Postop Reactive Enhancement After Resection of Brain Tumors
Postop Reactive Enhancement After Resection of Brain Tumors
Object Early postoperative MRI within 72 hours after brain tumor surgery is commonly used to assess residual contrast-enhancing tumor. The 72-hour window is commonly accepted because previous 1.5-T MRI studies have not found confounding postoperative reactive contrast enhancement in this time frame. The sensitivity to detect contrast enhancement increases with the field strengths. Therefore, the authors aimed to assess whether the 72-hour window is also appropriate for the MRI scanner with a field strength of 3 T.
Methods The authors retrospectively analyzed findings on early postsurgical MR images acquired in 46 patients treated for high-grade gliomas. They performed 3-T MRI within 7 days before surgery and within 72 hours thereafter. The appearance of enhancement was categorized as postoperative reactive enhancement or tumoral enhancement by comparison with the pattern and location of presurgical enhancing tumor.
Results Postoperative reactive enhancement was present in 15 patients (32.6%). This enhancement, not seen on presurgical MRI, had a marginal or leptomeningeal/dural pattern. In 13 patients (28.3%) postsurgical enhancement was found within the first 72 postoperative hours, with the earliest seen 22:57 hours after surgery. Subsequent MR scans in patients with postoperative reactive enhancement did not reveal tumor recurrence in these regions.
Conclusions Postoperative reactive enhancement earlier than 72 hours after brain tumor surgery can be expected in about one-third of the cases in which a 3-T scanner is used. This might be due to the higher enhancement-to-brain contrast at higher field strengths. Therefore, the time window of 72 hours does not prevent reactive enhancement, which, however, can be recognized as such comparing it with presurgical enhancing tumor.
In patients with malignant gliomas, the poor prognosis is determined by the extent of tumor removed, tumor histopathology, age, and symptoms of the patient. The resection of an enhancing tumor (gross-total resection) is known to prolong progression-free and overall survival time of patients. Most tumor progressions are detected within the 1st year after surgery; thus, accurate postoperative assessment is important. In the past, the extent of surgical tumor removal was estimated by the neurosurgeons. By allowing a comparison with the preoperative MRI findings, postoperative MRI, in recent years, has become the method of choice for determining the presence of any residual tumor.
Early postoperative MRI (within 72 hours) is commonly used to determine if a complete tumor resection has been achieved or to show how much enhancing tumor remains in situ. This postoperative MRI study is the basis for making postsurgical decisions and monitoring the effects of subsequent adjuvant therapy. The time window of 72 hours after surgery is recommended to avoid occurrence of nonneoplastic contrast enhancement due to surgical manipulation. Early postoperative enhancement and tumor-induced contrast enhancement can look very much alike. Therefore, benign postoperative enhancement can be difficult to distinguish from that caused by residual tumor. Because MRI studies have shown that reactive enhancement does not occur within 72 hours after surgery, enhancement within this time window indicates the presence of residual tumor tissue. The MRI studies in the past were performed at field strengths of 1.5 T. Today, MRI scanners with higher field strengths (mainly 3 T) are becoming more widely available. The magnetic field dependence of contrast enhancement in brain lesions including brain tumors has been addressed in several studies. The intravenous application of a standard dose of Gd-based contrast medium produces greater contrast between the lesion and normal brain at 3.0 T compared with 1.5 T. The T1 relaxation rate of both the nonenhancing brain tissue and contrast-enhancing tissue decreases with increasing field strength, reducing the T1 effect on T1-weighted images. However, the overall signal increases at 3 T, and the lower background contrast between gray and white matter yields a higher sensitivity to detect contrast-enhancing lesions. Until now, there has been no published systematic analysis of the reliability of the 72-hour window as it applies to 3-T MRI. Therefore, we aimed to evaluate if this timeframe is also appropriate for the 3-T MR images. To this end, we retrospectively analyzed the clinical and MRI data of patients with high-grade gliomas who underwent tumor resection.
Abstract and Introduction
Abstract
Object Early postoperative MRI within 72 hours after brain tumor surgery is commonly used to assess residual contrast-enhancing tumor. The 72-hour window is commonly accepted because previous 1.5-T MRI studies have not found confounding postoperative reactive contrast enhancement in this time frame. The sensitivity to detect contrast enhancement increases with the field strengths. Therefore, the authors aimed to assess whether the 72-hour window is also appropriate for the MRI scanner with a field strength of 3 T.
Methods The authors retrospectively analyzed findings on early postsurgical MR images acquired in 46 patients treated for high-grade gliomas. They performed 3-T MRI within 7 days before surgery and within 72 hours thereafter. The appearance of enhancement was categorized as postoperative reactive enhancement or tumoral enhancement by comparison with the pattern and location of presurgical enhancing tumor.
Results Postoperative reactive enhancement was present in 15 patients (32.6%). This enhancement, not seen on presurgical MRI, had a marginal or leptomeningeal/dural pattern. In 13 patients (28.3%) postsurgical enhancement was found within the first 72 postoperative hours, with the earliest seen 22:57 hours after surgery. Subsequent MR scans in patients with postoperative reactive enhancement did not reveal tumor recurrence in these regions.
Conclusions Postoperative reactive enhancement earlier than 72 hours after brain tumor surgery can be expected in about one-third of the cases in which a 3-T scanner is used. This might be due to the higher enhancement-to-brain contrast at higher field strengths. Therefore, the time window of 72 hours does not prevent reactive enhancement, which, however, can be recognized as such comparing it with presurgical enhancing tumor.
Introduction
In patients with malignant gliomas, the poor prognosis is determined by the extent of tumor removed, tumor histopathology, age, and symptoms of the patient. The resection of an enhancing tumor (gross-total resection) is known to prolong progression-free and overall survival time of patients. Most tumor progressions are detected within the 1st year after surgery; thus, accurate postoperative assessment is important. In the past, the extent of surgical tumor removal was estimated by the neurosurgeons. By allowing a comparison with the preoperative MRI findings, postoperative MRI, in recent years, has become the method of choice for determining the presence of any residual tumor.
Early postoperative MRI (within 72 hours) is commonly used to determine if a complete tumor resection has been achieved or to show how much enhancing tumor remains in situ. This postoperative MRI study is the basis for making postsurgical decisions and monitoring the effects of subsequent adjuvant therapy. The time window of 72 hours after surgery is recommended to avoid occurrence of nonneoplastic contrast enhancement due to surgical manipulation. Early postoperative enhancement and tumor-induced contrast enhancement can look very much alike. Therefore, benign postoperative enhancement can be difficult to distinguish from that caused by residual tumor. Because MRI studies have shown that reactive enhancement does not occur within 72 hours after surgery, enhancement within this time window indicates the presence of residual tumor tissue. The MRI studies in the past were performed at field strengths of 1.5 T. Today, MRI scanners with higher field strengths (mainly 3 T) are becoming more widely available. The magnetic field dependence of contrast enhancement in brain lesions including brain tumors has been addressed in several studies. The intravenous application of a standard dose of Gd-based contrast medium produces greater contrast between the lesion and normal brain at 3.0 T compared with 1.5 T. The T1 relaxation rate of both the nonenhancing brain tissue and contrast-enhancing tissue decreases with increasing field strength, reducing the T1 effect on T1-weighted images. However, the overall signal increases at 3 T, and the lower background contrast between gray and white matter yields a higher sensitivity to detect contrast-enhancing lesions. Until now, there has been no published systematic analysis of the reliability of the 72-hour window as it applies to 3-T MRI. Therefore, we aimed to evaluate if this timeframe is also appropriate for the 3-T MR images. To this end, we retrospectively analyzed the clinical and MRI data of patients with high-grade gliomas who underwent tumor resection.