Value of SPECT/CT in Diagnostic I-131 MIBG Scintigraphy in Patients with Neuroblastoma

Navigating new horizons: Prospects of NET-targeted radiopharmaceuticals in precision medicine

In the evolving landscape of precision medicine, NET-targeted radiopharmaceuticals are emerging as pivotal tools for the diagnosis and treatment of a range of conditions, from heart failure and neurodegenerative disorders to neuroendocrine cancers. This review evaluates the advancements offered by 18F-labeled PET tracers and 211At alpha-particle therapy, juxtaposed with current 123I-MIBG SPECT and 131I-MIBG therapies. The enhanced spatial resolution and capability for quantitative analysis render 18F-labeled PET tracers potential candidates for improved detection and management of diseases. Alpha-particle therapy with 211At may offer increased specificity and tumoricidal efficacy, pointing towards a shift in therapeutic protocols. While preliminary data is promising, these innovative approaches require thorough validation against current modalities. Ongoing clinical trials are pivotal to confirm the expected clinical benefits and to address safety concerns. This review underscores the need for rigorous research to verify the clinical utility of NET-targeted radiopharmaceuticals, which may redefine precision medicine paradigms and significantly impact patient care.

Does the Incremental Value of 123I-Metaiodobenzylguanidine SPECT/CT over Planar Imaging Justify the Increase in Radiation Exposure?

Purpose

Planar scintigraphy with ¹²³I-radiolabeled metaiodobenzylguanidine (¹²³I-mIBG) is an important imaging modality to evaluate neuroblastoma. In recent years, Single Photon Emission Computed Tomography combined with Computed Tomography (SPECT/CT) has revolutionized nuclear medicine. Nevertheless, the addition of the CT has increased the patients' irradiation. We aimed to evaluate the incremental benefits of ¹²³I-mIBG SPECT/CT over conventional planar imaging and to estimate the relative increase of radiation dose.

Methods

We retrospectively evaluated the added value of 56 SPECT/CT performed in 40 children in terms of better characterization of the lesion and its locoregional extension, better lymph node staging, detection of new lesions, and elimination of false positives by a paired comparison between the planar images and the SPECT/CT ones. Then, we calculated the percentage contribution of the additional radiation of the CT in this hybrid imagery.

Results

In 88% (49 out of 56) of the examinations, SPECT/CT provided additional information, which was crucial in 20% of the cases. It allowed a better characterization of the lesion and its locoregional extension in 44 cases, a better lymph node staging in 28 cases, the detection of 33 new lesions, and the elimination of 9 false positives. The CT effective dose was significantly lower than the SPECT one. The average additional radiation exposure due to CT was 12% (4-23%).

Conclusion

¹²³I-mIBG SPECT/CT has an undeniable added value that improves planar imaging interpretation and impacts patient management. These potential benefits would justify the low additional radiation induced by the CT.

Evaluation of Iodine-123 and Iodine-131 SPECT activity quantification: a Monte Carlo study

Purpose

The quantitative accuracy of Nuclear Medicine images, acquired for both planar and SPECT studies, is influenced by the isotope-collimator combination as well as image corrections incorporated in the iterative reconstruction process. These factors can be investigated and optimised using Monte Carlo simulations. This study aimed to evaluate SPECT quantification accuracy for ¹²³I with both the low-energy high resolution (LEHR) and medium-energy (ME) collimators and ¹³¹I with the high-energy (HE) collimator.

Methods

Simulated SPECT projection images were reconstructed using the OS-EM iterative algorithm, which was optimised for the number of updates, with appropriate corrections for scatter, attenuation and collimator detector response (CDR), including septal scatter and penetration compensation. An appropriate calibration factor (CF) was determined from four different source geometries (activity-filled: water-filled cylindrical phantom, sphere in water-filled (cold) cylindrical phantom, sphere in air and point-like source), investigated with different volume of interest (VOI) diameters. Recovery curves were constructed from recovery coefficients to correct for partial volume effects (PVEs). The quantitative method was evaluated for spheres in voxel-based digital cylindrical and patient phantoms.

Results

The optimal number of OS-EM updates was 60 for all isotope-collimator combinations. The CF_point with a VOI diameter equal to the physical size plus a 3.0-cm margin was selected, for all isotope-collimator geometries. The spheres’ quantification errors in the voxel-based digital cylindrical and patient phantoms were less than 3.2% and 5.4%, respectively, for all isotope-collimator combinations.

Conclusion

The study showed that quantification errors of less than 6.0% could be attained, for all isotope-collimator combinations, if corrections for; scatter, attenuation, CDR (including septal scatter and penetration) and PVEs are performed. ¹²³I LEHR and ¹²³I ME quantification accuracies compared well when appropriate corrections for septal scatter and penetration were applied. This can be useful in departments that perform ¹²³I studies and may not have access to ME collimators.

Comparison of the detecting capability between 123I-mIBG and post-therapeutic 131I-mIBG scintigraphy for curie scoring in patients with neuroblastoma after chemotherapy

OBJECTIVE

To evaluate the detecting capability between planar imaging (PI) and PI combined with single-photon emission computed tomography/computed tomography (PICWS), including 123I- and 131I-labeled metaiodobenzylguanidine (mIBG) and to compare the detecting capability between 123I-mIBG and post-therapeutic 131I-mIBG scintigraphy including PI and PICWS for Curie scoring in patients with neuroblastoma.

METHODS

Sixty-two patients with 66 pairs of complete images with neuroblastoma were enrolled in this retrospective study.

RESULTS

Comparing the Curie scoring between 123I-mIBG PI and PICWS and between post-therapeutic 131I-mIBG PI and PICWS, findings were concordantly negative in 28.79% and 18.18% of studies, concordantly positive in 66.67% and 74.24% of studies, and discordant in 4.54% and 7.58% of studies, respectively. PICWS was superior to PI including 123I- and 131I-mIBG in the evaluation of Curie scoring for neuroblastoma patients (both P < 0.001). Comparing the Curie scores between 123I- and post-therapeutic 131I-mIBG PI and between 123I- and post-therapeutic 131I-mIBG PICWS, concordantly negative imaging was visualized in 22.73% and 19.70% of studies, concordantly positive imaging in 66.67% and 69.70% of studies, and discordant imaging in 10.60% and 10.60% of studies, respectively. Post-therapeutic 131I-mIBG was significantly better than that of 123I-mIBG scintigraphy including PI and PICWS in detecting the Curie scoring for neuroblastoma patients (both P < 0.001).

CONCLUSION

The present study demonstrates that 131I- or 123I-mIBG PICWS are more helpful in the evaluation of Curie scores than that of conventional PI and that post-therapeutic 131I-mIBG is superior to 123I-mIBG scintigraphy for the detecting capability of Curie scoring in patients with neuroblastoma.

Renal Metastasis From Neuroblastoma Shown on MIBG Imaging

A 6-year-old girl with high-risk neuroblastoma underwent a I-MIBG scan to monitor the disease status. In addition to the known lesion in the right retroperitoneal region, there were additional foci of increased activity in the right upper quadrate of the abdomen, which were not typical bowel activity. SPECT/CT images located the activity in the cortex of the lower pole of the right kidney, which was partially calcified. Subsequent biopsy confirmed neuroblastoma metastasis to the right kidney, which is extremely rare.