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PET/CT PATIENT DOSE AND IMAGE QUALITY

PET/CT PATIENT DOSE AND IMAGE QUALITY. Olivera Šveljo 1 , Silvija Lučić 2 , Andrea Peter 2 , Dejan Kozarski 1 , Miloš Lučić 1 1 Diagnostic Imaging Centre, Oncology Institute of Vojvodina, 2 Department of Nuclear Medicine, Oncology Institute of Vojvodina Sremska Kemnica, Serbia

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PET/CT PATIENT DOSE AND IMAGE QUALITY

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  1. PET/CT PATIENT DOSE AND IMAGE QUALITY Olivera Šveljo1, Silvija Lučić2, Andrea Peter2, Dejan Kozarski1, Miloš Lučić1 1Diagnostic Imaging Centre, Oncology Institute of Vojvodina, 2Department of Nuclear Medicine, Oncology Institute of Vojvodina Sremska Kemnica, Serbia RAD2012, April 25-27, 2012 Niš

  2. Hybrid PET/CT Imaging • “Simultaneosly” obtains anatomical (CT) and functional (PET) data • Image fusion and CT based attenuation correction instead of separately mesured data • Increased clinical application – more and more scanners being installed in hospitals and clinics worldwide

  3. Both (PET and CT) as stand alone are considered as high dose diagnostic imaging procedure. • PET/CT examinations increased patient radiation exposure compared to stand-alone PET or CT examinations • PET/CT is a relatively new imaging modality and the aim of this study was to clarify some aspects of this complex diagnostic procedure regarding effective patient dose and image quality

  4. CT PET • Two sources of radiation: • Internal dose from radiopharmaceuticals (PET) and • External from X-rays (CT)

  5. Aim: to evaluate patient doses and CT image quality for PET/CT examinationsin a period of one month in our Centre • 5 head examinations • 4 female and one male (mean age 44,8±8,2, range 35-55y) • 20 whole body examinations • 5 female and 15 male (mean age 52,45±12,07; range 30-73y) • Biograph 64 (Siemens, Erlangen, Germany)

  6. PET - 18F-FDG ([fluorine -18]-fluoro-2-deoxy-D-glucose) • HEAD • 10 min per bed position (one bed position) • Whole Body • 3 min per bed position (6-8 bed positions) • CT • HEAD • Low dose spiral CT (120kV; sw 3mm; p 1.2; r 1s; AEC) • Whole Body • Low dose spiral CT (120kV; sw 5mm; p 1.2; r 0.5s; AEC) • Total imaging time • HEAD • ~11 min • Whole Body • ~30 min

  7. Internal dose calculation: • Absorbed dose DTto a tissueorgan T of activity A of FDG: ГTFDG- ICRP 80 • Overall internall effective doses: WT – ICRP 103

  8. External effective dose was calculated from DLP acording to method proposed by Huda et al. • Overall patient’s effective dose was calculated according to: W. Huda, K.M. Ogden, M.R and M.R. Khorasani, “Converting dose-length product to effective dose at CT” Radiology 2008; 248(3): 995-1003

  9. CT image quality was assesed by radiologiast with ten years of expirience according to five point scale: • 1 unacceptable, • 2 substandard, • 3 acceptable, • 4 above average, • and 5 superior

  10. Effective patient dose and image quality for Hybrid PET/CT imaging AVERAGE min/max

  11. CT Image quality • Head • Rated with maximal score (5) for all exams • Whole Body • mean rate 3.8±0.8 All images were rated as acceptable or better,except in extreme case of oversized patient who was not able to hold arms above head

  12. Potential risk from radiation exposure is important aspect in all medical procedure with ionising radiation • PET/CT offers variety of imaging options with different effective patient doses. It has bean reported that combined dose for PET/CT exams could be up to 32mSv • It also has bean reported that external dose compromise 50-81% of overall patient dose in hybrid PET/CT imaging

  13. Our surveyshows that low dose CT protocols reduces effective patient doses with out compromising CT image quality in majority of the PET/CT exams. • Minimal overall patient dose in our study was ~1.5 of worldwide effective dose from background radiation over 1y [2.4mSv] • Our results shows that using low dose AEC CT protocols external dose could be decreased to ~ 30% of overall patient dose with out compromising CT diagnostic image quality • AEC CT protocols fail to meat criteria of diagnostically acceptable image quality only in extreme case of obese patient who was not able to hold his arm above head.

  14. instead of conclusions • Internal dose depends mainly on administered radiopharmaceutical activity which is related to patient body parameter and posibilities of internal dose reduction for given PET modality and given radiofarmaceutical are relatively small • On the other hand CT offer wide variety of imaging options and optimisations CT protocols considering image quality and patient dose provide a good basis for patient dose reduction in PET/CT procedure

  15. instead of conclusions • Clinical demands for PET/CT diagnostics are increased, especially for nononcological patients • PET/CT scanning is accompanied by substantial radiation dose and as a consequence potential cancer risk. It is general recommendation that any PET/CT examination should be carefully justified prior to any study especially in younger patient. • It is important to fully understood sources of patient doses in PET/CT imaging and to clarify various possibilities of dose reduction in order to rich full diagnostic potential of this complex imaging modality.

  16. Thank you! Novi Sad

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