Advantages and Challenges of Total-Body PET/CT at a Tertiary Cancer Center: Insights from Sun Yat-sen University Cancer Center

Wanqi Chen; Yinghe Li; Zhijian Li; Yongluo Jiang; Yingpu Cui; Jiling Zeng; Yiwen Mo; Si Tang; Shatong Li; Lei Liu; Yumo Zhao; Yingying Hu; Wei Fan

doi:10.2967/jnumed.123.266948

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FIGURE 1.
Application of total-body PET/CT at SYSUCC. (A) Disease distribution. (B) Age distribution. (C) Disease stage distribution. (D) Disease distribution in pediatric patients younger than 15 y. Others = nononcologic patients or patients who have not yet been followed up.
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FIGURE 2.
Selection of PET/CT devices according to patients’ medical conditions at SYSUCC.
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FIGURE 3.
Example of total-body PET scan with one-fifth dose of ¹⁸F-FDG (0.79 MBq/kg) activity. Thirteen-year-old boy diagnosed with relapsed anaplastic lymphoma kinase-positive anaplastic large cell lymphoma underwent ninth PET/CT examination for follow-up after chemotherapy. Slight radiotracer uptake of inflammatory lymph node in right neck (arrow) is shown. Axial PET image of liver displays good background quality.
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FIGURE 4.
Comparison of image quality between CT-Dx and LDCT combined with different ¹⁸F-FDG injection doses. Five-year-old boy diagnosed with B-cell lymphoblastic leukemia underwent complete remission after systemic chemotherapy. Total-body PET/CT examinations were performed during 2-y follow-up. One-half dose of ¹⁸F-FDG (1.85 MBq/kg) combined with reduced CT dose was used for latter examination (right) to minimize radiation exposure. Representative CT images, axial PET images, and fused PET/CT images of liver show diagnostic and staging efficacy is not compromised. CT-Dx = diagnostic CT scan with higher x-ray dose; LDCT = low-dose CT.
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FIGURE 5.
Advantages of full-body coverage using ¹⁸F-FDG (3.7 MBq/kg) total-body PET/CT. (A) PET images of 32-y-old man diagnosed with right pelvic melanoma and lymph nodal metastases. Arrowheads indicate venous thrombosis within right leg veins. (B) 65-y-old man with malignant melanoma. Diagnostic accuracy of total-body PET was confirmed by extensive detection of cutaneous primary lesion and lymph node metastases throughout entire body. (C) 9-y-old girl with lymphoma revealed by biopsy of left orbital mass. Total-body PET image shows lymph, cutaneous, and bone involvement. (D) 3-y-old child diagnosed with B lymphoblastic lymphoma. Multiple masses in liver, spleen, and kidney with multisystem invasion, including lymph nodes and focal distal bones, were detected.
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FIGURE 6.
Example of intraindividual comparison of ¹⁸F-FDG (3.7 MBq/kg) total-body PET (left) and conventional PET (right) images in lung cancer patient with liver and bone metastases. Axial PET images of total-body PET scans revealed 4 lesions in liver (arrows) that were barely recognizable in conventional PET/CT scans, because radiotracer uptake of liver lesions was similar to physiologic liver background.
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FIGURE 7.
Example of retroperitoneal small lymph nodes posing challenges for diagnosis. Fifty-five-year-old woman with surgically removed cervical cancer was referred for ¹⁸F-FDG (3.7 MBq/kg) total-body PET/CT scan. Axial PET images and fused PET/CT images display paraaortic small lymph nodes (arrowheads) with higher ¹⁸F-FDG uptake (SUV_max, 6.5) than physiologic background.

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TABLE 1.

Key Parameters of Total-Body PET/CT Acquisition Protocols at SYSUCC

				CT-AC parameters		CT-Dx parameters			Reconstruction parameters of PET
Age	Protocol	Dose (MBq/kg)	Time (min)	Tube voltage (kV)	Fixed tube (mAs)	Tube voltage (kV)	Ref.mAs of TCM (mAs)	Rotation time (s)	Iterations	Subsets	Matrix	FOV (mm)
>20 y, torso or TB routine	Torso routine	3.70	5	120	10	120	80	0.5	3	20	256 × 256	600
	Torso NPC	3.70	3	120	5	120	80	0.5	2	20	256 × 256	600
	TB routine	1.85	8	NA	NA	120	120	0.5	3	20	256 × 256	600
	TB NPC	1.85	6	NA	NA	120	120	0.5	3	20	256 × 256	600
≤20 y, TB routine only	0- to 4-y nonlymphoma	1.85	10	NA	NA	100	75	0.3	3	20	512 × 512	600
	0- to 4-y lymphoma	1.85	10	NA	NA	100	70	0.3	3	20	512 × 512	600
	0- to 4-y lymphoma follow-up	1.85	10	NA	NA	100	55	0.3	3	20	512 × 512	600
	4- to 7-y nonlymphoma	1.85	10	NA	NA	100	80	0.3	3	20	512 × 512	600
	4- to 7-y lymphoma	1.85	10	NA	NA	100	70	0.3	3	20	512 × 512	600
	4- to 7-y lymphoma follow-up	1.85	10	NA	NA	100	60	0.3	3	20	512 × 512	600
	7- to 15-y nonlymphoma	1.85	10	NA	NA	120	60	0.3	3	20	512 × 512	600
	7- to 15-y lymphoma	1.85	10	NA	NA	120	55	0.3	3	20	512 × 512	600
	7- to 15-y lymphoma follow-up	1.85	10	NA	NA	120	50	0.3	3	20	512 × 512	600
	15- to 20-y nonlymphoma	3.70	6	NA	NA	120	65	0.5	3	20	360 × 360	600
	15- to 20-y lymphoma	3.70	6	NA	NA	120	60	0.5	3	20	360 × 360	600
	15- to 20-y lymphoma follow-up	3.70	6	NA	NA	120	55	0.5	3	20	360 × 360	600
	>45-kg nonlymphoma	3.70/1.85	6/10	NA	NA	120	60	0.5	3	20	256 × 256	600
	>45-kg lymphoma	3.70/1.85	6/10	NA	NA	120	50	0.5	3	20	256 × 256	600
	>45-kg lymphoma follow-up	3.70/1.85	6/10	NA	NA	120	40	0.5	3	20	256 × 256	600

CT-AC = low-dose CT scan for attenuation correction; CT-Dx = diagnostic CT scan with higher x-ray dose; Ref.mAs = reference milliampere·seconds; TCM = tube current modulation; FOV = field of view; TB = total body; NA = not applicable.
For patients >45 kg, injection dose is based on age (1.85 MBq/kg applied for pediatric patients younger than 15 y and 3.70 MBq/kg for patients from 15- to 20-y old).

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TABLE 2.

Clinical Studies Exploring Low-Dose Injection Activity of ¹⁸F-FDG Using Total-Body PET/CT

Year	Author	Patients (n)	Population	Disease	Injection dose	Conclusion
2022	Chen et al. (12)	100	Pediatric patients	Oncology	Half dose (1.85 MBq/kg)	Sufficient image quality and lesion conspicuity could be maintained at fast acquisition time of 1 min with half-dose activity of ¹⁸F-FDG
2022	He et al. (17)	46	Adults	Oncology	Half dose (1.85 MBq/kg)	Half dose of ¹⁸F-FDG with acquisition times ≥ 5 min could be applied in clinical practice
2021	Tan et al. (13)	56	Adults	Lung cancer	Half dose (1.85 MBq/kg)	Total-body PET/CT with half dose of ¹⁸F-FDG in 2 and 4 min achieved comparable image quality to conventional PET/CT
2022	Hu et al. (18)	30	Adults	Oncology	Ultralow dose (0.37 MBq/kg)	Ultralow ¹⁸F-FDG activity with 8-min acquisition in total-body PET/CT can achieve acceptable image quality equivalent to that in full-activity group after 2-min acquisition
2022	Abdelhafez et al. (54)	30	Adults	AIA	Ultralow dose (78.1 ± 4.7 MBq)	Systemic joint evaluation in AIA (and non-AIA) is feasible with total-body PET/CT and ultra-low-dose ¹⁸F-FDG protocol
2022	Tan et al. (55)	62	Adults	CRC	Ultralow dose (0.37 MBq/kg)	Total-body PET/CT with ultralow dose of ¹⁸F-FDG can maintain satisfactory image quality and lesion detectability in CRC
2023	Tan et al. (56)	30	Adults	Oncology	Ultralow dose (0.37 MBq/kg) vs. half dose (1.85 MBq/kg)	Total-body PET/CT with ultra-low-dose activity of ¹⁸F-FDG, corresponding acquisition time of 8 min, provides acceptable image quality and lesion detection