18F-FDG PET/CT of patients with cancer: comparison of whole-body and limited whole-body technique

Frequency and clinical implications of findings on true whole-body 18F-FDG PET in the assessment of breast cancer

INTRODUCTION

In the assessment of breast cancer using 18-F FDG PET/CT, the incremental clinical benefit in performing a true whole-body PET/CT (with a field of view (FOV) from the vertex to the toes) over a limited whole-body PET/CT (with a FOV from the base of skull to the mid-thighs) is uncertain.

METHODS

Two hundred and one studies of 120 patients who underwent staging or restaging true whole body 18F-FDG PET/CT for breast cancer were retrospectively identified. Any abnormal hypermetabolic or structural focus outside the limited FOV was recorded and characterised, and referenced with the patient's known disease status and any symptomatology.

RESULTS

A total of 18 (9.0%) studies had FDG avid and/or structural abnormalities detected outside the limited whole-body FOV which were identified as malignant. Seventeen out of 18 (94.4%) were skeletal and of these, 15/17 (88.2%) were located within the lower limbs. In three cases, there were de novo findings but identified in the presence of interval progression of other metastases within the limited whole-body FOV. None of these additional findings is known to have resulted in a change to staging or clinical management.

CONCLUSION

In the assessment of breast cancer, a true whole-body PET/CT can reveal metastases outside the limited whole-body FOV, but these are unlikely to be encountered in isolation and therefore may have little bearing on clinical stage or management. Ultimately, while the choice of FOV should still be based on the individual patient situation, routine utilisation of the true whole-body FOV in the asymptomatic patient may not be necessary.

Local imaging to interpret tumor size in F18 fluorodeoxyglucose positron emission tomography/CT in lung cancers

OBJECTIVE

This study aimed to determine the thoracic and extra-thoracic extension of the disease in patients diagnosed with lung cancer and who had whole-body F18-fluorodeoxyglucose positron emission tomography/CT imaging and to investigate whether there is a relationship between tumor size and extrathoracic spread.

METHODS

A total of 308 patients diagnosed with lung cancer were included in this study. These 308 patients were first classified as group 1 (SPN 30 mm>longest lesion diameter ≥10 mm) and group 2 (lung mass (longest lesion diameter ≥30 mm), and then the same patients were classified as group 3 (nodular diameter of ≤20 mm) and group 4 (nodular size of >20 mm). Group 1 was compared with group 2 in terms of extrathoracic metastases. Similarly, group 3 was compared with group 4 in terms of frequency of extrathoracic metastases. F18 fluorodeoxyglucose positron emission tomography/CT examination was used to detect liver, adrenal, bone, and supraclavicular lymph node metastasis, besides extrathoracic metastasis.

RESULTS

Liver, bone, and extrathoracic metastasis in group 1 was statistically lower than in group 2 (p<0.001, p<0.01, and p=0.03, respectively). Liver, extrathoracic, adrenal, and bone metastasis in group 3 was statistically lower than that in group 4 (p<0.001, p=0.01, and p=0.04, p<0.01, respectively). The extrathoracic extension was observed in only one patient in group 3. In addition, liver, adrenal, and bone metastases were not observed in group 3 patients.

CONCLUSION

Positron emission tomography/CT may be more appropriate for cases with a nodule diameter of ≤20 mm. Performing local imaging in patients with a nodule diameter of ≤20 mm could reduce radiation exposure and save radiopharmaceuticals used in positron emission tomography/CT imaging.

FDG PET/CT reveals bone marrow oligometastasis in laryngeal squamous carcinoma: a case report with favorable outcome

Laryngeal carcinoma is the most common head and neck cancer. The vast majority of laryngeal carcinomas are of squamous-cell histologic type. Metastasis of laryngeal cancer typically occurs within the cervical lymph nodes and seldom in other regions. Although a small percentage of patients experience distant metastases, bone marrow metastasis from laryngeal cancer is among the least common metastatic sites. Previous literature has suggested that bone marrow carcinomatosis is aggressive and has a poor outcome, particularly in patients with supraglottic tumors. Ante-mortem diagnosis of this metastatic pattern has been limited. To our knowledge, this case report highlights the first documented occurrence wherein the utilization of 18-fluorine fludeoxyglucose positron emission tomography/CT imaging played a pivotal role in the early detection of bone marrow metastasis in a patient diagnosed with transglottic laryngeal cancer. A solitary metastatic distant bone marrow lesion was identified early during follow-up. As a consequence, the patient exhibited a remarkable and unforeseen favorable clinical outcome.

Heart and bladder detection and segmentation on FDG PET/CT by deep learning

Purpose

Positron emission tomography (PET)/ computed tomography (CT) has been extensively used to quantify metabolically active tumors in various oncology indications. However, FDG-PET/CT often encounters false positives in tumor detection due to ¹⁸fluorodeoxyglucose (FDG) accumulation from the heart and bladder that often exhibit similar FDG uptake as tumors. Thus, it is necessary to eliminate this source of physiological noise. Major challenges for this task include: (1) large inter-patient variability in the appearance for the heart and bladder. (2) The size and shape of bladder or heart may appear different on PET and CT. (3) Tumors can be very close or connected to the heart or bladder.

Approach

A deep learning based approach is proposed to segment the heart and bladder on whole body PET/CT automatically. Two 3D U-Nets were developed separately to segment the heart and bladder, where each network receives the PET and CT as a multi-modal input. Data sets were obtained from retrospective clinical trials and include 575 PET/CT for heart segmentation and 538 for bladder segmentation.

Results

The models were evaluated on a test set from an independent trial and achieved a Dice Similarity Coefficient (DSC) of 0.96 for heart segmentation and 0.95 for bladder segmentation, Average Surface Distance (ASD) of 0.44 mm on heart and 0.90 mm on bladder.

Conclusions

This methodology could be a valuable component to the FDG-PET/CT data processing chain by removing FDG physiological noise associated with heart and/or bladder accumulation prior to image analysis by manual, semi- or automated tumor analysis methods.

Achievements of true whole-body imaging using a faster acquisition of the lower extremities in variable-speed continuous bed motion

Variable-speed continuous bed motion ¹⁸F-fluorodeoxyglucose positron emission tomography/computed tomography (¹⁸F-FDG-PET/CT), a reliable imaging technique, allows setting the bed motion speed for arbitrary sections of the body. The purpose of this study was to evaluate the relationship between the PET image quality and the bed speed following shortening of the scanning time for the lower extremities to achieve whole-body acquisition optimization of the examination time. Four sets of images were created by editing four-phase dynamic whole-body PET/CT images acquired at a bed speed of 6 and 14 mm/s in the trunk and lower extremities, respectively. The signal-to-noise ratio (SNR) was calculated using regions of interest in the liver, gluteus muscles, thigh, and lower legs, and the relationship between the bed speed and the SNR was assessed. The number of patients with findings in the lower extremities among 967 cases was evaluated. Based on this relationship between the SNR and bed motion speed, it is reasonable to increase the speed of the lower extremities by up to three times that of the trunk. The findings from whole-body FDG-PET imaging revealed that the number of patients with detected lesions in the lower extremities was 6.6% (64/967), bone metastases were found in 2.6%, soft lesions in 1.8%, and inflammation in 2.3%. Images of the lower extremities, which have a better SNR than the trunk, can be acquired at a faster bed speed using the variable-speed continuous bed motion PET.

Total-Body PET/Computed Tomography Highlights in Clinical Practice: Experiences from Zhongshan Hospital, Fudan University

"The initial experience of using total-body PET/computed tomography (CT) (uExplorer) in Zhongshan Hospital, Fudan University, is described. Compared with conventional PET/CT, total-body PET/CT imaging provides more comprehensive information for evaluation of disease. Using fludeoxyglucose F 18, regular-dose (3.7 MBq/kg), low-dose (1.85 MBq/kg), or extra low-dose (0.37 MBq/kg) scanning, as well as high-quality imaging, protocols were used in clinical practice according to the situation. Dynamic studies were also used to assess tumor biological characteristics or for radiotracer angiography."

[A Nationwide Survey on Additional Scan in Nuclear Medicine Imaging]

The aim of the present study was to clarify the routine protocols and the frequency of added or omitted imaging on nuclear medicine imaging in Japan. A nationwide survey on routine protocols and current state of added or omitted imaging in major nuclear medicine imaging were performed for Japanese nuclear medicine technologist. The survey showed that the routine protocols were almost 100% fixed, some of the routine protocols were found to be useful and percentage of imaging techniques such as single photon emission computed tomography/computed tomography that increased patient burden and reduced through put were low. Furthermore, the survey showed that additional or omission imaging were frequently performed on bone scintigraphy and positron emission tomography and added or omitted judgements were often depend upon the rule of thumb by nuclear medicine technologist. In this study, we have concluded that the quality of examination and the diagnosis might depend on the knowledge of nuclear medicine technologist, performed added or omitted imaging.

Whole-Body versus Routine Skull Base to Mid-thigh 18F-Fluorodeoxyglucose Positron Emission Tomography/ Computed Tomography in Patients with Malignant Melanoma

Objectives:

The objectives of this study are to assess the utility of whole-body ¹⁸F-fluorodeoxyglucose positron emission tomography/computed tomography (¹⁸F-FDG PET/CT) (skull vertex to toes) imaging relative to the standard field of view (skull base to mid-thigh) in patients with primary melanoma site that is not located in the lower extremities.

Material and Methods:

The primary site of the melanoma and metastatic disease was determined based on ¹⁸F-FDG PET/CT findings in 26 patients. The FDG avid sites were tabulated as the primary site, lower extremity, brain, and other sites. The hypothesis is that routine skull base to mid-thigh versus whole-body ¹⁸F-FDG PET/CT in patients with malignant melanoma will not change management.

Results:

Patients (26) were divided into those with primary melanoma site in either the lower extremities (six patients) or other site (20 patients). Four of the six patients with the primary site in the lower extremities also had positive findings in the ipsilateral inguinal lymph nodes. One of the patients with a positive inguinal lymph node had metastatic sites in the external iliac region and lungs on the initial study. On follow-up imaging, this patient also exhibited diffuse metastatic disease, including a lower extremity. None of the remaining patients in this group had positive findings other than the primary site in the lower extremity. Of the remaining 20 patients with the primary site not in the lower extremity, one had diffuse metastatic disease that included a lower extremity. However, lower extremity involvement would not change patient management in this case. A second patient in this group had diffuse metastatic disease that also involved the brain. However, no metastatic disease was present in the lower extremities in this patient. None of the remaining 18 patients in this group had metastatic disease in a lower extremity. Two patients in the entire study group of 26 had brain metastasis on contrast-enhanced head CT, with one having multiple brain metastasis. PET failed to demonstrate some of the brain lesions. In the other patient with solitary brain metastasis detected on contrast-enhanced head CT, PET was negative.

Conclusion:

¹⁸F-FDG PET/CT imaging of the lower extremity may not be justified if the primary neoplasm is not located in the lower extremities. Elimination of lower extremity imaging will reduce scanning time and additional radiation exposure. Similarly, PET/CT imaging of the brain may not be justified if contrast-enhanced CT or magnetic resonance imaging of the head is already obtained since these are more sensitive.

Distribution of Femoral Metastases; Potential Role for Extended FDG PET/CT Scanning

This study investigates the distribution of femoral metastases in cancer patients, specifically addressing the incidence of distal femoral metastases. PET/CT examinations routinely extend only to mid-thigh level, precluding detection of distal metastases. We found a total of 208 femoral metastases in 112 patients. 30% had distal femoral metastases in addition to other areas of involvement. 7% of patients with femoral metastases had only distal femur disease. 6 patients had distal pathologic fractures. Exclusion of the distal femur during PET/CT may result in a missed or delayed diagnosis that could contribute to the development of a pathologic fracture with increased morbidity.

Malignant Cutaneous Melanoma: Updates in PET Imaging

BACKGROUND

Cutaneous malignant melanoma is a neoplasm whose incidence and mortality are dramatically increasing. 18F-FDG PET/CT gained clinical acceptance over the past 2 decades in the evaluation of several glucose-avid neoplasms, including malignant melanoma, particularly for the assessment for distant metastases, recurrence and response to therapy.

OBJECTIVE

To describe the advancements of nuclear medicine for imaging melanoma with particular attention to 18F-FDG-PET and its current state-of-the-art technical innovations.

METHODS

A comprehensive search strategy was used based on SCOPUS and PubMed databases. From all studies published in English, we selected the articles that evaluated the technological insights of 18FFDG- PET in the assessment of melanoma.

RESULTS

State-of-the-art silicon photomultipliers based detectors ("digital") PET/CT scanners are nowadays more common, showing technical innovations that may have beneficial implications for patients with melanoma. Steady improvements in detectors design and architecture, as well as the implementation of both software and hardware technology (i.e., TOF, point spread function, etc.), resulted in significant improvements in PET image quality while reducing radiotracer dose and scanning time.

CONCLUSION

Recently introduced digital PET detector technology in PET/CT and PET/MRI yields higher intrinsic system sensitivity compared with the latest generation analog technology, enabling the detection of very small lesions with potential impact on disease outcome.

Optimization of a shorter variable-acquisition time for legs to achieve true whole-body PET/CT images

The present study aimed to qualitatively and quantitatively evaluate PET images as a function of acquisition time for various leg sizes, and to optimize a shorter variable-acquisition time protocol for legs to achieve better qualitative and quantitative accuracy of true whole-body PET/CT images. The diameters of legs to be modeled as phantoms were defined based on data derived from 53 patients. This study analyzed PET images of a NEMA phantom and three plastic bottle phantoms (diameter, 5.68, 8.54 and 10.7 cm) that simulated the human body and legs, respectively. The phantoms comprised two spheres (diameters, 10 and 17 mm) containing fluorine-18 fluorodeoxyglucose solution with sphere-to-background ratios of 4 at a background radioactivity level of 2.65 kBq/mL. All PET data were reconstructed with acquisition times ranging from 10 to 180, and 1200 s. We visually evaluated image quality and determined the coefficient of variance (CV) of the background, contrast and the quantitative %error of the hot spheres, and then determined two shorter variable-acquisition protocols for legs. Lesion detectability and quantitative accuracy determined based on maximum standardized uptake values (SUV_max) in PET images of a patient using the proposed protocols were also evaluated. A larger phantom and a shorter acquisition time resulted in increased background noise on images and decreased the contrast in hot spheres. A visual score of ≥ 1.5 was obtained when the acquisition time was ≥ 30 s for three leg phantoms, and ≥ 120 s for the NEMA phantom. The quantitative %errors of the 10- and 17-mm spheres in the leg phantoms were ± 15 and ± 10%, respectively, in PET images with a high CV (scan < 30 s). The mean SUV_max of three lesions using the current fixed-acquisition and two proposed variable-acquisition time protocols in the clinical study were 3.1, 3.1 and 3.2, respectively, which did not significantly differ. Leg acquisition time per bed position of even 30-90 s allows axial equalization, uniform image noise and a maximum ± 15% quantitative accuracy for the smallest lesion. The overall acquisition time was reduced by 23-42% using the proposed shorter variable than the current fixed-acquisition time for imaging legs, indicating that this is a useful and practical protocol for routine qualitative and quantitative PET/CT assessment in the clinical setting.

Clinical validation of high-resolution image reconstruction algorithms in brain 18F-FDG-PET: effect of incorporating Gaussian filter, point spread function, and time-of-flight

OBJECTIVES

Accurate estimation of radiopharmaceutical uptake in the brain is difficult because of count statistics, low spatial resolution, and smoothing filter. The aim of this study was to assess the counting rate performance of PET scanners and the image quality with different combinations of high-resolution image reconstruction algorithms in brain F-2-fluorodeoxy-D-glucose (F-FDG)-PET.

MATERIALS AND METHODS

Using 23 patient studies, we analyzed the coincidence rates of true and random, random fraction, and the noise equivalent counts per axial length (NECpatient) in brain and liver bed positions. The reconstruction algorithms were combined with baseline ordered subsets expectation maximization, Gaussian filter (GF), point spread function (PSF), and time-of-flight (TOF). The image quality of the brain cortex was quantitatively evaluated with respect to spatial resolution, contrast, and signal-to-noise ratio (SNR).

RESULTS

The true coincidence rate in the brain was higher by 1.86 times and the random coincidence rate was lower by 0.61 times compared with that in the liver. In the brain, random fraction was lower and NECpatient was higher than that of the liver. Although GF improved the SNR, spatial resolution and contrast were reduced by 12 and 11%, respectively (P<0.01). PSF improved spatial resolution and SNR by 11 and 53%, respectively (P<0.01), and TOF improved SNR by ∼23% (P<0.01).

CONCLUSION

We have demonstrated that a high-resolution image reconstruction algorithm for brain F-FDG-PET is promising without the use of a GF because of high true coincidence counts and that combined with PSF and TOF is optimal for obtaining a better SNR of the image.

18F-FDG-avid plantar nodules on true whole-body 18F-FDG PET/CT in cancer patients

Plantar pain is a common problem endured by most adults at some point in their life that may result in considerable disability. Plantar fibromatosis is a locally invasive neoplasm, with the development of fibrous nodules on the plantar aspect of the feet, which can remain asymptomatic for years. (18)F-Fluorodeoxyglucose ((18)F-FDG) PET/CT has been more prevalent as the imaging modality of choice for cancer patients, but the imaged field of view is often from the base of the skull to the upper thighs. Therefore, the feet are typically not included in the field. However, true whole-body imaging from the top of the skull to the bottom of the feet is performed at some institutions and can provide clinically useful findings. One such finding is the presence of (18)F-FDG-avid plantar nodules. This review is intended to help clinicians become aware of these potential false-positive nodules that can affect a patient's staging and management.

FDG PET/CT: EANM procedure guidelines for tumour imaging: version 2.0

The purpose of these guidelines is to assist physicians in recommending, performing, interpreting and reporting the results of FDG PET/CT for oncological imaging of adult patients. PET is a quantitative imaging technique and therefore requires a common quality control (QC)/quality assurance (QA) procedure to maintain the accuracy and precision of quantitation. Repeatability and reproducibility are two essential requirements for any quantitative measurement and/or imaging biomarker. Repeatability relates to the uncertainty in obtaining the same result in the same patient when he or she is examined more than once on the same system. However, imaging biomarkers should also have adequate reproducibility, i.e. the ability to yield the same result in the same patient when that patient is examined on different systems and at different imaging sites. Adequate repeatability and reproducibility are essential for the clinical management of patients and the use of FDG PET/CT within multicentre trials. A common standardised imaging procedure will help promote the appropriate use of FDG PET/CT imaging and increase the value of publications and, therefore, their contribution to evidence-based medicine. Moreover, consistency in numerical values between platforms and institutes that acquire the data will potentially enhance the role of semiquantitative and quantitative image interpretation. Precision and accuracy are additionally important as FDG PET/CT is used to evaluate tumour response as well as for diagnosis, prognosis and staging. Therefore both the previous and these new guidelines specifically aim to achieve standardised uptake value harmonisation in multicentre settings.

FDG-PET images of acrometastases

Skeletal metastasis is common in patients with malignancy, but very few patients have acrometastasis, that is, metastasis to the hand or foot. We present 2 cases of acrometastasis from lung cancer where primary and metastatic foci were demonstrated on FDG-PET. The first case involves a 53-year-old man who complained of left foot pain and had osteolytic metastasis in the left calcaneus due to lung adenocarcinoma. True whole-body PET demonstrated lung cancer with calcaneal metastasis. Another case involves a 62-year-old man with large cell carcinoma of the right lung who complained of right wrist pain. Osteolytic metastasis of the hamate was demonstrated on images.

Evaluation of clinical contributions provided by addition of the brain, calvarium, and scalp to the limited whole body imaging area in FDG-PET/CT tumor imaging

Purpose. The aim of this study was to detect additional findings in whole body FDG-PET/CT scan including the brain, calvarium, and scalp (compared to starting from the base of the skull) in cancer patients and to determine contributions of these results to tumor staging and treatment protocols. Materials and Methods. We noted whether the findings related to the brain, calvarium, and scalp in 1359 patients had a potential to modify staging of the disease, chemotherapy protocol, radiotherapy protocol, and surgical management. We identified rates of metastatic findings on the brain, calvarium, and scalp according to the tumor types on FDG-PET/CT scanning. Results. We found FDG-PET/CT findings for malignancy above the base of the skull in 42 patients (3.1%), one of whom was a patient with an unknown primary tumor. Twenty-two of the metastatic findings were in the brain, 16 were in the calvarium, and two were in the scalp. Conclusion. This study has demonstrated that addition of the brain to the limited whole body FDG-PET/CT scanning may provide important contributions to the patient's clinical management especially in patients with lung cancer, bladder cancer, malignant melanoma, breast cancer, stomach cancer, and unknown primary tumor.

Frequency and clinical implications of incidental new primary cancers detected on true whole-body 18F-FDG PET/CT studies

OBJECTIVE

To determine the frequency of additional primary malignancies in patients undergoing staging/restaging with PET/computed tomography (CT) and to determine the frequency with which these unsuspected findings change clinical management.

METHODS

This is a retrospective review of 556 patients who had undergone a total of 804 PET/CTs for staging/restaging. Lesions that were at an atypical location for a metastasis from the primary malignancy (indication for the study) and had a maximum standardized uptake value greater than 2.5 were considered suspicious. Suspicious lesions were followed up by a combination of clinical examination, biopsy, and additional and/or follow-up imaging.

RESULTS

Forty-three (7.7%) patients had lesions that were suspicious for a newly discovered primary malignancy that was different from the known/suspected malignancy (indication for study). Eight (1.4% of 556) of these patients had biopsy confirmation of an additional synchronous or metachronous primary malignancy. However, these suspicious lesions changed the clinical management for 18 (3.2% of 556) patients. Patients with early-stage disease (stages 1 and 2) based on the malignancy for which the study was conducted were three times more likely to have these suspicious lesions biopsied, evaluated by clinical examination or by additional immediate imaging than were patients with advanced-stage disease (stages 3 and 4); however, this difference was not statistically significant (P=0.08).

CONCLUSION

Unsuspected additional primary malignancies are rarely identified in patients undergoing staging/restaging with PET/CT but have the potential to significantly impact clinical management.

Value of true whole-body FDG-PET/CT scanning protocol in oncology: optimization of its use based on primary diagnosis

BACKGROUND

No standardized field of view (FOV) currently exists for whole-body (WB) positron emission tomography/computed tomography (PET/CT). Limited WB PET/CT FOV can exclude portions of the head, upper, and lower extremities, because there is little perceived clinical benefit to be gained from imaging these areas.

PURPOSE

To determine how often utilizing WB PET/CT changes the clinical stage and management compared to each of the limited WB FOVs used for PET/CT.

MATERIAL AND METHODS

We retrospectively identified 556 oncologic patients (804 PET/CT studies) who underwent staging or restaging PET/CT between November 2010 and November 2011. Abnormal hypermetabolic areas that were suspicious for malignancy in areas that are outside of some of the limited fields of view including in the brain, scalp, and calvarium (above the orbital ridge), in the proximal upper extremity (distal to the humeral neck), distal upper extremity (beyond the elbow), proximal lower extremity (distal to the lesser trochanter), and distal lower extremity (beyond the knees) were recorded.

RESULTS

A total of 8.5% (47/556) of patients had abnormal findings outside the most limited FOV (skull base to upper thighs) used in PET/CT. More patients had abnormal hypermetabolic lesions in the lower extremity (5.9%) than in the upper extremity (2.3%). Similarly, more patients had abnormal lesions in the proximal (6.5%) compared to the distal (1.4%) upper and lower extremities. The stage was only changed in one patient (0.2%), however new lesions noted in the brain changed management in six patients (1.1%). Melanoma, lymphoma, multiple myeloma, sarcomas and stage IV lung, breast, prostate, bladder, testicular, and renal cancer were more likely to have findings outside the most limited FOV (skull base to upper thighs).

CONCLUSION

WB FOV detects additional sites of disease compared to the limited WB FOV, and although these lesions rarely change stage, some of these lesions may change clinical management.

The Incremental Added Value of Including the Head in (18)F-FDG PET/CT Imaging for Cancer Patients

Purpose: To assess the value of extending the routinely used base-of-skull (BOS) to upper-thigh field of view (FOV) to include the head on ¹⁸F-FDG PET/CT in cancer patients.

Methods: We retrospectively reviewed 1000 consecutive top-of-head to foot PET/CT studies. Abnormalities above BOS were categorized as unsuspected or known and were correlated with pathology, MRI/CT, and clinical follow-up.

Results: Of the 1000 patients, 102 (10.2%) had potentially significant findings above BOS. Of these, 70/102 (69%) were known and 32/102 (31%) were unsuspected. Of the patients with unsuspected findings, follow-up data was unavailable in 7/32 (22%) and abnormalities were confirmed in 25/32 (78%). Of the 25 confirmed unsuspected findings, 4/25 (16%) were false positives and 21/25 (84%) were true positives. Of these, 13/21 (62%) were confirmed metastatic, and 8/21 (38%) were benign. Unsuspected finding of brain metastasis changed the management in 11/13 (85%) and staging in 4/13 (31%).

Conclusion: Including the head in PET/CT FOV incidentally detected clinically significant findings in 2.1% (21/1000) of patients. The detection of previously unsuspected metastasis had significant impact on patient management and provided more accurate staging.