Whole-body Survey Research Articles

Utility of Fluorine18 Fluoro-2-deoxy-D-glucose Positron Emission Tomography/Computed Tomography in Metabolic Characterization of Solid Renal Mass Lesion and Localization of Extra Renal Lesions in the Body - A Prospective Study from the Tertiary Care Center in South India.

Renal mass lesions in majority of the cases are due to malignant etiology and about one-third of them are reported with metastatic lesions at the time of presentation. Thus proper investigational workup is needed for staging and thereby treatment planning. The current fluorine18 fluoro-2-deoxy-D-glucose positron emission tomography/computed tomography (F18-FDG PET/CT) study was designed to characterize renal mass lesions metabolically and identifying other metabolically active lesions in the body suggesting metastatic disease. A total of 24 patients (males - 18 and females - 6) with a mean age of 53.8 ± 12.3 years were recruited in this study for dual time-point PET/CT scan. All patients with renal mass lesions underwent contrast-enhanced CT prior to PET/CT. Metabolic parameters such as maximum standardized uptake value (max.SUV) with a cut off ≥2.5 and retention index (RI) of ≥10% were used to label the lesion as malignant and remaining less than cutoff as benign. The final diagnosis of lesion on imaging was confirmed with a histopathological examination (HPE). Using max.SUV cut off value, 17/24 renal mass lesions were characterized as malignant and remaining 7/24 renal lesions of benign etiology. PET/CT showed sensitivity, specificity, positive predictive value, negative predictive value, and accuracy were 80%, 75%, 94.1%, 42.8%, and 79.1%, respectively, by considering HPE as a gold standard. Nine patients were diagnosed with distant site involvement suggestive of metastases. F18-FDG PET/CT can efficiently characterize solid renal mass lesion as benign and malignant using metabolic parameters such as max.SUV and RI. In addition, whole-body survey identified distant site involvement in 25% of the patients, thus contributing change in management.

"Picture-in-Picture" Artifact in Post-therapeutic 131I Whole-body Survey: Deceiving Spot View but Unraveling Whole-body Scanning.

Artifacts originated from imaging hardware or instrumentation may be, on some occasions, confusing and peculiar to both physicians and technicians. Various artifacts from a variety of sources have been reported. In this note, we intend to describe a new one with an interesting pattern in whole-body scanning, which is strikingly different from its pattern in static spot view, in a patient presented for post-therapeutic 131I survey after total thyroidectomy.

Hyperphosphatemic Tumoral Calcinosis: A Classical Clinico-Radio-Scintigraphic Presentation.

Tumoral calcinosis is a rare entity presenting with periarticular calcium deposits, leading to multiple swellings and biochemical hyperphosphatemia and normocalcemia. Skeletal scintigraphy in these cases is helpful by providing a whole-body survey and delineating the common multifocality of this entity. We present the case of a 16-year-old boy with multiple swellings around the knee and elbow joints, having developed over 4 years and diagnosed as tumor calcinosis.

Ultra-Fast List-Mode Reconstruction of Short PET Frames and Example Applications.

Standard clinical reconstructions usually require several minutes to complete, and this time is mostly independent of the duration of the data being reconstructed. Applications such as data-driven motion estimation, which require many short frames over the duration of the scan, become unfeasible with such long reconstruction times. In this work, we present an infrastructure whereby ultra-fast list-mode reconstructions of very short frames (≤1 s) are performed. With this infrastructure, it is possible to have a dynamic series of frames that can be used for various applications, such as data-driven motion estimation, whole-body surveys, quick reconstructions of gated data to select the optimal gate for a given attenuation map, and, if the infrastructure runs simultaneously with the scan, real-time display of the reconstructed data during the scan and automated alerts for patient motion. Methods: A fast ray-tracing time-of-flight projector was implemented and parallelized. The reconstruction parameters were optimized to allow for fast performance: only a few iterations are performed, without point-spread-function modeling, and scatter correction is not used. The resulting reconstructions are thus not quantitative but are acceptable for motion estimation and visualization purposes. Data-driven motion can be estimated using image registration, with the resultant motion data being used in a fully motion-corrected list-mode reconstruction. Results: The infrastructure provided images that can be used for visualization and gating purposes and for motion estimation using image registration. Several case studies are presented, including data-driven motion estimation and correction for brain studies, abdominal studies in which respiratory and cardiac motion is visible, and a whole-body survey. Conclusion: The presented infrastructure provides the capability to quickly create a series of very short frames for PET data that can be used in a variety of applications.

Synchronous Pure Epithelioid Angiomyolipoma of the Kidney and Retroperitoneal Schwannoma in the Same Patient on 18F-FDG PET/CT Imaging

A 21-year-old woman was admitted to our hospital after incidental detection of a left renal lesion on ultrasound scan. Abdominal contrast-enhanced CT scan revealed a moderately enhanced lesion in the left kidney and a round mass with slight enhancement in the retroperitoneum. FDG PET/CT imaging was performed for whole-body survey, showing increased tracer accumulation in both the left renal and the retroperitoneal lesions. Left renal cell carcinoma with retroperitoneal metastasis was suspected. Synchronous pure epithelioid angiomyolipoma of the left kidney and retroperitoneal schwannoma were diagnosed by pathology. This case highlights that epithelioid angiomyolipoma should be considered as one of the differential diagnosis in renal lesions with increased FDG uptake.

Simultaneous Rectal Schwannoma and Prostatic Adenocarcinoma Detected on FDG PET/CT

A case of an 84-year-old man with suspicious rectal cancer has been reported. The patient underwent FDG PET/CT for whole-body survey. Unexpectedly, FDG PET/CT demonstrated abnormally increased FDG uptake in rectum (SUVmax: 3.33) and prostate (SUVmax: 5.66) simultaneously. Ultimately, biopsies of rectal tumor and prostatic gland confirmed diagnoses of synchronous schwannoma in the rectum and adenocarcinoma in the prostate. To our best knowledge, this is the first case of rectal schwannoma with representative FDG PET/CT scan in the literature.

Interest of (18)F‐FDG PET‐CT scanning for staging and management of merkel cell carcinoma: a retrospective study of 15 patients

The additional benefit of 18FDG-Positron Emission Tomography-Computed Tomography (FDG PET-CT) compared with conventional imaging is still a controversial issue in MCC. This study was designed to evaluate the ability of FDG PET-CT to detect secondary lesions clinically inconspicuous and not shown by conventional imaging. Clinical records of 15 MCC patients were retrospectively reviewed to investigate the specific interest of FDG PET-CT compared with X-computed tomography (CT). The main endpoint was the ability of FDG PET-CT to detect secondary lesions and the possible resulting changes in disease staging and management compared with pre-FDG PET-CT data including clinical examination, sentinel lymph node biopsy (SLNB), and diagnostic CT. FDG PET-CT was relevant with a single false negative result and led to significant changes in disease staging and management in 46% of patients compared with clinical examination alone. However, additional secondary lesions not detected by CT were evidenced during follow-up in a single patient with an already known metastatic disease, data which did not result in any change in staging and treatment. Sensitivity, specificity, positive predictive value and negative predictive value were respectively 0.66, 1, 1 and 0.8 for SLNB, 0.89, 1, 1 and 0.93 for CT and 0.89, 1, 1 and 0.93 for FDG PET-CT. No additional neoplasm was detected by FDG PET-CT. Although FDG PET-CT is of questionable value in MCC management when used in parallel with CT, it may be considered as a valuable option as a single whole-body survey procedure.

Significance of incidental fluorodeoxyglucose uptake in the parotid glands and its impact on patient management

Minimal-to-low grade fluorodeoxyglucose (FDG) uptake in the parotid glands is regarded as a normal variant in a whole-body survey with FDG-PET. Not frequently, however, a relatively intense or asymmetric FDG uptake is encountered in the parotid glands. The aim of this study was to determine the causes and characteristics of this 'FDG accumulation of uncertain significance' in the parotid glands in patients without any known or suspected pathologies at the time of whole-body FDG-PET. In addition, we also examined patients in whom there was no documented evidence of parotid pathology before FDG-PET scan and a suspicion of disease involvement was first raised in the reports in view of focal uptake in the FDG-PET images. A total of 25 patients with 49 PET examinations [46 PET and three PET/computed tomography (CT) scans] were identified from the retrospective examination of PET reports and were analyzed in this study. Only those cases with no earlier history of disease involvement of parotid gland or known parotid pathology before FDG-PET were selected for this analysis. These patients were selected from a population of patients with a known malignancy elsewhere who underwent conventional whole-body FDG-PET or PET/CT for staging, disease viability assessment, or treatment monitoring purposes and had demonstrated varying patterns of FDG uptake (unilateral, bilateral, symmetric, or asymmetric) in the parotid glands. FDG uptake in the parotid glands was reported to be of uncertain significance in the majority of these patients and further correlation was suggested in the PET reports. In five patients with asymmetric and focally enhanced FDG uptake, a suspicion of disease involvement was raised in the reports. The results of appropriate correlative investigations with MRI, low-dose nonenhanced attenuation CT images (based on PET/CT scans), and histopathology (in cases in which focal lesions were revealed by the anatomic imaging modalities and biopsy was performed) carried out subsequent to the FDG-PET scans were reviewed for a definitive conclusion with regard to the significance of the FDG uptake in the parotid glands in these patients. In the absence of any focal pathology, clinical and follow-up FDG-PET data were reviewed for a logical conclusion, which were available in a majority of these patients. Standardized uptake values (maximum) were calculated by generating a manual region of interest over FDG activity. The pattern and the intensity of the FDG uptake were correlated with the final diagnosis. In six of the 25 patients with diffuse and symmetrical FDG uptake no clearcut pathology was demonstrated by clinical or radiological examinations. Five patients of this subgroup also demonstrated associated enhanced FDG activity in the submandibular salivary glands. Nineteen patients (76%) demonstrated asymmetric FDG uptake. Among these, focally enhanced uptake was observed in seven patients (28% of the total number of patients and 36.8% of the patients who demonstrated asymmetric FDG uptake in the parotids). Twelve patients (48% of total patients and 63.2% of the patients who demonstrated asymmetric FDG uptake) demonstrated asymmetric and diffuse FDG uptake pattern. No revelation of disease either by the MRI or follow-up clinical and FDG-PET examinations was observed in patients with asymmetric diffuse uptake. Five of the seven patients, who had asymmetric focal uptake in one of the parotids, were found to have focal lesions in either correlative MRI or low-dose nonenhanced CT. The final diagnosis based upon histopathology revealed primary parotid tumors (e.g., Warthin's tumor and pleomorphic adenoma, which presented as FDG-avid parotid incidentaloma) or metastatic disease involvement. Both the pattern and intensity of FDG uptake have important implications for differential diagnosis in the salivary glands in whole-body FDG-PET. A bilaterally symmetrical increased uptake is usually physiological. An asymmetrical uptake, especially when focal, would warrant further radiological and histopathological correlation to rule out disease involvement. At times, this can lead to the detection of an asymptomatic hitherto unknown etiology, which would have been otherwise interpreted as a metastatic disease in the background of an existing malignancy in these patients; this is noteworthy as it may have a bearing on the subsequent management of these patients.

Technology Insight: advances in molecular imaging and an appraisal of PET/CT scanning

PET/CT imaging has rapidly emerged as an important imaging tool in oncology. The success of PET/CT imaging is based on several features. First, patients benefit from a comprehensive diagnostic anatomical and functional (molecular) whole-body survey in a single session. Second, PET/CT provides more-accurate diagnostic information than PET or CT alone. Third, PET/CT imaging allows radiation oncologists to use the functional information provided by PET scans for radiation treatment planning. In this Review we discuss the technical features of PET/CT, its economic aspects within the health-care system, and its role in diagnosis, staging, restaging and treatment monitoring as well as radiation planning in patients with cancer.

FDG-PET in the clinical management of carcinoma of unknown primary with metastatic cervical lymphadenopathy: shifting gears from detecting the primary to planning therapeutic strategies

Dear Sir, With the introduction of FDG-PET in clinical oncology, one of several unresolved areas that are being investigated is detection of the primary tumor in patients with nodal metastases from an unknown site. The results, however, have indicated varying degrees of success, with the rate of detection of putative primary tumors ranging from 10% to 60%. This wide variation can be attributed to the criteria adopted to define the “unknown primary” in different clinical settings. According to the strict definition, the term “unknown primary” should be used when clinical examination, CT/MRI and panendoscopy fail to reveal a primary tumor. Unfortunately, only a few studies have adhered to such a strict definition. A careful analysis of the studies which employed these uniform criteria reveals only a modest increase in the detection rate when using FDGPET. Systematic reviews [1–4] published at various stages of evolution of PET have continued to contradict each other on this issue; the two most recent reports [1, 2] estimated the benefit to be modest at best (27% and 25% respectively) after all other modalities had failed. A head-to-head comparison of the performance of CT, PET, PET and CT side-by-side, and co-registered PET-CT documented a success rate of 25%, 25%, 29%, and 33% respectively, with no statistically significant difference among the modalities [5]. There are reports from prospective studies [6] that FDG-PET does not add significantly in finding the occult primary in a carefully worked-up CUP, especially if conventional imaging modalities are negative. In practice, it is not uncommon to find that a primary detected by FDGPET was actually a “missed primary” rather than an unknown primary in the true sense. While the results of FDG-PET in detecting an occult primary in the setting of CUP are not encouraging, an important observation which has gradually become obvious as an offshoot in several studies (including those in which FDG-PET was found to be non-contributory in detecting the primary after conventional work-up) has been the serendipitous discovery of multiple sites of disease, which has implications for the treatment strategy. By virtue of its exquisite sensitivity, FDG-PET whole-body survey can be extremely useful in guiding the therapeutic strategy by identifying or ruling out additional sites of disease in patients who present with a single metastatic site. The study by Fogarty et al. [6], which found a limited role for FDGPET in diagnosing occult primaries, concluded that the modality is of substantial benefit in the detection of unsuspected distant disease in patients with undifferentiated nodal disease and in the delineation of regional disease in patients with N2 disease. In a cohort study reported by Johansen et al. [7], whole-body F-FDG PET had treatment-related implications in 24% of patients. Finally, a systematic review [2] of 16 studies on 302 patients found that FDG-PET detected previously unrecognized metastases in 27% of patients, of which 11% were distant metastases, and resulted in changes in treatment in 24.7% of cases. This is an important consideration while planning treatment for patients with CUP with cervical node metastasis. While locoregional treatment is planned for those with one site, it is rarely considered for those with distant metastatic sites. Also, the detection of distant metastases can lead to a change in the treatment intent, from cure to palliation. Eur J Nucl Med Mol Imaging (2007) 34:427–428 DOI 10.1007/s00259-006-0313-1

The role of 67Ga in the early detection of spinal epidural abscesses.

In this study, we evaluated the role of 67Ga whole-body and single photon emission tomographic (SPET) imaging in the early diagnosis and lesion localization of spinal epidural abscess before confirmation by gadolinium-enhanced magnetic resonance imaging (MRI). Six patients with fever of unknown origin had a 67Ga whole-body scan, four of whom also underwent SPET imaging. For further confirmation of a spinal epidural abscess, gadolinium-enhanced MRI was performed in all patients. All patients had increased 67Ga uptake in a spinal or paraspinal area on the whole-body scan. They were later confirmed to have a spinal epidural abscess after gadolinium-enhanced MRI. Of these six patients, five underwent surgical drainage plus parenterally administered antibiotics, and had complete or partial recovery. One died before operation due to sepsis. In conclusion, we suggest performing a 67Ga whole-body survey as early as possible in patients with fever of unknown origin, fever and back pain and/or the spinal syndrome, before MRI is performed. If a spinal epidural abscess is strongly suspected, SPET is needed for further confirmation of spinal versus non-spinal and contiguous versus non-contiguous lesion(s). If MRI is unavailable, then 67Ga scintigraphy is a satisfactory method for investigating spinal epidural abscesses.