Jpn J Radiol DOI 10.1007/s11604-015-0429-y
ORIGINAL ARTICLE
Can CT angiography reconstructed from CT perfusion source data on a 320‑section volume CT scanner replace conventional CT angiography for the evaluation of intracranial arteries? Masafumi Kidoh1 · Toshinori Hirai3 · Seitaro Oda1 · Daisuke Utsunomiya1 · Takayuki Kawano2 · Shigetoshi Yano2 · Hideo Nakamura2 · Keishi Makino2 · Yasuhiko Iryo1 · Minako Azuma1 · Eri Hayashida1 · Takeshi Nakaura1 · Yasuyuki Yamashita1 Received: 29 March 2015 / Accepted: 24 April 2015 © Japan Radiological Society 2015
Abstract Purpose To compare conventional CT angiography (CTA) and CTA reconstructed from CT perfusion source data (perfusion CTA) acquired on a 320-section CT scanner for the evaluation of intracranial arteries. Materials and methods Our study included 7 patients who had undergone trapping of an intracranial aneurysm and placement of a bypass. All underwent conventional and perfusion CTA and digital subtraction angiography (DSA). Using DSA as the gold standard, 2 radiologists evaluated 10 arterial segments on conventional and perfusion CTA images. On a 4-point scale they independently scored the image quality and vascular visualization of the intracranial arteries on the conventional and perfusion CTA images. The effective radiation dose to each patient was also recorded. Results A total of 65 arterial segments without apparent abnormalities were assessed. While the mean image quality score tended to be slightly higher for conventional than perfusion CTA, there was no significant difference. The effective dose for perfusion and conventional CTA with unenhanced CT was 4.2 mSv and 3.1 mSv, respectively, for all patients. Conclusion For the evaluation of intracranial arteries using DSA as the gold standard, perfusion CTA yields * Masafumi Kidoh [email protected] 1
Department of Diagnostic Radiology, Faculty of Life Sciences, Kumamoto University, 1‑1‑1, Honjo, Kumamoto 860‑8556, Japan
2
Department of Neurosurgery, Faculty of Life Sciences, Kumamoto University, 1‑1‑1, Honjo, Kumamoto 860‑8556, Japan
3
Department of Radiology, School of Medicine, Miyazaki University, Miyazaki, Japan
image quality and vascular visualization similar to conventional CTA at an acceptable radiation dose. Keywords Computed tomography (CT) · CT Angiography (CTA) · Perfusion CTA · Diagnosis Abbreviations CTA CT angiography CTP CT perfusion CBF Cerebral blood flow CBV Cerebral blood volume MTT Mean transit time DSA Digital subtraction angiography
Introduction Recent developments in computed tomography (CT) technology facilitate the rapid assessment of both the blood vessel diameter and the tissue blood flow. CT perfusion (CTP) imaging, a simple way to measure the cerebral blood flow (CBF), cerebral blood volume (CBV) and mean transit time (MTT) [1], has been used for the assessment of acute stroke [2–4] and delayed cerebral ischemia related to vasospasm [5, 6] and for brain tumor imaging [7, 8]. CTP imaging involves cine scanning with repetitive imaging through several sections of the brain to track the first pass of the contrast bolus [9]. A major concern is the high radiation dose associated with CTP imaging, which is often performed in combination with unenhanced CT and CT angiography (CTA) [10]. The new, second-generation 320-section CT unit combines faster gantry rotation, wide volume coverage (16 cm), a larger power generator and a newer-generation iterative reconstruction algorithm [11]. It may make it possible to
13
perform diagnostic-quality whole-brain CTP studies at low radiation exposure without having to move the patient. If CTA images are reconstructed from CTP source data, neither additional radiation exposure nor the administration of a contrast agent for CTA is necessary. This technique may represent a substitute for conventional CTA for the evaluation of the cerebral vasculature. As no systematic comparison of conventional CTA with CTA reconstructed from CTP source data (perfusion CTA) obtained on the second-generation 320-section CT has been reported, we performed conventional and perfusion CTA for the evaluation of intracranial arteries and compared our findings. We used digital subtraction angiography (DSA) as the gold standard.
Materials and methods This study was approved by our institutional review board; informed consent was obtained from all patients. Patient population In our radiology database we identified 7 consecutive patients who had undergone contrast-enhanced head CT (conventional CTA and CTP) and DSA between January 2014 and March 2014: 3 males and 4 females ranging in age from 40−64 years (mean age, 56.1 years); all had undergone trapping of an intracranial aneurysm and bypass surgery. CT data acquisition and image processing All CT images were obtained on a second-generation 320-section CT scanner (Aquilion ONE ViSION, Toshiba Medical Systems, Otawara) in one session and
Jpn J Radiol
reconstructed with 3D adaptive iterative dose reduction (AIDR 3D, Toshiba, Otawara, Japan). The data acquisition parameters for conventional CTA and unenhanced CT for bone subtraction were sequential acquisition, 320 × 0.5-mm detector collimation, 1.0-s tube rotation time, 300-mA tube current and 120-kVp tube voltage. For conventional CTA, 50 ml of 370-mgI/ml iodinated contrast material was delivered via a 20-gauge catheter inserted into the antecubital vein at 5.0 ml/s; a power injector (Dual Shot GX; Nemoto-Kyorindo, Tokyo) was used. This was followed by the administration of 30 ml saline solution delivered at the same injection rate. Unenhanced CT for bone subtraction was performed before contrast injection. Next, we performed conventional CTA using a bolus tracking technique that optimizes the scanning delay for arterial scanning. Unenhanced CT and conventional CTA data sets were transferred to an image processing workstation (Vitrea ver. 6.4, Toshiba) equipped with a software tool for bone-subtraction CTA; its algorithm selectively eliminates bone from the CTA data set while retaining both soft-tissue and contrast-enhanced vessels. The data acquisition parameters for CTP were sequential acquisition, 320 × 0.5-mm detector collimation, 1.0-s tube rotation time, 100 mA tube current and 80-kVp tube voltage. After the delivery of 50 ml of 370-mgI/ml iodinated contrast material at 5.0 ml/s, 30 ml saline was injected at the same rate. The scan was started 5 s after contrast injection. The CTP protocol consisted of 20 dynamic volumes; the total acquisition time was 55 s, and the acquisition interval was 2 s for pre-contrast- and arterial phase scanning and 5 s for venous-phase scans (Fig. 1). Perfusion CTA images were derived from the CTP source data on an image processing workstation (Vitrea, version 6.4, Toshiba). Multiple pre-contrast CTP images were selected and averaged to reconstruct a mask image. The software subtracted the unenhanced mask image from
Fig. 1 Schematic representation of the CTP protocol. The scan was started 5 s after contrast injection. The CTP protocol consisted of 20 dynamic volumes, with a total acquisition time of 55 s (acquisition interval was 2 s for pre-contrast- and arterial phase and 5 s for venous phase)
13
Jpn J Radiol
the contrast-enhanced CTP images to ensure that only the vessels remained visible. Multiple subtracted images with high arterial contrast (5 arterial phases) were selected; they were averaged to reconstruct a CTA image.
derived from the product of DLP and a conversion coefficient for the head (k = 0.0021 mSv mGy−1 cm−1) [12].
DSA technique
The Wilcoxon signed-rank test was used for assessment of the image quality and vascular visualization. Interobserver and intermodality agreements were assessed with Cohen’s kappa statistics. All statistical analyses were performed using the statistical software package JMP 9.0.2 (SAS Institute, Cary, NC, USA). Differences of p
ORIGINAL ARTICLE
Can CT angiography reconstructed from CT perfusion source data on a 320‑section volume CT scanner replace conventional CT angiography for the evaluation of intracranial arteries? Masafumi Kidoh1 · Toshinori Hirai3 · Seitaro Oda1 · Daisuke Utsunomiya1 · Takayuki Kawano2 · Shigetoshi Yano2 · Hideo Nakamura2 · Keishi Makino2 · Yasuhiko Iryo1 · Minako Azuma1 · Eri Hayashida1 · Takeshi Nakaura1 · Yasuyuki Yamashita1 Received: 29 March 2015 / Accepted: 24 April 2015 © Japan Radiological Society 2015
Abstract Purpose To compare conventional CT angiography (CTA) and CTA reconstructed from CT perfusion source data (perfusion CTA) acquired on a 320-section CT scanner for the evaluation of intracranial arteries. Materials and methods Our study included 7 patients who had undergone trapping of an intracranial aneurysm and placement of a bypass. All underwent conventional and perfusion CTA and digital subtraction angiography (DSA). Using DSA as the gold standard, 2 radiologists evaluated 10 arterial segments on conventional and perfusion CTA images. On a 4-point scale they independently scored the image quality and vascular visualization of the intracranial arteries on the conventional and perfusion CTA images. The effective radiation dose to each patient was also recorded. Results A total of 65 arterial segments without apparent abnormalities were assessed. While the mean image quality score tended to be slightly higher for conventional than perfusion CTA, there was no significant difference. The effective dose for perfusion and conventional CTA with unenhanced CT was 4.2 mSv and 3.1 mSv, respectively, for all patients. Conclusion For the evaluation of intracranial arteries using DSA as the gold standard, perfusion CTA yields * Masafumi Kidoh [email protected] 1
Department of Diagnostic Radiology, Faculty of Life Sciences, Kumamoto University, 1‑1‑1, Honjo, Kumamoto 860‑8556, Japan
2
Department of Neurosurgery, Faculty of Life Sciences, Kumamoto University, 1‑1‑1, Honjo, Kumamoto 860‑8556, Japan
3
Department of Radiology, School of Medicine, Miyazaki University, Miyazaki, Japan
image quality and vascular visualization similar to conventional CTA at an acceptable radiation dose. Keywords Computed tomography (CT) · CT Angiography (CTA) · Perfusion CTA · Diagnosis Abbreviations CTA CT angiography CTP CT perfusion CBF Cerebral blood flow CBV Cerebral blood volume MTT Mean transit time DSA Digital subtraction angiography
Introduction Recent developments in computed tomography (CT) technology facilitate the rapid assessment of both the blood vessel diameter and the tissue blood flow. CT perfusion (CTP) imaging, a simple way to measure the cerebral blood flow (CBF), cerebral blood volume (CBV) and mean transit time (MTT) [1], has been used for the assessment of acute stroke [2–4] and delayed cerebral ischemia related to vasospasm [5, 6] and for brain tumor imaging [7, 8]. CTP imaging involves cine scanning with repetitive imaging through several sections of the brain to track the first pass of the contrast bolus [9]. A major concern is the high radiation dose associated with CTP imaging, which is often performed in combination with unenhanced CT and CT angiography (CTA) [10]. The new, second-generation 320-section CT unit combines faster gantry rotation, wide volume coverage (16 cm), a larger power generator and a newer-generation iterative reconstruction algorithm [11]. It may make it possible to
13
perform diagnostic-quality whole-brain CTP studies at low radiation exposure without having to move the patient. If CTA images are reconstructed from CTP source data, neither additional radiation exposure nor the administration of a contrast agent for CTA is necessary. This technique may represent a substitute for conventional CTA for the evaluation of the cerebral vasculature. As no systematic comparison of conventional CTA with CTA reconstructed from CTP source data (perfusion CTA) obtained on the second-generation 320-section CT has been reported, we performed conventional and perfusion CTA for the evaluation of intracranial arteries and compared our findings. We used digital subtraction angiography (DSA) as the gold standard.
Materials and methods This study was approved by our institutional review board; informed consent was obtained from all patients. Patient population In our radiology database we identified 7 consecutive patients who had undergone contrast-enhanced head CT (conventional CTA and CTP) and DSA between January 2014 and March 2014: 3 males and 4 females ranging in age from 40−64 years (mean age, 56.1 years); all had undergone trapping of an intracranial aneurysm and bypass surgery. CT data acquisition and image processing All CT images were obtained on a second-generation 320-section CT scanner (Aquilion ONE ViSION, Toshiba Medical Systems, Otawara) in one session and
Jpn J Radiol
reconstructed with 3D adaptive iterative dose reduction (AIDR 3D, Toshiba, Otawara, Japan). The data acquisition parameters for conventional CTA and unenhanced CT for bone subtraction were sequential acquisition, 320 × 0.5-mm detector collimation, 1.0-s tube rotation time, 300-mA tube current and 120-kVp tube voltage. For conventional CTA, 50 ml of 370-mgI/ml iodinated contrast material was delivered via a 20-gauge catheter inserted into the antecubital vein at 5.0 ml/s; a power injector (Dual Shot GX; Nemoto-Kyorindo, Tokyo) was used. This was followed by the administration of 30 ml saline solution delivered at the same injection rate. Unenhanced CT for bone subtraction was performed before contrast injection. Next, we performed conventional CTA using a bolus tracking technique that optimizes the scanning delay for arterial scanning. Unenhanced CT and conventional CTA data sets were transferred to an image processing workstation (Vitrea ver. 6.4, Toshiba) equipped with a software tool for bone-subtraction CTA; its algorithm selectively eliminates bone from the CTA data set while retaining both soft-tissue and contrast-enhanced vessels. The data acquisition parameters for CTP were sequential acquisition, 320 × 0.5-mm detector collimation, 1.0-s tube rotation time, 100 mA tube current and 80-kVp tube voltage. After the delivery of 50 ml of 370-mgI/ml iodinated contrast material at 5.0 ml/s, 30 ml saline was injected at the same rate. The scan was started 5 s after contrast injection. The CTP protocol consisted of 20 dynamic volumes; the total acquisition time was 55 s, and the acquisition interval was 2 s for pre-contrast- and arterial phase scanning and 5 s for venous-phase scans (Fig. 1). Perfusion CTA images were derived from the CTP source data on an image processing workstation (Vitrea, version 6.4, Toshiba). Multiple pre-contrast CTP images were selected and averaged to reconstruct a mask image. The software subtracted the unenhanced mask image from
Fig. 1 Schematic representation of the CTP protocol. The scan was started 5 s after contrast injection. The CTP protocol consisted of 20 dynamic volumes, with a total acquisition time of 55 s (acquisition interval was 2 s for pre-contrast- and arterial phase and 5 s for venous phase)
13
Jpn J Radiol
the contrast-enhanced CTP images to ensure that only the vessels remained visible. Multiple subtracted images with high arterial contrast (5 arterial phases) were selected; they were averaged to reconstruct a CTA image.
derived from the product of DLP and a conversion coefficient for the head (k = 0.0021 mSv mGy−1 cm−1) [12].
DSA technique
The Wilcoxon signed-rank test was used for assessment of the image quality and vascular visualization. Interobserver and intermodality agreements were assessed with Cohen’s kappa statistics. All statistical analyses were performed using the statistical software package JMP 9.0.2 (SAS Institute, Cary, NC, USA). Differences of p
