# Technetium Tc-99m PSMA agents (PSMA-I&S)

Source: https://nuclide.cc/drugs/tc-99m-psma-imaging/  
Nuclide record `tc-99m-psma-imaging` (Agent). Data CC BY-NC 4.0, attribute "Data from Nuclide (nuclide.cc)"; commercial use needs a licence.

## TL;DR

A version of the PSMA prostate cancer scan that uses the same cheap, widely available radioactive tag as a standard bone scan instead of the PET tracers. Surgeons can also carry a small radiation detector into the operating room to help find and remove cancerous lymph nodes. It has not been through formal drug approval; it is used as an academic, in-house preparation.

## Summary

99mTc-PSMA-I&S ([99mTc]Tc-mas3-y-nal-k(Sub-KuE)) was developed at the Technical University of Munich as a cost-effective, kit-based alternative to 111In-PSMA-I&T for PSMA-targeted radioguided surgery, first reported in the Journal of Nuclear Medicine in 2017. In that first-in-human report, preoperative SPECT/CT at 12 hours after injection showed high uptake in all lesions previously identified by 68Ga-PSMA-11 PET/MR, and a handheld gamma probe successfully guided intraoperative resection of metastatic lymph nodes down to 3 mm.

Beyond radioguided surgery, retrospective single-centre series have used PSMA-I&S SPECT/CT as a stand-alone diagnostic tool: one series reported patient-based sensitivity, specificity and accuracy of 86%, 100% and 92% for detecting primary prostate cancer, and for restaging in biochemical recurrence, sensitivity of 67% with specificity of 100%, generally trailing PSMA-PET's reported sensitivity in the low-PSA setting but offering same-day, low-cost imaging with equipment most nuclear medicine departments already own. Because it is produced from an academic cold-kit under local institutional protocols rather than an FDA- or EMA-reviewed marketing application, it has no formal regulatory approval or labelled dose; reported clinical activities have ranged from roughly 500-700 MBq for combined SPECT-and-surgery protocols.

## Fields

- Kind: Agent
- Status: emerging
- Last checked: 2026-09-22
- Also known as: 99mTc-PSMA-I&S; Tc-99m PSMA imaging and surgery
- Tags: PSMA; SPECT; radioguided surgery; academic cold kit
- Modality: SPECT tracer
- Mechanism: PSMA-I&S ("imaging and surgery") is a urea-based small-molecule PSMA inhibitor labelled with technetium-99m via a MAS3 chelator. It binds prostate-specific membrane antigen on prostate cancer cells; because technetium-99m is a gamma emitter available from any hospital's own generator (unlike gallium-68 or fluorine-18, which need a generator or cyclotron dedicated to PET production), it can be used both for pre-operative SPECT/CT localisation and, with a handheld gamma probe, for intraoperative radioguided surgery.

## Sources

- Robu et al., J Nucl Med 2017: preclinical evaluation and first patient application of 99mTc-PSMA-I&S for SPECT imaging and radioguided surgery in prostate cancer: https://jnm.snmjournals.org/content/58/2/235.full.pdf
- Diagnostic value of 99mTc-PSMA-I&S SPECT/CT for prostate cancer detection and staging (2024): https://pmc.ncbi.nlm.nih.gov/articles/PMC10798073/

## Connected records

- drugs: [Copper-64 SAR-bisPSMA](https://nuclide.cc/drugs/cu-64-sar-bispsma/), [Indium-111 pentetreotide](https://nuclide.cc/drugs/in-111-pentetreotide/)
- isotopes: [Gallium-68](https://nuclide.cc/isotopes/ga-68/), [Indium-111](https://nuclide.cc/isotopes/in-111/), [Technetium-99m](https://nuclide.cc/isotopes/tc-99m/)
- indications: [Biochemical recurrence of prostate cancer](https://nuclide.cc/indications/prostate-bcr/), [Prostate cancer](https://nuclide.cc/indications/prostate/)
- technologies: [SPECT & bone scan](https://nuclide.cc/technologies/spect/), [SPECT/CT](https://nuclide.cc/technologies/spect-ct/)
- targets: [PSMA](https://nuclide.cc/targets/psma/)

---
JSON: https://nuclide.cc/api/v1/entities/tc-99m-psma-imaging.json