FDG uptake also occurs in nonmalignant tissues, most prominently the brain and heart. Lesser activity is seen in liver, spleen, and bone marrow. FDG is excreted by the kidneys, so prominent uptake is seen in the kidneys, ureters, and bladder. In females, certain physiological conditions of the reproductive system and benign lesions may be associated with increased uptake of FDG. Functional uptake in endometrium related to cyclic changes (Fig. 6.1) and menstruation (Fig. 6.2) is the most common cause of intense activity seen in the uterus in women without known malignancy of the reproductive tract [1, 2].

Uptake may be seen in the ovaries related to maturing or growing follicles (Fig. 6.3), especially in younger or premenopausal women [3]. Increased ovarian uptake of FDG in postmenopausal patients would raise the suspicion for malignancy (Fig. 6.4). Though high uptake suggests malignant disease, there is significant overlap in uptake for benign versus malignant lesions. In a reported study, a standardized uptake value (SUV) of 7.9 in ovary separated benign from malignant uptake with 57 % sensitivity and 95 % specificity [4]; an average SUV of 9.1 ± 4 was seen in malignant lesions versus 5.7 ± 1.5 in nonmalignant conditions. It is recommended that uptake in uterus or ovaries be correlated with history and corresponding CT scans. Other benign causes of uptake may be related to functional cyst, corpus luteum, adenoma, dermoid cyst, endometriosis, inflammation, and teratoma, reported to show variable uptake of FDG (Figs. 6.5 and 6.6) [3–6]. Uterine uptake can vary during the various phases of the menstrual cycle. Uterine fibroids are also a common benign cause of uptake of FDG in the uterus, generally appearing as low-grade, heterogeneous uptake (Fig. 6.7) but sometimes appearing as prominent activity; correlation with CT findings can help delineate the fibroids (Fig. 6.8) [6, 7]. Contamination may cause false focal uptake and should be ruled out (Fig. 6.9) [8].

Most primary cervical cancers concentrate FDG, especially those with poorly differentiated and squamous histology (Figs. 6.10 and 6.11). For staging, FDG PET-CT is useful in assessing pelvic or extrapelvic nodal involvement and detecting distant metastases (Figs. 6.12 and 6.13). This information is useful in planning the primary treatment of the patient, including surgery, radiation therapy, or both. Sensitivity and accuracy in detecting lesions are higher for advanced disease and are low for early-stage disease, up to stage 1A2 or 2A [9–11]. The primary advantage of FDG PET-CT is the detection of unknown distant metastases and lymph node metastases that are benign by mere size criteria (Fig. 6.14). The use of FDG PET imaging for routine staging prior to radical hysterectomy and pelvic lymph node dissection is still controversial, though the high specificity and negative predictive value of PET may be helpful in appropriate treatment planning [12, 13]. Low-volume disease and micrometastasis are the most frequent causes for false negative FDG PET findings. The use of larger scanning areas can also detect extra-abdominal disease (Fig. 6.15) [14]. Involvement of para-aortic metastasis is linked to prognosis and progression-free survival [15].

FDG PET helps in early detection of recurrent disease, evaluation of distant lesions, and followup of treatment (Fig. 6.16). The overall sensitivity for detection of recurrence was reported to be as high as 86 %, with specificity of 94 %; the positive predictive value was 85.7 % and the negative predictive value was 86.7 % [16]. It also is useful for assessing response to chemoradiation therapy (Fig. 6.17). Early metabolic response can be assessed, whereas anatomic changes may lag or may be difficult to assess.