Inter- and intraobserver agreement in standard and ultra-fast single-photon emission computed tomography/computed tomography for the assessment of bone metastases

Inter-observer variability between readers in detection of bone metastases comparing different modalities; PET/CT, SPECT/CT and planar bone scintigraphy

OBJECTIVE

To assess the inter-observer variability between readers in the detection of bone metastases for different modalities [planar bone scintigraphy (BS), single photon emission computed tomography/computed tomography (SPECT/CT), and fluorine-18 fluorodeoxyglucose positron emission tomography/computed tomography (PET/CT) (F-18 FDG PET/CT)].

METHODS

Patients with known primary tumors referred for metastatic workup either by F-18 FDG PET/CT or conventional planar BS and SPECT/CT were enrolled in this prospective study. The three modalities (BS, SPECT/CT, and PET/CT) were acquired for each patient. Interpretation was done by two independent nuclear medicine physicians separately and blindly; reader 1 (R1) and reader 2 (R2). A three-point subjective scale was used (1 = negative for bone metastases, 2 = equivocal, and 3 = positive). The findings were compared to the final patient status based on clinical and radiological follow-up for at least 6 months. The Kappa test was used to assess the degree of agreement between readers in their interpretation of each modality.

RESULTS

A total of 54 patients (39 females and 15 males, ages 26-76; mean: 54.7 ± 12) were eligible for this study. Fair agreement 0.372 between R1 and R2 in interpretation of BS was noticed that improved to 0.847 after addition of SPECT/CT. Perfect agreement was achieved between R1 and R2 while interpreting PET/CT images (kappa = 0.964, P < 0.001).

CONCLUSION

F-18 FDG PET/CT significantly improved the inter-observer variability between readers, allowing for better diagnosis of bone metastases in known cancer patients. Also, it was superior to BS and SPECT/CT in the detection of bone metastases.

Sub 4 minute superfast single-photon emission computed tomography/computed tomography as an add-on for problem-solving in planar bone scintigraphy: a time-saving solution for departments without whole-body single-photon emission computed tomography/computed tomography

Whole-body bone scintigraphy remains widely used in nuclear medicine as it is a relatively inexpensive and quick test in which the whole body can be imaged with good sensitivity. However, one downside of the technique is its lack of specificity. The difficulty comes when there is a single 'hot spot' which usually requires further anatomical imaging to identify the cause and differentiate malignant from benign lesions. In this situation, hybrid imaging with single-photon emission computed tomography/computed tomography (SPECT/CT) can be a useful problem solver. The addition of SPECT/CT can however, be time-consuming, adding up to 15-20 min for every bed position required, a process that can tax the compliance of the patient and reduce the scanning capacity of the department. We report the successful implementation of a new superfast SPECT/CT protocol comprising a 1 s per view over 24 views point and shoot approach, reducing the SPECT scan time to less than 2 min and the whole SPECT/CT to under 4 min while still producing images that allow diagnostic certainty in previously equivocal lesions. This is faster than previously reported ultrafast SPECT/CT protocols. The utility of the technique is demonstrated in a pictorial review of four disparate causes of solitary bone lesions: fracture, metastasis, degenerative arthropathy and Paget's disease. This technique may prove a cost-effective problem-solving adjunct in nuclear medicine departments unable to yet offer whole-body SPECT/CT to every patient, without adding much burden to the department's gamma camera usage and patient throughput.

Detection of prostate cancer bone metastases with fast whole-body 99mTc-HMDP SPECT/CT using a general-purpose CZT system

BACKGROUND

We evaluated the effects of acquisition time, energy window width, and matrix size on the image quality, quantitation, and diagnostic performance of whole-body ^99mTc-HMDP SPECT/CT in the primary metastasis staging of prostate cancer.

METHODS

Thirty prostate cancer patients underwent ^99mTc-HMDP SPECT/CT from the top of the head to the mid-thigh using a Discovery NM/CT 670 CZT system with list-mode acquisition, 50-min acquisition time, 15% energy window width, and 128 × 128 matrix size. The acquired list-mode data were resampled to produce data sets with shorter acquisition times of 41, 38, 32, 26, 20, and 16 min, narrower energy windows of 10, 8, 6, and 4%, and a larger matrix size of 256 × 256. Images were qualitatively evaluated by three experienced nuclear medicine physicians and quantitatively evaluated by noise, lesion contrast and SUV measurements. Diagnostic performance was evaluated from the readings of two experienced nuclear medicine physicians in terms of patient-, region-, and lesion-level sensitivity and specificity.

RESULTS

The originally acquired images had the best qualitative image quality and lowest noise. However, the acquisition time could be reduced to 38 min, the energy window narrowed to 8%, and the matrix size increased to 256 × 256 with still acceptable qualitative image quality. Lesion contrast and SUVs were not affected by changes in acquisition parameters. Acquisition time reduction had no effect on the diagnostic performance, as sensitivity, specificity, accuracy, and area under the receiver-operating characteristic curve were not significantly different between the 50-min and reduced acquisition time images. The average patient-level sensitivities of the two readers were 88, 92, 100, and 96% for the 50-, 32-, 26-, and 16-min images, respectively, and the corresponding specificities were 78, 84, 84, and 78%. The average region-level sensitivities of the two readers were 55, 58, 59, and 56% for the 50-, 32-, 26-, and 16-min images, respectively, and the corresponding specificities were 95, 98, 96, and 95%. The number of equivocal lesions tended to increase as the acquisition time decreased.

CONCLUSION

Whole-body ^99mTc-HMDP SPECT/CT can be acquired using a general-purpose CZT system in less than 20 min without any loss in diagnostic performance in metastasis staging of high-risk prostate cancer patients.

Clinical impact of targeted single-photon emission computed tomography/computed tomography (SPECT/CT) bone scintigraphy on the assessment of bone metastasis in cancer patients

OBJECTIVES

We investigated the clinical impact of single-photon emission computed tomography/computed tomography (SPECT/CT) bone scintigraphy combined with 16-slice CT on metastatic workup and treatment planning in a large cancer patient series.

METHODS

Between January 2019 and January 2020, a total of 600 cancer patients were prospectively evaluated with whole-body planar bone scan (wbPBS) for staging or restaging purposes. 272/600 had equivocal lesions on wbPBS and 265/272 underwent additionally a targeted SPECT/CT bone scintigraphy on designated regions. Findings were classified as benign (score 1), metastatic (score 2) and inconclusive (score 3). Findings from SPECT/CT bone scintigraphy were compared with the results of wbPBS.

RESULTS

A total of 668 lesions were considered as unclear οn wbPBS and were re-evaluated through targeted SPECT/CT bone scintigraphy. Definite diagnostic findings on SPECT/CT bone scintigraphy were obtained in 227/265 (85.7%) patients and in 592/668 (88.6%) lesions vs. 15.4% of wbPBS alone. On per-patient analyses, 38.9% of patients were considered definitely nonmetastatic and 46.8% as definitely metastatic. On per lesion analyses using SPECT/CT bone scintigraphy, corresponding diagnostic rates were 47.5 and 41.2%. Although the addition of SPECT/CT bone scintigraphy significantly reduced the rate of equivocal wbPBS results (83.1%), it failed to provide a conclusive diagnosis in a relatively small proportion of lesions 76/668 (11.4%) in 38 patients.

CONCLUSIONS

SPECT/CT bone scintigraphy afforded a significant reduction of the number of patients with equivocal findings who needed further evaluation with other imaging modalities, preventing unnecessary delays in diagnosis and potential changes in disease staging and treatment planning. Moreover, SPECT/CT bone scintigraphy slightly increased diagnostic sensitivity.

Clinical Use of Quantitative Analysis of Bone Scintigraphy to Assess the Involvement of Arthritis Diseases in Patients with Joint Symptoms

We aimed to compare the diagnostic ability of quantitative analysis of bone scintigraphy with that of visual analysis for identifying arthritis disease involvement in patients with joint symptoms. We retrospectively included 93 patients with joint symptoms who underwent Tc-99m methylene diphosphonate bone scintigraphy for evaluating arthritis disease involvement. Bone scintigraphy images were visually and quantitatively analyzed using an in-house software by two reviewers. On quantitative analysis, joint uptake ratio was measured for 64 joints in 14 joints areas. The inter-rater agreement of visual and quantitative analyses was assessed, and diagnostic abilities were compared based on the area under the receiver operating characteristic (ROC) curve (AUC) values. Regarding visual analysis, there was a moderate degree of inter-rater agreement (kappa coefficient of 0.597), while there was a substantial inter-rater agreement (concordance correlation coefficient of 0.987) in the measurement of the joint uptake ratio. The comparisons of ROC curves for the total 5941 joints revealed that the joint uptake ratio had a significantly higher AUC value (0.789) to detect the affected joint than that of the visual analysis (p < 0.001). Quantitative analysis using joint uptake ratio showed substantial reproducibility and higher diagnostic ability to detect joints involving arthritis diseases than visual analysis on bone scintigraphy.