Tsukasa Sasaki

Quantification of myocardial blood flow using dynamic 320-row multi-detector CT as compared with 15O-H2O PET

AbstractObjectivesThis study introduces a method to calculate myocardium blood flow (MBF) and coronary flow reserve (CFR) using the relatively low-dose dynamic 320-row multi-detector computed tomography (MDCT), validates the method against 15O-H2O positron-emission tomography (PET) and assesses the CFRs of coronary artery disease (CAD) patients.MethodsThirty-two subjects underwent both dynamic CT perfusion (CTP) and PET perfusion imaging at rest and during pharmacological stress. In 12 normal subjects (pilot group), the calculation method for MBF and CFR was established. In the other 13 normal subjects (validation group), MBF and CFR obtained by dynamic CTP and PET were compared. Finally, the CFRs obtained by dynamic CTP and PET were compared between the validation group and CAD patients (n = 7).ResultsCorrelation between MBF of MDCT and PET was strong (r = 0.95, P < 0.0001). CFR showed good correlation between dynamic CTP and PET (r = 0.67, P = 0.0126). CFRCT in the CAD group (2.3 ± 0.8) was significantly lower than that in the validation group (5.2 ± 1.8) (P = 0.0011).ConclusionsWe established a method for measuring MBF and CFR with the relatively low-dose dynamic MDCT. Lower CFR was well demonstrated in CAD patients by dynamic CTP.Key Points• MBF and CFR can be calculated using dynamic CTP with 320-row MDCT. • MBF and CFR showed good correlation between dynamic CTP and PET. • Lower CFR was well demonstrated in CAD patients by dynamic CTP.

Thrombosis in the Pulmonary Vein Stump After Left Upper Lobectomy as a Possible Cause of Cerebral Infarction

BACKGROUND Thrombus in the stump of the pulmonary vein (PV) is not a well-known complication after lung resection, and it has the potential to cause embolism to vital organs. To clarify the frequency, risk factors, and cause of this complication, a retrospective clinical study of patients who underwent lobectomy was performed. METHODS The study evaluated 193 patients with primary lung cancer who underwent lobectomy from 2005 to 2011 and contrast-enhanced chest computed tomography (CT) within 2 years after lobectomy. Contrast-enhanced CT was retrospectively interpreted to check for thrombus in the PV stump. RESULTS The operative procedures were 65 right upper lobectomies, 14 right middle lobectomies, 40 right lower lobectomies, 52 left upper lobectomies (LUL), and 22 left lower lobectomies. Thrombus developed in the PV stump in 7 of the 193 patients (3.6%) after lobectomy. All patients with thrombus had undergone LUL, and 13.5% of those who had undergone LUL developed thrombus. Univariate analyses revealed that LUL and operation time were significant risk factors and that adjuvant chemotherapy was marginally significant. It appears that thrombus may be attributable to the length of the PV stump. Measurement of the length of the PV stump using 3-dimensional CT images of the PV revealed that the stump of the left superior PV was longer than the others. CONCLUSIONS Thrombus in the PV stump occurred in 13.5% of patients after LUL. These findings suggest that contrast-enhanced CT should be recommended for patients after LUL to help identify those with a high risk for thromboembolism.

Realization of reliable cerebral-blood-flow maps from low-dose CT perfusion images by statistical noise reduction using nonlinear diffusion filtering.

X-ray computed tomographic perfusion (CTP) imaging, a rapid method for measuring cerebral blood flow (CBF), is an effective modality for assessment of the severity and extent of brain tissue ischemia. Low-dose scanning has been required for CTP imaging for reducing the radiation exposure to patients, because the same plane is scanned repeatedly. Low-dose CTP imaging, however, results in substantial statistical noise in the images, which may negatively impact the accuracy of CBF values. Because CBF values are calculated from the set of CTP images, it is important to reduce the statistical noise in raw CTP images to make the values reliable. Noise reduction must be performed without blurring of vessel structures, because such blurring will overestimate CBF values. For this purpose, two-dimensional nonlinear diffusion filtering (NLDF) was introduced. It was applied to CTP images of a CTP phantom for evaluating the accuracy of CBF values in low-dose CTP and to clinical low-dose CTP images for determining its effectiveness in actual CTP examinations. NLDF successfully reduced the statistical noise in the CTP images while preserving the sharp edges. This feature generated CBF values close to the reference value, producing reliable CBF maps from low-dose CT perfusion images. The CBF maps obtained with NLDF were comparable to or better than those obtained by other, commercial CTP software programs. The use of NLDF was thus effective for manipulation of low-dose CT perfusion images.

Tunnel Enlargement and Coalition After Anatomic Double-Bundle Anterior Cruciate Ligament Reconstruction With Hamstring Tendon Autografts A Computed Tomography Study

Background: Tunnel enlargement and coalition following double-bundle anterior cruciate ligament (ACL) reconstruction with hamstring tendon autografts has not yet been sufficiently studied. Hypothesis: The incidence and the degree of femoral tunnel enlargement will be significantly greater than those for tibial tunnel enlargement after anatomic double-bundle ACL reconstruction using hamstring tendon autografts. There will be no significant correlation between tunnel enlargement and coalition and the postoperative knee laxity. Study Design: Case series; Level of evidence, 4. Methods: Thirty-nine patients who underwent anatomic double-bundle ACL reconstruction using semitendinosus and gracilis tendon autografts were followed up for 1 year after surgery. The grafts were simultaneously fixed at 10° of knee flexion with EndoButtons and spiked staples. All patients were examined with computed tomography and the standard clinical evaluation methods at 2 weeks and 1 year after surgery. Results: The degree of tunnel enlargement of the femoral anteromedial and posterolateral tunnels averaged 10% to 11% and 7% to 9%, respectively, while that of the tibial anteromedial and posterolateral tunnels averaged 3% to 7% and 1% to 6%. The degree and incidence of the anteromedial and posterolateral tunnel enlargement were significantly greater in the femur than in the tibia (P < .0335 and P < .0405, respectively). On the femoral and tibial intra-articular surface, tunnel outlet coalition was found in 5% and 77% of the knees, respectively, at 1 year after surgery. There was no significant correlation between tunnel enlargement and coalition and the clinical outcome. Conclusion: The incidence and the degree of each tunnel enlargement in the femur were significantly greater than that in the tibia. However, the incidence of tunnel coalition in the femur was significantly less than that in the tibia after double-bundle ACL reconstruction with a transtibial technique. There was no significant correlation between tunnel enlargement and coalition and the clinical outcome. Clinical Relevance: The present study provides orthopaedic surgeons with important information on double-bundle ACL reconstruction with hamstring tendons.

Calibration method for lumbosacral dimensions in wearable sensor system of lumbar alignment

Anteflexion of the spine is essential for many physical activities in everyday life. However, this motion places the lumbar disks under heavy load due to changes in the shape of the lumbar spine and can lead to low back pain. With the aim of reducing low back pain, here we developed a wearable sensor system that can estimate lumbosacral alignment and lumbar load by measuring the shape of the lumbar skin when the lumbosacral alignment changes. In addition, we used this system to measure the parameters of anteflexion and studied the change in dimensions of the lumbar spine from changes in posture. By determining the dimensions of the lumbosacral spine on an X-ray image, a lumbosacral dimensions calibration method based on body surface area and height was developed. By using this method, lumbosacral alignment and lumbar load could be accurately estimated using the wearable sensor system.

Volume-rendering and endocardial views of partially unroofed coronary sinus with 64-slice multidetector CT

We diagnosed unroofed coronary sinus preoperatively by the 3D volume rendering and endocardial views with 64-slice MDCT, and those clearly showed the defect of the roof of the coronary sinus and the relationship with the surrounding structure. MDCT is a good non-invasive tool for the evaluation of unroofed coronary sinus, and the reconstructed endocardial view is useful for preoperative surgical planning.

Evaluation of dose efficiency index compared to receiver operating characteristics for assessing CT low-contrast performance

The dose efficiency index (DEI) is a dose independent measure that quantifies the low-contrast performance of CT scanners. The purpose of this paper is to compare the results of DEI analysis with those of ROC analysis. A custom-made phantom consisting of diluted contrast targets of various sizes and densities was scanned at 80 & 120 kV on a multislice CT scanner (Hispeed Advantage RP, GE). Eight radiographers reviewed the images and identified discernable targets. The likelihood of detection was measured as a function of the target size and scan conditions. The results of the DEI & ROC analyses showed that the low-contrast resolution was higher at 80kV than at 120kV. The p-value obtained by the paired-t test was 0.000 for both analyses, indicating that the difference was significant. Under the conditions used in this study, the DEI analysis was found to be an effective alternative to ROC analysis for characterizing the low-contrast performance of CT scanners. The evaluation time was about 1/6 compared with ROC analysis. It is much simpler to calculate than ROC and is useful in comparing scanners from different manufacturers or as part of ongoing quality assurance.

Assessment of congenital nasal stenosis by shaded surface display reconstruction images

A girl, born at 38 weeks and 3 days of gestation by normal vaginal delivery, weighed 2660 g at birth. Her Apgar score was 7 at 1 min. Because generalized cyanosis and retraction were noted when she did not cry, congenital nasal obstruction was suspected and oral endotracheal intubation given to her. It was not possible to pass a nasogastric tube (size 5 Fr) through her nostrils into the nasopharynx, but expiratory air flow from her nostrils was apparent. She needed no mechanical ventilation. Blood gas values and chest X-ray findings were normal. No other anomalies were detected. In skull X-ray pictures (Fig. 1), while bilateral pyriform apertures were patent, the maximum distance between them was 9 mm, which is much smaller than the distance between bilateral orbits (15 mm). Its ratio to the width of mandibula (56 mm) was 0.16 (normal range 0.22–0.28),2 indicating hypoplasia of bony nasal cavities. Nasal airway fiberscopy by oral approach disclosed the patency of choanae, but gave no further information regarding the severity and location of the obstruction. Plain computed tomography (CT) showed scant air at the anterior space of the nasal airways, but disclosed no apparent lesions such as bony stenoses and abnormal mass (Fig. 2). We diagnosed the patient with congenital nasal stenosis and continued the conservative treatments, including oral endotracheal intubation without mechanical ventilation, orogastric tube feeding and intranasal medication of naphazoline nitrate and betamethasone sodium phosphate. Even after she was extubated on the 67th day of life, until she had adapted to mouth breathing, oral feeding was impossible and apneic episodes occurred constantly. We then performed helical CT with a Somatom Plus 40 scanner (Siemens, Erlangen, Germany). Slice thickness was settled at 1 mm and table speed at 1 mm/rotation per s. The X-ray tube potential and current were set at 145 mA and 137 kV, respectively. Total scanning time was 34 s. In order to obtain the selective visualization of airway, shaded surface display (SSD) reconstructions were performed with a software package provided by the manufacturer. The choice of threshold level was between 200 and 555 Hounsfield Units (HU). The SSD images of nasal airways on the 88th day showed no air spaces at lower portions of meatus nasi and interruptions of bilateral airways between anterior space and meatus nasi superior (Fig. 3a). We concluded from these findings that severe stenoses existed at bilateral conchae nasalis inferior. On the 116th day, transnasal resection of bilateral conchae nasalis inferior was performed. After this operation, the patient gradually grew accustomed to oral feeding and no more apneic episodes occurred. She was discharged on the 146th day. The SSD images on the 154th day showed air spaces at lower portions of meatus nasi and neither stenoses nor interruptions were noted in bilateral nasal airways (Fig. 3b).

Variations of pulmonary vein drainage critical for lung resection assessed by three-dimensional computed tomography angiography: Pulmonary veins assessed by 3D-CT

It is important to understand pulmonary vein drainage pattern variations and their frequency in order to perform safe anatomical pulmonary resection.

Diagnostic value of quantitative coronary flow reserve and myocardial blood flow estimated by dynamic 320 MDCT scanning in patients with obstructive coronary artery disease

Abstract We have developed the method for dynamic 320-row multidetector computed tomography (MDCT)-derived quantitative coronary flow reserve (CFRCT) and hyperemic myocardial blood flow (MBFCT). We evaluated diagnostic value of CFRCT and hyperemic MBFCT for detecting obstructive coronary artery disease (CAD) in per-patient and per-vessel analysis, and their relations with the severity of CAD burden. Adenosine stressed and rest dynamic myocardial perfusion MDCT were prospectively performed in patients with known or suspected CAD. Per-patient and per-vessel MBFCT were estimated from dynamic perfusion images in rest and hyperemic phases, and per-patient and per-vessel CFRCT were calculated from the ratio of rest and hyperemic MBFCT. Degree of stenosis was evaluated by coronary CT angiography (CTA) and invasive coronary angiography (ICA). Obstructive stenosis was defined as ≥70% stenosis in ICA. CAD burden with MDCT was calculated by logarithm transformed coronary artery calcium (CAC) score and the CTA-adapted Leaman risk score (CT-LeSc). A logistic regression analysis was used to measure the receiver-operating characteristic curve and corresponding area under the curve (AUC) for the detection of obstructive CAD. Twenty-seven patients and 81 vessels were eligible for this study. Sixteen patients had obstructive CAD, and 31 vessels had obstructive stenosis. Using an optimal cutoff, the CFRCT and hyperemic MBFCT had the moderate diagnostic values in per-patient (AUC = 0.89 and 0.86, respectively) and per-vessel (AUC = 0.79 and 0.76, respectively). Per-patient CFRCT and hyperemic MBFCT exhibited a moderate inverse correlation with CAC score and the CT-LeSc. Per-patient and per-vessel CFRCT as well as hyperemic MBFCT had moderate diagnostic value for detecting obstructive CAD. These per-patient values exhibited a moderate inverse correlation with CAD burden. CFRCT and hyperemic MBFCT might add quantitative functional information for evaluating patients with CAD.