F.U. Chowdhury

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.

Re: Sarcoid-like reaction to malignancy on whole-body integrated (18)F-FDG PET/CT: prevalence and disease pattern

AIMnTo evaluate the prevalence of sarcoid-like reaction to malignancy detected using integrated 2-[(18)F]-fluoro-2-deoxy-d-glucose (FDG) positron-emission tomography and computed tomography (PET/CT) in patients undergoing staging or restaging of solid-organ malignancy.nnnMATERIALS AND METHODSnA systematic search was performed using the institutional radiology information system of 2048 consecutive PET/CT examinations performed in cancer patients at a tertiary-referral centre. Cases that were considered suspicious for sarcoid-like reaction were identified from the initial radiological report and were retrospectively reviewed by three experienced PET/CT reporters.nnnRESULTSnSarcoid-like reaction was initially suspected in 23 of the 2048 (1.1%) FDG PET/CT examinations, with the diagnosis confirmed histologically or by clinico-radiological follow-up in 13 of the 23 cases (57%). Sarcoid-like reaction was more commonly seen in patients undergoing FDG PET/CT for restaging of suspected recurrence rather than for primary tumour staging (77% versus 23%; p=0.05). The mean maximum standardized uptake value (SUV(max)) of confirmed hilar and mediastinal sarcoid-like reaction was 7.3 (range 3.1-13.6). Symmetric hilar uptake was demonstrated in 11 of the 13 (85%) and all 13 had additional mediastinal nodal uptake. Pulmonary uptake was seen in seven of the 13 cases (54%). Extra-thoracic involvement was present in eight of the 13 (61.5%), including nodal, splenic, and hepatic lesions.nnnCONCLUSIONnSarcoid-like reaction was suspected in 1.1% of cancer patients at FDG PET/CT examination, with confirmation of the diagnosis in 0.6%. With the increasing use of FDG PET/CT in cancer patients, it is important to be aware of the prevalence of this uncommon, but important, disease entity and to consider this diagnosis in appropriate cases in order to avoid a false-positive interpretation of metastatic disease.

FDG PET/CT in infection and inflammation—current and emerging clinical applications

Integrated positron emission tomography/computed tomography (PET/CT) with the glucose analogue, 2-[(18)F]-fluoro-2-deoxy-d-glucose (FDG), is an evolving hybrid imaging technique in the evaluation of an important and diverse group of pathological conditions, which are characterised by infection and aseptic inflammation. With a rapidly expanding body of evidence, it is being increasingly recognised that, in addition to its established role in oncological imaging, FDG PET/CT also has clinical utility in suspected infection and inflammation. The technique can identify the source of infection or inflammation in a timely fashion ahead of morphological changes on conventional anatomical imaging techniques, such as computed tomography (CT) and magnetic resonance imaging (MRI), map the extent and severity of disease, identify sites for tissue sampling, and assess therapy response. FDG PET/CT exhibits distinct advantages over traditional radionuclide imaging techniques in terms of shorter duration of examination, higher spatial resolution, non-invasive nature of acquisition, ability to perform quantitative analyses, and the provision of a synergistic combination of functional and anatomical imaging. With the use of illustrative clinico-radiological cases, this article discusses the current and emerging evidence for the use of FDG PET/CT in a broad spectrum of disorders, such as fever of unknown origin, sarcoidosis, large vessel vasculitis, musculoskeletal infections, joint prosthesis or implant-related complications, human immunodeficiency virus (HIV)-related infections, and miscellaneous indications, such as IgG4-related systemic disease. It will also briefly summarise the role of more novel tracers such as FDG-labelled leukocytes and gallium-68 PET tracers in this arena.

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 role of 18F-FDG PET/CT in the evaluation of oesophageal carcinoma

Integrated positron-emission tomography/computed tomography (PET/CT) with 2-[fluorine-18] fluoro-2-deoxy-D-glucose (FDG) is now established in the management of oncology patients. With increasing availability and a constantly advancing body of evidence, the role of FDG PET/CT in oesophageal cancer is set to expand to include initial staging, assessment of disease response, therapy planning, and detection of disease recurrence. This article reviews the utility of FDG PET/CT in the management of oesophageal carcinoma, discussing its role and limitations in the imaging of these patients.

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.

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

AIMSnTo 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).nnnMATERIAL AND METHODSnForty-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.nnnRESULTSnMedian 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%).nnnCONCLUSIONnThe 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.

Tc99m-hepatobiliary iminodiacetic acid (HIDA) scintigraphy in clinical practice.

There have been evolutionary changes in the management of pathological conditions of the hepatobiliary system over recent years, particularly with an increasing emphasis on modern hepatobiliary surgical techniques. Concurrent advances have occurred in imaging technology and availability, leading to a greater use of ultrasound, multidetector computed tomography (CT), and magnetic resonance imaging (MRI) in the primary evaluation of hepatobiliary disease. Radionuclide imaging using technetium(99m) (Tc(99m)) hepatobiliary iminodiacetic acid (HIDA) derivatives is an established technique that complements morphological imaging, providing valuable functional information in both pre- and postoperative evaluation of patients with suspected or known hepatobiliary disease. This review discusses the current clinical indications for Tc(99m) HIDA scintigraphy using clinical cases to demonstrate how this technique continues to play a valuable diagnostic role in the assessment of the functional integrity of the hepatobiliary system.

Multi-technique imaging of sarcoidosis

Sarcoidosis is a multisystem granulomatous disorder of unknown aetiology. The diagnosis is suggested on the basis of wide ranging clinical and radiological manifestations, and is supported by the histological demonstration of non-caseating granulomas in affected tissues. This review highlights the multisystem radiological features of the disease across a variety of imaging methods including multidetector computed tomography (CT), magnetic resonance imaging (MRI) as well as functional radionuclide techniques, particularly 2-[(18)F]-fluoro-2-deoxy-d-glucose (FDG) positron emission tomography/computed tomography (PET/CT). It is important for the radiologist to be aware of the varied radiological manifestations of sarcoidosis in order to recognize and suggest the diagnosis in the appropriate clinical setting.

Optimizing the role of FDG PET–CT for potentially operable metastatic colorectal cancer

Recent treatment advances now allow a realistic chance of cure in selected patients with metastatic colorectal carcinoma (CRC). Accurate pre-treatment staging is crucial to ensure appropriate management by identification of patients with more advanced disease who will not benefit from surgery. 18Fluorine 2-fluoro-2-deoxy-d-glucose positron emission tomography–computed tomography (PET–CT) has a firmly established role in staging, restaging, and recurrence detection of a range of tumors. This article will review the role of PET–CT in patients with CRC with a particular emphasis on optimizing the technique in patients with potentially operable metastatic disease.