Paul Roach

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.

Enhancing Lung Scintigraphy With Single-Photon Emission Computed Tomography

Although widely used for many years in the assessment of pulmonary embolism, planar ventilation-perfusion (V/Q) scintigraphy has well-recognized limitations. Single-photon emission computed tomography (SPECT) imaging, which can be readily performed in most modern nuclear medicine centers equipped with multihead gamma cameras, overcomes many of these limitations through its ability to generate 3-dimensional imaging data. V/Q SPECT has been shown to have a greater sensitivity and specificity than planar imaging and has a lower nondiagnostic rate. For reporting clinicians who may be reluctant to abandon conventional planar V/Q images, planar-like images can also be readily obtained from V/Q SPECT with the use of postacquisition techniques. The use of SPECT can also facilitate advances in V/Q imaging, including the generation of parametric V:Q ratio images, coregistration with computed tomography, respiratory gating, and more accurate quantification of regional lung function. Although direct comparisons in the literature are limited in number, V/Q SPECT appears to have comparable, or greater, sensitivity than multidetector computed tomography pulmonary angiography and is not associated with contrast-related complications such as allergy and nephropathy. It also involves significantly less radiation dose to breast tissue, an important consideration, particularly in young women. For the V/Q scan to remain relevant in the evaluation of patients with suspected pulmonary embolism, it is essential that image data are obtained so as to maximize their accuracy and diagnostic usefulness. V/Q SPECT can achieve this and, furthermore, may have a role in conditions other than pulmonary embolism, including both clinical and research fields.

V/Q Scanning Using SPECT and SPECT/CT

Planar ventilation–perfusion (V/Q) scanning is often used to investigate pulmonary embolism; however, it has well-recognized limitations. SPECT overcomes many of these through its ability to generate 3-dimensional imaging data. V/Q SPECT has higher sensitivity, specificity, and accuracy than planar imaging and a lower indeterminate rate. SPECT allows for new ways to display and analyze data, such as parametric V/Q ratio images. Compared with CT pulmonary angiography, SPECT has higher sensitivity, a lower radiation dose, fewer technically suboptimal studies, and no contrast-related complications. Any nuclear medicine department equipped with a modern hybrid scanner can now perform combined V/Q SPECT with CT (using low-dose protocols) to further enhance diagnostic accuracy. V/Q SPECT (with or without CT) has application in other pulmonary conditions and in research.

SPECT/CT in V/Q scanning.

Combining the functional data provided by single-photon emission computed tomography (SPECT) with the anatomical information provided by CT has been shown to improve overall diagnostic accuracy in many areas of nuclear medicine. Although planar lung scans have often relied on correlation with a chest x-ray to help optimize scan interpretation, the advent of 3D lung imaging with SPECT provides the opportunity to combine lung perfusion data with CT images. This can be done by performing the study on a hybrid SPECT/CT scanner, with the CT acquisition typically performed with the use of low-dose parameters, rather than full diagnostic quality settings, or by software fusion with a fully diagnostic CT or a contrast-enhanced CT pulmonary angiogram. Such an approach has been shown to improve specificity and overall accuracy of ventilation/perfusion scintigraphy as well as facilitating more accurate clot localization. With the increased availability of hybrid SPECT/CT scanners, such an approach can be implemented in most imaging departments with little additional acquisition time or radiation dose. Misregistration caused by respiratory motion can impact combined studies, although this can be minimized with attention to patient breathing patterns during image acquisition. For patients with lung cancer, ventilation/perfusion SPECT/CT may have a role in allowing the optimal selection of radiotherapy fields and can improve the preoperative quantification of lung function before resection.

The Utility of Metaiodobenzylguanidine Single Photon Emission Computed Tomography/Computed Tomography (MIBG SPECT/CT) for the Diagnosis of Pheochromocytoma

BackgroundThe enhancement of metaiodobenzylguanidine single photon emission computed tomography (MIBG SPECT) imaging through the addition of CT images fused with SPECT data (coregistered MIBG SPECT/CT imaging) is new technology that allows direct correlation of anatomical and functional information. We hypothesized that MIBG SPECT/CT imaging would provide additional information and improve diagnostic confidence for the radiological localization of a pheochromocytoma, in particular for patients at high risk of multifocal or recurrent disease.MethodsA retrospective study of all patients investigated by MIBG SPECT/CT at our institution from 2006 to 2008 for a suspected pheochromocytoma was performed. Each case was compared with conventional radiological investigations to determine whether MIBG SPECT/CT was able to improve diagnostic confidence and provide additional diagnostic information compared with conventional imaging alone.ResultsTwenty-two patients had MIBG SPECT/CT imaging for a suspected pheochromocytoma. Fourteen patients had positive MIBG SPECT/CT imaging results correlating with imaging by CT or magnetic resonance imaging in all cases. In six cases, MIBG SPECT/CT provided additional information that altered the original radiological diagnosis. Five patients with a pheochromocytoma-associated germline mutation had multifocal disease excluded by MIBG SPECT/CT. Patients without a germline mutation that had positive biochemistry and a solitary lesion with conventional imaging had no diagnostic improvement with MIBG SPECT/CT imaging.ConclusionsMIBG SPECT/CT fusion imaging is a sensitive and specific radiological imaging tool for patients suspected to have pheochromocytoma. The particular strengths of MIBG SPECT/CT are detection of local recurrence, small extra-adrenal pheochromocytomas, multifocal tumors, or the presence of metastatic disease.

The value of oblique pinhole images in pre-operative localisation with 99mTc-MIBI for primary hyperparathyroidism

Technetium-99m labelled 2-methoxyisobutylisonitrile (MIBI) has been extensively utilised for pre-operative localisation of parathyroid adenomas. Imaging techniques have varied widely, with many centres not performing routine oblique images; thus this study aimed to examine the value of routine oblique pinhole imaging. Ninety-two patients underwent pre-operative (99m)Tc-MIBI imaging including early and delayed anterior oblique pinhole images in addition to standard anterior pinhole images and a thyroid study prior to surgery for primary hyperparathyroidism. These studies were reviewed blindly comparing anterior and oblique images and anterior images only in relation to surgical findings. Of the 92 patients, 83 were found to have 86 parathyroid adenomas or parathyroid adenoma/hyperplasia at surgery. When compared to anterior images only, oblique views improved overall sensitivity from 76% to 88% (P<0.05), correctly localised 11 more adenomas than anterior images alone (13%) and improved the confidence of interpretation in 17 patients (20%). In conclusion, routine oblique pinhole views result in greater sensitivity and reporter confidence in pre-operative parathyroid localisation with (99m)Tc-MIBI.Abstract. Technetium-99m labelled 2-methoxyisobutylisonitrile (MIBI) has been extensively utilised for pre-operative localisation of parathyroid adenomas. Imaging techniques have varied widely, with many centres not performing routine oblique images; thus this study aimed to examine the value of routine oblique pinhole imaging. Ninety-two patients underwent pre-operative 99mTc-MIBI imaging including early and delayed anterior oblique pinhole images in addition to standard anterior pinhole images and a thyroid study prior to surgery for primary hyperparathyroidism. These studies were reviewed blindly comparing anterior and oblique images and anterior images only in relation to surgical findings. Of the 92 patients, 83 were found to have 86 parathyroid adenomas or parathyroid adenoma/hyperplasia at surgery. When compared to anterior images only, oblique views improved overall sensitivity from 76% to 88% (P<0.05), correctly localised 11 more adenomas than anterior images alone (13%) and improved the confidence of interpretation in 17 patients (20%). In conclusion, routine oblique pinhole views result in greater sensitivity and reporter confidence in pre-operative parathyroid localisation with 99mTc-MIBI.

Transition from Planar to SPECT V/Q Scintigraphy: Rationale, Practicalities, and Challenges

Compared with planar imaging, ventilation/perfusion scintigraphy performed with single-photon emission computed tomography (SPECT) has a greater sensitivity and specificity, greater accuracy, improved reproducibility, and a lower number of inconclusive reports in the detection of pulmonary embolism. Despite these improvements, there are several challenges that must be overcome for the transition from planar imaging to SPECT imaging to be successful, including a lack of familiarity with 3D imaging of the lungs by some reporting specialists, the selection of a ventilation agent appropriate for SPECT acquisitions, and a different approach in the image reporting. The transition to SPECT imaging can be facilitated by generating planar-like images from the SPECT data, with which many reporting specialists are more familiar. SPECT ventilation/perfusion acquisition times are generally equal to or shorter than conventional planar imaging, studies are easier for technologists to acquire, and modern computing provides several new approaches to image processing and display.

The impact of 68Ga-PSMA PET/CT on management intent in prostate cancer: results of an Australian prospective multicenter study

68Ga-PSMA PET/CT scanning has been shown to be more sensitive than conventional imaging techniques in patients with prostate cancer. This prospective Australian multicenter study assessed whether 68Ga-PSMA PET/CT imaging affects management intent in patients with primary or recurrent prostate cancer. Methods: Before undertaking 68Ga-PSMA PET imaging, referring medical specialists completed a questionnaire detailing relevant demographic and clinical data as well as their proposed management plan. A separate follow-up questionnaire was completed after the 68Ga-PSMA PET/CT scan results were available to determine whether the management plan would change. Results: A total of 431 patients with prostate cancer from 4 Australian centers had pre– and post–68Ga-PSMA management plans completed. Scans were obtained for primary staging of intermediate- and high-risk disease in 25% of patients and for restaging/biochemical recurrence in 75% of patients. Overall, 68Ga-PSMA PET/CT scanning led to a change in planned management in 51% of patients. The impact was greater in the group of patients with biochemical failure after definitive surgery or radiation treatment (62% change in management intent) than in patients undergoing primary staging (21% change). Imaging with 68Ga-PSMA PET/CT revealed unsuspected disease in the prostate bed in 27% of patients, locoregional lymph nodes in 39%, and distant metastatic disease in 16%. Conclusion: 68Ga-PSMA PET/CT scans detect previously unsuspected disease and may influence planned clinical management in a high proportion of patients with prostate cancer. The impact was greater in patients with biochemical recurrence. These results demonstrate the potential clinical value of 68Ga-PSMA PET/CT in management of prostate cancer.

A clinical comparison between traditional planar V/q images and planar images generated from Spect V/q scintigraphy

PurposeTo compare interpretation of traditional planar ventilation–perfusion lung scan images with planar images reformatted from single photon emission computed tomography (SPECT) data using two different techniques. MethodsPlanar and SPECT ventilation–perfusion (V/Q) data were acquired from 50 patients referred with suspected pulmonary embolism. In addition to traditional six-view planar images, six-view planar images were also generated from SPECT data using two methodologies: an angular summing technique (angular summed planar images) and a forward projection technique (reprojected planar images). Three experienced nuclear medicine clinicians reviewed the images in a blinded, randomized fashion. Results were analysed by comparing the two reprojected techniques with the traditional true planar scans, examining for differences in the defects seen (number, type and confidence), and the impact on final clinical interpretation. ResultsCompared with true planar scintigraphy, angular summed images demonstrated fewer mismatched defects (P<0.0001), while the reprojected planar images had more matched defects (P=0.013). In addition, there was a significant change in the clinical interpretation of the angular summed planar images resulting in clinicians perceiving a decreased likelihood of pulmonary embolism (P<0.016). No such difference in interpretation was observed for the reprojected planar images. ConclusionsAngular summed planar images result in a perceived decreased likelihood of pulmonary embolism compared with true planar images. In contrast, while reprojected planar images result in an increased number of matched defects compared to true planar scans, there was no change in the clinical interpretation. Caution should be exercised when interpreting SPECT derived angular summed planar images in isolation.

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.