Bone islands incidentally detected on computed tomography: frequency of enostosis and differentiation from untreated osteoblastic metastases based on CT attenuation value

OBJECTIVE

The frequency of enostosis incidentally found on CT and CT attenuation value to distinguish them from untreated osteoblastic metastases (UOM).

METHODS

Enostosis group: 46 polytrauma patients underwent thoracoabdominal CT. Inclusion criteria: age range 14-35 years. Exclusion criteria: cancer, previous fractures. UOM group: 20 patients with radiological diagnosis of UOM. Analyzed data: number, size, location and density of enostoses and metastases. The density was measured with the broadest possible region of interest at the center of the lesion by two radiologists independently. Receiver operatingcharacteristic analysis to determine the sensitivity and specificity, area under the curve 95% confidence intervals and cutoff values of CT density to differentiate metastases from enostoses.

RESULTS

Patients were 28 ± 7 years old (72% males). 41 (89%) patients had 124 enostoses (2-15 mm) with an average density of 1007 ± 122 Hounsfiled unit (HU, observer1) and 1052 ± 107 (observer2). The most common sites of occurrence were the proximal femur (34%), the pelvis (22%), the acetabulum (20%), the proximal humerus (11%), the vertebrae (11%) and the rib (2%). 13 patients had 1 bone island, 8 patients had 2, 9 cases had 3 and 11 cases had more than 3 enostoses. Overall, 114 UOM were evaluated, their average density was 728 ± 163 HU (observer1) and 712 ± 178 HU (observer2). The area under the curve value of mean density to distinguish enostoses from UOM was 0,982. Using a cut-off of 881 HU for mean density, sensitivity was 98% and specificity 95%.

CONCLUSION

The frequency of enostosis in this study is 89%. The average density identified can help to distinguish enostoses from UOM.

ADVANCES IN KNOWLEDGE

We report the exact frequency of enostosis.

Incidentalomas in Spine and Spinal Cord Imaging

Incidentalomas are common in magnetic resonance imaging (MRI) of the spine. These incidental findings (IFs) can be seen involving the spinal cord, nerve root, vertebral body, posterior arch and the extraspinal region. This review article describes the imaging findings, stratifies the IFs similar to the computed tomography (CT) colonography reporting and data system and briefly mentions the current recommendations for further evaluation and management of IFs. Radiologists are the first to detect these lesions, suggest further evaluation and management of IFs. It is therefore mandatory for them to be aware of recommendations in clinical practice in order to avoid increased patient anxiety, excessive healthcare expenditure and inadvertent therapeutic procedures.

Increased FDG Uptake in a Giant Bone Island Mimicking Malignancy

Histologically proven bone islands exhibiting increased FDG uptake have been rarely reported before. We present a case with active giant bone island in the left humerus showing increased FDG uptake with SUVmax of 3.8. The diagnosis was confirmed by open biopsy and follow-up. Increased osteoblastic activity, proliferating and active fibroblasts, and increased blood flow may contribute to the increased FDG uptake of this giant bone island. This case indicates bone island should be included in the differential diagnosis of abnormal FDG uptake in focal sclerotic bone lesions, especially in patients with known malignancy.

Imaging of Benign Tumors of the Osseous Spine

The purpose of this paper is to present an overview of the imaging features of the most prevalent benign bone tumors involving the spine. Benign tumors of the osseous spine account approximately for 1% of all primary skeletal tumors. Many lesions exhibit characteristic radiologic features. In addition to age and location of the lesion, radiographs are an essential step in the initial detection and characterization but are limited to complex anatomy and superposition. CT and MR imaging are often mandatory for further characterization, assessment of local extension and guiding biopsy.

Accuracy of CT Attenuation Measurement for Differentiating Treated Osteoblastic Metastases From Enostoses

OBJECTIVE

The objective of our study was to assess whether the maximum and mean CT attenuations are accurate for differentiating between enostoses and treated sclerotic metastases.

MATERIALS AND METHODS

We retrospectively reviewed CT studies of 165 patients (167 lesions) that included 49 patients with 49 benign lesions, 69 patients with 71 sclerotic treated lesions, and 47 patients with 47 untreated lesions, and calculated the mean and maximum CT attenuations of each lesion. ROC curves were used to identify thresholds for differentiating enostoses from treated sclerotic metastases and from untreated sclerotic metastases.

RESULTS

The maximum CT attenuation of enostoses (1212.0 HU) was higher from that of untreated (754.7 HU) (p = 9.7 × 10^-16) and that of treated (891.7 HU) (p = 9.9 × 10^-10) sclerotic metastases. The maximum CT attenuation of treated sclerotic metastases (891.7 HU) was higher than that of untreated sclerotic metastases (754.7 HU) (p = 0.003). Enostoses had higher mean CT attenuation (1123.0 HU) than untreated (602.0 HU) (p < 2.2 × 10^-16) and treated (731.7 HU) (p = 9.6 × 10^-15) sclerotic metastases. A threshold mean CT attenuation of 885 HU had an accuracy of 91.7% and 81.7% to differentiate enostoses from untreated and treated metastases, respectively, whereas a threshold maximum CT attenuation of 1060.0 HU had an accuracy of 81.3% and 72.5% to differentiate enostoses from untreated and treated metastases.

CONCLUSION

The mean and maximum CT attenuations can differentiate between enostoses and sclerotic metastases; however, the accuracy of both metrics decreases after treatment.

MR imaging features of hemispherical spondylosclerosis

OBJECTIVE

Hemispherical spondylosclerosis (HS) is a rare degenerative entity characterized by dome-shaped sclerosis of a single vertebral body that may pose a diagnostic dilemma. The goal of this study was to describe the MR imaging features of HS.

MATERIALS AND METHODS

We identified spine radiographs and CT examinations of subjects with HS who also had MR imaging for correlation. Two musculoskeletal radiologists independently assessed sclerosis characteristics, presence of endplate erosions, marrow signal intensity, and disk degeneration (Pfirrmann scale).

RESULTS

We identified 11 subjects (six males, five females, mean 48 ± 10 years) with radiographic/CT findings of HS. The most commonly affected vertebral body was L4 (6/11; 55%). On MR imaging, variable signal intensity was noted, being most commonly low on T1 (8/11, 73%) and high on fat-suppressed T2-weighted (8/11, 73%) images. In two subjects, diffuse post-contrast enhancement was seen in the lesion. Moderate disk degeneration and endplate bone erosions adjacent to sclerosis were present in all subjects. Erosions of the opposite endplate were present in two subjects (2/11, 18%). CT data from nine subjects showed the mean attenuation value of HS was 472 ± 96 HU.

CONCLUSIONS

HS appearance on MR imaging is variable and may not correlate with the degree of sclerosis seen on radiographs or CT. Disk degenerative changes and asymmetric endplate erosions are consistent markers of HS.

Quantitative contrast-enhanced CT attenuation evaluation of osseous metastases following chemotherapy

PURPOSE

Osseous metastases often undergo an osteoblastic healing response following chemotherapy. The purpose of our study was to demonstrate the quantitative CT changes in attenuation of osseous metastases before and after chemotherapy.

MATERIALS AND METHODS

Our study was IRB approved and HIPAA compliant. Our cohort consisted of 86 consecutive cancer patients with contrast-enhanced CTs before and 14 ± 2 (12-25) months after initiation of chemotherapy (60 ± 11 years, 36 males, 50 females). The average and maximum metastasis attenuations were measured in Hounsfield units (HU) by two readers. Treatment effects were assessed using paired t-tests and Fisher exact tests. Intraclass correlation coefficients (ICCs) were calculated. Patient records were reviewed to determine the patient's clinical status (worse, unchanged, or improved) at the time of follow-up CT.

RESULTS

The distribution of lesion types was as follows: lytic (30/86, 35%), blastic (43/86, 50%), and mixed lytic-blastic (13/86, 15%). There was a significant increase in average and maximum CT attenuation of metastases following chemotherapy for all patients, which remained statistically significant when stratified by lesion type, clinical status (worsening or improving/stable), cancer type (breast, lung), and radiation therapy (P < 0.05). In a subgroup of patients whose osseous metastases decreased in average attenuation (14/86, 16%), more patients had a worse clinical status (11/14, 79%) (P = 0.02). ICC was almost perfect for average attenuation and substantial for maximum attenuation.

CONCLUSION

Quantitative assessment of osseous metastatic disease using CT attenuation measurements demonstrated a statistically significant increase in attenuation more than 12 months after initiation of chemotherapy.

The incidental bone lesion on computed tomography: management tips for abdominal radiologists

Incidental bone lesions are commonly seen on abdominal and pelvic computed tomography (CT) examinations. These incidental bone lesions can be diagnostically challenging to the abdominal radiologist who may not be familiar with their appearance or their appropriate management. The characterization of such bone lesions as non-aggressive or aggressive based on their CT appearance involves similar principles to their morphologic evaluation on radiographs. Knowledge of the age of the patient and the presence of symptoms, mainly bone pain, can improve analysis. Examples of bone lesions that may be encountered include solitary or multifocal bone lesions, osteochondromatous and chondroid tumors, Paget's disease, avascular necrosis/bone infarctions, iatrogenic lesions, and periarticular lesions. This pictorial essay aims to provide a framework for the analysis of incidental bone lesions on CT and when further imaging and clinical work-up should be recommended.