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Thursday, February 7, 2019

Efficacy and Radiation Expoure of Ultra-Low-Dose Chest CT at 100 kVp with Tin Filtration in CT-Guided Percutaneous Core Needle Biopsy for Small Pulmonary Lesions Using a Third-Generation Dual-Source CT Scanner 


Clinical question
What is the efficacy and radiation dose performing a percutaneous core needle biopsy using an ultra-low-dose CT at 100 kVp with tin filtration?

Take-away point
Ultra-low-dose CT utilizing a Tin filtration can decrease patient effective dose by over 92% during percutaneous lung lesion biopsy.

Reference
Li, Chunhai et al. Efficacy and Radiation Exposure of Ultra-Low-Dose Chest CT at 100 kVp with Tin Filtration in CT-Guided Percutaneous Core Needle Biopsy for Small Pulmonary Lesions Using a Third-Generation Dual-Source CT Scanner. Journal of Vascular and Interventional Radiology. January, 2019. 30: 95-102.

Study design: Randomized Control Trial

Funding source: Self-funded or unfunded

Setting: Single Institution

Summary


Percutaneous lung biopsy (PLB) is a minimally invasive procedure to guide subsequent treatment. Radiation dose continues to be a hot topic within radiology with continued research in minimizing patient dose during diagnostic and interventional procedures. Prior studies have demonstrated that low-dose protocols using kVp less than or equal to 100 can significantly lower radiation dose during PLB with comparable technical success to standard CT technique (120 kVp). While decreasing kVp reduces patient dose, the lower photon energy range of the polyenergetic spectrum does not exit the patient. Newer technology in third-generation dual-source CT scanners with tin filtration allow spectral shaping to minimize this dose effect by removing much of the low-energy photons that predominantly lead to patient exposure. While low-dose CT with tin filtration has been studied for diagnostic purposes, to this date, there has been no study to evaluate the purpose for PLB.

Using a third-generation dual source CT scanner (SOMATOM Force; Siemens), 210 patients were randomly assigned to standard low-dose CT (110 kVp, 70 patients) or ultra-low-dose CT with filtration (100 kVp, 140 patients). Biopsies were evaluated for diagnostic accuracy and subjective image quality. Technical success was achieved in 97.1% vs 98.5% (ultra-low-dose vs low-dose CT). Pulmonary hemorrhage, pneumothorax and chest tube placement rates were comparable between the two groups: 50.7%, 21.4% and 13.3% vs 45.7%, 18.5% and 7.6% (ultra-low-dose versus low-dose CT). On a subjective 1-5 scale, diagnostic quality was lower in the ultra-low-dose CT group (3.67 vs 4.32, p=0.33). Mean total dose length product and effective dose were significantly lower in the ultra-low-dose CT group (9.84 mGy-cm vs 110.52 mGy-cm, P < .001 and 0.14 mSv vs 1.78 mSv , p < .001) with an 92.1% average reduction of effective dose. The authors concluded that despite decreased image quality, PLB can be performed with comparable safety and accuracy and with a significant decrease in patient dose.



Fig 3. Ultra-lowe dose CT-guided PCNB of a small pulmonary lesion. (a, b) Diagnostic quality CT images at 120 kVp showed a 1.9 cm lesion (arrow) in the left upper lobe before the lung biopsy. Note also the biopsy pathway should not cross a lung fissure (arrowhead). (c, d) The position of the lesion and the needle tip were clearly seen by ultra-low-dose CT scanning at 100Sn kVp and 70 mAs (total DLP, 9.6 mGy-cm; ED, 0.13 mSv). PCNB was conducted successfully without complications. The lesion was confirmed as adenocarcinoma on both biopsy and surgical resection.

Commentary


CT guided biopsies and drainage are common procedures. This study demonstrates there is comparable safety and accuracy while utilizing an ultra-low-dose CT technique with tin filter for PLB. This result may be reproducible in other parts of the body and with other procedures such as ablation and drainage. However, the lung may be the optimal organ for ultra-low-dose CT given the drastic differentiation between lesion (solid) and back ground tissue (predominantly air). As such, degraded image quality may be a larger hindrance for performance in other locations. Additional investigation, will further determine how widespread this technique should be employed, however any protocol that can significantly lower effective dose should be strongly considered for its benefits compared to risks.

Post Author:
David M Mauro, MD
Assistant Professor
Department of Radiology
Vascular and Interventional Radiology
University of North Carolina
@DavidMauroMD

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