Effect of Stereotactic Body Radiotherapy on the Growth Kinetics and Enhancement Pattern of Primary Renal Tumors.

OBJECTIVE: The objective of our study was to assess the growth rate and enhancement of renal masses before and after treatment with stereotactic body radiotherapy (SBRT). MATERIALS AND METHODS: This retrospective study included all patients with renal masses who underwent SBRT during a 5-year period. Orthogonal measurements of renal masses were obtained on pre- and posttreatment CT or MRI. Pre- and posttreatment growth rates were compared for renal mass diameter and volume using the t test. Pre- and posttreatment tumor enhancement values were compared for tumors that underwent multiphasic contrast-enhanced MRI. RESULTS: Forty patients underwent SBRT for the treatment of 41 renal tumors: clear cell renal cell carcinomas (RCCs) (n = 16), papillary RCCs (n = 6), oncocytic neoplasms (n = 8), unclassified RCCs (n = 2), urothelial carcinoma (n = 1), and no pathologic diagnosis (n = 8). The mean maximum tumor diameter before treatment was 3.9 cm (range, 1.6-8.3 cm). Three hundred thirty-eight pre- and posttreatment imaging studies were analyzed: 214 MRI studies and 124 CT studies. The mean pre- and posttreatment lengths of observation were 416 days (range, 2-1800 days) and 561 days (83-1366 days), respectively. The mean pretreatment tumor growth rate of 0.68 cm/y decreased to -0.37 cm/y post treatment (p < 0.0001), and the mean tumor volume growth rate of 21.2 cm(3)/y before treatment decreased to -5.35 cm(3)/y after treatment (p = 0.002). Local control-defined as less than 5 mm of growth-was achieved in 38 of 41 (92.7%) tumors. The Response Evaluation Criteria in Solid Tumors (RECIST) 1.1 showed progression in one tumor (2.4%), stability in 31 tumors (75.6%), partial response in eight tumors (19.5%), and complete response in one tumor (2.4%). No statistically significant change in tumor enhancement was shown (mean follow-up, 142 days; range, 7-581 days). CONCLUSION: Renal tumors treated with SBRT show statistically significant reductions in growth rate and tumor size after treatment but do not show statistically significant differences in enhancement in the initial (mean, 142 days) posttreatment period.

C-arm fluoroscopic cone beam CT for guidance of minimally invasive spine interventions.

BACKGROUND: Isocentric C-arm fluoroscopic cone beam CT (CBCT) is a new technique for near real time 3-D volume imaging guidance of percutaneous interventional procedures. In combination with digital flat panel detectors, CBCT has high spatial resolution with isotropic voxel size, allowing for high resolution image reconstruction in any plane, including 3D rotational reconstructions. CBCT combines the advantages of conventional CT imaging guidance with the improved spatial resolution, patient positioning, and access of fluoroscopy. OBJECTIVE: The aim of this study is to demonstrate the advantages of CBCT over conventional CT and biplane fluoroscopy for imaging guidance of minimally invasive spinal and paraspinal interventional procedures. METHODS: Five patients referred to the department of interventional neuroradiology for percutaneous spinal or paraspinal interventional procedures were intraoperatively evaluated with CBCT to assist in guidance of instrumentation placement. Procedures included transoral cervical vertebral biopsy, percutaneous thoracic vertebral biopsy, vertebroplasty, pelvic paraspinal/epidural abscess drainage, and paraspinal fiducial marker placement for treatment of osteoid osteoma. RESULTS: All procedures were successfully performed with satisfactory diagnostic yield or therapeutic effect without procedure-related complications. CONCLUSION: Isocentric C-arm fluoroscopic cone beam CT (CBCT) is a new technique for 3D volume imaging guidance of interventional procedures of the spine with the capability to produce near real time high resolution image reconstructions in any plane. Compared to conventional CT and biplane fluoroscopy, CBCT offers improved anatomic visualization allowing high accuracy instrumentation placement, improving procedure results and minimizing risk of complications.

Asparagine deamidation in recombinant human lymphotoxin: hindrance by three-dimensional structures.

The chemical stability of recombinant human lymphotoxin (rhLT) was evaluated at pH 7, 9, and 11 and 40 degrees C using quantitative tryptic map and urea-IEF methods. Degradation products were characterized by mass spectrometry. The stability of denatured rhLT protein was also evaluated to elucidate the effects of three-dimensional structures on Asn deamidation in rhLT. Two sites that underwent Asn deamidation were identified in rhLT, Asn(19) and Asn(40)-Asn(41). At pH 11 and 40 degrees C, deamidation at Asn(19) and Asn(40)-Asn(41) had half-lives of 14 +/- 4 and 80 +/- 24 days, respectively. Upon denaturation, 31- and ninefold acceleration in the degradation rates was observed at the Asn(19) and Asn(40)-Asn(41) sites, respectively. The rate of Asn(19) degradation in denatured rhLT was comparable to that of the model peptide possessing the same primary sequence as the Asn(19)-containing region in rhLT. Analysis of the rhLT crystal structure revealed that both Asn deamidation sites were located in beta-turn structures with extensive hydrogen-bonding networks created with nearby residues in the tertiary structures. The results suggested that these tertiary and secondary structures, if held true in solution, were probably responsible for the stabilization of Asn in the native rhLT protein by reducing flexibility, thus preventing adoption of the favorable conformation required for cyclic-imide formation.