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Very good website. The Dual source CT is new technology of CT. We are in Indonesia need experience from another country
Thorsten R. C. Johnson, M.D:
Thanks for your reply, I want to ask another question: If we want to get good images, how to scan for lung perfusion. For exam, we must use 4ml/s?5ml/s…… injecting speed? or we use 70ml?80ml…… contrast material ?can we change two tube~s kv and mas?
best wishes to you!
In our experience, 4 ml/s is the preferable injection rate to avoid beam hardening artifacts. 70-80 ml should be adequate for typical asian body habitus and weight. You should not change the kV settings (which is not possible anyway except for special research protocols). You may want to increase the mAs for very heavy patients, but the preset value should work fine in general.
we’ve done a DE KUB on 10 patients with a proven chemical analysis of one stone. however , if we cange the protocol from the default seimens, some results may be confusing. also i would like to know if any modification can be done so that tiny calculii (which otherwise are not characterised) could be characterised. would a smaller fov in the recon help??
Our experience shows that the reduction of the calculation range is helpful in the depiction of small urinary calculi. This parameter can be set on the advanced definition dialog card. In addition, the limits for calculation can be adjusted. This can be of interest when you examine stones with very low or very high attenuation values. So far – to my knowledge – there is no information on the optimal field of view. On the other hand, the slice acquisition plays an important role. For example Primak et al. showed that the accuracy in the determination of stone compositions depends on the collimation used with dual-source dual-energy CT.
can the DSCT identify the fibrous cap and distinct the various components in the plaque?
it was a pity ,just saw it
hi , i appreciated your delicated word in the field of ECG-edition,would you send the edited ECG chart of this case? thank you
The ECG edit has been the saving grace for a few of our challenging patients. The aberrant beat is easy, but the pesky pacemaker is not. I have found in attempting to clear the aberrant beat, the area of interest is easier to address than the entire dataset. Pick your battle. Delete a sync prior and reconstruct the segmeted area, post and try to change the temporal resolution to 145 ms or 165 ms over that area of fault. The pacemaker steps have kicked into play if the patient happens to drop below the dial down during the scan. Reviewing the ecg tracing, delete the sync on each of the pacer spikes, set a median TR, you might also try using the Best systolic phase if the heartrate still remains high after the count is adjusted. I have had what began as a horrible scan, become a motion free dataset with this technique.
Please, give me a advise, How to compare between CT perfusion and MR perfusion, which one is better than? thank you and best regards
Dear Anders Persson !
Then, in the furture, Can we be scan CTA without i.v.contrast (for clinical diagnostic) ?( it’s only in my mind ), I think that we could reformat on the VRT, something like this ( similar to your figure 4) but How is it on the MPR or 2D ?
By the way, please give a answer about DSA (for neuro)
all of the vendors (GE, Phillip, Siemens, Toshiba…) have had the DSA software also.
Thank you and best regards
Minh Truong
I thank you for your reply. As you know, the favourite topic by the compettition, is that the Dual Source CT has double the radiation!
I am surprised at how many Physicians are not aware of the difference between the DSCT and the Multislice CT for instance.
Could you perhaps take some time and explain the differences please?
Regards.
We have a record 175 bpm and achieved extraordinary images in a systolic recontruction. The DSCT scanner gives the the best systolic and diastolic phases in seconds and made a VSD apparent only by providing both these reconstructions to the radiologist. Amazing detail.
It is interesting case where most of cases that we are ignore to look for pulmonary veins.
But anyway, what the different or the advantages of use DSCT compare to MSCT?
i do believe that nothing much except of faster scan time.
what the best recommandation contrast flow rate selection.
is there any different if we use high flow rate(6ml/s and above).
how about contrast flow at the distal of arteries?
i just wonder, for this chest pain protocol, are you recommend to use test bolus or care bolus(monitoring technique).
For further information on the topic Dual Source CT and radiation dose, please see the following publications:
- Stolzmann P et al. Radiation dose estimates in dual-source computed tomography coronary angiography.
Eur Radiol. 2008 Mar;18(3):592-9.
- Leschka S et al. Low kilovoltage cardiac dual-source CT: attenuation, noise, and radiation dose.
Eur Radiol. 2008 Sep;18(9):1809-17.
- Stolzmann P et al. Dual-Source CT in Step-and-Shoot Mode: Noninvasive Coronary Angiography with Low Radiation Dose.
Radiology. 2008 Oct;249(1):71-80.
Kind regards
It is wise to increase contrast flow rate in difficult patients (e.g. patients with stents or obese patients). Of course, it is important not to run out of contrast towards the end of the scan. Duratio nof contrast injection therefore also needs to be increased to compensate for the higher flow rate.
Our policy at our institution is to inject contrast for the same duration as data acquisition will take, nbut to inject at least 10 seconds.
So, if the scan will take 12 seconds, we will inject 60 cc at a flow rate of 6ml/s or 72 cc at a flow rate of 6 cc/s
If the scan taes only 8 seconds, we inject for 10 seconds. 50 cc at a rate of 5cc/s or 6 cc at a rate of 6 cc/s.
We generally recommend bolus tracking in the aortic root for this application, because it does not require additional contrast and it is not affected by variability due to breathing, and the bolus geometry corresponds to the actual bolus. There is a specific paper addressing this matter: J Comput Assist Tomogr. 2007 Mar-Apr;31(2):265-71.
Regarding pulmonary veins without cardiac mode (retrospective ECG gating) DSCT system acquires the CT data with 64 slices and therefore there is no significant difference compared with a 64-slice MDCT.
the picture 1 is wrong.
why the right kidney seems more contrast enhanced then the left?
sincerely yours
ubachuster
very important study I was just searching for such information!
Thank You!
It is not for free? The article seems tobe interesting not only for AHA members. Where can i get it?
Good observation !!! Image 1 is indeed incorrect, this image should be a non-enhanced image and not an enhanced image a shown here, this needs to be corrected.
The conventional images are combination images of 80 kV and 140 kV (no color coding), using 70 % of the image information from the 140 kV tube and 30 % of the 80 kV tube. As 80 kV is very iodine sensitive, the net enhancement is greater inside the 80 kV field of view. A good example is the left kidney. The hilar region is within the 80kV fiel odf view, the rest not. The hilar part is more enhancing than the rest of the kidney that is outside the 80 kV field of view (compare with color coded image).
is there any documentation regarding the analysis of gallstones with dual energy?
Regarding DECT in the characterization of gallstones, there is not much work out there. There is some preliminary work and I have included an abstract from the RSNA 2006 please see below, hope this answers your question.
SESSION: Gastrointestinal (Dual Energy, Innovations)
Dual-source CT Characterization of Gallstones Using a Dual-Energy Analysis
DATE: Wednesday, November 29 2006
PURPOSE
Standard treatment for symptomatic and non-symptomatic cholecystolithiasis is cholecystectomy. Non-invasive approaches such as oral litholysis are mainly limited to patient with pure cholesterol stones, which often is difficult to assess when using either ultrasound or conventional CT. This study examines the possibility of a novel clinically available dual-source CT using two tubes mounted in the gantry applying dual energy technique to non-invasively characterize gallstones in vitro (DECT).
METHOD AND MATERIALS
Pathology provided 40 randomly selected gallstones excised during cholecystectomy. They were individually embedded in ultrasound gel. Scanner settings were: 2 x 64 slices per rotation, collimation 0.6 mm, tube 1: 80 kV, 175 mAs and tube 2: 140 kV, 170 mAs. Pitch 1.4, reconstruction slice with 1.0 mm, recon increment 1.0 mm. For comparison scans were repeated using the same scanner setting using monoenergetic scans at either 80 kV as well as 140 kV. Dual energy analysis was performed image based. Gold standard was pathological classification.
RESULTS
Pathological analysis revealed 7 calcified stones, 15 pigmented stones, 7 pure cholesterol stones 6 mixed cholesterol stones and 5 mixed pigmented stones. Dual energy analysis was able to distinctively differentiate between all subtypes. Moreover DECT was able to differentiate between two different subtypes of cholesterol. One subgroup had 4 cholesterol stones that were not visible in conventional 140kV monoenergetic CT and had a lesser density. Pathology differentiated these types by surface analysis. The non-visible group had a smooth surface whereas the other group had a structured surface. This other group was visible at both energy levels.
CONCLUSION
These primary results indicate that DECT permits subtle characterization of gallstones in vitro using a clinically available dual source CT. It also allows for detection of primarily non radio opaque cholesterol stones at 140kV, an energy level often used for obese patients.
CLINICAL RELEVANCE/APPLICATION
Reliable detection and characterization of cholesterol stones could permit better treatment decision for obese patients at elevated risk during surgery, whether to undergo oral litholysis or surgery.
To Johnson
Hello!
My name is Mi-Jin, Kang, Seoul National University Hospital, Korea.
Actually I presented educational exhibit of ‘thoracic application of dual energy CT’, at RSNA 2009.
And My presentation was received invitation of Radiographics.
If you don’t mind, I would like to use your figure 2 and 3, printed at Eur Radiol 2007;17:1510-1517.
I will wait for your answer, sincerely.
Thank you.
I agree with you Dr Suranyi, but I think with a minimal dose of the new technology and the quality of the images like aquired by the DSCT, there are enough evidence to replace the MIBI with the CTA, and even the core 64 study was negative because of the high threshold of the level of the stenosis(more than 50%), it showed that the cta may point the finger at the target vessel to treat,
on the other hand the ACCURACY trial had better result and was multi vendor study.
Thank you for your response. I may have failed to mention, the pediatrics that we scan have congenital anomalies and many have had step surgical interventions. The mapping of the anatomy is critical for the surgeon. In the interum, we have adapted a total 80/20 blend of contrast, using a lesser kVp is possible because of that. Injecting in a saphenous vein decreased the SVC contrast artifact possibility, so again allows a decrease radiation dose. Many of our peds have a HR in the 130-150 bpm range. A 3-4 second scan at most. Aain, I appreciate your response to my question.
Thanks for your interest. Of course I had to transfer the copyright of the article including its images to the publisher, i.e. Springer. According to their guidelines I think you have to give reference to the original article in the figure caption. Please refer to the Springer website to make sure you’re meeting their copyright requirements.
Dear Dr. Hadjadj,
Thank you for your reply to my earlier comment.
While I am similarly convinced that cardiac CT will (and should) be utilized more and more, it is important to bear in mind that even if we were able to perfectly visualize all coronary arteries and all segments, with the conventional CT methods we would still not be able to reliably quantify tissue perfusion.
For the assessment of myocardial perfusion, nuclear cardiac scans are considered the gold standard (even though some would argue they are more the “old standard”), and MRI is emerging to compete for becoming the modality of choice.
Newer methodologies, such as dual-energy cardiac CT, which was pioneered here at MUSC, attempting to assess the iodine content of the myocardium, and other efforts aimed at studying myocardial perfusion with CT even during adenosine stress may provide us with the technology in the future that allows us to reliably assess the severity of the coronary artery disease at the tissue level.
On the other hand, CT angiography has another important advantage over conventional angiography, which is the ability to visualize coronary artery plaques. To identify lesions with a high potential of becoming culprit lesions in acute coronary syndromes, it is crucial to differentiate calcified plaques from noncalcified (fibrous and lipid rich) plaques. This is definitely one strength of coronary CTA, with which none of the other modalities can compete with.
Thank you for your continued interest in our website and in promoting cardiac CT. We are looking forward to hearing from you again.
Best regards,
Pal Suranyi , MD, PhD
Dear Colleague,
Could you please inform us about the usage contrast media in coronary CTA for Philips Brilliance (64-slice)?
Sincerely,
Dr.Ersin Ozturk
the advanced of DSCT
Dear User
The injection protocols for contrast agent do not vary significantly between different scanners. We currently recommend the following:
Use a flow rate of 5 ml/s. In difficult patients, such as obese patients or patients with stents or known severe calcification, increase to 6 ml/s or even 7 ml/s.
Inject for the same duration as the scan. If the daza acquisition will last 12 seconds, inject for 12 seconds. If it lasts 16 seconds, inject for 16 seconds.
Always inject for at least 10 seconds. If your data acquisition is shorter than 10 seconds (i.e. 6 seconds), still inject for 10 seconds.
Add 4 seconds if you use a bolus tracking approach. Do not add anything is you use a test bolus approach. If you use a test bolus, start your scan with a delay that is 2 seconds longer than the contrast agent transit time that you measured.
Follow your contrast injection with 60 ml of saline or 60 ml of a mixture 20% contrast/80% saline, at a flow rate of 5 ml/s.
If you do a test bolus approach, us 10 ml of contrast agent at 5 ml/s and follow by 60 ml of saline at 5 ml/s.
I wish you success with your scanning
Stephan Achenbach
Excellent visualization and clinical workup, shows the awesome technology and diagnostic care available.
Dear Sirs,
Where can I find the basic algoritms to compute dual enegy images made with DR (flat panel detectors) ?
Does anyone knows if specific Z-images (specific atom number) can be obtained in that way ?
Thanks in advance,
Francis Cuigniez
MD. radiologist.
The field of DR (digital radiography) works with projection images. In cross-sectional Dual Energy modalities like Dual Source CT it is possible to reconstruct effective z and rho values (atom number and electron density) based on the photo effect and the absolute density in the individual image voxel. However, this is not possible or would make little sense in projection images, because the individual image pixel contains a sum of several different structures. It is possible to vary the weighting of photon energy in these DR images to produce “soft and hard” images to accentuate soft tissue or calcified structures, e.g. to identify and differentiate lung nodules or coronary calcifications. Still, from my perspective the summarized effective z value of a pixel in the projection image would not convey more information than that, even if one tried to quantify it. I can recommend the July 2003 issue of the Journal of Thoracic Imaging which gives quite a wide overview of available techniques and diagnostic performance of DR.
Best regards,
Dr. Thorsten Johnson
I was reading up on the CT Siemens Daul Souce Technology and was quite impressed. I am actually a Toshiba fan and believe their 320 slice scanner is as good as it gets. So what scanner is best for brain perfusion and cardiac imaging. Dual Source vs 320 Slice
Dr. Stephan Achenbach, M.D.
I agree with the injections protocols you describe; at our insitution we have a GE equipment of 64 channels, and we use the amount of contrast and its flow depending the weight of the patient, for example : 70 kg we use 85 to 90 cc at 5.5 to 6 ml/sec of flow rate. We use two flows of contrast, the first flow is 5.5 ml/sec using 55 cc and the second flow is 6 ml/sec using 45 cc following of 30 ml of saline at 6 ml/s. The purpose of this technique is to visualize the distal arteries of the heart and we obtained very good results.
And we needed to know the limits of the flow of the contrast, and you described before we can use 6 or 7 ml/s in obese and stent cases.
Thank you for your instructions and recommendations.
Thank you for your interest in the DSCT community.
Regarding your question on brain perfusion, I cannot really give you a good answer because of no experience in this body region.
In regard to cardiac imaging, I certainly can recommend the dual-source CT technology. It has proven more accurate at lower heart rates than 64-slice CT, it is – to my knowledge – the only scanner that is able to scan hearts in an accurate fashion also at higher heart rates, and finally, it must be considered very dose efficient. With a standard retrospective spiral protocol that is required in patients with high and/or irregular heart rates, you will end up with around 7-9 mSv. When you use a standard step-and-shoot protocol at 2-4 mSv (which can be used in patients with heart rates below 70 bpm), and when using the recently introduced Flash- (or high pitch) mode, you end up at a dose below 1 mSv for a coronary CT angiography examination.
I have no experience with the 320-slice CT scanner for cardiac imaging. So the only thing I can recommend is to review the (sparse) literature. Here you can see that the lowest reported radiation dose of a cardiac CT using this scanner is around 5 mSv (when using a protocol that requires lowering the heart rate with beta-blockers).
Best regards and good luck with your scanner choice.
Hatem Alkadhi
sir,
i am too working on a dual source siemens scanner and have done a lot of coronart angios with conventional step and shoot method and in most of the cases end up with radiation dose of 2 – 3mSV (including the calcium score). most of the times i do calcium scan with 80 KV and coronary angios with 100kv depending mainly on chest circumference and BMI.But have not yet tried reducing the effective mAS a lot since i do scans with care dose 4D on mAS will be selected automatically.if i do reduce mAS are there any standards so that the images will be not very noisy.
Hello-
perhaps this is a premature question, but are the billing codes for Siemans Somatom different from those of traditional C/Ts? One would think the reimbursement for this new modality would warrant seperate CPT codes. I have searched both the 2101 CPT book and Siemans website to no avail and thought perhaps someone @ DSCT may have the answer?
Dear User,
in order to give an satisfying answer it is necessary to know which country you are working in. Billing codes differ in every country and thus health care system. Speaking for Germany billing codes unfortunatley do not represent technical advances very well.
With best regards
Marco Das
Could I please know the field of view for the two tubes for COW and craniocervical angiograms?
Regards
Amogh
Dear Sandra, I have been practicing Cardiac Imaging on 64 Slice MDCT. We had similar case recently and found these videos and images useful as reference. I would like to thank you for this Excellent useful blogs.
This is my first visit to dsct.com. Looks fantastic site with so many bloggers. I would recommend you to visit my another radiology blog website – http://www.iradix.in/Blogs.html
Here you would find more than 150 blogs on various radiology issues. All are worth reading!
I wanted to add my question to the above question about Dual Energy CT Scans. I am also looking for any additional CPT codes that would be used for this type of exam. Our facility is located in Pittsburgh, Pennsylvania, USA.
Thank You,
Kim Pavlic
Very impressive… super images… fantastic technology… Thank you ver much.
The CTDI value written here is 6,33 mGy, how small dose I think. how can it be, can you tell me? because most of CT examinations in my country resulting CTDI about 50’s mGy
This case demonstrates the considerable dose savings of prospective ECG gating acquisition and 100 kV tube currents. These dsoe savings have beeen well documented in several recent publications involving the Definition scanner-thank you, Chip Gilkeson
Dr. Bauer-
For your lung and abdomen scans you recommend using CareDose4D and various mAs settings. Does this refer to the quality reference mAs?
Thanks,
Robert
Yes, these values do refer to the quality reference mAs.
as a trainer in ct background needs more information to sent about dual source
ct .
best regard
Dear dr Johnson,
Can you tell me what the HU are of the coronary and pulmonary tree? Did you find that optimal for evalutating both the coronaries and pulmonary arteries? Kind regards, Marc Kock
What is the efficiency of each anode material and is made up?
Thanks for your interest. I had anonymized the image when exporting it, so I cannot tell you the actual values of that dataset. But we are acquiring TRO scans quite frequently these days, and one of today which I am just reading has between 500 and 600 HU in both the pulmonary and coronary arteries, which is certainly sufficient. If you are specifically interested in bolus optimization for this purpose, you may want to have a look at a study I performed on this (Optimization of contrast material administration for electrocardiogram-gated computed tomographic angiography of the chest. Johnson TR, Nikolaou K, Wintersperger BJ, Fink C, Rist C, Leber AW, Knez A, Reiser MF, Becker CR. J Comput Assist Tomogr. 2007 Mar-Apr;31(2):265-71.).
De Dual Source CT experts community… Sjiek hoor!
In my experience bone extraction of distal third tibia is poor with both DEBR or manually. how do you deal with it. please guide for the same
Dear Dr. Mahshwari,
thanks for your question. Indeed, the extremely narrow residual lumen in distal crural arteries can pose a challenge for DEBR if these are very dense calcified plaques, especially in severe smokers’ PAOD. As the individual voxel in the image dataset mostly contains more calcium than iodine, DEBR has physically no chance to provide an accurate depiction of the residual patent lumen.
We deal with this in the first place by using a rather long injection scheme and scanning rather late in order to avoid overtaking the bolus. In cases of critical ischemia, we additionally perform a dynamic multi-phase acquisition (‘adaptive 4D spiral’) with a small, short contrast bolus. Then, we see the bolus passing through the arteries, making it possible to differentiate patent and occluded vessels even in very small residual diameters in presence of dense circular calcified plaques. Like that, we have the complete information about large and small arteries, about bypass patency, about plaque distribution and composition, and about perfusion dynamics and severe ischemia. As renal insufficiency is also extremely common in these patients, we sometimes only acquire this latter dynamic dataset with only 40 ml of contrast material, just to clarify whether there is any residual blood supply or not.
Kind regards,
Thorsten Johnson
I read ur article with interest. Scan done on low mAs on 100 kVp with limited coverage of KUB region, followed by low dose dual energy for covering the calculus will yield lower radiation dose.
What are the requirements for Xenon ventilation? Is it difficult or dangerous?
Many thanks,
CM
Is their any clinical study on to evaluate the effects of iterative recons in calcified coronary arteries?
Requirements for xenon gas application include, of course, the gas itself, which can only be extracted from the atmosphere in very low concentrations and is therefore quite expensive. AirLiquide holds the license for medical Xenon gas in Europe. Apart from that, a device for administration is needed, i.e. either, in general anesthesia, an anesthesiology apparatus which is specifically designed for xenon based narcosis (for example Tangens from EKU). For awake, freely breathing patients, a respirator can be used (for example Anzai AZ-725). Although xenon does have narcotic effects, a relevant sedation is not expected at concentrations below 30% for a few breaths. Still, close monitoring including pulse oximetry and support from an anesthesiologist are advisable. For more details refer to the respective chapter of the book “Dual Energy CT in Clinical Practice” (Springer, ISBN: 978-3-642-01739-1) which will appear within the next few weeks.
Unfortunately, there are currently no clinical studies that are investigating the effect on calcified vessels in a systematic manner. One could expect that the lower noise allows usage of higher resolution reconstructions (thinner slices and sharper kernels), thus improving image quality and eradability, but this has not been proven yet.
Some colleagues and I have actually just concluded a study on a Siemens SOMATOM Definition Flash scanner with our focus being the possible advantages of using the X-Care function and we found that with X-Care being a kind of x/y mA-modulation, it is not possible to run CareDose x/y-modulation simultaneously, which ends up increasing the dose (CTDI) by an average of 30%. I do agree with everything else being stated about the scanner in this reply though.
Regards
Ali F. Corap
If X-CARE is used, CARE Dose 4D is modulating along the z-axis of the object only. However this does not mean that X-CARE increases dose compared to the x/y profile of the tube current.
By adjusting the Q.ref.mAs in your x-CARE protocol to a level that the eff.mAs of this protocol correspond to the reference level of your non X-CARE protocol, you can make sure that your X-CARE protocols are consistently CTDIvol neutral. While decreasing direct surface entrant exposure anteriorly.
hi im have a question , I wonder if the equipment could be used at the entrance to a penitentiary to find out if the visits intimate use drugs in the areas of internal female sex ?
thank you
leonardo david
Please,i want to know every thing about contrast injection protocol for chest pain (urgent)
Dear Mr. Hesham,
on behalf of Dr. Johnson we can recommend you his paper paper about the injection of contrast media that might help you:
Optimization of contrast material administration for electrocardiogram-gated computed tomographic angiography of the chest.
Johnson TR, Nikolaou K, Wintersperger BJ, Fink C, Rist C, Leber AW, Knez A, Reiser MF, Becker CR.
J Comput Assist Tomogr. 2007 Mar-Apr;31(2):265-71.
Thank you for your question.
Best regards,
The DSCT.com team
Hello. I am a graduate student undergoing masters in radiology, interested to do a thesis paper on DECT. A basic question, from the raw data that is acquired using DECT, how do we post process them to get the virtual unenhanced and iodine map data? Thank you for entertaining beginners like me!
The postprocessing is not performed on the raw data itself but on reconstructed images, so the first step is a filtered backprojection to obtain normal CT images from both spiral datasets. The decomposition into iodine maps and virtual non-contrast images is then performed using a procedure called “three material decomposition”. Please refer to the “technical implementation” chapter on DSCT.COM (http://www.dsct.com/index.php/technical-implementation-of-dual-energy-ct-t-johnson/) for details.
Best regards,
T. Johnson
Dear Dr.Kerl,
Can SAFIRE be incorporated in the protocols to reduce dose/improve IQ further?
I mean is there any further scope for improvement with SAFIRE?
Dear Dr. Niraj Garg,
Thank you very much for your comment. At our institution we did not evaluate SAFIRE in our protocols for high-pitch CT of the paranasal sinus. However, I think it is an interesting question and there might be a further scope for improvement with SAFIRE.
Best regards, Matthias Kerl
Dr.Johnson,
Is it feasible to combine DE ‘post-processing’ with Iterative recons with a view to improve DE evaluation for certain applications? Is there a potential to reduce DE dose further, with this combination- assuming that it is feasible in the first place?
Yes, Dual Energy and iterative reconstructions go together very well. The fact that the two simultaneous acquisitions represent low-dose exams makes dose efficiency a crucial point, and iterative reconstructions help to improve contrast to noise ratio in this respect. This beneficial effect on both single-energy datasets adds in Dual Energy postprocessing and improves its results. It is important to use Q or I kernels which do not change object edges. And yes, it is feasible to reduce the dose and get the same or better results with iterative reconstructions. The degree of feasible dose reduction depends on the individual application. I would estimate some 20-30% for most protocols; yet, systematic scientific evidence is lacking (although I know some is “in press”).
Please let me know the best protocol of coronary CTA using DSCT Flash mode when bolus tracking method is preferred. How long is the duration should we keep above the expected CT value of contrast? We are certain to install Somatom Definition Flash in this April.
I appreciate for putting this together! This post “Maxillary Sinus Cancer Symptoms” is obviously one great post. Para Nasal Sinus Cancer is also one of the dangerous diseases. Causes of Para Nasal Sinus Cancer are not yet known, however, certain occupational groups have an increased susceptibility to the disease. People who work in leather and textile mills, nickel refining, those dealing with chromium, radium and isopropyl alcohol are prone to sinus cancer. Nice post, keep going on.
Thank you.
On Our FLASH coronary protocols we do not use bolus tracking, but test bolus.
We use 20cc of Isovue 370 at 6 cc/sec for the test injection at the ascending aorta.
For the main bolus we use 60 cc of Isovue 370, followed by 55cc of a 40/60 split of Isovue/saline followed by 40cc of saline, all at 6cc/sec.
For timing of the bolus, we add 5 sec to the peak injection time at the ascending aorta.
Very good!
May you please send us latest articles on PET-CT.
Dr.Johnson,
How does the DE per se, play a role in this study.Since most of the action is taking place in the High KeV range, and the contribution from the 80/100KVp tube to the high KeV range may not be very significant,in this case?
Of course it is helpful that the Sn140kVp spectrum is quite hard, because it just penetrates metal better. However, the monoenergetic reconstruction is based on an extrapolation of density from the images that have been acquired. In order to extrapolate what the image would look like at even higher energies, an image obtained at a lower photon energy is required additional to the high energy image. It’s basically like drawing the graph of a linear equation: you need two points (i.e. density values at 80 and Sn140 kVp) in order to find a third point (i.e. the density at the extrapolated monoenergetic energy).
VERY INFORMATIVE SITE
If you see a perfusion defect without identifiable PE on DE CTPA, might it not reflect gas trapping related vasoconstriction rather than an occult Subsegmental PE? How does do you distinguish between the two?
This differentiation can be quite difficult. However, if the perfusion defect is caused by air trapping, you would expect to see a corresponding decrease in density in the respective lobule in the normal average image in lung window and in both dual energy acquisitions. If the perfusion defect is caused by subsegmental PE, you would expect a normal “background” density in lung window.
So in doubt, you may get a clearer impression by measuring density values in “general viewing” and in the “lung PBV”, so you get the density in both acquitisions, the average “background” density and the “iodine related density”. The “iodine related density” will be decreased both in PE and air trapping with reference to surrounding normal lung parenchyma, but the “background density” should be normal in PE but decreased in case of air trapping. Also, lobular air trapping usually has causes like bronchiolitis that affect both lungs or whole lobes, so that lobular air trapping is quite unlikely to occur in a singular location, while this does occur with PE.
I hope these considerations are helpful.
thank you very much. I am wondering whether you ever make a diagnosis of PE based on a perfusion defect, in the absence of an identifiable arterial filing defect, or whether the perfusion scan just increased your diagnostic confidence if there is an equivocal filling defect.
I had imagined that the advantages of using FLASH mode to reduce repiratory and cardiac induced blurring of small vessels in the middle lobe. left lower lobe and lingula would be greater than any additional information provided by DE CTPA. DO you use FLASH for CTPA at all, and if so in what clinical setting?
Finally, how much of a limitation is the 33cm FoV for FLASH / DE modes in your experience?
- Yes, it does happen that you can’t identify an intravascular clot but do see a wedge-shaped perfusion defect, especially in small subsegmental locations and disseminated peripheral PE. And it does increase diagnostic confidence if there is an small but occlusive clot and a corresponding perfusion defect. On the other hand (and that’s what I like about it), if you see that at least 90% of the lung is normally perfused, you feel very comfortable at calling an exam negative, because even if you should have missed a tiny non-occlusive PE, it will not be relevant for the patient.
- Yes, our standard PE protocol is a DE protocol. This does allow to analyze lung perfusion but does not reduce motion artifacts. If this is your main concern, use the dual spiral (“flash”) mode. Then, the whole chest is scanned in 0.7 seconds, and there are absolutely no motion artifacts – but then there’s no dual energy information, because both single energy spiral paths fit into each other, so there’s no spectral data.
- The 33 cm diameter of the inner FoV does not represent a relevant limitation any more, in clear contrast to the 27.5 cm of the previous generation DSCT. Now with the 33 cm, virtually all patients’ bony thorax fits in, so the entire lung is included also with the basolateral parts. Previously, there had mostly been a 4-5 cm basolateral edge which had not been covered, but now this is resolved. You should still routinely use an a.p. and a lateral topogram to ensure correct positioning.
Thank you very much indeed. Just so I am absolutely clear, how do you report a scan in which you can’t identify an intravascular clot but do see on or more wedge-shaped perfusion defects? Will you call this as PE, or will you say “might be subsegmental PE”, or will you say “cannot exlude subsegmental PE”?
I assume you run into problems in the abdomen with 33cmFoV more oftern than in the chest?
If there’s a single wedge-shaped perfusion defect in an otherwise homogeneously perfused lung in a patient with clinical suspicion of PE, I’d clearly call this a single sub-segmental PE. If the perfusion of the remaining lung parenchyma is inhomogeneous, e.g. due to emphysema, COPD, fibrosis etc., I’d call it likely / suspicious of / potential PE, depending on the level of certainty.
Yes, 33 cm diameter is virtually always sufficient for the chest (at least inside the rib cage), and in the abdomen it always covers kidneys and also the ureters and bladder, so the evaluation of kidney tumors and renal stones, which represent the most frequent applications, is warranted in the vast majority of patients. Regarding the liver, e.g. for virtual non-contrast images and quantification of iodine content of focal lesions, there are patients in whom careful positioning would be essential to cover the entire organ and those who just don’t fit in. But in mid-European size patients this is rather uncommon (I’d guess 10-15%).
Dr. Johnson,
Hi, I’m very much interested in your study and I’d like to go into this technique. May I ask for a white paper of this study?
This initial study has been published in European Radiology (Eur Radiol. 2011 Jul;21(7):1424-9), so you can read the full paper there. I am also sending you a white paper directly by email.
A further, systematic study is under review; we optimized the protocol to achieve best-possible artifact reduction. It will take a few more weeks until this is published.
Thank you so much, Dr. Johnson.
Dear Dr.Lell,
What is the threshold of DSBs/cell which could be considered as dangerously high, from the perspective of inducing cancer.
Was there any specific reason why a time gap of 30mins was chosen post-scan, to collect the blood samples for fluoroscence microscopy, sir?
Dear Mr. Garg,
to your questions:
1. we are looking at stochastic radiation effects, with no threshold.
2. we determine the number of foci where DSB repair occurs but can not determine the success of repair 3. lymphocytes are differentiated cells which do not have the potential to proliferate
-> therefore at the moment we no not have models at hand to predict the risk of cancer induction.
A time gap of 30 minutes was chosen according to data published previously (In vivo formation and repair of DNA double-strand breaks after computed tomography examinations. Löbrich M et al. Proc Natl Acad Sci U S A. 2005 Jun 21;102(25):8984-9). Recent work suggests that the peak can be detected after 5 minutes (Leukocyte DNA damage after multi-detector row CT: a quantitative biomarker of low-level radiation exposure. Rothkamm K, et al.Radiology. 2007 Jan;242(1):244-51). Our aim was to compare different scan protocols which makes the exact timing less important, therefore we used a delay of 30 minutes which is well validated.
Best regards,
M. Lell
full text please.thanks.
full text please,thanks.
full text please,thanks.
This summer I concluded on yet another paper on X-Care finally showing that X-Care is not recommendable for use in regards to the ALARA principle. By modifying your Q.ref.mAs you might end up with an equally low mAs but due to the lack of proper x/y-modulation your signal will be unevenly distributed in the x/y plane resulting in an overall increase in noise at the same dose level.
Our findings still show an average dose increase of 30% to the entire scan field and up to a staggering 50% increase for the red bone marrow in the spinal column while maintaining the same noise level for p<0.05.
Dear Xinhhe, thank you for your interest. Unfortunately, we from DSCT.com are not allowed to publish complete publications as the rights are reserved from the official journal. Best regards, DSCT.com
Dear Xinhhe, thank you for your interest. Unfortunately, we from DSCT.com are not allowed to publish complete publications as the rights are reserved from the official journal. Best regards, DSCT.com
Thank you for your question
Based on our own research presented at the RSNA 2011 in and other papers listed below, in our hands at our institution performed with our physicist, we achieved a reduction in dose to the lenz anteriorly close to 40 percent while still maintaining good image quality and did not observe an increase in dose overall .
I have listed some of the papers
sincerely Dr Savvas Nicolaou
1. Dose Reduction to Anterior Surfaces With Organ-Based Tube- Current Modulation: Evaluation of Performance in a Phantom Study
Xinhui Duan1
Jia Wang1
Jodie A. Christner1 Shuai Leng1
Katharine L. Grant2 Cynthia H. McCollough1
AJR:197, September 2011
2. Bismuth Shielding, Organ Based TCM , and global reduction of tube current for dose reduction to the eye at Head CT.
Jia Wang
Xinhui Duan
Jodie A. Christner1 Shuai Leng1
Katharine L. Grant2 Cynthia H. McCollough1
Radiology january 2012 vol 262 number 1