Dynamic MRI follow-up of radiation encephalopathy in the temporal lobe following nasopharyngeal carcinoma radiotherapy

MRI-based radiomics models predict cystic brain radionecrosis of nasopharyngeal carcinoma after intensity modulated radiotherapy

Objective

To construct radiomics models based on MRI at different time points for the early prediction of cystic brain radionecrosis (CBRN) for nasopharyngeal carcinoma (NPC).

Methods

A total of 202 injured temporal lobes from 155 NPC patients with radiotherapy-induced temporal lobe injury (RTLI) after intensity modulated radiotherapy (IMRT) were included in the study. All the injured lobes were randomly divided into the training (n = 143) and validation (n = 59) sets. Radiomics models were constructed by using features extracted from T2WI at two different time points: at the end of IMRT (post-IMRT) and the first-detected RTLI (first-RTLI). A delta-radiomics feature was defined as the percentage change in a radiomics feature from post-IMRT to first-RTLI. The radiomics nomogram was constructed by combining clinical risk factors and radiomics signatures using multivariate logistic regression analysis. Predictive performance was evaluated using area under the curve (AUC) from receiver operating characteristic analysis and decision curve analysis (DCA).

Results

The post-IMRT, first-RTLI, and delta-radiomics models yielded AUC values of 0.84 (95% CI: 0.76-0.92), 0.86 (95% CI: 0.78-0.94), and 0.77 (95% CI: 0.67-0.87), respectively. The nomogram exhibited the highest AUC of 0.91 (95% CI: 0.85-0.97) and sensitivity of 0.82 compared to any single radiomics model. From the DCA, the nomogram model provided more clinical benefit than the radiomics models or clinical model.

Conclusion

The radiomics nomogram model combining clinical factors and radiomics signatures based on MRI at different time points after radiotherapy showed excellent prediction potential for CBRN in patients with NPC.

Evolution of radiation-induced temporal lobe injury after intensity-modulated radiation therapy in nasopharyngeal carcinoma: a large cohort retrospective study

BACKGROUND

Previous studies have demonstrated conflicting findings regarding the initial MRI patterns of radiotherapy-induced temporal lobe injury (RTLI) and the evolution of different RTLI patterns. The aim of this study was to evaluate the initial MRI pattern and evolution of RTLI in patients with nasopharyngeal carcinoma (NPC) by means of a large cohort study.

METHODS

Data of patients with RTLI were retrospectively collected from two hospitals between January 2011 and December 2021. The injured lobes were categorized into three patterns based on initial MRI patterns: isolated white matter lesions (WMLs), isolated contrast-enhanced lesions (CELs), and combined WMLs and CELs. The latency period, MRI appearances, and temporal changes in WMLs and CELs were evaluated.

RESULTS

A total of 913 RTLI patients with 1092 injured lobes were included in this study. The numbers of isolated WMLs, isolated CELs, and combined WMLs and CELs identified at the first MRI detection were 7 (0.6%), 172 (15.8%), and 913 (83.6%), respectively. The evolution of bilateral RTLI was different in the same patient, and that of unilateral RTLI combined with WMLs and CELs also may occur asynchronously. The time intervals from the initial MRI detection of isolated WMLs, isolated CELs, combined WMLs and CELs to the last negative MRI scan were 8.6, 8.9 and 11.0 months, respectively. A significant difference was observed in the time intervals between the three patterns (H = 14.287, P = 0.001). And the time interval was identified as an independent factor influencing the initial MRI pattern of RTLI after Poisson regression (P = 0.002).

CONCLUSION

Both WMLs and CELs could be the initial and only MRI abnormalities in patients with RTLI. This study is of great significance in accurately diagnosing RTLI early and providing timely treatment options. Additionally, it provides clinical evidence for guidelines on NPC, emphasizing the importance of regular follow-up of NPC patients.

Changes in brain gray matter volume in nasopharyngeal carcinoma patients after radiotherapy in long-term follow-up

OBJECTIVES

The aim of this study was to examine the changes in gray matter in nasopharyngeal carcinoma patients with normal hearing (Group 1) and nasopharyngeal carcinoma patients with hearing loss (Group 2) after radiotherapy using voxel-based morphological analysis and to analyze the relationship with the radiation doses of the temporal lobe.

METHODS

21 patients in Group 1, 14 patients in Group 2, and 21 healthy volunteers were selected. All participants underwent an otologic examination and three-dimensional magnetization preparatory rapid acquisition gradient echo sequence scan. The correlation between the variation of whole brain gray matter volume and the doses of the temporal lobe was analyzed by Data Processing & Analysis for Brain Imaging software.

RESULTS

Compared with the normal control group, the brain areas with reduced gray matter volume in nasopharyngeal carcinoma patients after radiotherapy were mainly in the left posterior cerebellar lobe (T = -8.797), left insular lobe (T = -7.96), and the right insular lobe (T = -6.632). Compared to Group 1, the brain areas of Group 2 patients with reduced gray matter volume were mainly in the left superior temporal gyrus (T = -2.366), left olfactory bulb (T = -2.52), left Rolandic operculum (T = -2.431), and right olfactory bulb (T = -3.100). Compared with Group 1, the brain areas of Group 2 patients with increased gray matter volume were mainly in the left calcarine sulcus (T=3.425) and right calcarine sulcus (T=3.169). There were no correlations between the changes of brain gray matter volume and the radiation doses of the temporal lobe in both Group 1 and Group 2.

CONCLUSIONS

The radiotherapy may cause the changes of brain areas associated with cognitive function in nasopharyngeal carcinoma in a long-term follow-up. At the same time, nasopharyngeal carcinoma patients with the radiation-induced hearing loss had abnormal gray matter volumes in the auditory center and other sensory centers. Our findings might provide new understanding into the pathogenesis of radiation-induced brain damage in normal-appearing brain tissue. Yet this exploratory study should be taken with caution.

Pre-symptomatic local brain activity and functional connectivity alterations in nasopharyngeal carcinoma patients who developed radiation encephalopathy following radiotherapy

Radiation encephalopathy (RE) is a common complication in patients with nasopharyngeal carcinoma (NPC) who have received radiotherapy (RT), and recent neuroimaging studies have shown brain alterations in Post-RT patients prior to RE. However, whether there are functional alterations between those Post-RT patients who are proved to have RE in follow-up and those who do not develop it remains largely unknown. Here, we used resting state functional MRI to explore regional homogeneity (ReHo) and functional connectivity (FC) alterations in Post-RT patients with (Post-RT _{RE proved}; n = 18) or without (Post-RT _non-RE; n = 22) RE at follow-up, also making comparisons with a Pre-RT group (n = 23). Compared with the Pre-RT group, patients in Post-RT _non-RE and Post-RT _{RE proved} groups showed concurrent increased and decreased ReHo values in different brain regions inside and/or outside the radiation field, with the alterations in ReHo tending to increase if RE occurred. Seed-based FC analysis showed that compared with the Post-RT _non-RE group, patients in the Post-RT _{RE proved} group had different changing patterns of FC between a region of interest (ROI) in the right temporal lobe and distant brain regions (mainly in the sensorimotor system and default mode network). Receiver operating characteristic (ROC) curve analysis showed that the altered ReHo value in the ROI had excellent diagnostic performance for differentiating NPC patients who developed RE in follow-up from those who did not, with an area under the curve (AUC) value of 0.94. These ReHo and FC findings may provide new insights into the early diagnosis of RE.

Standard radiotherapy for patients with nasopharyngeal carcinoma results in progressive tract-specific brain white matter alterations: A one-year follow-up via diffusion tensor imaging

BACKGROUND AND PURPOSE

Radiation therapy (RT)-induced neurocognitive disability may be mediated by brain tissue damage. The aim of the present study was to investigate the effects of standard RT on normal brain tissue via in vivo neuroimaging in patients with nasopharyngeal carcinoma (NPC).

MATERIALS AND METHODS

A total of 146 newly diagnosed NPC patients who were treated with standard RT were longitudinally followed up at multiple time points during the first year post-RT, with 19 comparable healthy controls followed up in parallel serving as normal age-related benchmarks. Magnetic resonance diffusion tensor imaging was used to evaluate longitudinal brain white matter tract changes in NPC patients. The relationships between RT-related white matter changes, hippocampal atrophy, and cognitive impairment were also assessed.

RESULTS

Bilateral cingulate angular bundle (CAB) fibers had progressive diffusion reduction [radial diffusivity (RD) and mean diffusivity] over time (P < 0.05, corrected for multiple comparisons) in NPC patients during the first year after RT. RT-associated progressive RD reduction in the left CAB correlated with longitudinal atrophy of the ipsilateral hippocampus (P = 0.033). Additionally, RT-associated progressive RD reduction in the left CAB correlated with progressive cognitive impairment in NPC patients post-RT (P = 0.048).

CONCLUSION

We present evidence of progressive RT-associated changes in the bilateral CAB in NPC patients, which may underlie RT-related cognitive impairment. These findings illustrate that the use of white matter tract alterations as potential biomarkers to detect RT-related brain injury in NPC patients may be useful for better understanding the pathogenesis of RT-induced cognitive decline.

Long-term recurrence and brain metastasis of nasopharyngeal carcinoma mimicking cystic radiation encephalopathy relapse: a case report

BACKGROUND

During medical imaging, cystic radiation encephalopathy and brain metastasis are difficult to differentiate, and hence they are easily misdiagnosed. To our knowledge, a nasopharyngeal carcinoma recurrence after more than seven years with cerebral metastasis that mimicked cystic radiation encephalopathy has not been reported.

CASE PRESENTATION

A 52-year-old man was admitted to the hospital owing to weakness of the right limb for one month, which increased in intensity for three days. He had been diagnosed with nasopharyngeal carcinoma in 2011, which was treated by radiotherapy. The patient successively developed cystic radiation encephalopathy and brain metastasis from the nasopharyngeal carcinoma, which mimicked cystic radiation encephalopathy relapse. Left frontotemporal craniotomy, surgical resection of brain metastasis, and repair of the skull base and dura were performed. Postoperative computed tomography showed that midline deviation recovered, and brain edema was reduced.

CONCLUSIONS

This report is significant because brain metastasis from nasopharyngeal carcinoma can masquerade as a benign entity and cause fatal consequences. In patients presenting with cystic radiation encephalopathy, brain metastasis should be considered as a differential diagnosis.

Radiation-Induced Optical Coherence Tomography Angiography Retinal Alterations in Patients With Nasopharyngeal Carcinoma

Aim: The aim of the study was to investigate the early neurovascular alterations of the retina in radiation encephalopathy (RE) patients with normal-ranged visual acuity after radiotherapy for nasopharyngeal carcinoma.

Methods: Fifty-five RE patients and 54 healthy age-matched subjects were enrolled in this retrospective cross-sectional case–control study. The best corrected visual acuity (LogMAR) of the included eye should not be more than 0. The vessel density and thickness of different locations in the retina were acquired automatically using optical coherence tomography angiography (OCTA). The data were then compared between the RE patients and the controls. The location included the whole retina, the superficial vascular plexus (SVP)/the ganglion cell complex (GCC), the deep vascular plexus (DVP), and the choroid in the macular area, as well as the inside disc and peripapillary area in the optic nerve head (ONH). The risk factors in OCTA retinal impairments were analyzed using a backward multiple linear regression. The relationships between mean deviation (MD) and pattern standard deviation (PSD) in the visual field (VF) and the OCTA parameters were also analyzed in RE patients.

Results: The vessel density of the GCC was significantly reduced in RE patients compared with controls (p = 0.018), and the reductions were mainly shown in the parafoveal (p = 0.049) and perifoveal fields (p = 0.006). The thickness of the GCC was correspondingly reduced (whole image GCC mean thickness: p = 0.044; parafoveal thickness: p = 0.038; perifoveal thickness: p = 0.038). In addition, the sub-foveal choroidal thickness (p = 0.039) was also reduced in RE patients. The vessel density of the GCC (R² = 0.643) and DVP (R² = 0.777) had a significant positive correlation with high-density lipoprotein cholesterol (HDL-C) and apolipoprotein A1 (ApoA1) and had a significant negative correlation with age (GCC: HDL-C, β = 29.89, p = 0.005; ApoA1, β = 78.92, p = 0.002; age, β = −0.886, p = 0.001; DVP: HDL-C, β = 40.09, p = 0.003; ApoA1, β = 62.65, p = 0.013; age, β = −1.31, p = 0.001). The vessel density of the GCC also had a significant negative correlation with apolipoprotein B (ApoB) (β = −32.18, p = 0.006). In the VF, MD had a significant positive correlation with the vessel density inside disc (R² = 0.241, β = 0.304, p = 0.045), whereas PSD showed a significant negative correlation with the vessel density inside disc and the average GCC thickness, respectively (R² = 0.437; vessel density inside disc, β = −0.358, p = 0.004; average GCC thickness, β = −0.510, p < 0.001).

Conclusion: With the aid of OCTA, we found that neurovascular alterations of the retina may exist in RE patients with normal-ranged visual acuity. Herein, we suggest the implementation of OCTA to assist ophthalmologists in the early detection and consistent monitoring of radiation-related eye diseases to avoid delayed diagnosis.

Intracranial long-term complications of radiation therapy: an image-based review

BACKGROUND AND PURPOSE

Radiation therapy is commonly utilized in the majority of solid cancers and many hematologic malignancies and other disorders. While it has an undeniably major role in improving cancer survival, radiation therapy has long been recognized to have various negative effects, ranging from mild to severe. In this manuscript, we review several intracranial manifestations of therapeutic radiation, with particular attention to those that may be encountered by radiologists.

METHODS

We conducted an extensive literature review of known complications of intracranial radiation therapy. Based on this review, we selected complications that had salient, recognizable imaging findings. We searched our imaging database for illustrative examples of these complications, focusing only on patients who had a history of intracranial radiation therapy. We then selected cases that best exemplified expected imaging findings in these entities.

RESULTS

Based on our initial literature search and imaging database review, we selected cases of radiation-induced meningioma, radiation-induced glioma, cavernous malformation, enlarging perivascular spaces, leukoencephalopathy, stroke-like migraine after radiation therapy, Moyamoya syndrome, radiation necrosis, radiation-induced labyrinthitis, optic neuropathy, and retinopathy. Although retinopathy is not typically apparent on imaging, it has been included given its clinical overlap with optic neuropathy.

CONCLUSIONS

We describe the clinical and imaging features of selected sequelae of intracranial radiation therapy, with a focus on those most relevant to practicing radiologists. Knowledge of these complications and their imaging findings is important, because radiologists play a key role in early detection of these entities.

Radiation induced temporal lobe necrosis in nasopharyngeal cancer patients after radical external beam radiotherapy

Radiation-induced temporal lobe necrosis (TLN) is one of the late post-radiotherapy complications in nasopharyngeal cancer (NPC) patients. Since NPC is common to have skull base infiltration, irradiation of the temporal lobes is inevitable despite the use of the more advanced intensity-modulated radiotherapy (IMRT). Moreover, the diagnosis and treatment of TLN remain challenging. In this review, we discuss the diagnosis of TLN with conventional and advanced imaging modalities, onset and predictive parameters of TLN development, the impact of IMRT on TLN in terms of incidence and dosimetric analyzes, and the recent advancements in the treatment of TLN.

Enlarging Perivascular Spaces Following Radiation Therapy in the Brain: A Report of 2 Cases and Literature Review

BACKGROUND

Virchow-Robin or enlarged perivascular spaces (PVS) are benign pial-lined spaces that surround penetrating arteries and arterioles through the brain parenchyma. We present 2 cases of enlarging PVS in adults following whole-brain radiation therapy.

CASE DESCRIPTION

Two patients underwent whole-brain radiation therapy for adult-onset medulloblastoma. Neither patient had enlarged PVS at the time of radiation treatment. The patients presented with PVS in the basal ganglia 6 and 8 years following the completion of radiation, respectively. One patient subsequently showed a decrease in size of PVS over time. Neither patient experienced symptoms, required surgical intervention, or had signs of tumor recurrence.

CONCLUSIONS

Enlarging PVS can occur years after radiation therapy to the brain parenchyma. Recognition of these benign PVS is important so as not to mistake the changes for more sinister pathology that could lead to unnecessary intervention. Moreover, focal cystic changes more frequently seen surrounding areas of focal brain radiation therapy might represent enlarged PVS.

Temporal lobe microstructural abnormalities in patients with nasopharyngeal carcinoma quantitatively evaluated by high-resolution DWI and DKI after concurrent chemoradiotherapy

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DKI could detect early radiation-induced microstructural abnormalities after CCRT.

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The ADC, Dmean, and FA of temporal lobe showed a unique time-dependent trajectory.

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Kmean might be more sensitive to detection of effects in the late delayed phases.

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White and grey matter all underwent microstructural changes after radiotherapy.

Purpose

To investigate temporal lobe microstructural abnormalities and neurocognitive function impairment after concurrent chemoradiotherapy (CCRT) in patients with nasopharyngeal carcinoma (NPC).

Methods

NPC patients who underwent CCRT were enrolled. High-resolution diffusion-weighted imaging (DWI) magnetic resonance imaging (MRI) and diffusion-kurtosis imaging (DKI) MRI, were performed 5 times per patient (once pre-CCRT, 1 week post-CCRT, 3 months post-CCRT, 6 months post-CCRT, and 12 months post-CCRT). Neurocognitive function was evaluated by Montreal Neurocognitive Assessment (MoCA) twice per patient, once pre-CCRT, and once 12-months after CCRT.

Results

Of 111 patients, 56 completed the entire protocol. The MRI derived apparent diffusion coefficient (ADC), mean of diffusion coefficient (Dmean) and fractional anisotropy (FA) values were significantly decreased (p < 0.05) over the 0–3 month period following CCRT and significantly increased (p < 0.05) over the 3–12 month period following CCRT. The mean of kurtosis coefficient (Kmean) continued to decline over a year post-CCRT. All parameters reveal more pronounced changes in white matter (WM) than in grey matter (GM). MoCA also declined after CCRT (p < 0.001). MoCA showed significant positive correlation with Kmean-WM-6 m, Kmean-WM-12 m and ΔKmean-WM.

Conclusions

High-resolution DWI and DKI should be considered as a promising method for the investigation of temporal lobe microstructural change in NPC patients after CCRT.

Chemotherapy Potentially Facilitates the Occurrence of Radiation Encephalopathy in Patients With Nasopharyngeal Carcinoma Following Radiotherapy: A Multiparametric Magnetic Resonance Imaging Study

Radiation encephalopathy (RE) is deemed to be a disease induced only by radiotherapy (RT), with the effects of chemotherapeutic agents on the brains of nasopharyngeal carcinoma (NPC) patients being largely overlooked. In this study, we investigated structural and functional brain alterations in NPC patients following RT with or without chemotherapy. Fifty-six pre-RT, 37 post-RT, and 108 post-CCRT (concomitant chemo-radiotherapy) NPC patients were enrolled in this study. A surface-based local gyrification index (LGI) was obtained from high resolution MRI and was used to evaluate between-group differences in cortical folding. Seed-based functional connectivity (FC) analysis of resting-state fMRI data was also conducted to investigate the functional significance of the cortical folding alterations. Compared with the Pre-RT group, patients in the Post-CCRT group showed LGI reductions in widespread brain regions including the bilateral temporal lobes, insula, frontal lobes, and parietal lobes. Compared with the Post-RT group, patients in the Post-CCRT group showed LGI reductions in the right insula, which extended to the adjacent frontal lobe. Seed-based FC analysis showed that patients in the Post-CCRT group had lower FC between the insula and the left middle frontal gyrus than patients in the Pre-RT group. The follow-up results showed that patients in the Post-CCRT group had a much higher RE incidence rate (20.4%) than patients in the Post-RT group (2.7%; P = 0.01). These findings indicate that chemotherapy potentially facilitated the occurrence of RE in NPC patients who underwent radiotherapy.