The vascular groove sign: a new CT finding associated with osteoid osteomas.

OBJECTIVE: We have observed that osteoid osteomas are frequently surrounded by thin curvilinear or serpiginous low-density grooves in the surrounding bone on CT examinations. We believe that these grooves represent prominent enlarged feeding arterioles, corresponding to recently published histologic findings. This study was performed to assess the sensitivity and specificity of this vascular groove sign for differentiating osteoid osteomas from other radiolucent bone lesions. MATERIALS AND METHODS: The study group consisted of 42 patients with pathologically proven osteoid osteomas. The control group included 29 patients with radiolucent bone lesions other than osteoid osteomas. Two readers scored CT examinations of these lesions for the presence of the vascular groove sign, defined as one or more radiolucent linear or serpiginous grooves extending from the periosteal surface of bone down to the radiolucent tumor. Sensitivity and specificity values were calculated for each reader. Positive and negative predictive values, p values, and interobserver agreement values were calculated. RESULTS: The sensitivity of the vascular groove sign for detection of osteoid osteoma was 73.8% for reader 1 and 76.2% for reader 2, specificity was 96.6% for reader 1 and 89.7% for reader 2, positive predictive value was 96.9% for reader 1 and 91.4% for reader 2, and negative predictive value was 71.8% for reader 1 and 72.2% for reader 2. The p value was less than 0.0001 for both readers. The interobserver agreement was very good, with a kappa value of 0.85. CONCLUSION: The vascular groove sign is a moderately sensitive but highly specific sign for distinguishing osteoid osteomas from other radiolucent bone tumors on CT.

Early experience with percutaneous cryoablation of extra-abdominal desmoid tumors.

OBJECTIVE: Surgical resection, radiation therapy and chemotherapy are all accepted as standard treatments for extra-abdominal desmoid (EAD) tumors, but their effectiveness has been limited by frequent local recurrence. The purpose of this article is to describe our early experiences with using percutaneous cryoablation for local control of extra-abdominal desmoid tumors in five patients whose tumors had failed to respond to standard therapy. MATERIAL AND METHODS: In a retrospective search of our institution's radiology database for patients who had undergone percutaneous cryoablation for treatment of EAD tumors between June 2004 and July 2007, we identified five patients (three female and two male). No patients were excluded from this review. Three of these patients had been referred for cryoablation for local tumor control, and two had been referred for palliation of inoperable tumors. The age range of the patients at the time of cryoablation was 9-41 years. The treated EAD tumors were located in the neck, shoulders and trunk and ranged in size from 3.0 cm to 10.0 cm. Medical records were reviewed for short-term and long-term follow-up, and patients were contacted for additional follow-up. Patients were asked to rate their pain as absent, mild, moderate or severe, and to compare it with their levels before cryoablation, describing it as improved, unchanged or worsened. Radiology records were reviewed to follow the size of the EAD tumors before and after cryotherapy. RESULTS: For the three patients referred for local control of EAD tumors, complete tumor coverage with the ablation zones was achieved. Two of these patients, with masses 3.0 cm and 4.9 cm in diameter, reported complete absence of pain at both short-term and long-term follow-up at 13 months and 49 months. Their tumors had completely resolved on long-term imaging follow-up at 19 months and 43 months. The third patient, with a 6.1 cm mass, reported improved mild pain at 6 months, and imaging showed a moderate decrease of tumor size. For the two patients referred for palliative therapy, initial partial pain relief was felt 2 weeks after the procedure, At long-term (58 months) follow-up of one patient with a 9.1 cm mass, the tumor was still present although reduced in size, and local pain had returned to its former moderate level. In the other patient who underwent only partial treatment of a 10.0 cm mass, at long-term follow-up (36 months) the mass had enlarged and pain had returned to the pretreatment, moderate level. CONCLUSION: Cryoablation appears to be an effective alternative treatment for the achievement of local control of small and moderately sized EAD tumors, but it is likely of limited use in patients with larger tumors that have untreatable regions due to involvement of vital structures. Continued research evaluating cryoablation for the treatment of EAD tumors is needed.

Iterative reconstruction technique for reducing body radiation dose at CT: feasibility study.

OBJECTIVE: The purpose of this study was to evaluate the image noise, low-contrast resolution, image quality, and spatial resolution of adaptive statistical iterative reconstruction in low-dose body CT. MATERIALS AND METHODS: Adaptive statistical iterative reconstruction was used to scan the American College of Radiology phantom at the American College of Radiology reference value and at one-half that value (12.5 mGy). Test objects in low- and high-contrast and uniformity modules were evaluated. Low-dose CT with adaptive statistical iterative reconstruction was then tested on 12 patients (seven men, five women; average age, 67.5 years) who had previously undergone routine-dose CT. Two radiologists blinded to scanning technique evaluated images of the same patients obtained with routine-dose CT and low-dose CT with and without adaptive statistical iterative reconstruction. Image noise, low-contrast resolution, image quality, and spatial resolution were graded on a scale of 1 (best) to 4 (worst). Quantitative noise measurements were made on clinical images. RESULTS: In the phantom, low- and high-contrast and uniformity assessments showed no significant difference between routine-dose imaging and low-dose CT with adaptive statistical iterative reconstruction. In patients, low-dose CT with adaptive statistical iterative reconstruction was associated with CT dose index reductions of 32-65% compared with routine imaging and had the least noise both quantitatively and qualitatively (p < 0.05). Low-dose CT with adaptive statistical iterative reconstruction and routine-dose CT had identical results for low-contrast resolution and nearly identical results for overall image quality (grade 2.1-2.2). Spatial resolution was better with routine-dose CT (p = 0.004). CONCLUSION: These preliminary results support body CT dose index reductions of 32-65% when adaptive statistical iterative reconstruction is used. Studies with larger statistical samples are needed to confirm these findings.