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The Usefulness of Q.Clear Technique in PET / CT

Yong Hoon Choi, Jung Yul Kim, Young Sook Choi, Han Sang Lim and Jae Sam Kim
Department of Nuclear Medicine, Severance Hospital, Yonsei University Health System, Seoul, Korea

Purpose

Recently, the performance of PET/CT scanner has been improved and various techniques have been developed to increase the image quality such as Sensitivity and Resolution. The purpose of this study is to evaluate the usefulness of Q.Clear (a fully convergent iterative reconstruction) technique of GE Discovery IQ equipment to enhance the image quality.

Materials and methods

All scans were acquired by Discovery IQ (GE Healthcare, MI, USA). In NEMA IEC Body Phantom test, Background to Hot-sphere (10 mm, 13 mm, 17 mm, 22 mm) ratio was 1:4 and scan time was 3 minutes. The images were reconstructed by VPHDs (VUE Point High-Definition + SharpIR) and Q.Clear to evaluate each Contrast. We injected 18F-FDG 187 MB to PET/SPECT Performance Phantom. And then it was scanned for 4 minutes to evaluate Resolution and Uniformity. T-test statistical analysis was performed on SUVmax of small lesions less than 2 cm in 100 clinical patients regardless of disease type.

Results

In the NEMA IEC Body Phantom, the Contrast was 63.6 ± 5.7% (VPHDs) and 75 ± 4.8% (Q.Clear). In the PET/SPECT Performance Phantom, the Resolution was 9.2 mm (VPHDs) and 7.3 mm (Q.Clear). Uniformity of Q.Clear was 10.8% better than VPHDs. T-test statistic of the clinical patients showed a significant difference of p value of 0.021.

Conclusion

Both the phantom test and the clinical results showed that the quality of the image was improved in Q.Clear was applied. The SUVmax was highly measured in Q.Clear and the lesions were clearly distinguished visually. Therefore Q.Clear can be useful in various aspects such as dose-reduction, patients evaluation and image analysis.

*Key Words: Q.Clear, VPHDs, SUVmax

 

Metal artifact Standardized Uptake Value estimation by using attenuation correction image and non attenuation correction image in PET-CT

June Kim, Jae-II Kim, Hong-Jae Lee and Jin-Eui Kim
Department of Nuclear Medicine, Seoul National University Hospital, Seoul, Korea

Purpose

Because of many advantages, PET-CT Scanners generally use CT image for attenuation correction. By using CT based attenuation correction, we can get anatomical information, reduce scan time and make more accurate correction of attenuation. However, in case metal artifact occurred during CT scan, CT-based attenuation correction may induce artifacts and quantitative errors that can affect the PET images. Therefore, the purpose of this study is to infer true SUV (Standardized Uptake Value) of metal artifact region from ratio of attenuation corrected image count to non attenuation corrected image count.

Materials and Methods

Micro phantom which inserted 18F- FDG 4mCi was used for phantom test and Biograph mCT S(40) was used for medical test equipment. We generated metal artifact at micro phantom by using metal. Then we figured out both correction factors of metal artifact region and non metal artifact region, by using ratio of attenuation correction image count to non attenuation correction image count. In case of clinical image, we reconstructed both attenuation corrected image and non attenuation corrected image of 10 normal patient(66±15age) who examined PET-CT scan in Seoul National University Hospital. Then, we standardized correction factor of several organs by using ratio of attenuation corrected image count to non attenuation corrected count. After that, we figured out correction factor of metal artifact region by using ratio of metal artifact region of attenuation corrected image count to non attenuation corrected count And we compared correction factor of several organs with correction factor of metal artifact region. Results: Phantom test results show that the metal artifact region correction factor is 12% bigger than the non-metal artifact region correction factor because metal artifacts cause an overestimate of the correction factor. In case of clinical test, correction factors of organs with high CT number(>1000) are 8±0.5%, correction factors of organs with CT number similar to soft tissue are 6±2% and correction factors of organs with low CT number(-100>) are 3±1%. Also correction factors of metal artifact are 20% bigger than correction factors of soft tissue which didn`t happened metal artifact.

Conclusion

Metal artifact lead to overestimation of attenuation coefficient. As a result, SUV in the metal artifact region is overestimated. Thus for more accurate quantitative evaluation, using a ratio of attenuation correction image count to non attenuation correction image count is one of the methods to reduce metal artifact affect

[keyword] PET/CT, CT attenuation correction, metal artifact, 18F-FDG

Corresponding author: June Kim
Department of Nuclear Medicine, Seoul National University Hospital
101 Daehang-ro, Jongno-gu, Seoul, 110-744, Korea
Tel: +82-2-2072-3937, Fax:
E-mail: pass852@hanmail.net

 

The effect of PET scan time on the offline PET image quality in proton therapy

Gun Chul Hong, Joon Yung Jang2, Se Joon Park2, Eun Sun Cha, Hyuk Lee
Department of Nuclear Medicine, Samsung Medical Center
2 Department of Radiation Oncology, Samsung Medical Center

Purpose: Proton therapy can deliver an optimal dose to tumor while reducing unnecessary dose to normal tissue as compared to the conventional photon therapy. As proton beams are irradiated into tissue, various positron emitters are produced via nuclear fragmentation reactions. These positron emitters could be used for the dose verification by using PET. However, the short half-life of the radioisotopes makes it hard to obtain the enough amounts of events. The aim of this study is to investigate the effect of off-line PET imaging scan time on the PET image quality.
Objectives and method: The various diameters of spheres (D=37, 28, 22 mm) filled with distilled water were inserted in a 2001 IEC body phantom. Then proton beams (100 MU) were irradiated into the center of the each sphere using the wobbling technique with the gantry angle of 0°. The modulation widths of the spread out Bragg peak (SOBP) were 16.4, 14.7, and 9.3 cm for the spheres of 37, 28, and 22 mm in diameters respectively. After 5 min of the proton irradiation, the PET/CT images of the IEC body phantom were obtained for 50 min. The PET images with different time courses (0~10 min, 11~20 min, 21~30 min, 31~40 min, and 41~50 min) were obtained by dividing the frame with a duration of 10 min. In order to evaluate the off-line PET image quality with the different time courses, the contrast-to-noise ratio (CNR) of the PET image calculated for each sphere.
Results: The CNRs of the sphere (D=37 mm) were 0.43, 0.42, 0.40, 0.31, and 0.21 for the time courses of 0~10 min, 11~20 min, 21~30 min, 31~40 min, and 41~50 min respectively. The CNRs of the sphere (D=28 mm) were 0.36, 0.32, 0.27, 0.19, and 0.09 for the time courses of 0~10 min, 11~20 min, 21~30 min, 31~40 min, and 41~50 min respectively. The CNR of 37 mm sphere was decreased rapidly after 30 min of the proton irradiation. In case of the spheres of 28 mm and 22 mm, the CNR was decreased drastically after 20 min of the irradiation.
Conclusion: The off-line PET imaging time is an important factor for the monitoring of the proton therapy. In case of the lesion diameter of 22 mm, the off-line PET image should be obtained within 25 min after the proton irradiation. When it comes to small size of tumor, the long PET imaging time will be beneficial for the proton therapy treatment monitoring.

 

Effect of the Angle of Ventricular Septal Wall on Left Anterior Oblique View in Multi-Gated Cardiac Blood Pool Scan

Yeon Wook You, Woo Jae Won, Ji-In Bang and Tae-Sung Kim
Department of Nuclear Medicine and Research Institute, National Cancer Center, Korea

Purpose

In order to calculate the left ventricular ejection fraction (LVEF) accurately, it is important to acquire the best septal view of left ventricle in the multi-gated cardiac blood pool scan (GBP). This study aims to acquire the best septal view by measuring angle of ventricular septal wall (θ) using enhanced CT scan and compare with conventional method using left anterior oblique (LAO) 45 view.

Subjects and Methods

From March to July in 2015, we analyzed the 253 patients who underwent both enhanced chest CT and GBP scan in the department of nuclear medicine at National Cancer Center. Angle (θ) between ventricular septum and imaginary midline was measured in transverse image of enhanced chest CT scan, and the patients whose difference between the angle of θ and 45 degree was more than 10 degrees were included. GBP scan was acquired using both LAO 45 and LAO θ views, and LVEFs measured by automated and manual region of interest (Auto-ROI and Manual-ROI) modes respectively were analyzed.

Results

Mean ± SD of θ on total 253 patients was 37.0 ± 8.5°. Among them, the patients whose difference between 45 and θ degrees were more than ± 10 degrees were 88 patients (29.3 ± 6.1°). In Auto-ROI mode, there was statistically significant difference between LAO 45 and LAO θ (LVEF 45 = 62.0 ± 6.6% vs. LVEF θ = 64.0 ± 5.6%; P = 0.001). In Manual-ROI mode, there was also statistically significant difference between LAO 45 and LAO θ (LVEF 45 = 66.7 ± 7.2% vs. LVEF θ = 69.0 ± 6.4%; P < 0.001). Intraclass correlation coefficients of both methods were more than 95%. In case of comparison between Auto-ROI and Manual ROI of each LAO 45 and LAO θ, there was no significant difference statistically.

Conclusion

We could measure the angle of ventricular septal wall accurately by using transverse image of enhanced chest CT and applied to LAO acquisition in the GBP scan. It might be the alternative method to acquire the best septal view of LAO effectively. We could notify significant difference between conventional LAO 45 and LAO θ view.

Key Words : Multi-gated cardiac blood pool scan (GBP), left anterior oblique (LAO),
ventricular septal wall, left ventricular ejection fraction (LVEF)

 

Comparison of administered activities  with DRLs 2015 Japan in nuclear medicine examination

Masashi Shimizu, Kazunori Saruwatari, Syogo Kojima, Minoru Tanaka
Department of Radiology, Fukuoka University Hospital, Fukuoka, Japan

Purpose

The optimization of radiation dose in radiological examinations is significantly important. Recently, the report for diagnostic reference levels in Japan, called Japan DRLs 2015, was published. The purpose of this study was to investigate administered radiopharmaceutical activities in nuclear medicine examination for a year and compared with Japan DRLs2015 in our hospital.

Materials and Method

We investigated administrated activities using radiological information system (RIS) for a year (April 1, 2016, to March 31, 2017). The data included radiopharmaceutical administered activities and injection time was recorded for RIS. The administered activities were calculated from the assay activities and injection time. Then, we compared the administered activities with Japan DRLs 2015.

Result

We compared the administered activities to Japan DRLs 2015. Almost the administered activities satisfied the DRLs; although, 95% examinations of bone scintigraphy and 87% dopamine transporter scintigraphy were not satisfied the DRLs. The examinations which could not satisfy the DRLs were administered the radiopharmaceuticals in the early morning.

Conclusion

We recorded the administered activities in nuclear medicine examinations for a year. Except for examinations of bone scintigraphy and dopamine transporter scintigraphy, we could achieve Japan DRLs 2015. Therefore, we consider reducing the administered activities about examinations of bone scintigraphy and dopamine transporter scintigraphy.

Key Words: DRLs, administrated activity

 

Non-invasive automatic radiography quantitative measurement method by using 123I-IMP (SIARG) for evaluation of regional cerebrovascular reactivity

Taeko Tomimatsu1, Daichi Koreeda1, Asato Ofuji1, Hiroki Ohura2, Akihiro Takaki3, Shigeki Ito4

1Graduate School of Health Sciences, Kumamoto University,
2National Organization Saga Hospital, 3Teikyo University,
4Faculty of Life Sciences, Kumamoto University.

Purpose

It is well established that the evaluation of regional cerebrovascular reactivity (rCVR) in response to a cerebral vasodilatory stimulus by acetazolamide (ACZ) loading is useful to stratify patients with ischemic cerebrovascular disease. We have developed the simple non-invasive I-123-N-isopropyl-p-iodoamphetamine (123I-IMP) autoradiography method (SIARG method). However the accuracy of SIARG method in high flow range after ACZ loading remains to be seen. To improve the feasibility of SIARG method, we investigated whether SIARG method could predict rCVR in the high flow range after ACZ loading.

Materials and Methods

The rCVR values were obtained by the split dose method of microsphere model in 30 patients. SIARG method and the one-point arterial blood sampling autoradiography (ARG) method for reference were simultaneously performed in each patient. All SPECT images were analyzed using a 3-dimensional stereotaxic ROI template (3DSRT) on anatomically standardized CBF SPECT images to objectively estimate the regional cerebral blood flow (rCBF). The rCBF values were defined as mean values of each segment. rCVR to ACZ loading was calculated as follows: rCVR(%)= ((ACZ rCBF – resting rCBF)/ resting rCBF)×100.

Results

The rCVR values obtained by SIARG method increased linearly as those obtained by ARG method increased. A good correlation was observed between the rCVR values obtained by the SIARG method and those obtained by the ARG method (r=0.88, p<0.001).

Conclusion

SIARG method predicted rCVR to ACZ loading reasonably well. Thus SIARG method is clinically useful for the evaluation of rCVR in patients with ischemic cerebrovascular disease.

Key Words:
Non-invasive autoradiography method, High flow range, Ischemic cerebrovascular disease

 

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