저선량 CT Guided Interventional Study의 유용성 평가

The Usefulness of Low-dose Interventional CT

Purpose The purpose of this study was to evaluate the possibility of bone biopsy and radio frequency ablation kidney under interventional procedures using a low radiation dose. In addition, AAPM phantom test scan evaluated the image quality and the radiation dose reduction in the same condition. Materials & Methods We retrospectively reviewed cases of bone biopsy CT(lower extremity, spine) and kidney RFA CT at our hospital from January to June 2007. The procedures inducted 37 bone biopsies and 23 kidney RFA CT. In this study, CT fluoroscopy was not used. The CT equipment used GE 4 channel LightSpeed QXi scanners 1. Bone biopsy CT To assess availability of low dose at 120kVp*40~100mAs 2.5mm with intervention CT, we reviewed 37 cases of bone biopsy CT image and evaluated the success rate. 2. Kidney RFA CT It compared with previously kidney CT of 120kvp*144mAs 2.5mm and low dose of 120kVp*40mAs*2.5mm RFA CT image. For each patients, effective radiation dose calculated with a program (impact CT Monte Carlo simulation version 0.99x20/01/06). And it executed rate of success for low dose intervention CT and an image evaluation 3. AAPM phantom test Test was taken with low dose parameter (120kVp*30~100mAs*2.5mm thickness) at 10mAs interval respectively and it measured the image quality with each 4 items (CT No. noise, uniformity and low contrast resolution). Results 1. 111e success or failure of low dose bone biopsy CT evaluated to pathological result come out accurately (malignant or benign) or result is normal. 2. Bone biopsy CT is successful in 29 out of 37 patients(78.4%) with 40~80 mAs; 8 people(21.6%) finished using 100~200 mAs. 3. Kidney RFA CT was successful in 22 out of 23 patients(95.7%). When biopsy needle approached the target lesion, scan parameter used 40mAs and contrast enhanced CT using below 80mAs. When applied to a routine dose of 120kVp*144mAs, 30mm scan range 1scan, the dose calculation is CTDIVOL 19.4mGy, DLP 58.0mGy.cm, eff.dose 1.30mSv and applying 40mAs, CTDIVOL 5.4mGy, DLP 16.0mGy.cm, eff.dose 0.35 mSv. The results of AAPM phantom test is CT No. of water 0.17~0.47HU, uniformity -0.6~2.61HU and low contrast resolution was 9.5mm but noise higher as 12.20~28.95HU. Conclusion In conclusion, there are several method in reducing the radiation dose but we found out that the most common interventional CT procedure can be performed safely and successfully if using 40~80mAs. This range promotes a good radiation close reduction to patients.