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Indian J Nucl Med
Indian J Nucl Med
IJNM
Indian J Nucl Med
Indian Journal of Nuclear Medicine : IJNM : The Official Journal of the Society of Nuclear Medicine, India
0972-3919
0974-0244
Wolters Kluwer - Medknow India

IJNM-39-237
10.4103/ijnm.ijnm_16_23
Letter to the Editor
Tc-99m UBI Scintigraphy as a Cost-effective Alternative to Ga-68 NOTA-UBI PET/CT for Imaging Infections
Maurya Satya Dev
Ballal Sanjana
Damle Nishikant Avinash
Tiwari Varsha
Bal Chandra Sekhar
Department of Nuclear Medicine, AIIMS, New Delhi, India
Address for correspondence: Dr. Nishikant Avinash Damle, Department of Nuclear Medicine, AIIMS, New Delhi, India. E-mail: nishikantavinash@gmail.com
May-Jun 2024
17 8 2024
39 3 237238
02 2 2023
01 4 2024
12 4 2024
Copyright: © 2024 Indian Journal of Nuclear Medicine
2024
https://creativecommons.org/licenses/by-nc-sa/4.0/ This is an open access journal, and articles are distributed under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike 4.0 License, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms.
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pmcSir,

Ubiquicidin (UBI) is an antimicrobial peptide with great potential for imaging infectious diseases. UBI can be labeled with 99mTc and 68Ga, with NOTA acting as a bifunctional chelator for the latter.[12]

For 68Ga labeling, NOTA-UBI was labeled with 68Ga. We adapted the method described by Ebenhan et al.[3] and standardized the procedure for our department. For 99mTc labeling, UBI was labeled with 99mTc by a reduction method adapted from the method described by Arjun et al.[4] and standardized for our department.

The results of 99mTc-UBI showed a labeling efficiency of 97.46 ± 1.06 (n = 25) in both mobile solvents, namely, saline and 5% HCl in methanol. Further, 68Ga-NOTA-UBI was also successfully labeled with a labeling efficiency of 98.25% ±1.32% (n = 4) in sodium citrate as mobile solvents. UBI labeling with 68Ga, and 99mTc resulted in a clear and colorless solution with pH of 5 and 6, respectively. For labeling 99mTc-UBI, heating was not required. However, 68Ga-NOTA-UBI labeling required heating at 90°C for 15 min. 68Ga-NOTA-UBI synthesis took a lesser time (18.15 ± 1.3 min) than the synthesis of 99mTc-UBI (29.36 ± 3.84 min). 99mTc-UBI and 68Ga-NOTA-UBI showed similar biodistribution in patients with suspected periprosthetic infection and satisfactory target to the nontarget ratio in true positive cases (one representative case each is shown) [Figure 1]. The cost of NOTA-UBI peptide was approximately Indian rupees 400,000/20 mg, thus allowing us to perform a theoretical maximum of 80 studies (250 μg/patient). However, our subsequent few studies revealed good biodistribution with 150 μg of the peptide too, keeping a patient injected activity of 4 mCi; thus, the theoretical maximum cases could be about 130 cases. Even then, the cost of the peptide per patient came out to be approximately Rs. 3000.[5] The cost of UBI peptide for 99mTc labeling was approximately Rs. 94,000/20 mg from which theoretically 400 syntheses can be done (50 μg/patient).[6] Thus, the cost of peptide per patient was approximately Rs. 3000 in NOTA-UBI and Rs. 230 in 99mTc-UBI studies. 99mTc-UBI and 68Ga-NOTA-UBI had similar biodistribution and depicted infection. 99mTc-UBI requires a gamma camera setup and can be synthesized in-house as per requirement, whereas positron emission tomography (PET)/computed tomography (CT) facility and 68Ge/68Ga generator are requirements for 68Ga-NOTA-UBI imaging. Overall, comparable labeling efficiency, similar biodistribution, satisfactory positive results, and cheap, ready availability make 99mTc-UBI scintigraphy a practically useful imaging modality with a good cost-to-benefit ratio compared to 68Ga-NOTA-UBI PET, especially in the setting of limited resources. A prospective study with an adequate sample size is needed to establish our early results in comparing the two tracers.

Figure 1 (a) 68Ga-NOTA-ubiquicidin (UBI) whole-body positron emission tomography (metallic implants) image at 1 h, A 25-year-old man with a history of right nonunion humerus shaft fracture and operated multiple times (metallic implants). Tracer uptake was noted in the region of the mid-shaft of the right humerus with nonunion of the proximal and distal fragment with intervening tracer avid soft tissue (Blue arrow). 99mTc-ubiquicidin anterior, (b) 99mTc-UBI anterior whole-body images at 1h, and posterior, (c) 99mTc-UBI posterior whole-body images at 1 h, whole-body images at 1 h diffuse radiotracer uptake is seen in the lower one-third of the left arm reaching up to the elbow joint (peri-implant infection at the lower one-third left arm) in the above images (Black arrow)

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship

This study was financially supported by ICMR, New Delhi.

Conflicts of interest

There are no conflicts of interest.

Acknowledgment

This study was funded by the ITR division, ICMR, New Delhi.
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1 Hiemstra PS van den Barselaar MT Roest M Nibbering PH van Furth R Ubiquicidin, a novel murine microbicidal protein present in the cytosolic fraction of macrophages J Leukoc Biol 1999 66 423 8 10496312
2 Lepareur N Cold Kit Labeling: The future of 68Ga radiopharmaceuticals? Front Med (Lausanne) 2022 9 812050 35223907
3 Ebenhan T Sathekge MM Lengana T Koole M Gheysens O Govender T 68Ga-NOTA-functionalized ubiquicidin: Cytotoxicity, biodistribution, radiation dosimetry, and first-in-human PET/CT imaging of infections J Nucl Med 2018 59 334 9 29051342
4 Arjun C Mukherjee A Bhatt J Chaudhari P Repaka KM Venkatesh M Studies on batch formulation of a kit for the preparation of the 99mTc-ubiquicidin (29-41): An infection imaging agent Appl Radiat Isot 2016 107 8 12 26405838
5 Vilche M Reyes AL Vasilskis E Oliver P Balter H Engler H 68Ga-NOTA-UBI-29-41 as a PET tracer for detection of bacterial infection J Nucl Med 2016 57 622 7 26769861
6 Gandomkar M Najafi R Shafiei M Mazidi M Goudarzi M Mirfallah SH Clinical evaluation of antimicrobial peptide [(99m) Tc/Tricine/HYNIC(0)]ubiquicidin 29-41 as a human-specific infection imaging agent Nucl Med Biol 2009 36 199 205 19217532
