MR Imaging Evaluation of Intracerebral Hemorrhages and T2 Hyperintense White Matter Lesions Appearing after Radiation Therapy in Adult Patients with Primary Brain Tumors
MR Imaging Evaluation of Intracerebral Hemorrhages and T2 Hyperintense White Matter Lesions Appearing after Radiation Therapy in Adult Patients with Primary Brain Tumors
Dong Hyun Yoo 0 1 2
Sang Woo Song 0 1 2
Tae Jin Yun 0 1 2
Tae Min Kim 0 1 2
Se-Hoon Lee 0 1 2
Ji- 0 1 2
Hoon Kim 0 1 2
Chul-Ho Sohn 0 1 2
Sung-Hye Park 0 1 2
Chul-Kee Park 0 1 2
Il Han Kim 0 1 2
Seung Hong Choi 0 1 2
0 Current address: Department of Neurosurgery, Konkuk University Medical Center , Seoul , Korea
1 1 Department of Radiology, Seoul National University Hospital , Seoul , Korea , 2 Department of Neurosurgery, Seoul National University Hospital , Seoul , Korea , 3 Department of Internal Medicine, Cancer Research Institute, Seoul National University Hospital , Seoul , Korea , 4 Department of Pathology, Seoul National University Hospital , Seoul , Korea , 5 Department of Radiation Oncology, Cancer Research Institute, Seoul National University Hospital , Seoul , Korea
2 Editor: Jiani Hu, Wayne State University , UNITED STATES
The purpose of our study was to determine the frequency and severity of intracerebral hemorrhages and T2 hyperintense white matter lesions (WMLs) following radiation therapy for brain tumors in adult patients. Of 648 adult brain tumor patients who received radiation therapy at our institute, magnetic resonance (MR) image data consisting of a gradient echo (GRE) and FLAIR T2-weighted image were available three and five years after radiation therapy in 81 patients. Intracerebral hemorrhage was defined as a hypointense dot lesion appearing on GRE images after radiation therapy. The number and size of the lesions were evaluated. The T2 hyperintense WMLs observed on the FLAIR sequences were graded according to the extent of the lesion. Intracerebral hemorrhage was detected in 21 (25.9%) and 35 (43.2) patients in the three- and five-year follow-up images, respectively. The number of intracerebral hemorrhages per patient tended to increase as the follow-up period increased, whereas the size of the intracerebral hemorrhages exhibited little variation over the course of follow-up. T2 hyperintense WMLs were observed in 27 (33.3%) and 32 (39.5) patients in the three and five year follow-up images, respectively. The age at the time of radiation therapy was significantly higher (p < 0.001) in the patients with T2 hyperintense WMLs than in those without lesions. Intracerebral hemorrhages are not uncommon in adult brain tumor patients undergoing radiation therapy. The incidence and number of intracerebral hemorrhages increased over the course of follow-up. T2 hyperintense WMLs were observed in more than one-third of the study population.
Data Availability Statement: Data are from
electronic medical records and MR images of the
patients at Seoul National University Hospital. The
MR images, which is the most important material in
our study, cannot be made available to another
person or party due to legal restriction by Korean
medical law. The reader may contact one of the
author (Dong Hyun Yoo, email: psydong8@gmail.
com) for tabulated data with limited information
(deidentified and coded).
Funding: This study was supported by a grant from
Korea Healthcare Technology R&D Projects, Ministry
for Health, Welfare & Family Affairs, grant number
HI13C0015 (http://www.mw.go.kr/), recipient SHC,
and the Research Center Program of IBS (Institute
for Basic Science) in Korea (no grant number, http://
www.ibs.re.kr/), recipient SHC. The funders had no
role in study design, data collection and analysis,
decision to publish, or preparation of the manuscript.
Competing Interests: The authors have declared
that no competing interests exist.
Various complications, ranging from asymptomatic to fatal, occur in the central nervous
system after radiation therapy of the brain, and magnetic resonance (MR) imaging is useful in
detecting these complications [1,2]. Intracerebral hemorrhages and T2 hyperintense white
matter lesions (WMLs) are frequently encountered complications on follow-up MR imaging.
Hemorrhagic complications likely result from radiation-induced telangiectasia, a type of
microangiopathy otherwise referred to as cryptic vascular malformation, which is caused by
radiation-induced endothelial injury and subsequent venous occlusion [3,4]. Hyperintense
WMLs on T2-weighted or fluid-attenuated inversion recovery (FLAIR) T2-weighted images
are caused by radiation-induced demyelination . Although these complications have been
reported previously, the majority of these studies were conducted on pediatric patients with
limited study populations and variable follow-up periods [6–8].
The purpose of this study is to evaluate the brains in a relatively large number of adult
primary brain tumor patients previously treated with radiation using FLAIR T2-weighted and
gradient echo (GRE) sequence MR images. We aimed to determine the incidence and severity
of intracerebral hemorrhages and T2 hyperintense WMLs over a specific period of time
following radiation therapy for brain tumors in adult patients.
Materials and Methods
This retrospective study was approved by the institutional review board of Seoul National
University College of Medicine and Hospital, and the need for written informed consent was
waived. The patient name and study date was not de-identified prior to the image analysis.
However, other patient information was blind to the radiologists.
Between 1983 and 2009, 648 adult patients (age of 18 years or older) with newly diagnosed
primary brain tumors received radiation therapy of the brain. From the original study population,
we selected 88 patients for whom MR images consisting of a GRE and FLAIR T2-weighted
sequence were available for three years and five years following the radiation therapy. An
additional seven patients were excluded because extensive tumor progression prevented analysis of
the MR images. As a result, 81 patients (44 males and 37 females) with a mean age of 39.7 years
(range 22 to 69 years, SD ±10.0) at the time of the radiation therapy were enrolled as the final
study population for analysis. Among the study population, 48 patients underwent a brain MR
study seven years after radiation therapy, and these MR images were also reviewed as well. The
pathological diagnoses included astrocytoma (n = 3), anaplastic astrocytoma (n = 19),
anaplastic oligoastrocytoma (n = 5), oligodendroglioma (n = 16), anaplastic oligodendroglioma
(n = 34), ependymoma (n = 2), subependymoma (n = 1) and anaplastic ganglioglioma (n = 1).
Brain Radiation Therapy and Clinical Data
Radiation therapy was initiated 2 to 4 weeks following surgery. Conventional external field
radiation in fractions of 1.8–2.0 Gy 5 times a week was performed with a mean total dose of 58
Gy (range: 46.8–61.2 Gy), using 4-6MV x-rays generated from a linear accelarator. The
3-dimensional radiotherapy technique with a multileaf collimator (MLC) system was utilized
after optimization by a radiotherapy planning system. The field size was determined to
encompass a 1.5 cm margin from the tumor bed or gross tumor initially and a 5 mm margin after
field reduction, with an additional 3 mm margin for possible physical error. The dose
constraint was 54 Gy for the brainstem, 54-58Gy for the optic apparatus, and 45–50 Gy for the
upper cervical cord. All the patients minus one underwent involved-field radiation therapy,
and one patient with an infratentorial ependymoma received whole brain irradiation.
Chemotherapy was administered in 63 patients as follows: before radiation therapy in 16 patients,
after radiation therapy in 41 patients, and concurrent with radiation therapy in 6 patients. The
medical records were reviewed for other data, such as the clinical course and adverse radiation
effects. The end of the follow-up period was defined as December 2012. For the patients who
were lost to follow-up, the end of the follow-up period was defined as the most recent date on
which follow-up information was obtained.
From the medical records, we analyzed the symptoms known to be common adverse
radiation effects, including the following: headache, dizziness, somnolence, skin problems, cognitive
dysfunction, and newly developed seizures. In patients with tumor progression or
hydrocephalus, we analyzed the data before these events or the onset of symptoms related to these events
for symptomatic analysis.
MR Imaging and Evaluation
The MR images were obtained using 1.0 T (Magnetom Expert, Siemens), 1.5 T (Signa, GE
Healthcare, Milwaukee, WI; or Magnetom Vision Plus, Siemens) or 3T (Signa, GE Healthcare;
or Magnetom Verio, Siemens) MR imaging system. The MR imaging sequences included
FLAIR T2-weighted images (TR/TE/NEX, 8802–9902/119–164/1, 5-mm-thick sections, 1.0–
2.0-mm intersection gap) and GRE sequence images (TR/TE/NEX, 467-800/20-26/1,
5-mmthick sections, 1.0–2.0-mm intersection gap).
The images were evaluated by two independent radiologists (S.H.C. and D.H.Y., with 12
and 6 years of experience in neuroradiology, respectively), and the final decision on discrepant
results was reached by mutual consent. The MR imaging data within a one-year range closest
to the three- and five-year follow-up date after the start of the radiation therapy were used for
the analysis. Pre-treatment FLAIR T2-weighted images were available for all the patients,
whereas pre-treatment GRE images were available for 47 patients.
The MR imaging data of the brain following radiation therapy were serially reviewed to
detect intracerebral hemorrhages. Intracerebral hemorrhage was defined as a hypointense dot
lesion on GRE sequence MR images. Lesions in the basal ganglia and thalamus, which is
known to be a predominant location for intracerebral hemorrhages in general population, were
excluded. Additionally, those adjacent to the surgical margins were excluded. The number and
size of the lesions were evaluated. The lesions were subdivided into the following three groups
according to size of the patient’s largest lesion; less than 5 mm (small), 5–9 mm (medium), and
larger than 9 mm (large).
T2 hyperintense WMLs observed on the FLAIR sequences were graded according to a
modification of the system of Wilson et al [7,9]. Grade 1 was defined as patchy, mildly increased
signal intensity in the periventricular white matter; grade 2 as moderate changes that extended
almost to the gray-white junction, sparing the subcortical U-fibers; and grade 3 as severe
changes, confluent from the level of the frontal horns to that of the trigones, with or without
involvement of the U-fibers. The MR images prior to radiation therapy were carefully reviewed
to exclude preexisting hyperintensity related to peri-tumoral edema, infiltration of tumor, and
The SPSS 17.0 package (SPSS Inc., Chicago, IL) was used for the statistical analysis. The
Student’s t-test was used for the comparison of the continuous variables (age) between the patients
with and without lesions. The number and size of the intracranial hemorrhages between the
three- and five-year follow-up data were also compared using the Student’s t-test. The
categorical values (gender, chemotherapy, symptoms) were compared using a chi-square test. The
cumulative incidence rates were determined by Kaplan-Meier estimation. The results with a
pvalue of less than .05 were considered statistically significant. No correction for p-value was
A typical case of intracerebral hemorrhage on GRE image is presented in Fig 1. The mean
follow-up period was 96.5 months (SD, 24 months; range, 58–152 months), and intracerebral
hemorrhage appeared in 60 of 81 patients (74.1%). The shortest follow-up interval in which an
intracerebral hemorrhage was detected was 11 months, whereas the longest interval was 122
months (mean, 59.7 ± 25.1 months). The cumulative incidence rates of intracerebral
hemorrhage after radiation therapy were 2.5% at one year, 12.3% at three years, 37.1% at five year,
62.0% at seven years, and 89.2% at ten years (Fig 2).
Table 1 summarizes the incidence, numbers, and sizes of the intracerebral hemorrhages
following radiation therapy. Between the three- and five-year follow-up interval, 17 patients
developed new intracerebral hemorrhages. In three patients, intracerebral hemorrhages were
detected on the three-year MR images; however, there was no intracerebral hemorrhage on the
five-year MR images. Among the 35 patients with intracerebral hemorrhages on the seven-year
MR images, 15 patients had no intracerebral hemorrhages on the previous MR images. In three
patients, intracerebral hemorrhages were detected on the five-year MR images, with no
intracerebral hemorrhage found on the seven-year MR images. Among the 35 patients with an
intracerebral hemorrhage on the five-year MR images, 12 patients did not have seven-year MR
The number of intracerebral hemorrhages per patient tended to increase as the follow-up
period increased, whereas the size of the intracerebral hemorrhages exhibited little variation in
the course of follow-up. Among the patients with intracerebral hemorrhages, the mean and
median number of intracerebral hemorrhages was 2.0 and 1 on the three-year MR images and
6.1 and 3 on the five-year MR images (p = 0.048 for the mean values). The largest intracerebral
hemorrhage measured was 11 mm on the three- and five-year MR images and 12 mm on the
seven-year MR images. The development of intracerebral hemorrhages showed no
preponderance of location.
The incidence of intracerebral hemorrhages did not significantly differ between genders on
the three-year (male vs. female; 27.3% vs. 24.3%, p = 0.763) or five-year (45.5% vs. 40.5%,
p = 0.657) follow-up MR images. Furthermore, there was no significant difference in age at the
time of radiation therapy between the patients with intracerebral hemorrhages and those
without: 36.9 vs. 40.7 (p = 0.129) on three-year and 38.3 vs. 40.8 (p = 0.275) on five-year follow-up.
The difference in the incidence of intracerebral hemorrhages between the patients who
received chemotherapy and those who did not was not significantly different on the three-year
(28.6% vs. 16.7%, p = 0.309) and five-year (47.6% vs. 27.8%, p = 0.134) images.
T2 hyperintense WMLs
The number of patients exhibiting a T2 hyperintense WML is presented in Table 2 according
to the grading. In eight patients, there was a progression of grade as follows: four patients from
grade 0 to 1, three patients from grade 1 to 2, and one patient from grade 0 to 2. No patient
exhibited downgrading of T2 hyperintense WMLs. In the three- and five-year follow-up MR
Fig 1. A of a 34-year-old female who received radiation therapy due to an ependymoma in the fourth ventricle. (A) A gradient echo (GRE) image
acquired five years following radiation therapy revealed a small dark dot lesion (arrow) in the subcortical white matter of the right frontal lobe. (B) A GRE
image acquired seven years following radiation therapy revealed a newly developed intracerebral hemorrhage (arrowhead) adjacent to the right lateral
ventricle frontal horn next to the previously noted intracerebral hemorrhage in the subcortical white matter of right frontal lobe (arrow).
images, the age at the time of radiation therapy was significantly higher (p < 0.001) in the
patients with T2 hyperintense WMLs than in those without WMLs (36.5 vs. 46.1 on the
threeyear and 36.2 vs. 45.0 on the five-year follow-up). There was no significant correlation between
the T2 hyperintense WMLs and gender or the administration of a chemotherapeutic agent.
Fig 2. Kaplan-Meier estimation of the cumulative incidence of intracerebral hemorrhage.
* Based on 48 patients for whom MR image data were available 7 years after brain radiation.
† If a patient had more than one hemorrhage, the one with the largest diameter was measured.
‡ Numbers of hemorrhages in one patients
3 year (n = 81)
5 year (n = 81)
7 year* (n = 48)
Symptomatic analysis after radiation therapy
The median clinical follow-up period was 91 months (range, 58–152). The median period to
disease progression or malignant transformation was 66 months (range, 18–117) in 26 patients, and
ventriculo-peritoneal shunts were performed 27, 54, 78, 84, and 129 months after radiation therapy
in 5 patients. After excluding the clinical adverse effects that occurred after the events mentioned
above for the symptomatic analysis, the median follow-up period was 83 months (range, 18–152).
The possible clinical adverse effects after radiation therapy and the time interval from
radiation therapy to symptom onset are presented in Table 3. The incidence of each symptom did
not significantly differ between the patients with and without intracerebral hemorrhages. The
time interval from radiation therapy to the onset of various symptoms was shorter than the
time interval to intracerebral hemorrhage, which represented a 70-month median interval
from radiation therapy.
Radiation therapy plays a major role in the treatment of brain tumor patients. Various
randomized trials have demonstrated a significant survival benefit from post-operative radiation
therapy in patients with a newly diagnosed malignant glioma . Additionally, early
postoperative radiation therapy increases the progression-free survival in low-grade glioma patients
[11,12]. However, radiation injury of the brain after cranial irradiation is a dose-limiting factor
that ranges from subclinical changes only detected on MR images to fatal complications such
as brain necrosis . Vascular damage is a major contributor to changes or complications in
the brain after radiation therapy. Radiation-induced occlusive large vessel vasculopathy occurs
Microhemorrhage +, n (%)
a Statistical significance of the difference in the incidence of each symptom between the patients with an intracerebral hemorrhage and without an
b Time interval from radiation therapy to symptom onset, median months (range)
c Eighteen patients who experienced seizure before radiation therapy were excluded from this analysis.
in large arteries, such as the internal carotid artery or middle cerebral artery, and might result
in Moyamoya vascularity. The latent period has been reported to be as long as 20 years .
No patient developed large vessel vasculopathy in our study.
An intracerebral hemorrhage is a result of changes in the microvascular structure after
radiation; thrombosis in small venules induces dilatation of the capillaries in an attempt to develop
collateral vessels, and a telangiectasia forms . These telangiectasias are prone to subclinical
hemorrhage, and subsequent perivascular calcification and hemosiderin deposition are detected
as hypointense dot-like lesions on GRE images. A previous study on survivors of pediatric acute
lymphoblastic leukemia (ALL) patients who were treated with brain radiation therapy reported
a 55% prevalence of intracerebral hemorrhages on GRE images . The mean interval from
diagnosis was 12.2 years (range: 5.0–18.8) in the study. In our study, the prevalence was 25.9%
over three years, 43.2% over five years, and 72.9% over seven years, whereas the cumulative
incidence rates were 2.5% at one year, 12.3% at three years, 37.1% at five year, 62.0% at seven years,
and 89.2% at ten years. We suspect that the somewhat higher incidence in our study could be
attributed to the natural incidence of intracerebral hemorrhages. In a large study conducted on
all the brain MRIs at single center over three years, the incidence of intracerebral hemorrhage
was 9.8% on the GRE images. In this study, the detection of intracerebral hemorrhages increased
with age, and intracerebral hemorrhages were usually observed in patients older than 40 years
. Among the patients with intracerebral hemorrhage in our study, a few might have
developed intracerebral hemorrhages independent of radiation therapy.
Most of the intracerebral hemorrhages detected in our study were smaller than 10 mm in
diameter. Of the patients with intracerebral hemorrhages, 80% or more had small (less than 5
mm) intracerebral hemorrhages on three-, five- and seven-year follow-up MR images. The
number of intracerebral hemorrhage per patient was less than ten in the majority of the
patients. The number of intracerebral hemorrhages tended to increase with longer follow-up,
possibly as the result of accumulation and new development of intracerebral hemorrhages over
time, as has been described in a previous study . The greatest number of intracerebral
hemorrhages detected in a patient was 10 and 67 on the three- and five-year follow-up, respectively.
An autopsy study has suggested that immature brains might be more sensitive to radiation
. One previous study in pediatric patients who received brain radiation reported a higher
incidence of telangiectasias on the T2-weighted MR images of younger patients . Because
our study subjects were adults with mature brains, there was no significant age difference
between those with and without intracerebral hemorrhages. Additionally, there was no
significant difference in the incidence of intracerebral hemorrhages between the group that did and
the group that did not undergo chemotherapy in our study. This finding is in accordance with
results from previous studies on pediatric patients [6,7].
The clinical implication of radiation-induced intracerebral hemorrhages remains uncertain.
In our study, the symptoms after radiation therapy appeared to be unrelated to intracerebral
hemorrhages. Intracerebral hemorrhages on the GRE images appeared much later than the
symptoms after radiation therapy according to the chronological analysis, and there was no
significant difference in the incidence of each symptom between the patients with intracerebral
hemorrhages and those without intracerebral hemorrhages.
In a study performed on stroke patients of various subtypes, the presence of intracerebral
hemorrhages on GRE images was an indicator of increased risk for bleeding . Therefore,
among patients who received radiation therapy, those with intracerebral hemorrhage might be
more susceptible to large intracranial hemorrhages than those without intracerebral
hemorrhage. In our study, intracerebral hemorrhages were detected in both patients who presented
with large intracranial hemorrhages. One patient had 41 intracerebral hemorrhages on the
GRE images acquired two years before the hemorrhagic event, whereas another patient had 8
intracerebral hemorrhages one year before the event. In these two patients, the onset of large
intracranial hemorrhage was 8 years and 9 years after the radiation therapy. This result is
comparable to the mean of 8.1 years (range 1 to 19 years) observed in a previous study in which the
authors described 20 cases of large intracranial hemorrhages in patients treated with radiation
therapy for central nervous system neoplasia in childhood .
Unlike intracerebral hemorrhages, the clinical implication of radiation-induced WMLs is
well documented. The extent of T2 hyperintense WMLs after radiation of the brain has been
reported to be associated with cognitive dysfunction [18–20]. Radiation-induced WMLs have
been widely investigated in various studies and frequencies of as low as 5% to as high as 100%
have been reported [1,5,7,19]. To our knowledge, no previous study has described the
incidence of T2 hyperintense WMLs as a function of time after radiation therapy. In our study, the
incidence of T2 hyperintense WMLs was 33.3% and 39.5% in three- and five-year follow-ups,
respectively. Although our study revealed stasis or progression of T2 hyperintense WMLs over
the course of follow-up, a decrease or resolution of WMLs has been observed. A study of
temporal lobe injury after radiation therapy for nasopharyngeal cancer revealed a decrease or
resolution of T2 hyperintense WMLs in approximately 28% of the lesions .
The age at the time of radiation therapy was higher in the patients with T2 hyperintense
WMLs in our study. As the natural prevalence and severity of WMLs increases with advancing
age, this finding might be a result of the aging process, and differentiation of WMLs from old
age versus those from radiation was not possible in our study [22,23]. A previous study
demonstrated more marked white matter changes with advancing age among those who received
radiation therapy compared with the control group . We hypothesize that the T2 hyperintense
WMLs in our study are much more attributable to radiation therapy. It is possible that
radiation therapy in the brain might cause small and subclinical infarcts by injuring and obstructing
the small vessels, thus accelerating normal white matter change.
There are several limitations in our study. First, there are various limitations in our MR
imaging data used for detecting intracerebral hemorrhages. Because a considerable number of
the intracerebral hemorrhages were small, a few intracerebral hemorrhages might have been
present in the intersection gap and not scanned in our MR imaging data. Thus, in three
patients, intracerebral hemorrhages were detected on the three-year MR images and not on the
five-year MR images. We might have underestimated the true incidence of intracerebral
hemorrhage. Additionally, we used MR imaging systems of various magnetic field strengths
throughout the study. Recently, susceptibility-weighted imaging (SWI) has been widely
available, with improved sensitivity in identifying vascular structures and malformations compared
with that of conventional imaging [25–27]. Using SWI might reveal increased detection of
intracerebral hemorrhages, which requires further investigation. Second, our study is subject to
selection bias because we excluded the patients for whom no appropriate MR imaging data
were available. The incidence of intracerebral hemorrhages and T2 hyperintense WMLs in
patients with short survival (of less than 5 year) or extensive disease could not be determined.
Our Kaplan-Meier estimation of the cumulative incidence of intracerebral hemorrhages suffers
from incomplete data because a number of patients recruited earlier did not undergo GRE
imaging within three years following radiation therapy. Pre-radiation therapy GRE images
were not available in 33 patients, and, although the possibility is low, it is possible that the
intracerebral hemorrhages we detected in these patients were present before the radiation
therapy. Third, the retrospective nature of this study and the lack of a questionnaire survey or
quantitative test inevitably limits thorough symptomatic analysis and could result in
underestimation of the outcomes. Close evaluation of cognitive function in patients receiving radiation
therapy could reveal clinical effect of intracerebral hemorrhage in the future.
Despite these limitations, this study provides valuable information on two complications
following radiation therapy in adult brain tumor patients. Intracerebral hemorrhage is not
uncommon in adult brain tumor patients following radiation therapy and the incidence and
number of intracerebral hemorrhages increased over the course of follow-up. T2 hyperintense
WMLs are not uncommon, and their incidence increases with advancing age.
This study was supported by a grant from the Korea Healthcare Technology R&D Projects,
Ministry for Health, Welfare & Family Affairs (HI13C0015) and by the Research Center
Program of IBS (Institute for Basic Science) in Korea.
Conceived and designed the experiments: DHY SWS TMK SHL SHP CKP IHK SHC.
Performed the experiments: DHY SWS SHP CKP IHK SHC. Analyzed the data: DHY SWS TJY
JHK CHS CKP IHK SHC. Contributed reagents/materials/analysis tools: DHY SWS IHK SHC.
Wrote the paper: DHY SWS TJY TMK SHL JHK CHS SHP CKP IHK SHC.
1. Valk PE , Dillon WP . Radiation injury of the brain . AJNR Am J Neuroradiol . 1991 ; 12 : 45 - 62 . PMID: 7502957
2. Rabin BM , Meyer JR , Berlin JW , Marymount MH , Palka PS , Russell EJ. Radiation- induced changes in the central nervous system and head and neck . RadioGraphics . 1996 ; 16 : 1055 - 1072 . PMID: 8888390
3. Gaensler EH , Dillon WP , Edwards MS , Larson DA , Rosenau W , Wilson CB . Radiation-induced telangiectasia in the brain simulates cryptic vascular malformations at MR imaging . Radiology . 1994 ; 193 ( 3 ): 629 - 636 . PMID: 7972799
4. Pozzati E , Giangaspero F , Marliani F , Acciarri N. Occult cerebrovascular malformations after irradiation . Neurosurgery . 1996 ; 39 ( 4 ): 677 - 682 ; PMID: 8880758
5. Ball WS Jr, Prenger EC , Ballard ET . Neurotoxicity of radio/chemotherapy in children: pathologic and MR correlation . AJNR Am J Neuroradiol . 1992 ; 13 ( 2 ): 761 - 776 . PMID: 1566726
6. Koike S , Aida N , Hata M , Fujita K , Ozawa Y , Inoue T. Asymptomatic radiation-induced telangiectasia in children after cranial irradiation: frequency, latency, and dose relation . Radiology . 2004 ; 230 ( 1 ): 93 - 99 . PMID: 14645879
7. Chan MS , Roebuck DJ , Yuen MP , Li CK , Chan YL. MR imaging of the brain in patients cured of acute lymphoblastic leukemia-the value of gradient echo imaging . AJNR Am J Neuroradiol . 2006 ; 27 ( 3 ): 548 - 552 . PMID: 16551991
8. Reddick WE , Glass JO , Johnson DP , Laningham FH , Pui CH . Voxel-based analysis of T2 hyperintensities in white matter during treatment of childhood leukemia . AJNR Am J Neuroradiol . 2009 ; 30 ( 10 ): 1947 - 1954 doi: 10.3174/ajnr. A1733 PMID: 19643920
9. Wilson DA , Nitschke R , Bowman ME , Chaffin MJ , Sexauer CL , Prince JR . Transient white matter changes on MR images in children undergoing chemotherapy for acute lymphocytic leukemia: correlation with neuropsychologic deficiencies . Radiology . 1991 ; 180 ( 1 ): 205 - 209 . PMID: 2052695
10. Laperriere N , Zuraw L , Cairncross G ; Cancer Care Ontario Practice Guidelines Initiative Neuro-Oncology Disease Site Group. Radiotherapy for newly diagnosed malignant glioma in adults: a systematic review . Radiother Oncol . 2002 ; 64 ( 3 ): 259 - 273 . PMID: 12242114
11. Karim AB , Afra D , Cornu P , Bleehan N , Schraub S , De Witte O , et al. Randomized trial on the efficacy of radiotherapy for cerebral low-grade glioma in the adult: European Organization for Research and Treatment of Cancer Study 22845 with the Medical Research Council study BRO4: an interim analysis . Int J Radiat Oncol Biol Phys . 2002 ; 52 ( 2 ): 316 - 324 . PMID: 11872276
12. van den Bent MJ , Afra D , de Witte O , Ben Hassel M , Schraub S , Hoang-Xuan K , et al. EORTC Radiotherapy and Brain Tumor Groups and the UK Medical Research Council. Long-term efficacy of early versus delayed radiotherapy for low-grade astrocytoma and oligodendroglioma in adults: the EORTC 22845 randomised trial . Lancet . 2005 ; 366 ( 9490 ): 985 - 990 . PMID: 16168780
13. Brant-Zawadzki M , Anderson M , DeArmond SJ , Conley FK , Jahnke RW . Radiation-induced large intracranial vessel occlusive vasculopathy . AJR Am J Roentgenol . 1980 ; 134 ( 1 ): 51 - 55 . PMID: 6766037
14. Tsushima Y , Aoki J , Endo K. Brain microhemorrhages detected on T2*-weighted gradient-echo MR images . AJNR Am J Neuroradiol . 2003 ; 24 ( 1 ): 88 - 96 . PMID: 12533332
15. Oi S , Kokunai T , Ijichi A , Matsumoto S , Raimondi AJ . Radiation-induced brain damage in children-histological analysis of sequential tissue changes in 34 autopsy cases . Neurol Med Chir (Tokyo) . 1990 ; 30 ( 1 ): 36 - 42 .
16. Kato H , Izumiyama M , Izumiyama K , Takahashi A , Itoyama Y. Silent cerebral microbleeds on T2*- weighted MRI: correlation with stroke subtype, stroke recurrence, and leukoaraiosis . Stroke . 2002 ; 33 ( 6 ): 1536 - 1540 . PMID: 12052987
17. Poussaint TY , Siffert J , Barnes PD , Pomeroy SL , Goumnerova LC , Anthony DC , et al. Hemorrhagic vasculopathy after treatment of central nervous system neoplasia in childhood: diagnosis and followup . AJNR Am J Neuroradiol . 1995 ; 16 ( 4 ): 693 - 699 . PMID: 7611024
18. Surma-aho O , Niemela M , Vilkki J , Kouri M , Brander A , Salonen O , et al. Adverse long-term effects of brain radiotherapy in adult low-grade glioma patients . Neurology . 2001 ; 56 ( 10 ): 1285 - 1290 . PMID: 11376174
19. Johannesen TB , Lien HH , Hole KH , Lote K. Radiological and clinical assessment of long-term brain tumour survivors after radiotherapy . Radiother Oncol . 2003 ; 69 ( 2 ): 169 - 176 . PMID: 14643954
20. Douw L , Klein M , Fagel SS , van den Heuvel J , Taphoorn MJ , Aaronson NK , et al. Cognitive and radiological effects of radiotherapy in patients with low-grade glioma: long-term follow-up . Lancet Neurol . 2009 ; 8 ( 9 ): 810 - 818 . doi: 10.1016/ S1474-4422(09)70204-2 PMID: 19665931
21. Wang YX , King AD , Zhou H , Leung SF , Abrigo J , Chan YL , et al. Evolution of radiation-induced brain injury: MR imaging-based study . Radiology . 2010 ; 254 ( 1 ): 210 - 218 doi: 10.1148/radiol.09090428 PMID: 20019142
22. Brant-Zawadzki M , Fein G , Van Dyke C , Kiernan R , Davenport L , de Groot J. MR imaging of the aging brain: patchy white-matter lesions and dementia . AJNR Am J Neuroradiol . 1985 ; 6 ( 5 ): 675 - 682 . PMID: 3933292
23. Meyer JS , Kawamura J , Terayama Y. White matter lesions in the elderly . J Neurol Sci . 1992 ; 110 ( 1-2 ): 1 - 7 . PMID: 1506848
24. Tsuruda JS , Kortman KE , Bradley WG , Wheeler DC , Van Dalsem W , Bradley TP . Radiation effects on cerebral white matter: MR evaluation . AJR Am J Roentgenol . 1987 ; 149 ( 1 ): 165 - 171 . PMID: 3495977
25. Lee BC , Vo KD , Kido DK , Mukherjee P , Reichenbach J , Lin W , et al. MR high-resolution blood oxygenation level-dependent venography of occult (low-flow) vascular lesions . AJNR Am J Neuroradiol . 1999 ; 20 ( 7 ): 1239 - 1242 . PMID: 10472978
26. Haacke EM , Xu Y , Cheng YC , Reichenbach JR . Susceptibility weighted imaging (SWI). Magn Reson Med . 2004 ; 52 ( 3 ): 612 - 618 . PMID: 15334582
27. Mittal S , Wu Z , Neelavalli J , Haacke EM . Susceptibility-weighted imaging: technical aspects and clinical applications , part2. AJNR Am J Neuroradiol . 2009 ; 30 ( 2 ): 232 - 252 . doi: 10.3174/ajnr. A1461 PMID: 19131406