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Daisuke Takenaka

Publications and source records attributed to Daisuke Takenaka.

9 recordsLinked to original sources
PubMed2003

Three-dimensional treatment planning using electrocardiographically gated multi-detector row CT.

PURPOSE: Information concerning the amount and nature of target motion is essential for the determination of internal margin size. However, there are few published reports outlining the motion with heart and aortic pulsation. We introduce a method for three-dimensional radiation treatment planning (3D-RTP) by using electrocardiographically (ECG) gated spiral scanning with a four-section CT system. We describe a new approach to visualize internal organ motion resulting from cardiac motion with ECG gated multidetector row CT. MATERIALS AND METHODS: Five patients with lung or liver tumors were studied with a multidetector row CT system under shallow inspiration breath-holding. With retrospective ECG gating, only data acquired within a predefined interval of the cardiac cycle are used for image reconstruction. All reconstructed image data at diastolic and systolic phases of the cardiac cycle were transferred to the 3D-RTP system. The shift of the internal organs between the cardiac cycles was evaluated. RESULTS: Cardiac contraction influences anterior thorax, pulmonary peripheral vessels, and liver position, in addition to locations near the heart. Apparent movements more than 5 mm between diastolic and systolic phases were observed in the left ventricle, right atrium, and superior vena cava. Two-phase imaging was useful for showing the movement of internal organs during cardiac contraction under breath-holding. CONCLUSIONS: Spatial information using ECG-gated CT has the potential to determine the planning target volume of moving lung and liver tumors more precisely than conventional CT planning.

Computer Systems↗
PubMed2003

Time-resolved contrast-enhanced pulmonary MR angiography using sensitivity encoding (SENSE).

PURPOSE: To evaluate the relationship between gadolinium concentration and signal-to-noise ratio (SNR) on sensitivity encoding (SENSE) images, and determine the appropriate bolus injection protocol for visualizing pulmonary circulation. MATERIALS AND METHODS: Eighteen different gadolinium concentration phantoms (0, 0.01, 0.05, 0.1, 0.2, 0.4, 0.6, 0.8, 1.0, 1.2, 1.5, 2.0, 5.0, 10.0, 20.0, 30.0, 50.0, and 100.0 mmol/L) were analyzed to determine the relationship between gadolinium concentration and SNR on SENSE images in a phantom study. In an in vivo study, 3 mL (protocol A) or 6 mL (protocol B) of Gd-DTPA BMA at 3 mL/second, and 5 mL of Gd-DTPA BMA at 5 mL/second (protocol C) were administered to eight normal volunteers for contrast-enhanced (CE) pulmonary MR angiography (MRA) with SENSE. The peak SNRs of pulmonary parenchyma and the difference in SNR between pulmonary artery (PA) and pulmonary vein (PV) at peak SNR in the PA were statistically evaluated. RESULTS: For each flip angle at each gadolinium concentration, the SNRs and contrast-to-noise ratios (CNRs) of the SENSE images were significantly lower than those acquired with a nonparallel imaging technique (P < 0.05). The peak SNR of the pulmonary parenchyma, and differences in SNR between the PA and PV at the peak SNR of the PA obtained with a 5-mL/second bolus injection protocol were found to be significantly higher than those obtained with other protocols (P < 0.05). CONCLUSION: 3D-CE-MRA using SENSE demonstrated linearity between gadolinium concentration and SNR, and resulted in MRA with high spatial and temporal resolution with the aid of a sharp bolus injection protocol.

Adult↗
PubMed2003

CT-guided transthoracic needle aspiration biopsy of small (< or = 20 mm) solitary pulmonary nodules.

OBJECTIVE: The purpose of our study was to determine the diagnostic accuracy and to analyze the factors influencing the diagnostic accuracy and incidences of pneumothorax and chest tube insertion rates for percutaneous CT-guided needle biopsy of small (< or = 20 mm) solitary pulmonary nodules. SUBJECTS AND METHODS: One hundred sixty-two patients with 162 small solitary pulmonary nodules underwent CT-guided transthoracic needle aspiration biopsy. The overall diagnostic accuracy, pneumothorax rate, and chest tube insertion rate were calculated. Factors influencing the diagnostic accuracy and pneumothorax rate were statistically evaluated. Influencing factors, diagnostic accuracies, pneumothorax rates, and chest tube insertion rates were statistically compared. RESULTS: Overall diagnostic accuracy, pneumothorax rate, and chest tube insertion rate were 77.2%, 28.4%, and 2.5%, respectively. Diagnostic accuracy was significantly affected by length of needle path and lesion size (p < 0.05). The pneumothorax rate was significantly affected by the percentage of predicted forced expiratory volume in 1 sec, the number of punctures, and the needle path length (p < 0.05). The chest tube insertion rate was significantly affected by the number of punctures (p < 0.05). For diagnostic accuracy, needle path lengths of 40 mm or less and lesion sizes greater than 10 mm were significantly more accurate than other factors (p < 0.05). For pneumothorax rates, a percentage of predicted forced expiratory volume in 1 sec of greater than 70%, a single puncture, and a needle path length of 40 mm or less were significantly lower than other factors (p < 0.05). CONCLUSION: CT-guided transthoracic needle aspiration biopsy is a useful diagnostic tool for small solitary pulmonary nodules smaller than 20 mm in diameter. The diagnostic accuracy is significantly improved for large (> 10 mm) lesion size and short (< or = 40 mm) needle path length.

Adult↗
PubMed2002

Dynamic oxygen-enhanced MRI reflects diffusing capacity of the lung.

The purpose of this study was to demonstrate the feasibility of dynamic oxygen-enhanced MRI in a clinical setting. We hypothesized that dynamic oxygen enhancement can reflect the regional diffusing capacity of the lung. Ten patients with pulmonary emphysema and seven healthy volunteers were examined with a respiratory-synchronized inversion recovery single-shot turbo spin-echo sequence (TR = 3200-5000 ms, TE = 16 ms, TI = 720 ms, ETS = 4 ms) following 100% oxygen inhalation, using a 1.5 T whole-body scanner. Maximum mean relative enhancement ratios calculated by averaging six defined regions of interest (ROIs) in both lungs were statistically compared between healthy volunteers and patients, and were correlated with diffusing lung capacity (%DL(CO)). In patients with pulmonary emphysema, maximum mean relative enhancement ratios were significantly decreased compared to those in healthy volunteers (P = 0.0008). Maximum mean relative enhancement ratio had excellent correlation with % DL(C0) (r(2) = 0.83). Dynamic oxygen-enhanced MRI may reflect the diffusing capacity of the lung; therefore, imaging of oxygen enhancement with MRI may provide maps of the diffusing capacity.

Adult↗
PubMed2002

Contrast-enhanced MR perfusion imaging and MR angiography: utility for management of pulmonary arteriovenous malformations for embolotherapy.

OBJECTIVE: The purpose of this study was to assess the capability of MR perfusion imaging and angiography (MRA) for management of pulmonary arteriovenous malformation (PAVM). METHODS AND PATIENTS: Eight patients, having 15 PAVMs underwent pulmonary angiography (PAG), CT, MR perfusion imaging and MRA. For the pretherapeutic management, MRA was compared with PAG and CT regarding detectability and diameter of vasculature. For post-therapeutic management, the change in size of aneurysmal sac, any residual contrast-enhancement and the blood supply within the sac were evaluated. RESULTS: All PAVMs with aneurysmal sac, feeding artery and draining vein diameters of equal to or more than 3 mm, were identified and measured with similar results by all modalities. On follow-up studies, 7 (58.4%) out of 12 treated PAVMs showed a decrease in size and residual contrast-enhancement. The residual contrast-enhancement was considered as bronchial artery-to-pulmonary artery collateral flow by MR perfusion imaging. CONCLUSION: MR perfusion imaging and MRangiography are useful for management of PAVMs over 3 mm in diameter.

Adolescent↗
PubMed2002

Differentiation of metastatic versus non-metastatic mediastinal lymph nodes in patients with non-small cell lung cancer using respiratory-triggered short inversion time inversion recovery (STIR) turbo spin-echo MR imaging.

OBJECTIVES: To differentiate between metastatic and non-metastatic lymph nodes in patients with non-small cell lung cancer using respiratory-triggered short inversion time inversion recovery (STIR) turbo spin-echo (SE) MR imaging. METHODS AND PATIENTS: One hundred and forty mediastinal lymph nodes were detected in 25 patients with non-small cell lung cancer who underwent respiratory-triggered STIR turbo SE imaging. Ratios of signal intensity of lymph nodes to 0.9% saline phantoms (lymph node-saline ratio) were compared by Student's t-test using the pathological diagnosis as the gold standard. The threshold value of the lymph node-saline ratio was determined for a positive test, and tested for its capability to provide a differential diagnosis. RESULTS: One hundred and forty lymph nodes were diagnosed and classified into two groups: metastatic lymph node (n=21) and non-metastatic lymph node (n=119). The mean lymph node-saline ratio in the non-metastatic lymph node group (0.42+/-0.01; mean+/-standard error) was significantly lower than that of the metastatic lymph node group (0.77+/-0.02, P<0.0001). When 0.6 was adapted as the threshold for a positive test, sensitivity, specificity, and accuracy for differentiating metastatic lymph node from non-metastatic lymph node per lymph nodes were 100, 96, and 96%, and sensitivity, specificity, and accuracy for differentiating metastatic lymph node from non-metastatic lymph node per patients were 100, 75, and 88%, respectively. CONCLUSIONS: Both metastatic and non-metastatic lymph nodes in patients with non-small cell lung cancer were well differentiated using respiratory-triggered STIR turbo SE imaging.

Adult↗
PubMed2002

Solitary pulmonary nodules: potential role of dynamic MR imaging in management initial experience.

PURPOSE: To evaluate the utility of dynamic magnetic resonance (MR) imaging in the management of solitary pulmonary nodules (SPNs). MATERIALS AND METHODS: Fifty-eight patients with 58 pathologic analysis-proved SPNs (diameter < 30 mm) underwent dynamic 1.5-T MR imaging. The 58 SPNs were classified into three groups at pathologic analysis: malignant SPNs (n = 38), active infections (n = 10), or benign SPNs (n = 10). From signal intensity-time curves generated after the bolus injection of contrast material, the maximum relative enhancement ratio and slope of enhancement were calculated and statistically compared among the three groups. Threshold values of these two dynamic MR indexes were determined on the basis of positive differentiations. RESULTS: The mean relative enhancement ratio and mean slope of enhancement for the malignant SPN group were significantly higher than those for the benign SPN group and significantly lower than those for the active infection group (P <.05). With 0.15 as the threshold maximum relative enhancement ratio for distinguishing the malignant SPN and active infection groups from the benign SPN group, the sensitivity, specificity, and accuracy were 100%, 70%, and 95%, respectively. With 0.025/sec as the threshold slope of enhancement, all SPNs with malignancy and active infection were clearly distinguished from benign SPNs. CONCLUSION: Dynamic MR indexes were useful in the differentiation between SPNs that necessitated further evaluation or treatment (malignancy and active infection) and SPNs that did not necessitate further evaluation or treatment (benign nodules).

Adolescent↗