초록
PET/CT 검사 시 호흡으로 인한 내부장기의 움직임은 여러 호흡주기 동안 영상화되어 종양크기는 실제보다 증가하고 SUV에도 영향을 미치게 된다. 호흡 동조 시스템들을 이용하여 종양크기와 SUV 변화 유무를 평가해보고자 한다. 장비는 Biograph mCT 64를 사용하였고 호흡 동조 시스템은 RPM과 Anzai 시스템을 사용하였다. 실험을 위해 Point source와 Micro-phantom을 환자는 2016년 8월에서 9월까지 폐 기저부 또는 간 상부에 고형종양이 확인된 환자 12명을 대상으로 호기-호흡상태에서의 PET영상과 호기 후 멈춤 상태의 CT영상을 얻어 기존 Static, RPM, Anzai방식에서의 방사능 농도(kBq/mL), SUVmax, Cylinder diameter(mm), Tumor diameter (mm) 변화 유무를 평가하였다. Point source 방사능 농도 측정 결과 Static 대비 RPM 94%, Anzai 91% 상승하였고 Micro-phantom에서 방사능량을 달리한 2개의 Cylinder에서 SUVmax값은 Static 대비 RPM 61%, 78%, Anzai 58%, 77%로 각각 상승하였고 Cylinder diameter는 RPM -26%, -28%, Anzai -28%, -26% 감소하였다. 환자의 경우 SUVmax값은 Static 대비 RPM은 최소 8.2%에서 최대 94.4%, Anzai는 최소7.6%에서 최대 68.3% 상승하였고 Tumor diameter는 RPM은 최소 -7.6%에서 최대 -28.9%, Anzai는 최소 -9.6%에서 최대 -27.7% 감소하였다. 호흡 동조 시스템 RPM과 Anzai에서 phantom study는 별 차이가 없었지만 환자의 종양에서는 유의미한 차이가 있었다(P<0.05). 호흡 동조 시스템 RPM과 Anzai는 호흡이 일정한 주기로 이루어지는 phantom study에서 별 차이가 없었지만 환자의 경우 일정하지 않은 호흡주기와 시스템간 차이 때문에 유의미한 차이가 발생함을 알 수 있었다. 하지만 호흡 동조 시스템은 기존 Static 대비 종양의 크기는 감소하고 SUV는 증가하여 정확한 진단과 SUV측정에 유용할 것으로 사료된다.
Purpose During PET/CT examinations, the movements of internal organs caused by respiration are captured in images during multiple breathing cycles, resulting in the increases in tumor size and effects on SUV. Respiratory synchronized systems were used to evaluate tumor sizes and SUV changes. Materials and Methods Biograph mCT 64 was used for the equipment, and RPM and Anzai systems were used for the respiratory synchronized systems. We used point source and micro-phantom for an experimentation. We were performed on 12 patients who had solid tumors discovered at the base of the lung or at the top of the liver from August through September 2016. The PET images of the exhalation-to-breathing state and the CT images of the post-exhalation suspension state were gained to evaluate changes in radioactivity concentration (KBq/mL), SUVmax, cylinder diameter (mm), and tumor diameter (cm) under the conventional Static, RPM, and Anzai methods. Results The result of measuring the radioactivity concentration of the point source was RPM 94% and Anzai 91% against Static, respectively. In the two cylinders of different radioactivity in the micro-phantom, the SUVmax increased to RPM 61% and 78%, and Anzai 58% and 77% against Static, whereas the cylinder diameters decreased by RPM -26% and -28%, and Anzai -28% and -26%, each respectively. Among the patients, the SUVmax increased from a minimum of RPM 8.2% to a maximum of 94.4% against Static, and from a minimum of Anzai 7.6% to a maximum of 68.3%, respectively. As for the tumor diameters, a minimum of RPM -7.6% to a maximum of -28.9% were achieved, while the Anzai fell by a minimum of -9.6% to a maximum of -27.7%, respectively. There was no significant difference discovered in the phantom study between the RPM and Anzai, yet there was a meaningful difference in the patients' tumors (P<0.05). Conclusion The respiratory synchronized systems of RPM and Anzai yielded no significant difference in the phantom study in which the respiration was executed at regular intervals. However, it was discovered that the patients had a meaningful difference for the irregular respiratory cycle and inter-system differences. Still, the respiratory synchronized systems would be useful for the accurate diagnosis and SUV measurement as the tumor decreased in size against the existing Static and the SUV increased.
