Andrew Scarsbrook

Clinical utility of ultrasound and 99mTc sestamibi SPECT/CT for preoperative localization of parathyroid adenoma in patients with primary hyperparathyroidism

AIM To evaluate the accuracy of ultrasound and parathyroid scintigraphy using single photon-emission computed tomography/computed tomography (SPECT/CT) for the preoperative localization of solitary parathyroid adenomas in patients with primary hyperparathyroidism who would be suitable for minimally invasive parathyroid surgery. MATERIALS AND METHODS Retrospective study of 63 consecutive patients with biochemical evidence of primary hyperparathyroidism referred for preoperative localization of parathyroid adenoma that proceeded to surgery in the same institution. All patients underwent high-resolution ultrasound and Technetium-99m sestamibi scintigraphy with planar and SPECT/CT imaging. The accuracy of preoperative imaging was compared to surgical and histological findings as the reference standard. RESULTS Fifty-nine patients had solitary parathyroid adenomas, three patients had multiglandular hyperplasia, and one patient had multiple parathyroid adenomas confirmed at surgery and histology. Thirty-five solitary parathyroid adenomas were identified preoperatively with ultrasound (64%) and 53 with SPECT-CT (90%). Concordant ultrasound and SPECT/CT findings were found in 35 cases (59%). An additional three adenomas were found with ultrasound alone and 18 adenomas with SPECT/CT alone. Fifty-one of the 56 adenomas localized using combined ultrasound and SPECT/CT were found at the expected sites during surgery. Combined ultrasound and SPECT/CT has an overall sensitivity of 95% and accuracy of 91% for the preoperative localization of solitary parathyroid adenomas. CONCLUSIONS The combination of ultrasound and SPECT/CT has incremental value in accurately localizing solitary parathyroid adenomas over either technique alone, and allows selection of patients with primary hyperparathyroidism who would be suitable for minimally invasive surgery.

The role of hybrid SPECT-CT in oncology: current and emerging clinical applications.

Single photon emission computed tomography - computed tomography (SPECT-CT) is an emerging dual-modality imaging technique with many established and potential clinical applications in the field of oncology. To date, there has been a considerable emphasis on the benefits of integrated positron emission tomography - computed tomography (PET-CT) in oncology, but relatively little focus on the clinical utility of SPECT-CT. As with PET-CT, accurate co-registration of anatomical and functional data from a combined SPECT-CT camera often provides complementary diagnostic information. Both sensitivity (superior disease localization) and specificity (exclusion of false-positives due to physiological tracer uptake) are improved, and the functional significance of indeterminate lesions detected on cross-sectional imaging can be defined. This article will review the scope of hybrid SPECT-CT in oncology and illustrate both current and emerging clinical applications.

False-positive uptake on 2-[18F]-fluoro-2-deoxy-d-glucose (FDG) positron-emission tomography/computed tomography (PET/CT) in oncological imaging

With the increasing utilization of integrated positron-emission tomography/computed tomography (PET/CT) using the glucose analogue 2-[¹⁸F]-fluoro-2-deoxy-D-glucose (FDG) in oncological imaging, it is important for radiologists and nuclear medicine physicians to be aware that FDG uptake is not specific for malignancy, as many different physiological variants and benign pathological conditions can also exhibit increased glucose metabolism. Such false-positive FDG uptake often arises outside the area of primary interest and may mimic malignant disease, thereby confounding accurate interpretation of PET/CT studies. With the use of illustrative clinical cases, this article will provide a systematic overview of potential interpretative pitfalls and illustrate how such unexpected findings can be appropriately evaluated.

The clinical impact of integrated FDG PET–CT on management decisions in patients with lung cancer

PURPOSE To retrospectively evaluate the clinical impact of FDG PET-CT on the management pathway of patients with lung cancer. PATIENTS AND METHODS One hundred and sixty-one patients with suspected lung cancer undergoing FDG PET-CT during the study period were analyzed. Before PET-CT, lung cancer MDT recorded scan indication, conventional clinical stage, and proposed treatment plan. The accuracy of integrated PET-CT compared with stand alone CT in preoperative staging of lung cancer was evaluated with pathological staging used as the reference standard. The effect of PET-CT on the subsequent management of patients was also evaluated. RESULTS The agreement between CT and integrated PET-CT in preoperative staging of lung cancer was significant (p<0.001). In 16 (10%) patients PET-CT excluded tumour as there was no FDG uptake. PET-CT revealed occult metastasis in 25 (16%) patients. It was also a better overall predictor for T status (64% vs. 58%) and N status (78% vs. 65%). For N staging PET-CT was more accurate for N1 (82% vs. 72%) and N2 (85% vs. 80%) disease. Regression analyses suggested that PET-CT was a better predictor of overall TNM staging for lung cancer. FDG PET scanning changed or influenced management decisions in 66 (41%) patients with lung cancer. Changes in TNM staging following PET-CT were significant predictors (p=0.02) in making a decision to abandon thoracotomies. CONCLUSION Addition of PET-CT to comprehensive evaluation of lung cancer can have significant clinical impact. There is marked improvement in staging the disease. Patients were frequently spared unnecessary treatment, and management was more appropriately targeted. PET permits reduction in the number of thoracotomies performed for non-resectable disease with predicted reduction in the morbidity rate and cost associated with unnecessary interventions.

Functional Imaging for Radiation Treatment Planning, Response Assessment, and Adaptive Therapy in Head and Neck Cancer

Patients with squamous cell carcinomas (SCCs) of the head and neck are increasingly treated nonsurgically. Imaging plays a critical role in helping define the targets for radiation therapy, especially intensity-modulated radiation therapy, in which the dose gradients are steep. Anatomic imaging with conventional modalities, particularly computed tomography (CT), has been used in patients with head and neck SCCs, but this approach has limitations. Functional imaging techniques, including positron emission tomography (PET) combined with CT or magnetic resonance (MR) imaging, offer complementary information and can be used noninvasively to assess a range of biomarkers in patients with head and neck SCCs, including hypoxia, cell proliferation and apoptosis, and epidermal growth factor receptor status. These biologic markers can be monitored before, during, and after treatment to improve patient selection for specific therapeutic strategies, guide adaptation of therapy, and potentially facilitate more accurate assessment of disease response. This article discusses the practical aspects of integrating functional imaging into head-and-neck radiation therapy planning and reviews the potential of molecular imaging biomarkers for response assessment and therapy adaptation. The uses of PET tracers for imaging cellular processes such as metabolism, proliferation, hypoxia, and cell membrane synthesis are explored, and applications for MR techniques such as dynamic contrast material-enhanced imaging, diffusion-weighted imaging, blood oxygenation level-dependent imaging, and MR spectroscopy are reviewed. The potential of integrated PET/CT perfusion imaging and hybrid PET/MR imaging also is highlighted. These developments may allow more individualized treatment planning in patients with head and neck SCCs in the emerging era of personalized medicine.

Risk of malignancy in pulmonary nodules: A validation study of four prediction models

OBJECTIVES Clinical prediction models assess the likelihood of malignancy in pulmonary nodules detected by computed tomography (CT). This study aimed to validate four such models in a UK population of patients with pulmonary nodules. Three models used clinical and CT characteristics to predict risk (Mayo Clinic, Veterans Association, Brock University) with a fourth model (Herder et al. [4]) additionally incorporating (18)Fluorine-Fluorodeoxyglucose (FDG) avidity on positron emission tomography-computed tomography (PET-CT). MATERIALS AND METHODS The likelihood of malignancy was calculated for patients with pulmonary nodules (4-30mm diameter) and data used to calculate the area under the receiver operating characteristic curve (AUC) for each model. The models were used in a restricted cohort of patients based on each models exclusion criteria and in the total cohort of all patients. RESULTS Two hundred and forty-four patients were studied, of whom 139 underwent FDG PET-CT. Ninety-nine (40.6%) patients were subsequently confirmed to have malignant nodules (33.2% primary lung cancer, 7.4% metastatic disease). The Mayo and Brock models performed similarly (AUC 0.895 and 0.902 respectively) and both were significantly better than the Veterans Association model (AUC 0.735, p<0.001 and p=0.002 respectively). In patients undergoing FDG PET-CT, the Herder model had significantly higher accuracy than the other three models (AUC 0.924). When the models were tested on all patients in the cohort (i.e. including those outside the original model inclusion criteria) AUC values were reduced, yet remained high especially for the Herder model (AUC 0.916). For sub-centimetre nodules, AUC values for the Mayo and Brock models were 0.788 and 0.852 respectively. CONCLUSIONS The Mayo and Brock models showed good accuracy for determining likelihood of malignancy in nodules detected on CT scan. In patients undergoing FDG PET-CT for nodule evaluation, the highest accuracy was seen for the model described by Herder et al. incorporating FDG avidity.

FDG PET/CT in oncology: “raising the bar”

Integrated positron-emission tomography/computed tomography (PET/CT) with 2-[(18)F]-fluoro-2-deoxy-D-glucose (FDG) has revolutionized oncological imaging in recent years and now has a firmly established role in a variety of tumour types. There have been simultaneous step-wise advances in scanner technology, which are yet to be exploited to their full potential in clinical practice. This article will review these technological developments and explore how refinements in imaging protocols can further improve the accuracy and efficacy of PET/CT in oncology. The promises, and limitations, of emerging oncological applications of FDG PET/CT in radiotherapy planning and therapy response assessment will be explored. Potential future developments, including the use of FDG PET probes in oncological surgery, advanced data analysis techniques, and the prospect of integrated PET/magnetic resonance imaging (PET/MRI) will be highlighted.

[18F]FDG PET/CT imaging of colorectal cancer: a pictorial review

Integrated positron emission tomography/CT (PET/CT) with 2-[18F]fluoro-2-deoxy-d-glucose (FDG) is a hybrid imaging modality which has recently become established in the staging, restaging and therapy response assessment of oncology patients. FDG PET/CT has several recognised applications in colorectal cancer (CRC) imaging including preoperative evaluation of apparently limited metastatic disease, detection of disease recurrence, clarification of equivocal lesions at initial staging, investigation of unexplained rising tumour markers, and incidental detection of occult primary colonic tumours. With a constantly advancing body of evidence and increasing availability, applications of PET/CT in CRC are likely to emerge in therapy response assessment, radiotherapy planning, use of novel tracers and ‘one-stop’ imaging techniques such as iodinated contrast-enhanced PET/CT. With the use of illustrative clinical examples, this article reviews the utility of FDG PET/CT in the management of CRC, discussing its role and limitations in the multimodality imaging of these patients.

Delayed response assessment with FDG-PET-CT following (chemo)radiotherapy for locally advanced head and neck squamous cell carcinoma

AIMS To analyse the diagnostic accuracy of delayed response assessment 2-[¹⁸F]-fluoro-2-deoxy-d-glucose (FDG) positron-emission tomography-computed tomography (PET-CT) following (chemo)radiation for locally advanced head and neck squamous cell carcinoma (HNSCC). MATERIAL AND METHODS Forty-four consecutive patients who underwent a baseline and response assessment using FDG PET-CT for HNSCC following (chemo)radiation between August 2008 and April 2011 were identified retrospectively. Clinicopathological findings and serial clinical follow-up provided the reference standard. RESULTS Median follow-up was 14 months (range 5-43 months). Response assessment FDG PET-CT was performed at 16.8 weeks (inter-quartile range 15.8-18.6 weeks). Thirty-one out of 44 (70%) response assessment examinations showed a complete metabolic response. Seven out of 40 (18%) assessable primary tumours were positive. Eight out of 41 (20%) patients with pre-treatment nodal disease had equivocal or positive FDG uptake at response assessment. The sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) for primary disease and nodal disease were 100, 89, 43, 100, and 100%, and 92, 63, and 100%, respectively. Seven patients had residual FDG-negative soft tissue detectable on the unenhanced CT component of the response assessment images; all remained disease free after clinical observation. Distant metastases were detected on response assessment FDG PET-CT in four out of the 44 patients (10%). CONCLUSION The diagnostic accuracy of response assessment with FDG PET-CT performed at approximately 16 weeks post-(chemo)radiotherapy is good. The very high NPV of a complete metabolic response can be used to guide management decisions. Although the PPV is limited for local residual disease, FDG PET-CT is a powerful screening tool for the detection of interim metastatic disease.

Clinical Utility of Hybrid SPECT-CT in Endocrine Neoplasia

OBJECTIVE Imaging of endocrine neoplasms often involves a combination of anatomic and functional techniques including sonography, CT, MRI, and scintigraphy. Recent technologic advances have enabled hybrid imaging using SPECT-CT, which combines anatomic and functional techniques to allow accurate localization of tumors, increased detection of recurrent and metastatic disease, and exclusion of physiologic uptake. CONCLUSION SPECT-CT provides improved specificity and diagnostic confidence helping to guide conventional management and assess suitability for targeted radionuclide therapy.