Diagnostic value of whole-body ultra-low dose computed tomography in comparison with spinal magnetic resonance imaging in the assessment of disease in multiple myeloma

Diagnosis and Treatment of Skipped Multifocal Spinal Tuberculosis Lesions

Spinal tuberculosis, also known as Pott's disease or tuberculous spondylitis, is usually secondary to primary infection in the lungs or other systems, and in most instances, is thought to be transmitted via blood. Typical manifestations of infection include narrowing of the intervertebral disc by erosion and bone destruction of adjacent vertebrae. Atypical spinal tuberculosis is a specific type of spinal tuberculosis. It mainly consists of single vertebral lesions, single posterior structure lesions, multiple vertebral lesions, and intra-spinal lesions. Skipped multifocal spinal tuberculosis is one of these types and is characterized by two or more vertebral lesions without the involvement of the adjoining intervertebral discs, regardless of their location. To date, only a few cases have been reported. Upon clinical admission, it can be treated conservatively or surgically, depending on the patient's symptoms. In addition, gene or biological therapies are being investigated. However, because of the exceptional imaging findings and insidious symptoms, it is often misdiagnosed as a neoplastic lesion, osteoporotic fracture, or other infectious spondylitis, increasing the risk of neurological deficit and kyphotic deformity, and delaying the optimal treatment window. In this study, we review the diagnosis and treatment strategies for skipped multifocal spinal tuberculosis lesions and enumerate the common differential diagnoses, to provide reference and guidance for clinical treatment and diagnosis direction.

Radiation exposure and establishment of diagnostic reference levels of whole-body low-dose CT for the assessment of multiple myeloma with second- and third-generation dual-source CT

BACKGROUND

In the assessment of diseases causing skeletal lesions such as multiple myeloma (MM), whole-body low-dose computed tomography (WBLDCT) is a sensitive diagnostic imaging modality, which has the potential to replace the conventional radiographic survey.

PURPOSE

To optimize radiation protection and examine radiation exposure, and effective and organ doses of WBLDCT using different modern dual-source CT (DSCT) devices, and to establish local diagnostic reference levels (DRL).

MATERIAL AND METHODS

In this retrospective study, 281 WBLDCT scans of 232 patients performed between January 2017 and April 2020 either on a second- (A) or third-generation (B) DSCT device could be included. Radiation exposure indices and organ and effective doses were calculated using a commercially available automated dose-tracking software based on Monte-Carlo simulation techniques.

RESULTS

The radiation exposure indices and effective doses were distributed as follows (median, interquartile range): (A) second-generation DSCT: volume-weighted CT dose index (CTDI_vol) 1.78 mGy (1.47-2.17 mGy); dose length product (DLP) 282.8 mGy·cm (224.6-319.4 mGy·cm), effective dose (ED) 1.87 mSv (1.61-2.17 mSv) and (B) third-generation DSCT: CTDI_vol 0.56 mGy (0.47-0.67 mGy), DLP 92.0 mGy·cm (73.7-107.6 mGy·cm), ED 0.61 mSv (0.52-0.69 mSv). Radiation exposure indices and effective and organ doses were significantly lower with third-generation DSCT (P < 0.001). Local DRLs could be set for CTDI_vol at 0.75 mGy and DLP at 120 mGy·cm.

CONCLUSION

Third-generation DSCT requires significantly lower radiation dose for WBLDCT than second-generation DSCT and has an effective dose below reported doses for radiographic skeletal surveys. To ensure radiation protection, DRLs regarding WBLDCT are required, where our locally determined values may help as benchmarks.

Ultra-Low-Dose Whole-Body Computed Tomography Protocol Optimization for Patients With Plasma Cell Disorders: Diagnostic Accuracy and Effective Dose Analysis From a Reference Center

BACKGROUND

The whole-body low-dose CT (WBLDCT) is the first-choice imaging technique in patients with suspected plasma cell disorder to assess the presence of osteolytic lesions. We investigated the performances of an optimized protocol, evaluating diagnostic accuracy and effective patient dose reduction using a latest generation scanner.

METHODS AND MATERIALS

Retrospective study on 212 patients with plasma cell disorders performed on a 256-row CT scanner. First, WBLDCT examinations were performed using a reference protocol with acquisition parameters obtained from literature. A phantom study was performed for protocol optimization for subsequent exams to minimize dose while maintaining optimal diagnostic accuracy. Images were analyzed by three readers to evaluate image quality and to detect lesions. Effective doses (E) were evaluated for each patient considering the patient dimensions and the tube current modulation.

RESULTS

A similar, very good image quality was observed for both protocols by all readers with a good agreement at repeated measures ANOVA test (p>0.05). An excellent inter-rater agreement for lesion detection was achieved obtaining high values of Fleiss' kappa for all the districts considered (p<0.001). The optimized protocol resulted in a 56% reduction of median DLP (151) mGycm, interquartile range (IQR) 128-188 mGycm vs. 345 mGycm, IQR 302-408 mGycm), of 60% of CTDIvol (2.2 mGy, IQR 1.9-2.7 mGy vs. 0.9 mGy, IQR 0.8-1.2 mGy). The median E value was about 2.6 mSv (IQR 1.7-3.5 mSv) for standard protocol and about 1.5 mSv (IQR 1.4-1.7 mSv) for the optimized one. Dose reduction was statistically significant with p<0.001.

CONCLUSIONS

Protocol optimization makes ultra-low-dose WBLDCT feasible on latest generation CT scanners for patients with plasma cell disorders with effective doses inferior to conventional skeletal survey while maintaining excellent image quality and diagnostic accuracy. Dose reduction is crucial in such patients, as they are likely to undergo multiple whole-body CT scans during follow-up.

Low diagnostic accuracy and inter-observer agreement on CT and MRI in diagnosis of spinal fractures in multiple myeloma

Skeletal disease is common in multiple myeloma. We investigated the inter-observer agreement and diagnostic accuracy of spinal fractures diagnosed by computer tomography (CT) and magnetic resonance imaging (MRI) from 12 myeloma patients. Two radiologists independently assessed the images. CT, MRI, and other images were combined to a gold standard. The inter-observer agreement was assessed with Cohen’s kappa. Radiologist 1 diagnosed 20 malignant spinal fractures on CT and 26 on MRI, while radiologist 2 diagnosed 12 malignant spinal fractures on CT and 22 on MRI. In comparison the gold standard diagnosed 10 malignant spinal fractures. The sensitivity for malignant fractures varied from 0.5 to 1 for CT and MRI, and the specificity varied from 0.17 to 0.67. On MRI, the specificity for malignant spinal fractures was 0.17 for both radiologists. The inter-observer agreement for malignant spinal fractures on CT was -0.42 (Cohen’s kappa) and -0.13 for MRI, while for osteoporotic fractures it was -0.24 for CT and 0.53 for MRI. We conclude that malignant spinal fractures were over-diagnosed on CT and MRI. The inter-observer agreement was extremely poor.

Organ dose and total effective dose of whole-body CT in multiple myeloma patients

OBJECTIVE

To evaluate organ dose and total effective dose of whole-body low-dose CT (WBLDCT) performed on different CT-scanner models in patients with multiple myeloma (MM) and to compare it to the effective dose of radiographic skeletal survey and representative diagnostic CTs.

MATERIAL AND METHODS

We retrospectively analyzed data from 228 patients (47.4% females, mean age 67.9 ± 10.4 years, mean weight 81.8 ± 22.4 kg) who underwent WBLDCT for the work-up or surveillance of MM. Patients were scanned using one of six multi-detector CT-scanners. Organ doses and total effective doses per scan were calculated using a commercially available dose-management platform (Radimetrics, Bayer Healthcare, Leverkusen, Germany). The median effective dose was compared to radiographic skeletal survey and representative diagnostic CTs.

RESULTS

The mean effective dose of our WBLDCT-protocol was 4.82 mSv. A significantly higher effective dose was observed in females compared to males (4.95 vs. 4.70 mSv, P = 0.002). Mean organ dose ranged from 3.72 mSv (esophagus) to 13.09 mSv (skeleton). Mean effective dose varied amongst different CT-scanners (range 4.34-8.37 mSv). The median effective dose of WBLDCT was more than twice the dose of a skeletal survey (4.82 vs. 2.04 mSv), 23% higher than a diagnostic contrast-enhanced chest CT (3.9 mSv), 46% lower than a diagnostic contrast-enhanced abdomen/pelvis CT (9.0 mSv), and 45% lower than a lumbar spine CT (8.7 mSv).

CONCLUSIONS

WBLDCT in MM has a higher effective dose than a radiographic skeletal survey, but a lower effective dose than diagnostic CTs of lumbar spine, abdomen and pelvis. This underlines the broad applicability of WBLDCT in the management of MM patients.

Imaging in multiple myeloma: How? When?

Bone disease is the most frequent feature of multiple myeloma (MM) and represents a marker of end-organ damage; it is used to establish the diagnosis and to dictate the immediate need for therapy. For this reason, imaging plays a significant role in the management of MM patients. Although conventional radiography has traditionally been the standard imaging modality, its low sensitivity in detecting osteolytic lesions and inability to evaluate response to therapy has called for the use of more sophisticated techniques, such as whole-body low-dose computed tomography (WBLDCT), whole-body magnetic resonance imaging, and ¹⁸F-fluorodeoxyglucose-positron emission tomography/computed tomography (PET/CT). In this review, the advantages, indications of use, and applications of the 3 techniques in the management of patients with MM in different settings will be discussed. The European Myeloma Network and the European Society for Medical Oncology guidelines have recommended WBLDCT as the imaging modality of choice for the initial assessment of MM-related lytic bone lesions. Magnetic resonance imaging is the gold-standard imaging modality for detection of bone marrow involvement, whereas PET/CT provides valuable prognostic data and is the preferred technique for assessment of response to therapy. Standardization of most of the techniques is ongoing.

Whole-body low-dose CT recognizes two distinct patterns of lytic lesions in multiple myeloma patients with different disease metabolism at PET/MRI

We evaluated differences in density and ¹⁸F-FDG PET/MRI features of lytic bone lesions (LBLs) identified by whole-body low-dose CT (WB-LDCT) in patients affected by newly diagnosed multiple myeloma (MM). In 18 MM patients, 135 unequivocal LBLs identified by WB-LDCT were characterized for inner density (negative or positive Hounsfield unit (HU)), where negative density (HU < 0) characterizes normal yellow marrow whereas positive HU correlates with tissue-like infiltrative pattern. The same LBLs were analyzed by ¹⁸F-FDG PET/DWI-MRI, registering DWI signal with ADC and SUV max values. According to HU, 35 lesions had a negative density (− 56.94 ± 31.87 HU) while 100 lesions presented positive density (44.87 ± 23.89 HU). In seven patients, only positive HU LBLs were demonstrated whereas in eight patients, both positive and negative HU LBLs were detected. Intriguingly, in three patients (16%), only negative HU LBLs were shown. At ¹⁸F-FDG PET/DWI-MRI analysis, negative HU LBLs presented low ADC values (360.69 ± 154.38 × 10⁻⁶ mm²/s) and low SUV max values (1.69 ± 0.56), consistent with fatty marrow, whereas positive HU LBLs showed an infiltrative pattern, characterized by higher ADC (mean 868.46 ± 207.67 × 10⁻⁶ mm²/s) and SUV max (mean 5.04 ± 1.94) values. Surprisingly, histology of negative HU LBLs documented infiltration by neoplastic plasma cells scattered among adipocytes. In conclusion, two different patterns of LBLs were detected by WB-LDCT in MM patients. Both types of lesions were indicative for active disease, although only positive HU LBL were captured by ¹⁸F-FDG PET/DWI-MRI imaging, indicating that WB-LDCT adds specific information.

Bones in Multiple Myeloma: Imaging and Therapy

F-fluorodeoxyglucose (FDG)-PET/CT, MRI, and other novel imaging modalities in the management of disease in patients with plasma cell dyscrasias. We also review the state of the art in treatment of MM bone disease (MMBD) and the role of bisphosphonates and denosumab, a monoclonal antibody that binds and blocks the activity of receptor activator of nuclear factor-kappa B ligand (RANKL), which was recently approved by the U.S. Food and Drug Administration for MMBD.

Whole-body ultra-low dose CT using spectral shaping for detection of osteolytic lesion in multiple myeloma

OBJECTIVES

The aim of this study was to investigate the radiation dose and image quality of a whole-body low-dose CT (WBLDCT) using spectral shaping at 100 kV (Sn 100 kV) for the assessment of osteolytic lesions in patients with multiple myeloma.

METHODS

Thirty consecutive patients were retrospectively selected, who underwent a WBLDCT on a third-generation dual-source CT (DSCT) (Sn 100 kV, ref. mAs: 130). They were matched with patients, who were examined on a second-generation DSCT with a standard low-dose protocol (100 kV, ref. mAs: 111). Objective and subjective image quality, radiation exposure as well as the frequency of osteolytic lesions were evaluated.

RESULTS

All scans were of diagnostic image quality. Subjective overall image quality was significantly higher in the study group (p = 0.0003). Objective image analysis revealed that signal intensities, signal-to-noise ratio and contrast-to-noise ratio of the bony structures were equal or significantly higher in the control group. There was no significant difference in the frequency of osteolytic lesions (p = 0.259). The median effective dose of the study protocol was significantly lower (1.45 mSv vs. 5.65 mSv; p < 0.0001).

CONCLUSION

WBLDCT with Sn 100 kV can obtain sufficient image quality for the depiction of osteolytic lesions while reducing the radiation dose by approximately 74%.

KEY POINTS

• Spectral shaping using tin filtration is beneficial for whole-body low-dose CT • Sn 100 kV yields sufficient image quality for depiction of osteolytic lesions • Whole-body low-dose CT can be performed with a median dose of 1.5 mSv.