Owing to its metabolic tracing capability, PET/CT can have a superior role in the detection of ovarian carcinoma recurrence with a power of accurate localization of the lesions; thus, it can alter the treatment plan [17,18,19,20,21,22,23,24].
Some pitfalls may be noted in PET–CT such as respiratory artifacts affecting the upper abdomen as well as normal physiologic uptake (loops of bowel and urinary bladder) [8, 24].
False-positive result is another problem as seen in the atherosclerotic plaques, inflammatory bowel process, and myomatosis [24, 25].
On the other hand, false-negative can be gained in ovarian clear cell carcinoma (due to low cellular glucose metabolism) as well as in cystic or necrotic lesions [8, 24, 25].
In the study of Fulham et al.  which was carried on 90 ladies with suspicion of ovarian carcinoma recurrence, PET–CT displayed a superior detection rate that was achieved by contrast CT which subsequently modified the treatment in 60% of cases.
In the current study, 36 subjects with suspicion of ovarian cancer recurrence were subjected to PET–CT. The PET/CT could detect recurrence in 32/36 patients with patient-based overall sensitivity and specificity of 96.87 and 75% while the accuracy was 94.44%.
On the other hand, in the current report, PET–CT could detect 62/67 recurrent lesions with lesion-based overall sensitivity and specificity of 85.7 and 97.89 and accuracy of 95.77%.
Our results are generally in matching with earlier studies [7, 26,27,28,29,30,31,32] which had patient-based specificity, sensitivity, and accuracy of 85–100%, 86–100%, and 85–100%, respectively, while at the region level, the sensitivity and specificity ranged from 41–78% and 75–99% and accuracy 72–96%.
Antunovic et al.  used non-contrast CT in their PET/CT report and had a sensitivity of 72% and specificity of 81% for PET/CT in the detection of OC recurrence.
Iagaru et al.  divided the lesions of OC recurrence to pelvic and extra-pelvic. They showed that PET–CT had a superior performance in the detection of extra-pelvic ones, and they attributed that to the false-negative results due to physiological bladder uptake obscuring the pathological pelvic uptake as well as false-positive results caused by the postoperative inflammatory changes.
On the other hand, Sala et al.  showed that PET/CT had the highest accuracy in the diagnosis of peritoneal lesions and limited in the local pelvis recurrence, distant organ metastases (liver and spleen), and distant lymph nodes (above renal hila), and they attributed this false-negative liver and spleen case to mislabeling rather than a non-visualization of lesion.
In the current study, PET/CT had the highest performance for the diagnosis of recurrent local pelvic lesions and metastases to distant organs, and the sensitivity, specificity, and accuracy of 100%, which was very close to the results of Gouhar et al.  who estimated 100% accuracy, sensitivity, and specificity of PET–CT in the detection of recurrence in the same areas.
False-negative can be seen in small-volume disease (5–7 mm), military or diffuse peritoneal metastases . In an earlier study of OC recurrence , PET/CT had sensitivity and specificity of 77% and 96% and accuracy of 90% in the detection of peritoneal metastasis.
While in the study of Fulham et al. , they detected unsuspected lesions in 61 patients (majority had peritoneal nodal or discrete lesions) while they found 8 subjects with FDG diffuse abdominal uptake (military peritoneal spread).
In the current study, PET/CT scan detected 16 lesions of peritoneal metastasis correctly with sensitivity and specificity of 76.19 and 95.65 and accuracy of 89.55%.
We had 5 false-negative peritoneal cases; 2 false-negative results had cystic or necrotic lesions without significant FDG uptake; however, follow-up showed the development of multiple peritoneal cystic lesions which were resolved after chemotherapy, while the other 3 false-negative cases developed peritoneal deposits after 5 months; this could be explained by microscopic lesions [37, 38]. On the other side, we had two cases of false-positive results with peritoneal metastasis, they had PET/CT in less than 5 weeks post-surgery, and finally, it was proved to be a postoperative inflammatory process which is previously described as being generally hard to be differentiated from residual lesions [25, 39, 40].
PET/CT has the power to detect metastasis with increased metabolic activity even in non-enlarged lymph nodes; however, small or necrotic lymph nodes can have false-negative results . In the study of Gouhar et al. , for lymph node detection, PET/CT had sensitivity and specificity of 80% and 99% and accuracy of 97% in pelvic lymph nodes and 89%, 100%, and 99% for distant lymph node while the corresponding values were 78%, 96%, and 94% for para-aortic lymph nodes, respectively.
In our study, PET/CT scan described recurrent lesions in 5 pelvic lymph nodes with sensitivity and specificity of 80 and 98.38% and accuracy of 97%. We had a false-positive lesion as well as one false-negative lesion, while it described suspicion of OC recurrence in 9 para-aortic lymph nodes with sensitivity and specificity of 66.67 and 94.82% and accuracy of 91.04% respectively (3 false-positive and same number for false-negative cases). In distant lymph node metastasis, PET/CT scan described 10 lesions with sensitivity and specificity of 90 and 98.24% and accuracy of 97.01% (1 case was false-negative, one case false-positive).
Our results coincide with the previous studies [22, 23, 42] that found a reliable correlation between PET–CT and surgical findings and showed high sensitivity and specificity for all regions except para-aortic lymph nodes and diffuse peritoneum carcinosis showing sensitivity of 83 and 79%, respectively. Also, this agrees with Iagaru et al.  who showed that PET/CT can assist in diagnosis and management of OC recurrence through accurate localization and extension assessment of recurrence and distant metastases which affect re-staging.
Mangili et al.  detected a high sensitivity of PET/CT compared to contrast CT alone (91% versus 62%) for diagnosis of recurrent OC with altering the treatment and plan in 44% of cases.
A meta-analysis done by Gu et al.  found a better ovarian cancer detection recurrence by PET/CT compared to CT or MRI (sensitivity of 91 versus 79 and 75% and specificity of 88 versus 84 and 78% respectively).
In the study of Fagotti et al.  to assess the role of PET/CT to predict optimal cytoreduction in recurrent OC, the PET/CT estimated specificity and sensitivity of 56 and 93% and accuracy 79%, while positive predictive and negative predictive value was 77% and 83%, and they concluded that PET/CT can efficiently affect the plan of surgical treatment of patients with recurrent OC.
In the study carried out by Simcock et al. , PET/CT had significantly changed the treatment plan of recurrent OC in 57% of the subjects.
We had some limitation in the current study: first, the gold standard (pathological confirmation) could not be achieved in all areas of FDG uptake as that was not ethically possible, and the second limitation was the small study cohort number.