• Nuclear Medicine and Molecular Imaging
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• v.40 no.3
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• pp.169-176
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• 2006

Purpose: According to the development of CT scanner in PET/CT system, the role of CT unit as a diagnostic tool has been more important. To improve the diagnostic ability of CT scanner, it is a key aspect that CT scanning has to be performed with high dose energy and intravenous (IV) contrast. So we investigated the effect of IV contrast media on the maximum SUV (maxSUV) of normal tissues and pathologic lesions using PET/CT scanner with high dose CT scanning. Materials & Methods: The study enrolled 13 patients who required PET/CT evaluation. At first, the patients were performed whole body non-contrast CT (NCCT-120 kVp, 130 mAs) scan. Then contrast enhanced CT (CECT) scan was performed immediately. Finally PET scan was followed. The PET omission data were reconstructed twice, once with the NCCT and again with the CECT. We measured the maxSUV of 10 different body regions that were considered as normal in ail patients. Also pathologic lesions were investigated. Results: There were not seen focal artifacts in PET images based on CT with IV contrast agent. Firstly, 130 normal regions in 13 patients were evaluated. The maxSUV was significantly different between two PET images (p<0.00)). The maxSUV was $1.1{\pm}0.5$ in PET images with CECT-corrected attenuation and $1.0{\pm}0.5$ in PET images with NCCI-corrected attenuation. The limit of agreement was $0.1{\pm}0.3$ in Bland-Altman analysis. Especially there were significant differences in 6 of 10 regions, apex and base of the right lung, ascending aorta, segment 6 & segment 8 of the liver and spleen (p<0.05). Secondly, 39 pathologic lesions were evaluated. The maxSUV was significantly different between two PET images (p<0.001). The maxSUV was $4.7{\pm}2.0$ in PET images with CECT-corrected attenuation and $4.4{\pm}2.0$ in PET images with NCCT-corrected attenuation. The limit of agreement was $0.4{\pm}0.8$ in Bland-Altman analysis. Conclusion: Although there were increases of maxSUVs in the PET images based on CT with IV contrast agent, it was very narrow in the range of limit of agreement. So there was no significant effect to clinical interpretation for PET images that were corrected attenuation with high dose CT using IV contrast.

• Nuclear Medicine and Molecular Imaging
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• v.41 no.4
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• pp.317-325
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• 2007

Purpose: Biological parameters can be quantified using dynamic PET data with compartment modeling and Nonlinear Least Square (NLS) estimation. However, the generation of parametric images using the NLS is not appropriate because of the initial value problem and excessive computation time. In irreversible model, Patlak graphical analysis (PGA) has been commonly used as an alternative to the NLS method. In PGA, however, the start time ($t^*$, time where linear phase starts) has to be determined. In this study, we suggest a new Multiple Linear Analysis for irreversible radiotracer (MLAIR) to estimate fluoride bone influx rate (Ki). Methods: $[^{18}F]Fluoride$ dynamic PET scans was acquired for 60 min in three normal mini-pigs. The plasma input curve was derived using blood sampling from the femoral artery. Tissue time-activity curves were measured by drawing region of interests (ROls) on the femur head, vertebra, and muscle. Parametric images of Ki were generated using MLAIR and PGA methods. Result: In ROI analysis, estimated Ki values using MLAIR and PGA method was slightly higher than those of NLS, but the results of MLAIR and PGA were equivalent. Patlak slopes (Ki) were changed with different $t^*$ in low uptake region. Compared with PGA, the quality of parametric image was considerably improved using new method. Conclusion: The results showed that the MLAIR was efficient and robust method for the generation of Ki parametric image from $[^{18}F]Fluoride$ PET. It will be also a good alternative to PGA for the radiotracers with irreversible three compartment model.

• Nuclear Medicine and Molecular Imaging
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• v.43 no.5
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• pp.429-435
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• 2009

Purpose: The purpose of this study was to assess the prognostic value of preoperative FDG-PET in colorectal cancer (CRC) patients with hepatic metastasis (HM). Materials and Methods: 24 CRC patients (M:F=14:10; age, $63{\pm}10$ yrs) with HM who had undergone preoperative FDG PET were included. Cure-intent surgery was performed in all the patients and HMs were controlled using resection (n=13), radio-frequency ablation (RFA) (n=7), and resection plus RFA (n=4). Potential prognostic markers tested were maxSUV of primary tumor, maxSUV of HM, maxSUV ratio of HM over primary tumor (M/P ratio), histologic grade, CEA level, venous/lymphatic/nerve invasion, T stage, N stage, no. of HM, no. of lymph node metastasis, and treatment modality of HM. Results: 14 CRC patients developed a recurrence with a median follow-up duration of 244 days, whereas 10 patients did not develop recurrence with a median follow-up duration of 504 days. M/P ratios but other potential prognostic markers were significantly higher in the recurrent patients ($0.72{\pm}0.14$) than recurrence-free patients ($0.54{\pm}0.23$) (p=0.038). M/P ratio only was found to predict recurrence by Cox multivariate analysis (hazard ratio 37.7, 95% confidence interval 2.01-706.1, p=0.016). The 11 patients with lower M/P ratio of <0.61 had significantly better disease-free survival rate than the 13 patients with higher M/P ratio (${\geq}0.61$) (p=0.026). Conclusion: maxSUV ratio of HM over primary tumor (M/P ratio) may be useful for prognosis prediction of CRC patients with HM. Higher FDG uptake of HM than that of primary tumor may indicate a more advanced status in stage IV CRC.

• Nuclear Medicine and Molecular Imaging
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• v.43 no.4
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• pp.337-343
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• 2009

Purpose: ((R)-1-(2-chlorophenyl)-N-1-[$^{11}$C]methyl-N(1-propyl)-3-isoquinoline carboxamide ((R)-PK11195) is a specific ligand for the peripheral type benzodiazepine receptor and a marker of activated microglia, used to measure inflammation in neurologic disorders. We report here that a direct and simple radiosynthesis of [$^{11}$C](R)-PK11195 in mild condition using NaH suspension in DMF and one-step loop method. Materials and Methods: (R)-N-Desmethyl-PK11195 (1 mg) in DMSO (0.1 mL) and NaH suspension in DMF (0.1 mL) were injected into a semi-prep HPLC loop. [$^{11}$C]methyl iodide was passed through HPLC loop at room temperature. Purification was performed using semi-preparative HPLC. Aliquots eluted at 11.3 min were collected and analyzed by analytical HPLC and mass spectrometer. Results: The labeling efficiency of [$^{11}$C](R)-PK11195 was 71.8$\pm$8.5%. The specific activity was 11.8:$\pm$6.4 GBq/$\mu$mol and radiochemical purity was higher than 99.2%. The mass spectrum of the product eluted at 11.3 min showed m/z peaks at 353.1 (M+1), indicating the mass and structure of (R)-PK11195. Conclusion: By the one-step loop method with the [$^{11}$C]CH3l automated synthesis module, [$^{11}C$](R)-PK11195 could be easily prepared in high radiochemical yield using NaH suspension in DMF.

• Nuclear Medicine and Molecular Imaging
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• v.43 no.4
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• pp.330-336
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• 2009

Purpose: We established radiolabeling conditions of NOTA and DOTA with a generator-produced PET radionuclide $^{68}$Ga and studied in vitro characteristics such as stability, serum protein binding, octanol/water distribution, and interference with other metal ions. Materials and Methods: Various concentrations of NOTA 3HCl and DOTA 4HCl were labeled with 1 mL $^{68}$GaCl$_3$ (0.18$\sim$5.75 mCi in 0.1 M HCl in various pH. NOTA 3HCl (0.373 mM) was labeled with $^{68}$GaCl$_3$(0.183$\sim$0.232 mCi/0.1 M HCl 1.0 mL) in the presence of CuCl$_2$, FeCl$_2$, InCl$_3$, FeCl$_3$, GaCl$_3$, MgCl$_2$ or CaCl$_2$ (0$\sim$6.07 mM) at room temperature. The labeling efficiencies of $^{68}$Ga-NOTA and $^{68}$Ga-DOTA were checked by ITLC-SG using acetone or saline as mobile phase. Stabilities, protein bindings, and octanol distribution coefficients of the labeled compounds also were investigated. Results: $^{68}$Ga-NOTA and $^{68}$Ga-DOTA were labeled optimally at pH 6.5 and pH 3.5, respectively, and the chelates were stable for 4 hr either in the reaction mixture at room temperature or in the human serum at 37$^{\circ}C$. NOTA was labeled at room temperature while DOTA required heating for labeling. $^{68}$Ga-NOTA labeling efficiency was reduced by CuCl$_2$, FeCl$_2$, InCl$_2$, FeCl$_3$ or CaCl$_3$, however, was not influenced by MgCl$_2$ or CaCl$_2$. The protein binding was low (2.04$\sim$3.32%). Log P value of $^{68}$Ga-NOTA was -3.07 indicating high hydrophilicity. Conclusion: We found that NOTA is a better bifunctional chelating agent than DOTA for $^{68}$Ga labeling. Although, $^{68}$Ga-NOTA labeling is interfered by various metal ions, it shows high stability and low serum protein binding.

• Nuclear Medicine and Molecular Imaging
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• v.43 no.5
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• pp.421-428
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• 2009

Purpose: We have evaluated characteristics of adrenal masses incidentally observed in nonenhanced F-18 FDG PET/CT of the oncologic patients and the diagnostic ability of F-18 FDG PET/CT to differentiate malignant from benign adrenal masses. Materials and Methods: Between Mar 2005 and Aug 2008, 75 oncologic patients (46 men, 29 women; mean age, $60.8{\pm}10.2$ years; range, 35-87 years) with 89 adrenal masses incidentally found in PET/CT were enrolled in this study. For quantitative analysis, size (cm), Hounsfield unit (HU), maximum standardized uptake value (SUVmax), SUVratio of all 89 adrenal masses were measured. SUVmax of the adrenal mass divided by SUVliver, which is SUVmax of the segment 8, was defined as SUVratio. The final diagnosis of adrenal masses was based on pathologic confirmation, radiologic evaluation (HU<0 : benign), and clinical decision. Results: Size, HU, SUVmax, and SUVratio were all significantly different between benign and malignant adrenal masses.(P < 0.05) And, SUVratio was the most accurate parameter. A cut-off value of 1.0 for SUVratio provided 90.9% sensitivity and 75.6% specificity. In small adrenal masses (1.5 cm or less), only SUVratio had statistically significant difference between benign and malignant adrenal masses. Similarly a cut-off value of 1.0 for SUVratio provided 80.0% sensitivity and 86.4% specificity. Conclusion: F-18 FDG PET/CT can offer more accurate information with quantitative analysis in differentiating malignant from benign adrenal masses incidentally observed in oncologic patients, compared to nonenhanced CT.

• Nuclear Medicine and Molecular Imaging
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• v.43 no.5
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• pp.411-420
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• 2009

Purpose: The aim of this study was to investigate the usefulness of $^{18}F$-FDG PET/CT with neck ultrasonography (neck US) in patients with recurrent, papillary thyroid cancer. Material and methods: This retrospective study (December 2006 to April 2008) enrolled sixty-one patients (ninety-one lesions) who underwent high-dose $^{131}I$-ablation therapy after total thyroidectomy, and evaluated recurred papillary thyroid cancer. All lesions were confirmed by histopathology and compared histopathologic findings to PET, PET/CT, and neck US findings. Results: In sixty-one patients (57 women, 4 men; age range, 24-81 years, mean 49 years; 61 papillary carcinomas), the sensitivity, specificity, accuracy of $^{18}F$-FDG PET/CT was 87.2%, 64.0%, 78.1% on a patient basis and 92.3%, 66.7%, 80.9% on a lesion basis, respectively. The sensitivity, specificity, accuracy of $^{18}F$-FDG PET was 71.8% (p=0.03), 59.0% (p=1.00), 67.2% (p=0.03) on a patient basis and 78.8% (p<0.01), 64.1% (p=1.00), 72.5% (p=0.02) on a lesion basis, respectively. The sensitivity, specificity, accuracy of neck US was 71.1% (p=0.07), 52.2% (p=0.75), 63.9% (p=0.05) on a patient basis and 71.2% (p<0.01), 61.5% (p=1.00), 67.0% (p=0.06) on a lesion basis, respectively. Combined $^{18}F$-FDG PET/CT with neck US improved the sensitivity, specificity, accuracy to 94.7% (p=0.50), 82.6% (p=0.13), 90.2% (p=0.03) on a patient basis and 96.2% (p=0.50), 89.7% (p<0.01), 93.4% (p<0.01) on a lesion basis, respectively. Conclusion: $^{18}F$-FDG PET/CT demonstrated significantly higher sensitivity than neck US for the detection of recurred papillary thyroid cancer lesions. Furthermore, combined $^{18}F$-FDG PET/CT with neck US showed more improved sensitivity, specificity, accuracy for diagnosis of recurrent papillary thyroid cancer.

• Nuclear Medicine and Molecular Imaging
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• v.43 no.5
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• pp.402-410
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• 2009

Purpose: The aim of this study was to determine the incidence and malignant rate of incidental asymmetric palatine tonsillar uptake (ATU) on $^{18}F$-FDG PET/CT in various clinical indications and to evaluate the clinical and PET/CT findings suggesting malignancy. Materials and Methods: We retrospectively reviewed a total of 2,901 patients ($58.4{\pm}12.3$ yrs, range 20~88 yrs, M:F = 1,841:1,060) who underwent $^{18}F$-FDG PET/CT during an 1-year period with various indications except primary tonsillar cancer and lymphoma evaluation. On $^{18}F$-FDG PET/CT, metabolic abnormality of the palatine tonsil and cervical lymph node were visually assessed. ATU was defined as increased palatine tonsillar uptake with diffuse, focal, or irregular pattern compared to contralateral side. The incidence and malignant ratio of ATU were evaluated according to clinical and PET/CT findings. Results: Of 2,901 cases, 290(10,0%) showed ATU. The incidence of ATU showed seasonal variation and was high in the winter (12.1%). Of 209 cases with ATU confirmed pathologically and/or clinically, five (2.4%) were malignant lesions. ATU with irregular uptake pattern (2/2) and in cases referred for cervical lymph node metastasis of unknown origin (3/5) were frequently associated with malignant lesion (p<0.05). Conclusion: ATU was not infrequently observed on $^{18}F$-FDG PET/CT, and the malignant risk of ATU was low. However, ATU with cervical lymph node metastasis or with irregular pattern on PET/CT would be further evaluated by the histopathologic examination.

• Nuclear Medicine and Molecular Imaging
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• v.43 no.4
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• pp.317-322
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• 2009

Purpose: $^{18}$F-flurodeoxyglucose (FDG) uptake on positron emission tomography (PET) scan has been found to reflect tumor aggressiveness and prognosis in various types of cancer. However, pattern of FDG uptake in biliary malignancies and its clinical significance have not been studied well. The purpose of this study was to assess the additional value of $^{18}$F-FDG PET in differential diagnosis and prognosis of cholangiocarcinoma (CC) according to the tumor location and tumor morphology. Materials and Methods: From April 2005 to May 2008, eighty two patients (M:F = 55:27, age 66.2$\pm$9.6 yrs) with CC underwent $^{18}$F-FDG PET. For semiquantitative analysis, the maximum standardized uptake value (SUV$_{max}$) was obtained from the primary tumor. The difference of SUV$_{max}$ according to the tumor location and tumor growth pattern, such as scirrhous type, nodular type, polypoid type were compared. Results: Overall sensitivity of PET scan was 81.7% in CC. SUV$_{max}$ on PET scan in intrahepatic CC was significantly higher compared to extrahepatic CC. In extrahepatic CC, polypoid type showed significantly higher SUV$_{max}$ compared to scirrhous type. Conclusion: $^{18}$F-FDG PET may have a significant impact on clinical decision-making and on the management of intrahepatic cholangiocarcinoma. And it is related to the shape of the tumor and the sensitivity of detection is higher in the mass-forming type than in the scirrhous type.

• Nuclear Medicine and Molecular Imaging
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• v.43 no.5
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• pp.395-401
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• 2009

Purpose: We evaluated $^{18}F$-FDG PET/CT findings in initially diagnosed adenoid cystic carcinoma (ACC) of the head and neck in association with pathological subtype, staging, uptake comparison with squamous cell carcinoma (SqCC) and prognosis. Materials and Methods: The subjects were 16 patients with initially diagnosed ACC of head and neck who underwent pretreatment $^{18}F$-FDG PET/CT. Histological subtype (solid pattern vs. tubular/cribriform pattern), $SUV_{max}$ of size-matched SqCC of the head and neck as control group, disease-free survival (DFS) were compared with the $SUV_{max}$ of ACC of the head and neck. Results: Of total 16 patients, 6 had solid pattern and the remaining 10 had tubular/cribriform pattern. The $SUV_{max}$ were significantly higher in solid pattern group than in tubular/cribriform pattern group ($6.7{\pm}3.2$ vs. $4.2{\pm}0.9$, p=0.03). PET/CT found unexpected distant metastasis in 18.7% of patients (3/16) and changed the therapeutic plan in those patients. The $SUV_{max}$ of ACC was significantly lower than that of size-matched SqCC ($5.1{\pm}2.4$ vs. $13.6{\pm}6.0$, p<0.001). DFS was not significantly different according to the histological subtype. In contrast, patients with high $^{18}F$-FDG uptake ($SUV_{max}$ ${\geq}$6.0) had significantly shorter DFS than those with low $^{18}F$-FDG uptake ($SUV_{max}$ <6.0). Conclusion: $^{18}F$-FDG uptake of ACC of the head and neck is significantly associated with histological subtype and DFS. $^{18}F$-FDG PET/CT may be useful for detecting unexpected metastasis. Since $^{18}F$-FDG uptake of tubular/cribriform ACC compared with SqCC is relatively low, it is necessary to interpret PET images carefully in patients without alleged ACC.