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SOMATOM Definition Flash - Scanning pediatric MAPCA patient without sedation or breath-holding

Author: Authors: Kaori Takada, MD* and Tomoko Fujihara**

*Department of Radiology, Sakakibara Heart Institute, Tokyo, Japan
**Application Department CT Team, Customer Service Division, Siemens-Asahi Medical Technologies, Tokyo, Japan

 

 

History

 


A 4-year-old boy with Tetralogy of Fallot (TOF), pulmonary atresia (PA) and major aorto-pulmonary collateral arteries (MAPCAs) was referred to the radiology department of Sakakibara Heart Institute for a follow-up examination using a SOMATOM Definition Flash, dual source CT in Flash spiral mode following treatment of his pulmonary artery stenosis.
The patient was diagnosed shortly after birth with TOF, PA, MAPCA. When he was 10 months old, a stent was inserted in the largest MAPCA and a central shunt was placed when he was 16 months old. When he was 2 years old, he underwent right and left modified Blalock-Taussig shunt surgeries (the subclavian artery is connected with the pulmonary artery) within 9 months. Then, at the age of 3, an artificial vessel was constructed from the right ventricle (RV) to the pulmonary artery by palliative Rastelli procedure.

The patient now underwent a percutanous transluminal angioplasty (PTA) of pulmonary artery. A low-dose, dual source CT scan in the Flash spiral mode was ordered to confirm his postoperative condition, in particular concerning the pulmonary circulation. The patient’s weight was 15.6 kg. He was not sedated and no breath-hold was needed during the scan. His mean heart rate was 95 bpm.


Diagnosis

The dual source CT images showed that the RV-pulmonay artery conduit was patent and that the anastomosis site had no stenosis (Fig. 5). Neither the right nor the left pulmonary arteries (about 4mm diameter) presented any significant stenosis (Fig. 3a-b).
A stent was confirmed in the biggest MAPCA, which bifurcated from the descending aorta at the level of the left atrium. It went to the right superior and inferior lung lobes, and connected one artery originating from right central pulmonary artery. Although the stent itself was patent, a stenotic part was seen distal of the stent (Fig. 6). The dual source CT images revealed a tortuous artery originating from a right subclavian artery that supplied the right and left inferior lung lobes. The left lung was perfused mainly by the left central pulmonary artery. The right middle lung lobe was perfused by the large right inferior diaphragmatic artery (its distal end is connected to an artery originating from the central pulmonary artery).
Incidentally, the right coronary artery (RCA) was found to originate from the aorta at the upper level of left coronary artery, the left coronary cusp (Fig. 4a-b), which could neither be seen in the previously performed catheter angiography nor 16-MSCT examination.
Based on these findings catheter PTA of pulmonary the artery stenosis at the distal part of the stent was planned.


Comments

Dual source CT angiography has emerged as an essential diagnostic tool for the assessment of complex congenital heart disease. Nevertheless, dose has remained a concern, in particular when referring pediatric patients for cardiac CT. With the Flash spiral mode of the second generation dual source CT, pediatric patients can be scanned at ultra-low dose, as in this case at 1.63 mGy (effective dose 0.644 mSv). Apart from dose concerns, additional challenges have been associated with imaging pediatric congenital heart disease patients: the patients have high heart rates, the cardiac vessels are tiny, sedation often presents a risk and most patients cannot hold their breath. This dual source CT Flash scan of 211 mm length was taken in only 0.51 sec without sedation or breath-hold. Vessels were clearly visualized without artifacts. Even coronary anomaly could be seen despite the patient’s high heart rate of 95 bpm. Pulmonary artery in-stent stenosis could also be evaluated. The dual source CT Flash images were extremely helpful for further treatment planning.

 

211 mm scan range in 0.51 sec without sedation or breath-holding.
Ventricular septal defect that is one characteristic of TOF.
Both, right and left pulmonary arteries (about 4 mm diameter) without significant stenosis.
Both, right and left pulmonary arteries (about 4 mm diameter) without significant stenosis.
RCA originating from left coronary cusp.
RCA originating from left coronary cusp.
The RV-pulmonay artery conduit was patent, and that the anastomosis site had no stenosis.
Stent embedded in largest MAPCA that had a stenosis (bold arrow) distal of stent (thin a.)

Examination Protocol

Scanner SOMATOM Definition Flash
Scan mode Split-second Thorax
Scan area Thorax
Scan length 211 mm
Scan direction Cranio - Caudal
Scan time 0.52 sec
Tube voltage 80 kV
Tube current 104 eff. mAs
CTDIvol 1.63 mGy
Dose 1.6 mSv
Rotation time 0.28 s
Pitch 3.0
Slice collimation 128 x 0.6 mm
Slice width 0.6 mm
Reconstruction increment 0.3 mm
Spatial resolution 0.33 mm
Reconstruction Kernel B26f, B46f (stent)
Contrast  
Volume 30 ml
Flow Rate 2.5 ml / sec
Start delay 17 s

 

 

The information presented in this case study is for illustration only and is not intended to be relied upon by the reader for instruction as to the practice of medicine. Any health care practitioner reading this information is reminded that they must use their own learning, training and expertise in dealing with their individual patients. This material does not substitute for that duty and is not intended by Siemens Medical Systems to be used for any purpose in that regard.


The drugs and doses mentioned herein are consistent with the approval labeling for uses and/or indications of the drug. The treating physician bears the sole responsibility for the diagnosis and treatment of patients, including drugs and doses prescribed in connection with such use. The Operating Instructions must always be strictly followed when operating the CT System. The source for the technical data is the corresponding data sheets. Results may vary.

Date: 2009-11-09


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