Ivan Ho Shon

SPECT/CT imaging using a spiral CT scanner for anatomical localization: Impact on diagnostic accuracy and reporter confidence in clinical practice.

Purpose To evaluate the incremental benefit in routine clinical practice of computed tomography (CT) scans acquired for anatomical localization on an integrated SPECT/CT which incorporates a spiral CT scanner, in comparison with conventional planar and SPECT scanning. Methods The first 50 studies acquired on the integrated system were evaluated by two experienced nuclear medicine physicians who were aware of the patients clinical history. These included bone scans, gallium scans, octreotide scans, sestamibi parathyroid scans and MIBG scans. For each patient study, abnormalities were assessed on planar and SPECT images for location and provisional diagnosis and a quantitative scale was used to assess reporter confidence. The fused SPECT/CT images were then reviewed and the location and provisional diagnosis noted and reporter confidence was assessed using the same quantitative scale. Results There were 129 abnormalities detected in 50 patient studies. For localization of abnormalities, the inclusion of the CT resulted in a minor change in 16% of cases and a significant change in 11% over planar/SPECT imaging alone. The confidence of localization was improved moderately in 19% and improved significantly in 6%. For diagnosis, SPECT/CT resulted in a minor change in 10% and a significant change in 9% over planar/SPECT imaging. The confidence of diagnosis was improved moderately in 10% and improved significantly in a further 10% of cases. For the final scan interpretation, there would have been no change in 44% patients, a minor change in 30% and a significant change in 26% with the use of SPECT/CT. Conclusion Use of integrated SPECT/CT with a high spatial resolution, spiral CT used for anatomical localization improves accuracy and reporter confidence in clinical practice. As a result, final reports were different in 56% of the cases, including being significantly different in 26% patients compared to reporting with planar/SPECT alone.

An empirical method for the prediction of T-cell epitopes

Identification of T-cell epitopes from foreign proteins is the current focus of much research. Methods using simple two or three position motifs have proved useful in epitope prediction for major histocompatibility complex (MHC) class I, but to date not for MHC class II molecules. We utilized data from pool sequence analysis of peptides eluted from two HLA-DR13 alleles to construct a computer algorithm for predicting the probability that a given sequence will be naturally processed and presented on these alleles. We assessed the ability of this method to predict know self-peptides from these DR-13 alleles, DRB1*1301 and *1302, as well as an immunodominant T-cell epitope. We also compared the predictions of this scoring procedure with the measured binding affinities of a panel of overlapping peptides from hepatitis B virus surface antigen. We concluded that this method may have wide application for the prediction of T-cell epitopes for both MHC class I and class II molecules.

F-18 FDG positron emission tomography and benign fractures.

Purpose F-18 2-fluoro-2-deoxy-D-glucose (FDG) positron emission tomography (PET) has been used extensively in the imaging of cancer, including metastatic skeletal disease. Although uptake into benign osseous disease has been reported, there is very limited information regarding uptake into benign fractures. This report provides additional information regarding the appearance of benign fractures on FDG-PET images. Materials and Methods Four case reports of FDG-PET scanning are presented in patients with proved benign fractures. Results In three of these cases, FDG uptake was noted in fractures when images were obtained 17 days to 8 weeks after injury, with the most avid uptake observed when FDG-PET imaging was performed 17 days after fracture. In the patient in whom imaging was performed 8 weeks after fracture, no uptake of FDG was seen in a benign fracture. Conclusions Fractures may accumulate FDG to varying degrees, and false-positive findings may occur when FDG-PET imaging is performed to assess for metastases, although the different pattern of uptake and clinical correlation usually allows accurate differentiation of fracture from skeletal metastases.

Imaging in cutaneous melanoma.

Cutaneous melanoma (CM) is a common malignancy and imaging, particularly lymphoscintigraphy (LS), positron-emission tomography with 2-fluoro-2-deoxyglucose (FDG-PET), ultrasound, radiography computed tomography (CT) and magnetic resonance imaging have important roles in staging and restaging, surgical guidance, surveillance and assessment of recurrent disease. This review aims to summarize the available data regarding these and other imaging modalities in CM and provide the basis for subsequent formulation of guidelines regarding the use of imaging in CM. PubMed and Medline searches were performed and reference lists from publications were also searched. The published data were reviewed and tabulated. There is level I evidence supporting the use of LS and sentinel lymph node biopsy in nodal staging for CM. There is level III evidence demonstrating the superiority of ultrasound to palpation in the assessment of lymph nodes in CM. There is level IV evidence supporting FDG-PET in American Joint Committee on Cancer stage III/IV and recurrent CM and that FDG-PET/CT may be superior to FDG-PET. Level IV evidence also supports the use of CT in the same group of patients and the role of CT appears to be complementary to FDG-PET. Various imaging modalities, especially LS/sentinel lymph node biopsy and FDG-PET/CT, add incremental information in the management of CM and the various modalities have complementary roles depending on the clinical situation.

Comparison of pinhole and SPECT 99mTc-MIBI imaging in primary hyperparathyroidism.

ObjectiveThis study aims to compare dual tracer, dual phase pinhole technetium-99m labelled 2-methoxyisobutylisonitrile (99mTc-MIBI) imaging (including oblique imaging), with single photon emission computed tomography (SPECT) and dual phase planar 99mTc-MIBI images, and combined SPECT, dual phase planar 99mTc-MIBI images and anterior pinhole thyroid images for the localization of parathyroid adenomas in the neck in primary hyperparathyroidism. MethodsSixty-two patients underwent 99mTc-MIBI dual phase, anterior and anterior oblique pinhole images of the neck, anterior planar images of the neck and chest and early phase neck/chest SPECT followed by [99mTc] pertechnetate anterior and anterior oblique pinhole thyroid images. Images were reviewed by consensus in three combinations – dual phase anterior and anterior oblique pinhole 99mTc-MIBI images and pinhole thyroid images; SPECT and dual phase planar 99mTc-MIBI images and combined SPECT, dual phase planar 99mTc-MIBI images and anterior pinhole thyroid images. ResultsFor 52 parathyroid adenomas in 50 patients, the sensitivity of dual phase anterior and anterior oblique pinhole 99mTc-images and pinhole thyroid images was 81%. Significantly lower sensitivities were observed with SPECT and dual phase planar 99mTc-MIBI images (54%, P=0.0005) and combined SPECT, dual phase planar 99mTc-MIBI images and anterior pinhole thyroid images (65%, P=0.0209). The positive predictive value for all imaging combinations was 88–92%. ConclusionDual phase anterior and anterior oblique pinhole 99mTc-MIBI images and pinhole thyroid images are significantly more sensitive than imaging combinations that included SPECT and remains the optimal imaging protocol for the localization of parathyroid adenomas in the neck in primary hyperparathyroidism.

Optimal pinhole techniques for preoperative localization with Tc-99m MIBI for primary hyperparathyroidism.

Purpose Technetium-99m–labeled 2-methoxyisobutylisonitrile (Tc-99m MIBI) has been used extensively to localize parathyroid adenomas before operation. Imaging techniques vary widely, and the aim of this study was to determine the optimal time of delayed imaging and the value of routine correlative pertechnetate thyroid imaging. Materials and Methods In this study, preoperative parathyroid localization was performed using pinhole anterior and oblique images (15 minutes and 2 and 4 hours after injection) with correlative pertechnetate thyroid images. Ninety-seven patients underwent dual- or triple-phase Tc-99m MIBI imaging and correlative pertechnetate thyroid imaging before surgery. Two nuclear medicine physicians blinded to the surgical findings interpreted all available images and various Tc-99m MIBI image combinations at 15 minutes alone; 15 minutes and 2 hours, 15 minutes and 4 hours; and 15 minutes and 2 and 4 hours each with and without correlative pertechnetate thyroid imaging. Results Ninety parathyroid adenomas were detected in 86 patients. The optimal results were achieved with 15-minute and 2- and 4-hour Tc-99m-MIBI images, with correlative thyroid scans resulting in a sensitivity rate of 88%. Fifteen-minute and 2-hour Tc-99m-MIBI images and correlative thyroid scans and 15-minute and 4-hour Tc-99m MIBI images and correlative thyroid scans produced similar results (sensitivity rate, 86% and 83%, respectively;P = not significant). Compared with all Tc-99m MIBI image combinations alone, the addition of the routine correlative thyroid scan significantly improved sensitivity and also improved reporter confidence in 45% of studies. Conclusions Of the pinhole techniques compared, 15-minute and 2-hour Tc-99m MIBI images with correlative thyroid scanning may be the preferred imaging protocol, because this yields results similar to imaging for as long as 4 hours after injection in a shorter, more logistically acceptable imaging time.

The prevalence and clinical significance of 18F–2-fluoro-2-deoxy-D-glucose (FDG) uptake in the thyroid gland on PET or PET-CT in patients with lymphoma†

F18–2‐fluoro‐2‐deoxy‐D‐glucose (FDG) positron emission tomography (PET) has become a well established tool in staging and assessing therapy response in lymphoma. Incidental thyroid uptake on PET is not uncommon and can pose a diagnostic and management challenge. We retrospectively evaluate the prevalence and clinical significance of incidental FDG uptake in the thyroid gland in patients with lymphoma. 1868 lymphoma patients underwent PET and PET‐CT between August 2002 and August 2008. 52 patients (2.8%) demonstrated FDG thyroid uptake (M = 17, F = 35; mean age 63 yr). Thyroid uptake was determined as focal or diffuse, maximum standardized uptake values (SUVmax) recorded as well as SUV max ratio compared to background mediastinum activity (SUVR). Corresponding CT findings on PET‐CT were evaluated independently. Results were correlated with clinical, histopathological and imaging follow‐up. 30 (1.6%) patients had focal thyroid uptake. 16 (53%) had histological confirmation either by surgery (n = 7) or FNA under USS (n = 9). The final diagnosis was benign in 12/30 patients and malignant in 9/30. The malignancy risk for focal thyroid uptake was 30%. Five patients had intercurrent thyroid cancer (four papillary, one microinvasive follicular) and four had lymphomatous involvement. There was no significant difference between the mean sizes of benign (23.7 mm, range 12–34) and malignant nodules (23.6 mm, range 8–48). The mean SUVmax of malignant and benign nodules was 4.4 (range 1.8–10.1) and 3.2 (range 1.8–6.9) respectively with no statistically significant difference. 22 (1.2%) patients had diffuse FDG uptake in thyroid and benign aetiology was found in all with adequate follow‐up (15/22). Focal FDG thyroid uptake on PET or PET‐CT in lymphoma patients warrants further investigations. The malignancy risk is 30% either due to intercurrent thyroid cancer or lymphomatous involvement. SUVmax, SUVR and CT attenuation characteristics are not helpful in distinguishing between benign and malignant aetiologies. Diffuse thyroid uptake has a benign aetiology. Copyright

Positron emission tomography and colorectal cancer

Colorectal cancer (CRC) is a major cause of cancer-related morbidity and mortality. Molecular imaging using positron emission tomography (PET) is now an integral part of multidisciplinary cancer care. In this review, we discuss the role of PET in CRC including well established indications in the assessment of recurrent disease and emerging applications such as initial staging, monitoring therapy efficacy and using PET for radiotherapy planning. With rapid advancement in imaging technology, we also discuss the future potential of combining PET and magnetic resonance imaging and the use of novel radiotracers.

Impact of FDG-PET on lung cancer delineation for radiotherapy

Purpose: The purpose of this study is to assess the impact of fused diagnostic F‐18 2‐fluoro‐2‐deoxy‐D‐glucose (FDG) positron emission tomography (PET)/computed tomography (CT) and planning FDG‐PET/CT scans on voluming of lung cancer for radiotherapy.

Guidelines for imaging in cutaneous melanoma.

The preceding article reviewed the available data on imaging modalities in cutaneous melanoma. Based on this review, this article aims to provide guidelines for the use of the various imaging modalities in cutaneous melanoma and to indicate the level of supporting evidence and strength of recommendation with associated explanatory notes.