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Annals of Nuclear Medicine (v.22, #6)

Improvement of the diagnostic accuracy of lymph node metastases of colorectal cancer in ¹⁸F-FDG-PET/CT by optimizing the iteration number for the image reconstruction by Kazumasa Inoue; Takashi Sato; Hideaki Kitamura; Masaaki Ito; Yoshiyuki Tsunoda; Akira Hirayama; Hideo Kurosawa; Takashi Tanaka; Masahiro Fukushi; Noriyuki Moriyama; Hirofumi Fujii (pp. 465-473).

Improvement in the diagnostic accuracy of lymph node (LN) metastases of colorectal cancer by optimizing the reconstruction parameters was studied, including a phantom study and clinical studies.In the experimental study, the contrast ratio was evaluated using a standard image quality phantom, changing the iteration number of ordered subsets expectation maximization algorithm from 2 to 6. In the clinical study, 89 patients with preoperative colorectal cancer who received ¹⁸F-2-deoxy-2-fluoro-d-glucose positron emission tomography/computed tomography (PET/CT) were studied. Their LN metastases were visually assessed when systematically changing the iteration number, and the optimal iteration number was determined. After the appropriate cut-off value of maximum standardized uptake value was determined, the improvement of the diagnostic accuracy of LN metastases was evaluated for the proximal nodes and the distal ones using the reconstructed images with the optimal iteration number. This was compared with the conventional method that had an iteration number of 2.In the phantom study, it was confirmed that the contrast ratio improved when the iteration number increased. In clinical evaluation, the optimal iteration number was determined to be 5 by visual assessment. When the cut-off value of 1.5 was used, which happened to be the best number, the sensitivity/specificity/accuracy improved from 52%/91%/72% to 77%/89%/83% for the proximal nodes, and from 63%/90%/84% to 91%85%/87% for the distal nodes, respectively.When the iteration number of the reconstruction algorithm was optimized, the sensitivity of LN metastasis improved by more than 20%, and the accuracy exceeded 80%. Optimization of the image reconstruction parameters in the diagnosis of LN metastases using PET/CT is clinically important.

Keywords: Iteration number; Lymph node; PET/CT; ¹⁸F-FDG; Colorectal cancer

Response of osteogenic sarcoma to neoadjuvant therapy: evaluated by 18F-FDG-PET by Zhaoming Ye; Jiangjun Zhu; Mei Tian; Hong Zhang; Hongwei Zhan; Chunlei Zhao; Disheng Yang; Weixu Li; Nong Lin (pp. 475-480).

The aim of this study was to evaluate the potential role of F-18-fluoro-2-deoxy-d-glucose positron emission tomography (FDG-PET) in assessing the chemotherapy response of osteosarcoma when compared with histologically assessed tumor necrosis.Fifteen patients were examined with whole-body FDG-PET prior to and following neoadjuvant therapy. The maximum standard uptake value (SUV_max) of tumor and tumor to background ratio (TBR) prior to and following chemotherapy was used for semiquantitative PET imaging analysis. The SUV_max of prechemotherapy and post-chemotherapy was recorded as SUV₁ and SUV₂. TBR₁ and TBR₂ represented prechemotherapy and post-chemotherapy TBR. TBR was calculated by drawing an identical region of interest over the tumor and the contralateral normal limb or pelvis. Tumor necrosis was classified according to Salzer-Kuntschik’s criteria.Eight patients with more than 90% tumor necrosis were classified as showing good responses and seven patients with less than 90% tumor necrosis as showing poor responses. SUV₂/SUV₁, TBR₂/TBR₁, and TBR₂ were significantly correlated with the tumor necrosis degree (P < 0.01, P < 0.001, P < 0.001). TBR₂/TBR₁ were below 0.46 in all the patients with favorable responses, and higher than 0.49 in all the patients with unfavorable responses. However, it was difficult to distinguish good responses from poor responses by SUV₂/SUV₁.FDG-PET is a promising tool to assess the chemotherapy response of osteosarcoma noninvasively. The TBR was better than SUV_max in evaluating the chemotherapy response in this study.

Keywords: Chemotherapy; Osteosarcoma; Necrosis; FDG-PET

The influence of I-131 therapy on FDG uptake in differentiated thyroid cancer by Guang-Uei Hung; Kwo-Whei Lee; Pei-Yung Liao; Li-Heng Yang; Kwang-Tao Yang (pp. 481-485).

18F-fluorodeoxyglucose positron emission tomography (FDG-PET) [or PET/computed tomography (CT)] is more likely to show false-negative results when it is performed shortly after chemotherapy and/or radiotherapy because of “metabolic stunning”. The present study aimed to evaluate the influence of I-131 therapy on FDG uptake and the detection of recurrence or metastasis of differentiated thyroid cancer (DTC).We retrospectively enrolled 16 consecutive FDG-PET/CT studies which had been performed in patients with DTC with elevated thyroglobulin (TG) but negative I-131 whole-body scan. All studies were performed under l-thyroxine suppression. The patients were divided into groups A and B for PET/CT performed within 4 months of I-131 therapy or no such therapy, respectively. Each lesion identified on PET/CT was characterized using a 5-point scale by visual analysis: 0 = definitely benign, 1 = probably benign, 2 = equivocal, 3 = probably malignant, and 4 = definitely malignant. The maximum standardized uptake value (SUV_max) in each lesion was also measured for semiquantitative analysis. We compared the visual grading and SUV_max of the lesion of highest FDG uptake between groups A and B.For visual analysis, group B had significantly more patients with an uptake score of 3 or 4 than group A (80% vs. 17%, P = 0.01). In addition, there were significantly more equivocal results from group A than from group B (67% vs. 10%, P = 0.02). If the patients with the highest uptake scores of 2, 3, and 4 were considered to be positive for local recurrence or metastasis, there would be no significant difference between the positive rates of groups A and B (83% vs. 90%, P = 0.7). However, the mean SUV_max of positive results was significantly lower for group A than for group B (3.1 ± 0.9 and 6.6 ± 3.5, respectively, P = 0.02).The preliminary results suggested that FDG uptake in DTC may be negatively influenced by I-131 therapy within 4 months, resulting in lower FDG uptake and more equivocal results. Further studies are necessary to determine whether it is secondary to “metabolic stunning” caused by I-131 therapy.

Keywords: Stunning; FDG; I-131 therapy; PET/CT; Differentiated thyroid cancer

Sentinel lymph node detection in early stage cervical cancer: a prospective study comparing preoperative lymphoscintigraphy, intraoperative gamma probe, and blue dye by P. Pelin Kara; Ali Ayhan; Biray Caner; Murat Gültekin; Omer Ugur; M. Fani Bozkurt; Alp Usubutun (pp. 487-494).

The objective of this prospective study was to determine the feasibility of sentinel lymph node (SLN) detection in patients with cervical cancer using lymphoscintigraphy (LS), gamma probe, and blue dye.A total of 32 patients with early stage cervical cancer (FIGO IA2-IIA) who were treated with total abdominal hysterectomy and bilateral pelvic and paraortic lymphadenectomy underwent SLN biopsy. LS was performed on all the patients following the injection of 74 MBq technetium-99m-nanocolloid pericervically. The first appearing persistent focal accumulation on either dynamic or static images of LS was considered to be an SLN. Blue dye was injected just prior to surgical incision in 16 patients (50%) at the same locations as the radioactive isotope injection. During the operation, blue-stained node(s) were excised as SLNs. For gamma probe, a lymph node was accepted as an SLN, if its ex vivo radioactive counts were at least 10-fold above background radioactivity. SLNs, which were negative by routine hematoxylin and eosin (H&E) examination, were histopathologically reevaluated for the presence of micrometastases by step sectioning and immunohistochemical staining with pancytokeratin.At least one SLN was identified for each patient by gamma probe. Intraoperative gamma probe was the most sensitive method with a technical success rate of SLN detection of 100% (32/32), followed by LS 87.5% (28/32) and blue dye 68.8% (11/16), respectively. The average number of SLNs per patient detected by gamma probe was 2.09 (range 1–5). The localizations of the SLNs were external iliac 47.8%, obturatory 32.8%, common iliac 9%, paraaortic 4.4%, and paracervical 6%. Micrometastases, not detected by routine H&E were found by immunohistochemistry in one patient. On the basis of the histopathological analysis, the negative predictive value for predicting metastases was 100%, and there were no false-negative results.Preoperative LS with radiocolloids, intraoperative lymphatic mapping with blue dye and gamma probe are all feasible methods comparable with each other for SLN detection in early stage cervical cancer patients, but gamma probe is the most useful method in terms of technical success.

Keywords: Cervical cancer; Lymphoscintigraphy; Blue dye; Sentinel lymph node biopsy; Micrometastases

Voxel- and ROI-based statistical analyses of PET parameters for guidance in the surgical treatment of intractable mesial temporal lobe epilepsy by Yoshihisa Ohta; Tadashi Nariai; Kenji Ishii; Kiichi Ishiwata; Masahiro Mishina; Michio Senda; Kimiyoshi Hirakawa; Kikuo Ohno (pp. 495-503).

Positron emission tomography (PET) can be used to locate epileptic foci in patients with mesial temporal lobe epilepsy (MTLE) by measuring multiple parameters of the brain. We investigated a series of patients with MTLE using PET measurements of three parameters: the cerebral blood flow measured with [¹⁵O] H₂O, the uptake of [¹⁸F] fluorodeoxyglucose (FDG), an index of the cerebral metabolism rate of glucose, and the distribution volume (DV) of [¹¹C] flumazenil (FMZ), an index of the binding potential of central benzodiazepine receptor. We compared predictive values obtained from two methods: a voxel-based statistical analysis using statistical parametric mapping (SPM) and an asymmetry index obtained by placing regions of interest (ROIs) on PET images.Preoperative PET data of 11 patients with surgically confirmed MTLE were retrospectively examined. In the voxel-based analysis, the PET data were analyzed using SPM99 by statistically comparing the voxel values of PET parameters between individual patients and the mean values of 12 normal volunteers. Voxels with values significantly lower than the normal control values were mapped on a standard brain atlas. In the ROI-based analysis, the asymmetry index was calculated to depict ROIs with abnormally decreased values when compared with the contralateral side.(1) Statistical parametric mapping and ROI analyses of the FDG uptake correctly determined epileptic temporal lobe in 73% and 82%, respectively. (2) The decreased DV of FMZ depicted by SPM revealed the mesial temporal pathology in 91%.Positron emission tomography measurement of FDG uptake was most sensitive in detecting the side of the epileptic focus. On the other hand, SPM analysis of the DV of FMZ was the most sensitive method for delineating the actual epileptic focus.

Keywords: Mesial temporal lobe epilepsy; Presurgical evaluation; Positron emission tomography; Fluorodeoxyglucose; Central benzodiazepine receptor

Standardized uptake values of uterine leiomyoma with ¹⁸F-FDG PET/CT: variation with age, size, degeneration, and contrast enhancement on MRI by Kazuhiro Kitajima; Koji Murakami; Erena Yamasaki; Yasushi Kaji; Kazuro Sugimura (pp. 505-512).

To assess the effect of age, size, the degree of degeneration, and contrast enhancement on magnetic resonance imaging (MRI) on ¹⁸F-fluoro-2-deoxyglucose (¹⁸F-FDG) uptake in uterine leiomyomas using quantitative standardized uptake values (SUVs).A total of 61 leiomyomas of 41 patients, who underwent combined positron emission tomography/computed tomography (PET/CT) using ¹⁸F-FDG and contrast-enhanced MRI were included in this study. Sixty-one leiomyomas were divided into two groups: “non-degenerated” leiomyomas showing distinct low signal intensity on T2-weighted images and intermediate signal intensity on T1-weighted images, and “degenerated” leiomyomas showing other types of signal intensity. Sixty-one leiomyomas were also divided into two groups of “strongly enhancing” leiomyomas and “weakly enhancing” leiomyomas in terms of their degree of contrast enhancement on MRI.The mean values of the maximum and average SUVs for the total of 61 leiomyomas were 2.34 ± 0.75 (range 1.59–5.15) and 1.74 ± 0.50 (0.66–3.95), respectively. There was a moderate negative correlation between the maximum and average SUVs and age (r = −0.43 and P = 0.00016, r = −0.31 and P = 0.029, respectively). Although there was a mild positive correlation between maximum SUV and size (r = 0.35 and P = 0.011), there was no significant difference between average SUV and size. Although there was no significant difference in average SUV between “degenerated” and “non-degenerated” leiomyomas, the maximum SUV of “degenerated” leiomyomas was significantly higher than that of “non-degenerated” leiomyomas (P = 0.0012). The degree of contrast enhancement on MRI was not significantly correlated with ¹⁸F-FDG uptake.Mild or moderate uptake of ¹⁸F-FDG is often observed in uterine leiomyoma and declines with age, and should not be confused with malignant accumulation.

Keywords: Uterine leiomyoma; ¹⁸F-fluoro-2-deoxyglucose (¹⁸F-FDG); Positron emission tomography/computed tomography (PET/CT); Standardized uptake value (SUV); Magnetic resonance imaging (MRI)

Quantitative evaluation of norcholesterol scintigraphy, CT attenuation value, and chemical-shift MR imaging for characterizing adrenal adenomas by Teruaki Yoh; Makoto Hosono; Yoshihiro Komeya; Sung-Woon Im; Ryuichiro Ashikaga; Taro Shimono; Norio Tsuchiya; Masahiro Okada; Kazushi Hanada; Yukinobu Yagyu; Yasumasa Nishimura; Takamichi Murakami (pp. 513-519).

The objective of our study was to evaluate diagnostic ability and features of quantitative indices of three modalities: uptake rate on norcholesterol scintigraphy, computed tomography (CT) attenuation value, and fat suppression on chemical-shift magnetic resonance imaging (MRI) for characterizing adrenal adenomas.Image findings of norcholesterol scintigraphy, CT, and MRI were reviewed for 78 patients with functioning (n = 48) or nonfunctioning (n = 30) adrenal masses. The norcholesterol uptake rate, attenuation value on unenhanced CT, and suppression on in-phase to opposed-phase MRI were measured for adrenal masses.The norcholesterol uptake rate, CT attenuation value, and MR suppression index showed the sensitivity of 60%, 82%, and 100%, respectively, for functioning adenomas of <2.0 cm, and 96%, 79%, and 67%, respectively, for those of ≥2.0 cm. A statistically significant correlation was observed between size and norcholesterol uptake, and between CT attenuation value and MR suppression index. Regarding norcholesterol uptake, the adenoma-to-contralateral gland ratio was significantly higher in cortisol releasing than in aldosterone-releasing adenomas.The norcholesterol uptake rate was reliable for characterization of adenomas among adrenal masses of ≥2.0 cm. CT attenuation value and MR suppression index were well correlated with each other, and were useful regardless of mass size.

Keywords: Adrenal adenoma; Norcholesterol; CT; MRI; Chemical-shift imaging

¹⁸F-FDG-PET/CT as an indicator for resection of pulmonary epithelioid hemangioendothelioma by Sadahiro Watanabe; Fuzuki Yano; Tamotsu Kita; Shigeyoshi Soga; Hiroshi Shinmoto; Shigeru Kosuda; Yuichi Ozeki; Shinsuke Aida; Ikuko Sakata (pp. 521-524).

A 60-year-old man with a 7-year history of multiple pulmonary nodules presented to our hospital because the nodules were seen to have increased in size on review of films on a regular medical checkup 1 week earlier. Computed tomography (CT) revealed multiple pulmonary nodules with calcification in the lungs. The largest nodule measuring 2.5 cm in the maximum dimension was lobulated and ill-defined. The patient underwent ¹⁸F-fluorodeoxyglucose positron emission tomography/CT (¹⁸F-FDG-PET/CT) to evaluate the multiple nodules and to search for a primary lesion. ¹⁸F-FDG-PET/CT revealed increased uptake in only two nodules with a standardized uptake value of 4.61 and 2.10, respectively. The two foci with increased ¹⁸F-FDG uptake were resected and pathologically proven to be pulmonary epithelioid hemangioendothelioma (PEH). PEH can transform into malignancy with metastasis. An ¹⁸F-FDG-PET/CT finding may be an indicator to decide on PEH resection.

Keywords: Positron emission tomography; Computed tomography; PET/CT; Epithelioid hemangioendothelioma; ¹⁸F-FDG

Peritoneal tuberculosis with elevated serum CA125 mimicking peritoneal carcinomatosis on F-18 FDG-PET/CT by Chao-Jung Chen; Wei-Jen Yao; Cheng-Yang Chou; Nan-Tsing Chiu; Bi-Fang Lee; Pei-Shan Wu (pp. 525-527).

¹⁸F-fluorodeoxyglucose positron emission tomography (F-18 FDG-PET) plays an important role in differentiating benign from malignant tumors. However, some false-positive findings, such as tuberculosis, may occur. We report a case referred for F-18 FDG whole-body PET computed tomography (PET/CT) scan owing to an elevated serum cancer antigen 125 (CA125). An FDG-PET/CT scan showed multiple hypermetabolic foci in the mesentery and peritoneum with further increase of FDG uptake on the delayed scan, mimicking peritoneal carcinomatosis. Subsequent laparoscopic biopsy showed granulomatous inflammation, and tuberculosis polymerase chain reaction showed a positive result. Serum CA125 returned to normal following treatment with anti-tuberculosis drugs. Peritoneal tuberculosis should be considered as a differential diagnosis in a tuberculosis endemic region.

Keywords: Peritoneal tuberculosis; CA125; F-18 FDG-PET/CT

Diagnosis and localization of renal cyst infection by 18F-fluorodeoxyglucose PET/CT in polycystic kidney disease by Michael Soussan; Rebecca Sberro; Myriam Wartski; Fadi Fakhouri; Alain-Paul Pecking; Jean-Louis Alberini (pp. 529-531).

Renal cyst infection in polycystic kidney disease is a serious complication. Early diagnosis and localization of infected cyst are crucial and usually require conventional imaging modalities, including ultrasound and computed tomography (CT). However, their contribution is limited because of nonspecific results. We report on a patient with suspected renal cyst infection for which 18F-fluorodeoxyglucose positron emission tomography (FDG-PET)/CT scan allowed the exact localization of the infected cyst and guided a drainage procedure. FDG-PET/CT imaging could be a valuable tool for early identification of infected renal cyst infection, and may contribute to better patient management.

Keywords: Cyst; Infection; Polycystic kidney disease; 18F-fluorodeoxyglucose; PET/CT

The feasibility of ¹¹C-methionine-PET in diagnosis of solitary lung nodules/masses when compared with ¹⁸F-FDG-PET by Hung-Jen Hsieh; Sheng-Hsiang Lin; Ko-Han Lin; Chien-Ying Lee; Cheng-Pei Chang; Shyh-Jen Wang (pp. 533-538).

To differentiate between benign and malignant lesions of the lung, ¹⁸F-fluorodeoxyglucose positron emission tomography (¹⁸F-FDG-PET) has limitations such as a lower specificity in cases of non-specific inflammation. The positive predictive value is unsatisfactory in countries where inflammatory lung disorders are prevalent. We present the preliminary results of the usefulness of combining ¹¹C-methionine-PET and ¹⁸F-FDG-PET in this context.Fifteen patients with indeterminate solitary pulmonary nodules/masses (10 men, 5 women; average age 64.7 ± 14.0 years, ranging from 25 to 87 years) were studied using ¹¹C-methionine- and ¹⁸F-FDG-PET. Interpretations were primarily made on visual analysis with five-point scale and a consensus of two nuclear medicine physicians, using standardized uptake value as an accessory reference. Foci of abnormal radiotracer uptake were subsequently correlated with clinical follow-up, imaging modalities such as chest radiography, chest computed tomography (CT), serial PET studies, and pathology results from bronchoscopic biopsy and/or surgical specimen.Diagnoses were established in 14 patients. The ¹¹C-methionine-PET and ¹⁸F-FDG-PET studies were both true positive in two cases of adenocarcinoma and true negative in two cases of clinical benign nodules. In one case of lymphoid hyperplasia both ¹¹C-methionine-PET and ¹⁸F-FDG-PET showed false-positive findings. Discordant results were obtained in nine cases. In spite of the false-positive results of ¹⁸F-FDG-PET, ¹¹C-methionine-PET was true negative in four cases with chronic inflammatory nodules and three cases of pulmonary tuberculosis. Furthermore, ¹¹C-methionine-PET was true positive in one case of lung metastasis of thyroid cancer, and in another with recurrence of gastric cancer, respectively, for which ¹⁸F-FDG-PET imaging was false negative.Our experience indicates that ¹¹C-methionine-PET seems more specific and sensitive when compared with ¹⁸F-FDG-PET for the purpose of differentiating benign and malignant thoracic nodules/masses. The possibility of an FDG-avid lesion being malignant is decreased if it shows a negative result by ¹¹C-methionine-PET.

Keywords: ¹⁸F-FDG; ¹¹C-methionine; Dual-tracer; PET; Solitary pulmonary nodule

Total Mini-Mental State Examination score and regional cerebral blood flow using Z score imaging and automated ROI analysis software in subjects with memory impairment by Eiji Ikeda; Kazumasa Shiozaki; Nobukazu Takahashi; Takashi Togo; Toshinari Odawara; Takashi Oka; Tomio Inoue; Yoshio Hirayasu (pp. 539-542).

The Mini-Mental State Examination (MMSE) is considered a useful supplementary method to diagnose dementia and evaluate the severity of cognitive disturbance. However, the region of the cerebrum that correlates with the MMSE score is not clear. Recently, a new method was developed to analyze regional cerebral blood flow (rCBF) using a Z score imaging system (eZIS). This system shows changes of rCBF when compared with a normal database. In addition, a three-dimensional stereotaxic region of interest (ROI) template (3DSRT), fully automated ROI analysis software was developed. The objective of this study was to investigate the correlation between rCBF changes and total MMSE score using these new methods.The association between total MMSE score and rCBF changes was investigated in 24 patients (mean age ± SD 71.5 ± 9.2 years; 6 men and 18 women) with memory impairment using eZIS and 3DSRT. Step-wise multiple regression analysis was used for multivariate analysis, with the total MMSE score as the dependent variable and rCBF change in 24 areas as the independent variable.Total MMSE score was significantly correlated only with the reduction of left hippocampal perfusion but not with right (P < 0.01).Total MMSE score is an important indicator of left hippocampal function.

Keywords: MMSE; SPECT; eZIS; 3DSRT; Left hippocampus

Variability of lesion detectability and standardized uptake value according to the acquisition procedure and reconstruction among five PET scanners by Yasuyuki Takahashi; Noboru Oriuchi; Hidenori Otake; Keigo Endo; Kenya Murase (pp. 543-548).

The objective of this study was to assess differences in the semiquantitative values of ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) uptake among different positron emission tomographic (PET) systems.A phantom study was performed to compare standardized uptake value (SUV) in five PET scanners including a dedicated PET scanner and four PET/computed tomography (CT) scanners. Radioactivity simulating the SUV of 2.5 was filled in the hot spheres (8 mm, 11 mm, 14 mm, 18 mm, 22 mm, and 27 mm) that were set in the cylindrical phantom with the background SUV of 1.0. Data acquisition and reconstruction were performed according to routine and standardized conditions. The standardized condition was as follows: CT acquisition (120 kVp, 50 mA) and PET acquisition (2-min acquisition with a slice thickness of 2 mm); reconstruction was performed by ordered subsets expectation maximization + Fourier rebinning. Detectability of hot spheres and SUV was compared between routine condition and standardized condition with five PET scanners.On routine condition, two cameras could detect a 14-mm sphere clearly. On the other hand, the visualization of hot spheres by the standardized condition was remarkably variable. Semiquantitative evaluation revealed that a maximum of 45.7% error was recognized with the 27-mm sphere by the routine condition, although the standardized condition could reduce the error to 22.6%.Detectability depends not only on the PET machine but also on the imaging protocol. The results indicate that SUV is variable with PET machines under routine conditions of data acquisition and reconstruction. Standardization of the reconditions can reduce variability and maximum difference in the SUV by half.

Keywords: PET/CT; ¹⁸F-FDG; SUV

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Annals of Nuclear Medicine (v.22, #6)