting (CAS) via a prefemoral approach under local anesthesia without any complications. Follow-up examinations performed 20 h postoperatively showed subarachnoid hemorrhage (SAH) and cerebral hyperperfusion syndrome (CHS) in the left frontal lobe. Although it is a relatively rare phenomenon, SAH resulting from CHS was determined to be specifically caused by CAS. In this case, the causes of SAH may have been related to multiple factors including increased regional CBF, loss of cerebrovascular autoregulation, contrast agent-mediated disruption of major cerebral vessels, and strong antiplatelet therapy.

Objective: To investigate the prognosis of patients with cerebrovascular steno-occlusive disease who have preserved baseline cerebral blood flow (CBF) and reduced cerebral vasoreactivity (CVR), they were followed up after scans of positron emission tomography (PET)., Methods: Fifty-seven patients with symptomatic unilateral major cerebral arterial occlusion or severe stenosis underwent O-15 gas and water PET scans to measure cerebral blood volume, metabolic rate of oxygen, oxygen extraction fraction (OEF), and CBF at the baseline and after acetazolamide administration. Thirty of them (mean age 60 +/- 10 years) had normal ipsilateral CBF, and were followed prospectively at least 30 months from the last ischemic event. They were medically treated for cerebral circulation and underlying diseases during follow-up periods. The primary endpoint was determined as stroke recurrence during the follow-up., Results: Thirty patients were divided into two groups of reduced CVR (N = 16, 63 +/- 8 years) and normal CVR (N = 14, 56 +/- 10 years) on the basis of CVR values from healthy volunteers. None of them showed significant laterality in baseline CBF and OEF between the hemispheres although patients with reduced CVR showed a tendency of ipsilateral increases in OEF and CBV. Patients were followed up for 50.5 +/- 19.0 and 48.1 +/- 12.4 months in the reduced and normal CVR groups, respectively. Although one patient with reduced CVR died of heart disease, there was no incidence of ischemic events during follow-up periods for either group., Conclusion: In the present prospective study, patients with sufficient baseline CBF showed good prognosis and no difference in recurrent stroke risks even though they had poor CVR in the affected hemisphere, indicating that these patients can be treated by medication for cerebral circulation and baseline diseases if they have high risk factors for neurosurgical treatment.

Objective: Adenosine triphosphate (ATP) is the parent compound of adenosine and well known as a powerful vasodilator. To investigate the effect of ATP on cerebral blood flow (CBF) and cerebral vessels, (15)O-water positron emission tomography (PET) studies were performed to evaluate changes in CBF and blood volume before and after ATP administration., Methods: Ten healthy young volunteers underwent (15)O-water PET scans under the conditions of baseline, 3 and 1 min after ATP continuous infusion. CBF values in cortical regions of the bilateral middle cerebral arteries and basal ganglia were obtained for each subject. Statistical parametric mapping (SPM) was applied for analysis of regional changes. Physiologic parameters, such as blood gas and blood pressure were also measured., Results: Cortical CBF showed no significant change after continuous infusion of ATP compared with the baseline. Dilatation of major vessels induced by ATP was visualized on SPM analysis. Heart rates increased and mean blood pressure decreased during ATP administration while blood gas data showed no changes between the different conditions., Conclusions: Intravenous ATP administration caused dilatation of major cerebral vessels but no significant change in CBF under normoventilation and decrease in systemic blood pressure, indicating that this no change in CBF under vasodilatory effect of ATP may be caused by cerebral microvascular autoregulation.

Positron emission tomography (PET) measurement of cerebral blood flow and metabolism has been a basic and standard method for evaluation of hemodynamics in patients with cerebral vascular disease (CVD). Despite the recent rapid spread of PET and PET/CT facilities, the number of patient examinations with (15)O-gas PET scans is declining because most facilities are used for cancer studies. They avoid (15)O-gas PET study because it is time consuming and the technique and calculation methods appear to be complicated. However, reconsidering the benefits and usefulness of conventional (15)O-gas PET study is a good opportunity to understand its potential possibility. Physiological evaluation of cerebral perfusion and metabolism provided the basic concept of hemodynamics in impaired circulation and the development of evidence-based medicine in neurosurgical treatment for CVD. This method can be used for two major objectives, clinical examination with a less-invasive simplified method, and quantitative precise measurements with model analysis for research purposes. Both are important for developing further practical and investigational approaches using (15)O-gas PET.

Several studies have reported the findings of fluorine-18-labeled fluoro-2-deoxy-D: -glucose positron emission tomography (FDG-PET) in benign lung disease with diffuse pulmonary injury; however, the characteristics and effectiveness of FDG-PET imaging for interstitial pneumonitis have not been substantiated. We report two cases of drug-induced pneumonitis in two patients treated for breast cancer who were diagnosed by FDG-PET examination. Both the cases showed diffuse interstitial infiltration in the bilateral lungs on computed tomography, but the degree of FDG accumulation was different. It is probable that the degree of FDG accumulation reflected the activity of the drug-induced pneumonitis. The present cases show very interesting FDG-PET imaging findings of diffuse lung disease.

16alpha-[(18)F]Fluoro-17beta-estradiol (FES) is an estrogen receptor (ER) ligand used for the detection of ER-positive malignant tumors such as breast cancer. We recently reported the feasibility of combined FES-and 2-[(18)F]fluoro-2-deoxy-D-glucose (FDG)-positron emission tomography (PET) scans for the differential diagnosis of endometrial tumors. ER expression measured by FES-PET was preserved in endometrial hyperplasia, whereas ERs were assumed to be reduced in endometrial carcinoma with accelerated glucose metabolism measured by FDG-PET. We report two postmenopausal patients under suspicion of endometrial carcinoma on the basis of cytology and/or magnetic resonance imaging (MRI), who were on tamoxifen treatment since undergoing surgery for breast cancer. Pelvic MRI suggested endometrial carcinomas, whereas FDG-and FES-PET showed no abnormal tracer accumulation. A postoperative histopathologic examination revealed that the lesions were endometrial hyperplasias with no malignant findings. FES-PET enables us to evaluate the ERalpha expression of endometrium noninvasively, whereas the evaluation of ER expression using FES-PET requires careful attention regarding the influence of hormonal therapy because tamoxifen greatly affects FES accumulation of even endometrial hyperplasia, which should be an FES-avid lesion.

Objective: There is much controversy about the correlation between the degree of 2-[(18)F]fluoro-2-deoxy-D: -glucose (FDG) uptake and clinical aggressiveness of non-Hodgkin's lymphoma (NHL). In this study, we investigated whether partial volume corrected FDG uptake based on count recovery coefficient in 3D-positron emission tomography (PET)/computed tomography (CT) correlates with the clinical aggressiveness of NHL and improves diagnostic accuracy., Methods: Forty-two patients with NHL underwent FDG-PET/CT scans (26 aggressive NHLs and 16 indolent ones). Count recovery curve was obtained using NEMA 2001 body phantom. Scan protocol and reconstructive parameters in the phantom study were the same as those in a clinical scan except for emission time. Relative recovery coefficient (RC) was calculated as RC = A/B (A, maximum pixel count of each hot sphere; B, maximum pixel count of greatest sphere). Partial volume corrected maximum count of standardized uptake value (PVC-SUV) was calculated as PVC-SUV = NC-SUV/RC (NC-SUV: non-corrected maximum count of SUV). Three parameters (NC-SUV, PVC-SUV, and size) between aggressive and indolent NHLs were compared., Results: Significant differences were shown in all parameters between aggressive and indolent NHLs. Means +/- SD of NC-SUV, PVC-SUV, and size was as following: NC-SUV (15.3 +/- 6.9, 8.7 +/- 7.0; P < 0.01), PVC-SUV (18.2 +/- 8.1, 12.7 +/- 7.8; P < 0.05), and size (mm, 32.4 +/- 18.3, 21.9 +/- 10.3; P < 0.05). When an NC-SUV of 9.5 was the cutoff for aggressive NHL, the receiver-operating-characteristic (ROC) analysis correctly identified 21 of 26 aggressive ones. Sensitivity and specificity were 81% each, and the positive and negative predictive values were 88% and 72%, respectively. When a PVCSUV of 11.2 was the cutoff, the ROC analysis revealed 81% sensitivity, 63% specificity, and positive and negative predictive values of 78% and 67%, respectively. At a cutoff for aggressive NHL of a size of 27 mm, the ROC analysis revealed 50% sensitivity, 81% specificity, and positive and negative predictive values of 81% and 50%, respectively. The comparison of area under the curve in ROC analyses indicated that NC-SUV showed the greatest diagnostic accuracy (NC-SUV 0.84, PVC-SUV 0.72, and size 0.69)., Conclusions: Diagnostic accuracy of PVC-SUV was inferior to that of NC-SUV. These results suggest that NC-SUV, which contains information on both size and FDG density, provides better differentiation between aggressive and indolent NHLs than PVC-SUV.

We recently experienced a case with uveitis suffering from fever of unknown origin suspected of being caused by sarcoidosis. Chest computed tomography showed right supraclavicular, bilateral mediastinal, and right hilar lymphadenopathy, and intensive abnormal uptake of 2-[18F]fluoro-2-deoxy-D-glucose (18F-FDG) was observed on positron emission tomography with 18F-FDG (FDG-PET). On the other hand, 67Ga scintigraphy showed almost no abnormal findings. Histopathological examination revealed the lesion to be a diffuse large B-cell lymphoma (DLBCL), namely, an aggressive non-Hodgkin lymphoma from a right supraclavicular lymph node biopsy specimen. Additional immunohistochemical analysis showed the negative expression of transferrin receptor (TfR) on the formalin-fixed paraffin-embedded specimen. Although DLBCL is generally considered to be a 67Ga-avid tumor, it does not always have a large number of TfRs and that leads to a discrepancy between the 67Ga scintigraphy and FDG-PET findings. FDG-PET should be more appropriate for the initial staging of DLBCL than 67Ga scintigraphy, whereas 67Ga scintigraphy might be able to provide additional information including prognostic factors and to support strategies that target TfR for cancer therapy.

The goal of this study was to develop a simple method for quantification of regional cerebral blood flow (rCBF) with 99mTc-ethyl cysteinate dimer (ECD) SPECT. Following an intravenous constant infusion of ECD for one minute, serial dynamic SPECT imaging was performed for 40 minutes in 6 healthy male volunteers with intermittent arterial blood sampling. PET scan with 15O-water was performed on the same day before the SPECT study for measurement of rCBF. Arterial blood data demonstrated rapid conversion of ECD to the hydrophilic metabolites, and most of the arterial input to the brain was completed within 5 minutes after the injection. Brain activity reached a peak value soon after the cessation of infusion, and was stable thereafter with very little washout. Net extraction of ECD in the brain calculated by arterial input of ECD and rCBF demonstrated a rapid decrease within a few minutes, reaching 42.7% at 5 minutes. The simulation study suggested that the arterial blood activity obtained by continuous drawing for 5 minutes and a single SPECT scan would provide a reasonable estimate of rCBF under the assumption of constant net extraction in the brain.

We have developed a new 62Zn/62Cu positron generator, and applied it for PET imaging of perfusion and plasma volume in 5 normal subjects. The generator makes it possible by a simple procedure to obtain 62Cu eluate and labeling compounds sufficiently every 40-60 minutes. 62Cu labeled pyruvaldehyde bis(N4-methylthiosemicarbazone) copper II (62Cu-PTSM) was employed for cerebral and myocardial perfusion imaging and 62Cu labeled human serum albumin-dithiosemicarbazone (62Cu-HSA-DTS) was used for plasma pool imaging. The images of cerebral blood flow, cerebral plasma volume and myocardial perfusion were excellent. In addition, the analysis of tissue activity and blood activity demonstrated the microspheric character of 62Cu-PTSM. Correction of arterial activity with the standard disappearance curve of 62Cu-PTSM suggested the possibility of quantifying blood flow. The results of this study indicate the capability of the 62Zn/62Cu generator for wide clinical use without an in-house cyclotron.

Accurate localization of epileptic foci is important for pre-surgical evaluation of patients with medically intractable epilepsy, and F-18 FDG PET has been proved to be a valuable method for this purpose. To examine the clinical value with interictal brain perfusion SPECT, we performed brain perfusion SPECT of Tc-99m HMPAO by means of a high resolution SPECT camera, and compared the results with F-18 FDG PET images and MRI in 10 patients with medically intractable epilepsy. In 9 of 10 patients (90%), FDG PET images showed focal hypo-metabolism in the area corresponding with the results of electroencephalography (EEG). SPECT images, however, demonstrated hypo-perfused lesions which corresponded with hypo-metabolic lesions on FDG PET images in only 6 cases (60%). Although MRI showed abnormal findings in 8 cases, the lesions were not directly related to epileptic foci in 2 cases. In conclusion, FDG PET is a valuable tool for accurate localization of epileptic foci. Brain perfusion SPECT, however, may not always be paralleled to metabolism visualized on FDG PET images.

In activation studies with the bolus method for O-15 water and PET, the radiotracer concentration may reach the limits of the system in terms of dead time correction and accidental coincidence. To obtain the optimal injection dose of O-15 water, we performed a normal volunteer study to evaluate the relationship between the injected dose and the radioactivity concentration in the brain and a phantom study to evaluate the performance of the PET scanner (PCT3600W) under high count rate conditions and the effect of averaging on the signal to noise ratio for the PET images. A linear relationship was noted between the injected dose (normalized for each body weight: x) and the mean radiotracer concentration in the brain measured by PET (y) (y = 2.52 + 30.1 x, n = 64, r = 0.87, p < 0.001). The percent error in the measurement of radioactivity with PET was within +/- 5% in the 100 to 2000 nCi/ml (3.7-74 KBq/ml) range. Below 100 nCi/ml (3.7 KBq/ml), the percent error increased due to the rapid increase in noise in the reconstructed images. Over 1000 nCi/ml (37 KBq/ml), on the other hand, the noise was almost unchanged. With our PET scanner, the optimal range of the radiotracer concentration in the brain is below 1000 nCi/ml (37 KBq/ml), corresponding to an injection dose of 33 mCi (1.22 GBq)/60 kg body weight. With the same total dose, the increment of number of repeated measurements for averaging provided the better signal to noise ratio. In designing a paradigm for an activation PET study, the injection dose and the number of repeated measurements for averaging should be considered.