123I-IMP SPET in the diagnosis of primary central nervous system lymphoma

Usefulness of dual isotope 123I-IMP and 201Tl SPECT for the diagnosis of primary central nervous system lymphoma and glioblastoma

BACKGROUND

Preoperative differential diagnosis between primary central nervous system lymphoma (PCNSL) and glioblastoma (GBM) is important because these tumors require different surgical strategies. This study investigated the usefulness of dual isotope, iodine-123-labeled N-isopropyl-p-iodo-amphetamine (¹²³I-IMP) and thallium-201 chloride single-photon emission computed tomography (²⁰¹Tl SPECT) for the differential diagnosis.

METHODS

Twenty-five PCNSL patients and 27 GBM patients who underwent dual isotope imaging, ¹²³I-IMP and ²⁰¹Tl SPECT, are included. Tumor-to-normal (T/N) ratio was calculated from the ratio of maximum tracer counts in the lesion to the mean counts in the contralateral cerebral cortex. The mean and minimum apparent diffusion coefficient values (ADC_mean and ADC_min, respectively) on magnetic resonance imaging were also analyzed.

RESULTS

Delayed phase ¹²³I-IMP SPECT was the most useful imaging examination for the differentiation between PCNSL and GBM compared with early phase ¹²³I-IMP SPECT, early and delayed phase ²⁰¹Tl SPECT, ADC_mean, and ADC_min. However, the median T/N ratios of PCNSL and GBM were 1.32 and 0.83, respectively, in the delayed phase ¹²³I-IMP SPECT. On the other hand, the median T/N ratios of PCNSL and GBM were 3.10 and 2.34, respectively, in the delayed phase ²⁰¹Tl SPECT, with excellent tumor detection.

CONCLUSION

Delayed phase ¹²³I-IMP SPECT could differentiate between PCNSL and GBM with high accuracy, but T/N ratio was low and tumor detection was poor. ²⁰¹Tl SPECT was useful for estimation of the malignancy and localization of the tumors with high T/N ratio. Dual isotope ¹²³I-IMP and ²⁰¹Tl SPECT was useful for the preoperative diagnosis of PCNSL and GBM.

The diagnostic value of 123I-IMP SPECT in ocular adnexal lymphoma

BACKGROUND

N-isopropyl- (¹²³I) p-iodoamphetamine (¹²³I-IMP) is specifically accumulated in primary central nervous system lymphoma (PCNSL) during single-photon emission tomography (SPECT) and contributes to its diagnostic imaging. However, whether ¹²³I-IMP is accumulated in ocular adnexal lymphoma (OAL), one of the malignant intraorbital tumors, remains unclear. This study aimed to evaluate the diagnostic value of ¹²³I-IMP SPECT in OAL.

METHODS

Between August 2005 and June 2020, 26 patients with intraorbital tumors underwent neurosurgery at the tertiary care center. Of these, 15 patients who underwent ¹²³I-IMPSPECT before surgery were retrospectively examined. The region of interest was set in the cerebellum ipsilateral to the intraorbital tumor on ¹²³I-IMP SPECT, and the tumor-to-cerebellum ratio (T/C ratio) was calculated using the following formula: T/C ratio = [accumulation of tumor (count/pixel)]/[accumulation of ipsilateral normal cerebellar hemisphere (count/pixel)].

RESULTS

Six patients were included in the OAL group, who were pathologically diagnosed with extranodal marginal zone B-cell lymphoma of mucosa-associated lymphoid tissue (MALT lymphoma), diffuse large B-cell lymphoma (DLBCL), and plasmacytoma. The T/C ratio in the OAL group was statistically higher than that in the non-OAL group (p < 0.01). The optimal cutoff values for both groups were between 0.76 and < 0.93. The sensitivity and specificity were 1.00, respectively.

CONCLUSIONS

¹²³I-IMP SPECT is useful as one of the examinations in the differential diagnoses of OAL, because it showed a significantly higher accumulation in OAL group than in non-OAL group.

Pharmacokinetics of a triarylmethyl-type paramagnetic spin probe used in EPR oximetry

The paramagnetic spin probe Oxo63 is used in oximetric imaging studies based on electron paramagnetic resonance (EPR) methods by monitoring the oxygen-dependent linewidth while minimizing the contributions from self-broadening seen at high probe concentrations. Therefore, it is necessary to determine a suitable dose of Oxo63 for EPR-based oxygen mapping where the self-broadening effects are minimized while signal intensity adequate for imaging can be realized. A constant tissue concentration of spin probe would be useful to image a subject and assess changes in pO2 over time; accumulation or elimination of the compound in specific anatomical regions could translate to and be mistaken for changes in local pO2, especially in OMRI-based oximetry. The in vivo pharmacokinetics of the spin probe, Oxo63, after bolus and/or continuous intravenous infusion was investigated in mice using a novel approach with X-band EPR spectroscopy. The results show that the half-life in blood was 17-21 min and the clearance by excretion was 0.033-0.040 min(-1). Continuous infusion following a bolus injection of the probe was found to be effective to obtain stable plasma concentration as well as image intensity to permit reliable pO2 estimates.

Combined 201Tl and 67Ga brain SPECT in patients with suspected central nervous system lymphoma or germinoma: clinical and economic value

BACKGROUND

Surgical resection is costly and an unfavorable prognostic factor for primary central nervous system (CNS) lymphoma and germinoma patients.

OBJECTIVE

To assess the diagnostic and economic impact of combined 201Tl and 67Ga brain SPECT on the management of patients suspected of having CNS lymphoma or germinoma.

METHODS

Sequential 201Tl and 67Ga brain SPECT was performed in 40 patients with cranial tumors to assess the diagnostic and economic impact of combined 201Tl and 67Ga SPECT on the management of patients suspected of having CNS lymphoma or germinoma. All intracranial masses were pathologically confirmed. The final diagnoses of a total of 47 foci were: 11 non-Hodgkin's lymphomas in 10 patients, 3 germinomas in 2 patients, 10 glioblastomas in 9 patients, 10 cerebral metastases in 8 patients, 13 meningiomas in 11 patients. Decision-tree sensitivity analysis for pretest probability regarding expected cost saving was performed for introduction of the combined study.

RESULTS

All but one focus of CNS lymphomas or germinomas (92.9%, 13/14) exhibited more intense uptake of 67Ga than of 201Tl (p < 0.001). All foci of glioblastomas (10/10) and meningiomas (13/13), and 60% of metastatic foci (6/10) exhibited higher uptake of 201Tl than of 67Ga (p < 0.035). Expected cost saving in the 1% to 50% range of pretest probability of CNS lymphoma or germinoma would be from minus dollars 842US to plus dollars 2,047US per patient for introduction of the combined study, because of substitution of stereotactic biopsy for craniotomy. The pretest probability was the key factor for cost saving of the combined study.

CONCLUSIONS

A 67Ga-positive and 201Tl-positive pattern with more intense uptake of 67Ga than 201Tl probably suggests CNS lymphoma or germinoma. This combination study appears to be cost-effective only in patients highly suspected of having CNS lymphoma or germinoma.