Physiological ¹8F-FDG uptake by the spinal cord: is it a point of consideration for cancer patients?

It is essential to be familiar with normal patterns of (18)F FDG distribution in the whole body for accurate PET interpretation. We assessed FDG uptake by the spinal cord to evaluate its characteristics in cancer patients. For 101 cancer patients who underwent (18)F FDG PET/CT the spinal cord along its segments was visually assessed for FDG uptake, regarding MaxSUV-measurement ≥1 as cut-off point. This assessment was correlated with the patient's database variables. MRI and FDG PET-CT follow-up were included in the evaluation of positive subjects with FDG cord uptake. Forty-nine (48.5%) were positive for FDG cord uptake. The most encountered sites were the eleventh and twelfth dorsal vertebrae (36/49; 73.5%), all cervical (24/49; 49%), and the first lumbar segments (19/49; 38.7%). 38/49 (77.6%) and 11/49 (22.4%) were detected in the winter and summer, respectively (P = 0.007). MRI was available for 25 of the positive FDG cord uptake patients and showed no cord abnormalities, and in follow-up FDG PET-CT studies within 3-6 months 41/49 (83.7%) faded completely, while stationary or reduced uptake was observed for the remainder (8/49; 16.3%). FDG uptake in multiple consecutive segments of the spinal cord is not uncommon in cancer patients. This must be recognized as physiological, to avoid misdiagnosis as malignant involvement. Such physiological uptake is mostly encountered in the cervical, last two dorsal, and first lumbar levels, and quite frequently in winter.

PET versus PET/CT dual-modality imaging in evaluation of lung cancer.

Software coregistration of FDG-PET and CT datasets as well as integrated FDG-PET/CT enable significantly more accurate assessment of NSCLC staging than either modality alone. Integrated FDG-PET/CT has been shown to be more accurate in NSCLC staging than FDG-PET and CT read side by side. However, the benefits of anatometabolic imaging using FDG-PET/CT can only be fully exploited if optimized acquisition protocols are implemented.

Can PET/CT replace separate diagnostic CT for cancer imaging? Optimizing CT protocols for imaging cancers of the chest and abdomen.

Stage-adapted treatment in oncology relies on correct tumor staging for patients with malignant diseases. To ensure accurate assessment of the tumor stage in thoracic and abdominal diseases by PET/CT, both CT and PET need to be optimized. In this setting, different malignant diseases require customized imaging protocols. Although in the clinical setting of therapy assessment, PET/CT with integration of low-dose, nonenhanced CT may be sufficient, tumor staging may require a more sophisticated CT protocol. This review focuses on potential CT protocols for imaging cancers of the chest and abdomen. Examples of CT protocols are presented and discussed for non-small cell lung cancer, breast cancer, colorectal cancer, gastrointestinal stromal tumors, and interventional liver therapy.

PET versus PET/CT dual-modality imaging in evaluation of lung cancer.

Non-small cell lung cancer (NSCLC) accounts for approximately 80% of bronchogenic malignancies. The choice of therapy options, including surgery, radiation therapy, and chemotherapy-used alone or in combination-is based on the tumor stage. Consequently, the accurate determination of tumor size, potential infiltration of adjacent structures, mediastinal lymph node involvement, and the detection of distant metastases are of central importance. The purpose of this article is to summarize the accuracy of dual-modality FDG-PET/CT imaging in staging of NSCLC as compared with FDG-PET alone, and with FDG-PET as well as CT read side by side. Furthermore, an optimized PET/CT protocol for patients who have lung cancer is outlined.

False-positive FDG PET uptake--the role of PET/CT.

Positron emission tomography (PET) is a powerful molecular imaging technique for the human body-imaging applications currently available. As altered glucose metabolism is characteristic for many malignancies, FDG-PET is mostly used in oncology for staging and therapy control. Although PET is a sensitive tool for detecting malignancy, FDG uptake is not tumor specific. It can also be seen in healthy tissue or in benign disease as inflammation or posttraumatic repair and could be mistaken for cancer. The experienced nuclear medicine physician mostly manages to differentiate malignant from non-malignant FDG uptake, but some findings may remain ambiguous. In these cases, the difficulties in differentiating physiologic variants or benign causes of FDG uptake from tumor tissue can often be overcome by combined PET and CT (PET/CT) as anatomic information is added to the metabolic data. Thus, PET/CT improves the diagnostic accuracy compared to PET alone and helps to avoid unnecessary surgery/therapy. However, PET/CT involves other sources of artifacts that may occur when using CT for attenuation correction of PET or by patient motion caused by respiration or bowel movements.

Dual modality of 18F-fluorodeoxyglucose-positron emission tomography/computed tomography in patients with cervical carcinoma of unknown primary.

OBJECTIVE: To evaluate an optimized F-18-flurodeoxyglucose-positron emission tomography/computed tomography (FDG-PET/CT) acquisition protocol for head and neck cancer and assess the usefulness of combined FDG-PET/CT in locating unknown primary tumors in patients with biopsy-proven cervical lymph node metastases. SUBJECTS AND METHODS: Twenty-one patients with cervical lymph node metastases of unknown primary tumors underwent staging with FDG-PET/CT. The images of FDG-PET alone, CT alone, FDG-PET/CT read side by side and fused and FDG-PET/CT were evaluated separately by 2 physicians. Imaging results were correlated with either histology (n = 14) or clinical follow-up (n = 7). RESULTS: On the fused FDG-PET/CT images, primary tumors were identified in 12 patients (57%); with FDG-PET alone and FDG-PET and CT read side by side 11 (52%) primary tumors were found while CT alone identified 5 (23%) primary tumors. CONCLUSION: Our data indicate that fused FDG-PET and CT images increased the sensitivity of detecting carcinoma of unknown primary (CUP) tumors compared to CT alone, but not to FDG-PET alone or FDG-PET and CT read side by side. Hence accurate fusion of functional and morphologic data by FDG-PET/CT is a promising imaging modality in the clinical workup of patients with cervical CUP tumors.