Image quality in low-dose multidetector computed tomography: a pilot study to assess feasibility and dose optimization in whole-body bone imaging.

OBJECTIVE: To study the impact of dose parameters on image quality at whole-body low-dose multidetector computed tomography (CT) in an attempt to derive parameters that allow diagnostic quality images of the skeletal system without incurring significant radiation dose in patients referred for investigation of plasma cell dyscrasias. METHODS: By using a single cadaver, 14 different whole-body low-dose CT protocols were individually assessed by 2 radiologists, blinded to acquisition parameters (kVp and mAs, reconstruction algorithm, dose reduction software). Combinations of kVps that range from 80-140 kVp, and tube current time product from 14-125 mAs were individually scored by using a Likert scale from 1-5 in 4 separate anatomical areas (skull base, thoracic spine, pelvis, and distal femora). Correlation between readers scores and effective doses were obtained by using correlation coefficient statistical analysis, statistical significance was considered P < .01. Interobserver agreement was assessed by using a Bland and Altman plot. Interobserver agreement in each of the 4 anatomical areas was assessed by using kappa statistics. A single set of parameters was then selected for use in future clinical trials in a cohort of patients referred for investigation of monoclonal gammopathy, including multiple myeloma. RESULTS: Several sets of exposure parameters allowed low-dose whole-body CT to be performed with effective doses similar to skeletal survey while preserving diagnostic image quality. Individual reader's and average combined scores showed a strong inverse correlation with effective dose (reader 1, r = -0.78, P = .0001; reader 2, r = -0.75, P = .0003); average combined scores r = -0.81, P < .0001). Bland and Altman plot of overall scores shows reasonable interobserver agreement, with a mean difference of 1.055. CONCLUSION: Whole-body low-dose CT can be used to obtain adequate CT image quality to assess normal osseous detail while delivering effective doses similar to those associated with conventional radiographic skeletal survey.

Perifissural nodules seen at CT screening for lung cancer.

PURPOSE: To describe and characterize the potential for malignancy of noncalcified lung nodules adjacent to fissures that are often found in current or former heavy smokers who undergo computed tomography (CT) for lung cancer screening. MATERIALS AND METHODS: Institutional review board approval and informed consent were obtained. Baseline and follow-up thin-section multidetector CT scans obtained in 146 consecutive subjects at high risk for lung cancer (age range, 50-75 years; > 30 pack-year smoking history) were retrospectively reviewed. Noncalcified nodules (NCNs) were categorized according to location (parenchymal, perifissural), shape, septal connection, manually measured diameter, diameter change, and lung cancer outcome at 7(1/2) years. RESULTS: Retrospective review of images from 146 baseline and 311 follow-up CT examinations revealed 837 NCNs in 128 subjects. Of those 837 nodules, 234 (28%), in 98 subjects, were adjacent to a fissure and thus classified as perifissural nodules (PFNs). Multiple (range, 2-14) PFNs were seen in 47 subjects. Most PFNs were triangular (102/234, 44%) or oval (98/234, 42%), were located inferior to the carina (196/234, 84%), and had a septal connection (171/234, 73%). The mean maximal length was 3.2 mm (range, 1-13 mm). During 2-year follow-up in 71 subjects, seven of 159 PFNs increased in size on one scan but were then stable. The authors searched a lung cancer registry 7(1/2) years after study entry and found 10 lung cancers in 139 of 146 study subjects who underwent complete follow-up; none of these cancers had originated from a PFN. CONCLUSION: PFNs are frequently seen on screening CT scans obtained in high-risk subjects. Although PFNs may show increased size at follow-up CT, the authors in this study found none that had developed into lung cancer; this suggests that the malignancy potential of PFNs is low. (c) RSNA, 2010.

Whole-Body MRI versus PET in assessment of multiple myeloma disease activity.

OBJECTIVE: The purpose of this study was to compare FDG PET; whole-body MRI; and the reference standard, bone marrow aspiration and biopsy, to determine the best imaging technique for assessment of disease activity in multiple myeloma. SUBJECTS AND METHODS: Twenty-four patients (13 women, 11 men; mean age, 67.1 years; range, 44-83 years) with bone marrow biopsy-proven multiple myeloma were included in the study. All patients underwent PET/CT and whole-body MRI within 10 days of each other. Eight patients underwent more than one follow-up PET/CT and whole-body MRI examination, for a total of 34 pairs of images. Activity was defined as lesions with a maximum standardized uptake value greater than 2.5 at PET and as evidence of marrow packing at whole-body MRI. PET and whole-body MRI results were correlated with findings at bone marrow aspiration biopsy. RESULTS: PET had a sensitivity of 59%, specificity of 75%, positive predictive value of 81%, and negative predictive value of 50% (p = 0.08). Whole-body MRI had a sensitivity of 68%, specificity of 83%, positive predictive value of 88%, and negative predictive value of 59% (p = 0.01). In 62% of cases, PET and whole-body MRI findings were concordant. When PET and whole-body MRI findings were concordant and positive, no false-positive results were found, yielding a specificity and a positive predictive value of 100% (p = 0.04). CONCLUSION: Whole-body MRI performed better than PET in the assessment of disease activity, having a higher sensitivity and specificity. The positive predictive value of whole-body MRI in the assessment of active disease was high at 88%. When used in combination and with concordant findings, PET and whole-body MRI were found to have a specificity and positive predictive value of 100%, which may be of value to clinicians assessing the effectiveness of aggressive and expensive treatment regimens.

Steady-state free-precession (SSFP) cine MRI in distinguishing normal and bicuspid aortic valves.

PURPOSE: To assess the diagnostic sensitivity and specificity of double-oblique true fast imaging with steady-state precession (SSFP) cine MRI in distinguishing normal and bicuspid aortic valves. MATERIALS AND METHODS: Echocardiograms on patients referred for MRI of the heart and thoracic aorta over a four-year period were reviewed retrospectively. A total of 17 patients with bicuspid aortic valve were identified and compared to 21 randomly chosen control patients. All patients had double-oblique SSFP (True FISP) cine MRI of the aortic valve independently assessed by two radiologists in a blinded fashion, and graded as bicuspid or normal. Image quality was graded as 1, 2, or 3. Discordance was resolved by consensus. RESULTS: A total of 38 cases were reviewed (27 men, 11 women; age range = 15-67 years, mean = 25.33 years). Interobserver agreement was 0.97 (36/38 cases). One case of normal tricuspid valve was reported as bicuspid by both readers (false-positive). All cases in which disparity arose were rated suboptimal by both readers (grade 2 or 3). Consensus review yielded sensitivity = 100%, specificity = 95.2%, positive predictive value = 94.4%, and negative predictive value = 100%; overall diagnostic accuracy was 97.36%. Interobserver agreement was 0.97. CONCLUSION: Double-oblique True FISP cine MR imaging of the aortic valve is 100% sensitive and 95% specific in distinguishing normal and bicuspid aortic valves.

Coronal oblique turbo STIR imaging of the sacrum and sacroiliac joints at routine MR imaging of the lumbar spine.

The objective of the study was to evaluate the clinical impact of coronal oblique imaging of the lumbrosacral junction and the sacrum at initial presentation for MR imaging of the lumbar spine in patients presenting with low back pain or sciatic pain. Two hundred and sixty consecutive patients attending for MRI of the lumbar spine underwent simultaneous coronal oblique turbo short tau inversion recovery (STIR; TR 2500, TE 40, TI 150, echo train length 7, number of scan acquisitions 2) imaging of the sacrum and the sacroiliac joints with a field of view of 30-cm and 3-mm slices (acquisition time 3 min and 20 s). Images were reviewed by two experienced radiologists to determine the cause of back pain, with and without images of the sacrum and sacroiliac joints. The added value of the additional sequence was assessed. Correlation was made with surgery, response to nerve root injection or clinical follow-up at 3 months. Subgroup analysis was performed to determine if patient stratification according to sex or symptoms would be useful. In total, in 19 of 260 patients (7.3%), abnormalities were identified at coronal STIR imaging. In 7 of 260 patients (2.7%), pathology was identified in the sacrum thought to account for back pain, altering the diagnosis made on the standard sequences. These diagnoses were sacroiliitis (n=2), sacral stress fracture (n=1), degenerative sacroiliac joints (n=1), degenerative accessory articulation between the lumbar spine and the sacrum (n=1), Tarlov cyst of nerve root (n=1) and retroverted uterus causing sciatic pain (n=1). Patient stratification according to sex or the presence or absence of sciatic symptoms was not useful in predicting the added benefit of the additional sequence. Routine coronal STIR imaging of the sacrum as part of lumbar spine MRI improves assessment of patients presenting with low back pain or sciatica in only a small number of patients.