Diagnostic performance of PET/CT with tracers other than F-18-FDG in oncology: an evidence-based review

Fluorine-18-fluorodeoxyglucose (F-18-FDG) is the most used positron emitter radiopharmaceutical worldwide. This glucose analogue allows to study the glucose metabolism which is often increased in many tumors. Nowadays the diagnostic performance of positron emission tomography/computed tomography (PET/CT) using F-18-FDG in different tumors is well known. On the other hand, to date, there is an increasing interest for the use of PET tracers other than F-18-FDG in oncology, because they allow to study different metabolic pathways or receptor expression. The aim of this review is to summarize the scientific literature about the diagnostic performance of PET/CT using tracers other than F-18-FDG in oncology through an evidence-based approach. In particular, the results of meta-analyses (representing the highest level of evidence) on the diagnostic performance of PET tracers other than F-18-FDG in different tumors are described. Furthermore, recommendations for the use of different PET tracers in oncology are provided based on existing literature data.     

18F - FDG PET / CT 显像对多发性骨髓瘤诊断效能的回顾性研究

目的：回顾性分析评价18F—FDGPET／CT显像对多发性骨髓瘤的诊断效能。方法：选择本院2011年3月-2013年6月临床可疑多发性骨髓瘤患者39例,其中男性22例,女性17例,年龄44—78岁,平均年龄（51．3±0．5）岁。均行PET／CT检查及临床骨穿或病理活检证实,分别统计其真假阳性例数及真假阴性例数,并计算灵敏度、特异性及准确性指标,评价诊断效能。结果：39例患者中真阳性18例,假阳性2例,真阴性16例,假阴性3例。PET／CT诊断灵敏度为85．7％（18／21）,特异性为88．9％（16／18）,准确性为87．2％（34／39）,阳性预测值为90％（18／20）,阴性预测值为84．2％（16／19）。结论：18F—FDGPET／CT可用于多发性骨髓瘤的诊断,结合患者临床表现及生化检查可提高诊断符合率。     

Diagnostic evaluation of cancer antigens RAK .1. Cervical and ovarian cancer

Three different tracers, Tc-99m-Sesta MIBI, In-111-Pentetreotide and F-18-FDG, were evaluated in a preliminary study in three different groups of 10 breast cancer patients programmed for breast cancer resection and axillary dissection. Planar scintigraphy and single photon emission tomography (SPET) technique were used for imaging with Tc-99m-Sesta-MIBI and In-111-Pentetreotide, positron emission tomography (PET) was used for imaging with F-18-FDG. We studied 30 breast cancer patients; their clinical stage according to the TNM classification was 30 T1-T2, 1 T4 and 1 Tx (one patient had bilateral cancer and one had bifocal cancer). The lymph nodal status ranged from NO to N2 (14 NO, 16 N1, 1 N2). Tc-99m-Sesta MIBI, In-111 Pentetreotide SPET and F-18-FDG PET were randomly performed before surgery to visualize the primary tumors and to detect axillary lymph node invasion. Tc-99m-Sesta MIBI correctly visualized 10 out of 11 primary cancers in 10 patients. In-111-Pentetreotide detected 9 out of 10 primary cancers. F-18-FDG imaged all the tumors (10). As regards the axillary nodes, Tc-99m-MIBI excluded axilla involvement in 7 out of 7 negative axillae (N-), while it was positive in 2 out of 3 positive cases (N+); In-111-Pentetreotide correctly identified 7 out of 8 negative axillae (N-), while it detected 2 of 3 positive sites. F-18-FDG visualized all positive axillary lymph nodes (4 out of 4 N+ patients) and correctly excluded involvement in all negative patients (6 out of 6 N- cases). This study demonstrated that all three tracers are adequate to be proposed as tumor seeking agents with the aim of developing non-invasive diagnostic methods for pre-operative detection of axillary metastases, so that surgical dissection can be limited to selected patients. The authors discuss the advantages and disadvantages of the different radiopharmaceuticals and conclude that in centers with PET facilities F-18-FDG is the best tumor seeking agent for the evaluation of axillary status. Between Tc-99m-Sesta MIBI and In-111-Pentetreotide the former seems to present more advantages in this kind of application, considering also its lower cost and easier availability. These results encourage further study, including the simultaneous comparison of these tracers in breast cancer staging.     

Positron emission tomography imaging in evaluation of cancer patients

Positron emission tomography (PET) is a diagnostic imaging technique that has progressed rapidly from being a research technique in laboratories to a routine clinical imaging modality. The most widely used radiotracer in PET is Fluorine18-fluorodeoxyglucose (F18-FDG), which is an analogue of glucose. The FDG uptake in cells is directly proportional to glucose metabolism of cells. Since glucose metabolism is increased many fold in malignant tumors PET has a high sensitivity and a high negative predictive value. PET with FDG is now the standard of care in initial staging, monitoring the response to the therapy, and management of lung cancer, colonic cancer, lymphoma, melanoma, esophageal cancer, head and neck cancer and breast cancer. Other indications of PET like bone tumor, ovarian cancer and cancer of unknown primary (CUP) has also been discussed in brief. The aim of this review article is to review the clinical applications of PET in various malignancies and only limited number of important studies will be discussed for this effort.     

Positron emission tomography in gynecological malignancies

Positron emission tomography (PET) is a functional diagnostic imaging technique. F-18 fluoro-2-deoxy-d-glucose (FDG) is a commonly used radiopharmaceutical that is an analog of glucose. PET with FDG is now the standard of care in initial staging, monitoring the response to the therapy and management of various cancers. There is not sufficient data to support the use of PET in the initial diagnosis of cervical cancer; however, FDG-PET has a role in initial staging in the detection of distant metastases in patients with cervical cancer. PET has limited value in lesion localization in early stages of ovarian cancer, but plays a significant role in identifying recurrent tumors in patients with rising tumor markers. In this article, the clinical application of PET in gynecological malignancies is reviewed.     

Positron emission tomography in gynecological malignancies

Positron emission tomography (PET) is a functional diagnostic imaging technique. F-18 fluoro-2-deoxy-d-glucose (FDG) is a commonly used radiopharmaceutical that is an analog of glucose. PET with FDG is now the standard of care in initial staging, monitoring the response to the therapy and management of various cancers. There is not sufficient data to support the use of PET in the initial diagnosis of cervical cancer; however, FDG-PET has a role in initial staging in the detection of distant metastases in patients with cervical cancer. PET has limited value in lesion localization in early stages of ovarian cancer, but plays a significant role in identifying recurrent tumors in patients with rising tumor markers. In this article, the clinical application of PET in gynecological malignancies is reviewed.     

Epithelial and Mesenchymal Tumor Compartments Exhibit In Vivo Complementary Patterns of Vascular Perfusion and Glucose Metabolism

Glucose transport and consumption are increased in tumors, and this is considered a diagnostic index of malignancy. However, there is recent evidence that carcinoma-associated stromal cells are capable of aerobic metabolism with low glucose consumption, at least partly because of their efficient vascular supply. In the present study, using dynamic contrast-enhanced magnetic resonance imaging and [F-18]fluorodeoxyglucose (FDG) positron emission tomography (PET), we mapped in vivo the vascular supply and glucose metabolism in syngeneic experimental models of carcinoma and mesenchymal tumor. We found that in both tumor histotypes, regions with high vascular perfusion exhibited a significantly lower FDG uptake. This reciprocity was more conspicuous in carcinomas than in mesenchymal tumors, and regions with a high-vascular/low-FDG uptake pattern roughly overlapped with a stromal capsule and intratumoral large connectival septa. Accordingly, mesenchymal tumors exhibited a higher vascular perfusion and a lower FDG uptake than carcinomas. Thus, we provide in vivo evidence of vascular/metabolic reciprocity between epithelial and mesenchymal histotypes in tumors, suggesting a new intriguing aspect of epithelial-stromal interaction. Our results suggests that FDG-PET-based clinical analysis can underestimate the malignity or tumor extension of carcinomas exhibiting any trait of “mesenchymalization” such as desmoplasia or epithelial-mesenchymal transition.     

[F-18]-Fluorodeoxyglucose PET and PET-CT in diagnostic imaging evaluation of locally recurrent and metastatic bladder transitional cell carcinoma

Background Little data is available on the utility of positron emission tomography (PET) and positron emission tomography-computed tomography (PET-CT) with [F-18]-fluorodeoxyglucose (FDG) in patients with bladder cancer. We retrospectively assessed the diagnostic utility of dedicated PET and hybrid PET-CT scans with [F-18]-FDG in the imaging evaluation of recurrent and metastatic bladder transitional cell carcinoma. Methods The study group included 35 patients who were previously treated for the primary disease. We performed PET in 17 patients and 23 PET-CT scans in 18 patients. Diagnostic validation was by biopsy in 1 patient and clinical and radiological follow-up for up to 5 years in the remaining patients. Results PET and CT were true negative (TN) in 12 patients and true positive (TP) in 19 patients. In 4 patients in this group, both locally recurrent pelvic mass and distant metastases were demonstrated, while in 3 of these patients, unsuspected skeletal and/or nodal metastases were detected by PET-CT and these patients received additional courses of chemotherapy. PET was discordant with CT in 4 patients. PET was negative in 2 of these patients, while post-chemotherapy CT showed enlarged nodes that were determined to represent successfully treated disease. In another patient, a hypometabolic soft-tissue mass was considered to represent a scar, and a wait-and-watch strategy was pursued. In the remaining patient, PET showed random hypermetabolic osseous lesions that represented early marrow metastatic infiltration. The combined diagnostic information provided by PET-CT affected the clinical management in 17% of patients. Conclusion FDG PET and PET-CT scanning may improve the imaging evaluation of patients with recurrent and metastatic bladder cancer. All authors have no financial disclosures     

鼻咽癌患者放射性骨坏死引起的正电子显像假阳性结果1例及文献复习

目的:探讨鼻咽癌(NPC)患者放射性骨坏死(osteoradionecrosis,ORN)引起正电子假阳性结果的原因及避免因此引发诊断错误的方法。方法:回顾性分析1例放疗后的鼻咽癌患者,行鼻咽部MRI及正电子显像后,再行组织病理学检查,对三种结果进行分析、比较。结果:MRI及正电子显像均诊断患者颅底区域肿瘤复发,组织病理学结果则显示鼻咽部病灶为放射性骨坏死。因此正电子扫描结果为假阳性结果。结论:鼻咽癌患者放疗后所致的放射性骨坏死容易引起正电子显像假阳性结果并可能引发不必要的治疗,因此NPC患者的正电子图像,对于可能的局限性肿瘤复发诊断,应该非常慎重。     

Evaluation of chemotherapy response in pediatric bone sarcomas by [F-18]-fluorodeoxy-D-glucose positron emission tomography

BACKGROUND: Response to neoadjuvant chemotherapy is a significant prognostic factor for osteosarcoma (OS) and the Ewing sarcoma family of tumors (ESFT). Conventional radiographic imaging does not discriminate between responding and nonresponding osseous tumors. [F-18]-fluorodeoxy-D-glucose (FDG) positron emission tomography (PET) is a noninvasive imaging modality that accurately predicts histopathologic response in patients with various malignancies. To describe the FDG PET imaging characteristics and to determine the correlation between FDG PET imaging and chemotherapy response in children with bone sarcomas, we reviewed our single institution experience. METHODS: Thirty-three pediatric patients with OS or ESFT with osseous primary sites were evaluated by FDG PET. All patients received standard neoadjuvant chemotherapy. FDG PET standard uptake values before (SUV1) and after (SUV2) chemotherapy were analyzed and correlated with chemotherapy response assessed by histopathology in surgically excised tumors. Twenty-six patients had SUV1, SUV2, and surgical excision. RESULTS: Although the mean SUV1 in children with OS or ESFT were similar (8.2. vs. 5.3, P = 0.13), mean SUV2 for OS patients was greater than the values for ESFT patients (3.3 vs. 1.5, P = 0.01). All ESFT patients and 28% of OS patients had a favorable histologic response to chemotherapy (>or= 90% necrosis). Combining ESFT and OS patients, both SUV2 and the ratio of SUV2 to SUV1 (SUV2:SUV1) were correlated with histologic response (P = 0.01 for both comparisons). CONCLUSION: FDG PET evaluation of pediatric bone sarcomas demonstrated significant alteration in response to neoadjuvant chemotherapy. SUV2 and SUV2:SUV1 correlated with histopathologic assessment of response and potentially could be used as a noninvasive surrogate to predict response in patients.     

18F-FDG PET-CT全身显像肠道高浓聚的临床意义分析

目的：评价PET-CT全身显像肠道摄取18F-FDG的临床意义.方法：本研究回顾性分析我院PET/CT中心2010年7月-2011年6月2387例检查者中肠道出现18F-FDG高代谢灶的227例检查者,通过病理结果及相关影像学检查及临床随访,确定最终结果.结果：227例肠道高浓聚中,局灶性浓聚165例,其中恶性病灶49例,总恶性率为29.70％,分组恶性率分别为体检组为8.51％,肠外原发肿瘤组为13.11％,查找原发病灶组为43.59％,临床怀疑为肠道肿瘤组为68.97％.弥漫性肠道代谢增高者62例,全部为生理性摄取或炎性改变.局灶性病灶中良性与恶性组SUV无统计学差异.结论：18F-FDG PET-CT全身显像对肠道肿瘤检出具有重要的意义,但其良恶性鉴别不能单纯依靠SUV,其病史在诊断中也具有非常重要的作用,最终诊断依靠肠镜活检.     

Increased fluorine-18 2-fluoro-2-deoxy-D-glucose (FDG) uptake in childhood CNS tumors is correlated with malignancy grade: a study with FDG positron emission tomography/magnetic resonance imaging coregistration and image fusion.

PURPOSE Positron emission tomography (PET) has been used in grading of CNS tumors in adults, whereas studies of children have been limited. PATIENTS AND METHODS Nineteen boys and 19 girls (median age, 8 years) with primary CNS tumors were studied prospectively by fluorine-18 2-fluoro-2-deoxy-D-glucose (FDG) PET with (n = 16) or without (n = 22) H(2)(15)O-PET before therapy. Image processing included coregistration to magnetic resonance imaging (MRI) in all patients. The FDG uptake in tumors was semiquantitatively calculated by a region-of-interest-based tumor hotspot/brain index. Eight tumors without histologic confirmation were classified as WHO grade 1 based on location, MRI, and clinical course (22 to 42 months). Results Four grade 4 tumors had a mean index of 4.27 +/- 0.5, four grade 3 tumors had a mean index of 2.47 +/- 1.07, 10 grade 2 tumors had a mean index of 1.34 +/- 0.73, and eight of 12 grade 1 tumors had a mean index of -0.31 +/- 0.59. Eight patients with no histologic confirmation had a mean index of 1.04. For these 34 tumors, FDG uptake was positively correlated with malignancy grading (n = 34; r = 0.72; P < .01), as for the 26 histologically classified tumors (n = 26; r = 0.89; P < .01). The choroid plexus papilloma (n = 1) and the pilocytic astrocytomas (n = 3) had a mean index of 3.26 (n = 38; r = 0.57; P < .01). H(2)(15)O-uptake showed no correlation with malignancy. Digitally performed PET/MRI coregistration increased information on tumor characterization in 90% of cases. CONCLUSION FDG PET of the brain with MRI coregistration can be used to obtain a more specific diagnosis with respect to malignancy grading. Improved PET/MRI imaging of the benign hypermetabolic tumors is needed to optimize clinical use.     

1818F-FDG PET显像在胃肠道恶性肿瘤术后监测的应用价值

目的:探讨18F-双脱氧葡萄糖(FDG)PET显像探察胃肠道恶性肿瘤患者术后肿瘤复发和远处转移的应用价值。方法:40例胃肠道恶性肿瘤术后患者,其中食管癌8例,胃癌8例,结肠癌15例,直肠癌9例;进行18F-FDG显像。结果:18F-FDGPET显像诊断胃肠道恶性肿瘤术后复发和或转移的灵敏度93.8%、特异性87.5%、准确性92.5%;在18F-FDGPET显像真阳性30例中,4例为局部复发,9例为局部复发伴转移;17例为远处转移。在有复发的13例中,9例18F-FDGPET显像结果与X-CT结果一致,4例X-CT检查未见异常。在有转移的26例患者中,18F-FDGPET显像共捡出转移灶109处。结论:18F-FDGPET显像是检测胃肠道恶性肿瘤术后复发和转移的灵敏而有效的方法,值得推广应用。     

Diagnostic Performance of F-18 FDG PET/CT Compared with CA125, HE4, and ROMA for Epithelial Ovarian Cancer

Objective: This study aimed to examine the diagnostic performance of F-18 fluorodeoxyglucose positron emission tomography with computed tomography (F-18 FDG PET/CT) compared with cancer antigen 125 (CA125), human epididymis protein 4 (HE4), and risk of ovarian malignancy algorithm (ROMA) score to distinguish epithelial ovarian cancer from benign tumors. Methods: A total of 46 patients with pelvic masses, who underwent F-18 FDG PET/CT, CA125, and HE4 before surgery between January 2015 and December 2018, were included in this retrospective study. The diagnostic performance of CA125, HE4, ROMA score, and maximum standardized uptake value (SUVmax) to differentiate epithelial ovarian cancer from benign pelvic tumors was examined by receiver operating characteristic curve analysis. Results: Among the 46 patients, 28 were cases of ovarian cancers and 18 were of benign. The mean values of CA125, HE4, ROMA score, and SUVmax were significantly higher in the ovarian cancer group than the benign group. In early cancer stages (stages I and II), Area under the curve for SUVmax was significantly higher than CA125 and ROMA score (0.778 for CA125, 0.753 for HE4, 0.682 for ROMA score, and 0.922 for SUVmax). Conclusion: SUVmax using F-18 FDG PET/CT showed a high diagnostic accuracy for differentiating epithelial ovarian cancer from benign pelvic tumors, including early stage ovarian cancer. F-18 FDG PET/CT can be a useful modality for the assessment of pelvic mass.     

The value of F-18-fluorodeoxyglucose PET for the 3-D radiation treatment planning of malignant gliomas

Purpose: The aim of the study was to determine the impact of positron emission tomography using the glucose analogue fluorine-18-fluorodeoxyglucose (FDG-PET) on the delineation of the target volume in three-dimensional radiation treatment planning of primary brain tumors.

Methods and Materials: In 18 patients with histologically proven (8× biopsy, 10× subtotal resection) primary brain tumors (8 astrocytomas °III, one mixed glioma °III, and 9 glioblastomas), magnetic resonance imaging (MRI) with gadolinium-DTPA and FDG-PET were performed in radiation treatment position within the same week. A computer program was developed for fusion of the PET and MR images. On corresponding axial slices, FDG uptake was compared to contrast enhancement in T1-weighted and to signal hyperintensity in T2-weighted MR images. Based on PET and MRI data, three-dimensional treatment planning was performed. All patients underwent linear accelerator (LINAC) radiotherapy.

Results: In MRI, all tumors and the surrounding edema were visible as hyperintense lesions in the T2-weighted images. 17/18 tumors showed contrast enhancement. In FDG-PET, 16 tumors showed hypermetabolism compared to normal white matter, whereas only 8/18 tumors showed hypermetabolism compared to normal gray matter. White matter edema was associated with decreased FDG uptake in all patients. The area of increased FDG uptake correlated closely with contrast enhancement, only in one case the volume of increased FDG uptake was larger than the area of contrast enhancement. Mean tumor volumes obtained by MRI T1 + Gd, T2, and PET were 30, 106, and 10 ml, respectively. Survival was comparable to data in the literature with a 1-year survival of 39% and a median survival of 310 days.

Conclusion: Only in a minority of patients did FDG-PET provide additional information for radiation treatment planning. This is mainly caused by the high intensity of FDG uptake in normal brain tissue. PET may be of greater value in the definition of regions that should obtain a radiation dose boost.     

Unique intense uptake demonstrated by (18)F-FDG positron emission tomography/computed tomography in primary pancreatic lymphoma: A case report

Patients with primary pancreatic lymphoma (PPL), which is rare, require a different therapeutic approach and have a better prognosis than those with pancreatic cancer. However, conventional imaging modalities alone are not able to differentiate between pancreatic cancer and other rare tumors such as PPL, although the accurate diagnosis of PPL is crucial. The development of new modalities such as F-18 2'-deoxy-2fluoro-D-glucose (FDG) positron emission tomography combined with computed tomography (PET/CT) contributes to the evaluation of lymphoma staging. However, few reports are currently available regarding PET/CT findings in PPL. In this study, a 56-year old man with PPL was examined using FDG PET/CT imaging, which showed the unique intense uptake of FDG in the pancreas with atypical findings of malignancy in the CT scan and magnetic resonance images.     

FDG—PET显像技术在恶性淋巴瘤诊断与治疗中的应用

对大多数肿瘤而言，^18F—FDGPET具有敏感性高、特异性强的优点。在淋巴结和结外淋巴瘤的诊断检出率、淋巴瘤分期和再分期、疗效预测和评估、检测微小残留病灶、监测复发和预后判断均优于CT或^67Ga。PET常上调淋巴瘤分期（约40％），PET的检出效能随淋巴瘤的组织类型而变动，尤其对弥漫性大B细胞淋巴瘤（DLBCL）和霍奇金病诊断率高。对骨髓累及的检出PET／CT可补充骨髓活检（BMB），但不能取代BMB。PET较^67Ga对脾淋巴瘤有更高的检出率。治疗早中期PET／CT是无进展生存期和总生存期独立的预后指标。FDG并非肿瘤特异性物质，FDG—PET存在假阳性和假阴性，需注意鉴别，可能时进行组织活检。     

Positron emission tomography imaging in lung cancer

Over the past several years, positron emission tomography (PET) has become a clinically useful, noninvasive study which complements conventional imaging (chest radiographs, computed tomography [CT], and magnetic resonance imaging [MRI]) in the evaluation of patients with lung cancer. PET imaging of lung cancer is typically performed with the radiopharmaceutical 18F-2-deoxy-D-glucose (FDG), a d-glucose analog. Increased glucose metabolism by malignant cells results in increased uptake and accumulation of FDG, which serves as the basis for tumor detection. This review will focus on the current applications of FDG-PET in lung cancer patients including evaluation of focal pulmonary abnormalities, staging lung cancer, determining tumor recurrence, and in assessing prognosis.     

A case of primary lung cancer lesion demonstrated by F-18 FDG positron emission tomography/computed tomography (PET/CT) one year after the detection of metastatic brain tumor

Cancer of unknown primary origin (CUP) is an aggressive disease with a poor prognosis. Metastatic brain tumors occur in approximately 15% of all cancer patients. F-18 2'-deoxy-2fluoro-D-glucose (FDG) positron emission tomography (PET) combined with computed tomography (PET/CT) contributes to the evaluation of cancer staging, although the benefits of PET/CT for detection of CUP origins has yet to be determined. In this study, we present a 37-year-old man with a brain tumor detected by magnetic resonance imaging. Surgical biopsy indicated a metastatic undifferentiated carcinoma, while clinical examination and a CT scan did not detect any abnormalities, with the exception of brain metastases. PET/CT did not reveal abnormal FDG uptake. PET/CT revealed abnormal intense FDG uptake in a small nodular lesion in the right lung 1 year following the detection of brain metastasis, and no other abnormal FDG uptake was observed elsewhere in the body. Right upper lobectomy and dissection of mediastinal lymph nodes were performed. The pathological diagnosis was poorly differentiated adenocarcinoma, which was similar to the brain metastatic lesion, and there was no lymph node metastasis. This case revealed an extremely rare lung cancer with primary lesions demonstrated by PET/CT 1 year after the detection of brain metastasis. This case reveals that F-18 FDG PET/CT imaging of CUP origin is capable of positively impacting on the identification of small primary tumor foci.     

Initial experience in small animal tumor imaging with a clinical positron emission tomography/computed tomography scanner using 2-[F-18]fluoro-2-deoxy-D-glucose

The feasibility of small animal imaging using a clinical positron emission tomography/computed tomography (PET/CT) scanner with [F-18]-fluoro-2-deoxy-D-glucose (FDG) was evaluated. As tumor-bearing small animal models, rabbits with VX-2 liver tumors, rats with mammary tumors on the back, and mice with LS174T human colon tumor xenografts were prepared. Two-dimensional PET, CT, and fused PET/CT images were obtained and reconstructed with a combined PET/CT system using a conventional protocol for humans and dedicated high-resolution mode protocols specialized for each species. Estimated radioactivity concentrations in tumors and normal organs determined noninvasively on FDG-PET/CT were compared with the actual tissue radioactivity levels determined from gamma-counting after vivisection in rats. In addition, recovery-corrected radioactivity concentrations were calculated and evaluated using the tumor/normal organ sizes measured on CT. Tumors in rabbits and rats were clearly visualized by FDG-PET/CT in the dedicated protocols, and images were considered suitable for research purposes. With the aid of thin-slice CT-mapping images, FDG uptake was correctly localized in the viable tumor regions. In mice, increased FDG uptake in tumors with varying activity levels was observed, but detailed anatomical information was not optimally provided from the images, even using specialized protocols. The estimated radioactivity concentrations of tumors and normal organs were close to the actual radioactivity concentrations obtained by gamma-counting (r = 0.97, P < 0.001, the estimated/actual slope: 1) when recovery correction was applied using the sample sizes measured on CT. FDG-PET/CT imaging with a modern clinical scanner was demonstrated to be feasible, of excellent quality, and quite quantitatively accurate for research in rabbits or rats with tumors of appropriate size (>2 cm without recovery correction and >1 cm with recovery correction). Evaluation of FDG uptake within a tumor was possible with the aid of CT images. Dedicated small animal PET/CT scanner would be better suited for evaluating tumor-bearing mice and likely could enhance imaging smaller tumors in rabbits or rats. Although it has limitations, small animal imaging with a clinical PET/CT scanner may be quite adequate for sequential noninvasive imaging in oncology research because the CT is of high resolution, allowing for localization of PET findings and for more precise noninvasive estimation of radioactivity concentration through partial volume corrections.