DDPI
 

Frequently Asked Questions
 
      FAQ for Mammoviewer
 
      FAQ for Vidiviewer
 
      FAQ for XeCT System
 
 
Mammoviewer
 

Q. Can I load different size mammography films on the belt?

 

Yes. When you order your MAMMOVIEWER, we will customize the film belt to your individual specifications. 
 

Q. Is it possible to mask films on the MAMMOVIEWER?

 

Yes. We collimate all excess light by: sliding the movable doors in from the sides; turning off a complete bank of lights; or applying black masking material directly to the film belt in select areas. 
 

Q. Is there a way to view three years’ mammo films on this viewer?

 

Yes. Just buy a MAMMOVIEWER 3D and you can load up to 6 over 6 over 6 films, therefore viewing the baseline, last year’s films, and the current study. 
 

Q. How many case studies does the MAMMOVIEWER film belt hold?

 

The 810CM holds 50 or 100, the 810CML holds 50, 75 or 100, the 1012 holds 50, 75 or 100, and the 3D holds 50 or 75 patient studies. 
 

Q. Are the lights bright enough to meet ACR requirements/recommendations?

 

Yes. We can exceed this by quite a bit. We offer you in excess of 6000 NIT of illumination. 
 

Q. Does the MAMMOVIEWER meet medical device standards? 

 

Yes. We have CSA certification. 
 

Q. Does the MAMMOVIEWER have a high capacity for film loading?

 

Yes. On the 3D, we can load up to 1350 mammography films.
 

Q. Can I buy the MAMMOVIEWER and not the console?

 

Yes.  They are sold individually.  If your requirements change, the console may be purchased at a later date and retrofitted in your facility. 
 
 
Vidiviewer
 

Q. Is it possible to put films on the screen smaller than the 14” x 17” size?

 

Yes. There are four strings on the upper film belt that hold the films securely. Films on the lower belt stay put because of the slanted front feature and no strings are required. 
 

Q. Is the bright light a standard feature on all VIDIVIEWER models?

 

Yes. There is no extra charge for this. The foot switches, as well, the film file slots on the console are standard features on every model. 
 

Q. Do I have to buy expensive, custom made light bulbs for my VIDIVIEWER?

 

No. You can buy any standard 15” – 15 watt bulbs, either locally or from us. 
 

Q. Can the VIDIVIEWER fit through the door to our radiology suite?

 

Yes. The VIDIVIEWER is only 29” from the front to the back and will fit through any standard door. 
 

Q. Do I have to contend with the loud clank-clanking of the panels moving up and down in my department?

 

No. The VIDIVIEWER is belt-driven, and runs quietly from the left to the right, and vice versa. 
 

Q. How long does the film belt last, and is it expensive to replace? 

 

The film belt will last 2-3 years with normal use, and is the least expensive in the industry to replace.  
 

Q. Can the portable control panel be located on either side of the work space?

 

Yes. A plug on the left as well as the right side of the shelf is provided.  
 

Q. Can I read mammography films on the VIDIVIEWER?

 

No. It is not recommended, as the light intensity is not bright enough. Masking is also required on mammography film reading, and there are none on this unit. 
 

Q. Is there an auto retrieval feature on the VIDIVIEWER?

 

Yes. You can buy units complete with this feature, which is installed directly on the portable control panel. 
 

Q. Is the VIDIVIEWER electrically approved?

 

Yes. We are CSA certified.
 

Q. Is there a limited, selective warranty?

 

NO. The warranty is for one full year, parts and labor. 
 
 
XeCT System
 

Q.Why is CBF important?

 

Most of the efforts of neurovascular patient care are directed toward the maintenance of a level of CBF consistent with cell life and subsequent cell function.

The heterogeneity of the cerebrovascular system has repeatedly demonstrated an inability to apply assumptions based on past experience to individual patient conditions. The heterogeneity also invalidates many indirect measurements of CBF such as ICP, CPP and TCD. Individual patient care must be based on knowledge of quantitative CBF prior to therapeutic manipulation and again after treatment to determine the actual effect. Assumptions about CBF and the CBF after manipulation will be wrong in a significant number of patients.

CBF can be measured quantitatively and repeatedly with Xenon CT.

Neurovascular problems require patient specific management to optimize outcome.

 

Q. Cerebral Blood Flow: How low can it go?

 

The brain receives blood from the carotid and vertebral arteries at a rate of about 750 ml/min.2 This continuous supply of blood normally provides the brain with enough oxygen and nutrients.
The average rate of cerebral blood flow is 50-55ml per 100g of brain tissue per minute. In actuality, though, the gray matter-or the outer surface of the brain-requires up to four times the blood supply of the white matter, or the inner portion.
When cerebral circulation is impaired, the supply of oxygen and nutrients to brain tissue can diminish, compromising neurological function. Quick action is needed to restore blood flow before permanent damage occurs. Ischemia with loss of brain function tends to occur when cerebral blood flow drops below 20ml/100g/min. Whether or not permanent deficit will result depends primarily on two things: how low blood flow to a particular area drops, and for how long.
The window of opportunity for reversing mild ischemia is generally four to six hours.3 
As blood flow measurements drop, infarction becomes more likely; the window of opportunity closes gradually so that, as blood flow approaches zero, the time frame for restoring circulation is only 15 to 20 minutes.3 After that, infarction and neuronal death are inevitable.
 

Q.What is Xenon Gas? Is it radioactive?

 

Xenon gas used in the XeCT/CBF studies is not radioactive.
Xenon is metabolically inert, monatomic, lipid-soluble and readily diffusible tracer, that rapidly crosses the blood brain barrier and is preferentially distributed within the highly lipid cells of the brain. Despite its lack of chemical reactivity, xenon associates preferentially but transiently with red blood cells, particularly the globin structure. 
Xenon gas produces an enhancing effect on computed tomography images because it is radiodense. It has atomic number of 54 close to that of iodine.
 
 

Q. Why is XeCT/CBF method superior to others?

 

The basis of XeCT/CBF is the Fick principle (1870) of a diffusible tracer (DT) as applied to the human brain in 1948 by Kety/Schmidt and refined by Kety in 1951 12,13,14. It has been validated against every known quantitative CBF method. CBF measured using DTs is a physiological measurement. Similar measurements with non-diffusible tracers (NDTs) are anatomical measurements claiming to be physiological measurements. Current attempts to quantify non-diffusible tracer studies will provide reasonable to excellent data in humans with a normal cerebrovascular (CV) system. In neurovascularly compromised patients, non-diffusible methods are destined to failure due to the following reasons:

a) NDTs are highly dependent on the vascularization of the brain, or “how it got there”. DTs answer the question “is it there?”. NDTs are a snapshot in time (MTT and TTP < 10 seconds), where a DT measures 4-5 minutes of tissue enhancement. This is an extremely important consideration in patients with collateral circulation. A NDT, which is route dependent, can not properly account for collateral circulation.
b) NDTs require an intact blood brain barrier (BBB). An intact BBB is not very common in significant CV compromise. Even in the early stages of stroke, the BBB begins to deteriorate early, and by six hours may be in great jeopardy 15. In many patients where quantitative CBF would be useful, the BBB is interrupted almost by definition, i.e., SAH and THI. Diffusible tracers have no such limitation.
c) The selection of a single blood vessel as an input function in order to quantify CBF with CT perfusion is highly suspect. The vessel selected is only valid for the tissue it supplies. Actually, the vessel selected is already through the tissue scanned and is more representative of the input to the tissue above. It is somewhat reasonable to assume that in the normal patient, a single vessel is representative of the entire brain, but in the diseased state, it is not so.

MR perfusion may have an advantage in this regard due to a more complete input function. Xenon CT uses end tidal Xenon concentrations that are in equilibrium with the arterial concentration, which is valid, except in patients with severe pulmonary compromise. This ,in fact, is the only assumption made with this method.
d) NDTs with CT are extremely limited in the volume information provided. This volume limitation must raise questions about its use even in the rapid triage of stroke patients. All strokes do not occur in the 10mm slice in the basal ganglia. 
e) Many of the most significant contributions that can be made by quantitative CBF measurements in neurovascular care arise in the area of a physiological challenge to the CV system. CT perfusion is inappropriate for this purpose due to iodine and radiation loads.
f) Attempts to quantify MR perfusion have many of the same problems with the exception of a much more representative input function and more complete volume rendering. The NDT limitations still apply. Quantification based on the assignment of a lambda (the partition coefficient for brain tissue) value is physiologically flawed. The use of a λ of 1.0 for the entire brain is not particularly objectionable in the normal brain, but it is for injured brain tissue.
g) The ability to do qualitative CBF imaging with either CT or MR has been clearly demonstrated. Qualitative CBF methodologies require that the operator assumes that brain tissue on the contralateral side is unaffected (normal). Diaschisis, a well known physiological phenomenon which occurs to some extent in over 50% of neurovascularly compromised patients, render qualitative imaging of questionable value when very serious decisions are to be made.

Other technologies worthy of mention are:

SPECT – A qualitative method encumbered by diaschisis.

MR Diffusion – A very interesting direct measurement of a physiological process; unfortunately, its meaning is not well understood.

TCD – A measure of the velocity through a single vessel in the brain. The standard interpretation of TCD velocity and classic CBF are coupled as often as they are uncoupled. May be an excellent bedside monitor once CBF has been determined.

PET – Is a true physiological monitor of the brain which provides an even higher level of information on all functions, i.e., metabolism. Its extraordinary capital and operating costs make it impractical as a diagnostic tool.
 

Q.What is the accuracy of this technique?

 

The methodology related error of quantitative CBF data approaches 10% as the size of the ROI moves above 100 voxels1. In a typical Xenon/CT, a single slice will contain over 20,000 voxels each with a calculated CBF value. One hundred voxels represents approximately 1cm2. The gray matter is composed of less lipid than blood, its solubility coefficient ( l ) compared with blood is 0.7, whereas white matter, which has more lipid content has l of 1.4. Xe/CT CBF is the only CBF technology that calculates l and integrates variations of this variable into the flow calculations. Therefore, this method is more likely than other quantitative CBF techniques to be accurate, even in disease states, in which the lipid content is often altered.

 
 

Q.Has Xenon/CT been validated against other proven quantitative CBF measurements in both normal and diseased states?

 

Xenon has been compared with all quantitative CBF methods as follows: microspheres 5,6,7 , iodoantipryrine8 , 133Xe9, 10 , and PET11 . Final validation is successful clinical application of the technology. Peer review articles now easily exceed 500 and cover every phase of neurovascular evaluation. 

 

Q. How long does XeCT/CBF study tie up the CT scanner?

 

The length of the procedure may vary depending on the patient preparation and cooperation, and the skills of the technologist. Once the patient is properly set up for the XeCT study, the scan time takes only 6-7 minutes.
 

Q. What is the patient preparation for the Xe/CT scan?

 

It is recommended that patient is limited to a clear liquid diet for 6 hours prior to the examination to prevent vomiting. The person in charge of performing the scan should obtain adequate medical history and explain the procedure. Establishing a rapport with the patient from the start will facilitate greater cooperation. Procedural explanation should include clinical indications, anticipated length of study and possible side effects.
Patient should be told, they might experience some unusual sensations during the xenon inhalation. The most common being euphoria. Patient must be aware that such sensations are transient and the clinician will be there to monitor them constantly throughout the examination.

 
 

Q. What are the staffing requirements and the time frame for completing the XeCT/CBF scan?

 

A team approach is a basic requirement for acquiring safe and technically adequate xenon-enhanced computed tomograpy cerebral blood flow (XeCT/CBF) studies. These studies demand not only the complete attention of the CT technologist, but also the direct involvement of a nurse, physician assistant, or physician whose primary focus is on patient management. Working together assures the no time is wasted once patient preparation has begun. Moreover, although xenon-delivery system includes many safety features to protect the patient against an inadequate supply of xenon and oxygen, it is not a patient monitor and should not be relied upon as such. Like angiography, Xe/CT studies always should be regarded as a special procedure that demands the full attention, cooperation, coordination, and commitment of all personnel involved.4
 

Q. What can be done to assure patient cooperation and eliminate motion during the Xe/CT CBF scan?

 

The greatest challenge in obtaining technically adequate imaging is the prevention of head motion. Because movement as small as a few millimeters in any plane can cause significant misregistration, no motion between images can be tolerated during the acquisition of baseline and enhanced scans. Several head immobilization techniques are effective, including a custom head holder that lies directly on the CT table for added stabilization. Additionally, using a vacuum-activated “bean bag”, which easily molds to the contour of the head aids in further head immobilization.
Despite head-immobilization techniques, motion continues to be the most frequent problem in XeCT/CBF studies. Maintaining verbal contact with the patient throughout the study us crucial. Laughing and crying are responses to xenon that patients may be unable to control and often result in head motion. Reassurance may be sufficient to stem these reactions, but sedation also may need to be considred.4

 

Q. What is the cost per study?

 

The cost per study averages about $100.00. This includes the cost of xenon gas and disposable face-mask.
 

Q. How are we reimbursed? Is there a CPT code?

 

Currently, there is no CPT code designed exclusively for Xe/CT scan. We are in a process of submitting a request for the CPT code approval. Most of the institutions use the head combined code as their reimbursement at this time.

 

1 Good W.F., Gus D., Shabason L., et al.: Errors associated with single-scan determination of regional cerebral blood flow by Xenon enhancer CT. Phys. Med. Biol. 27:531-537, 1982.

2 De Pace, D. (1994). Anatomy and physiology of the nervous system. In E. Barker (Ed.), Neuroscience nursing (pp. 3-47). St. Louis Mosby-Year Book.

3 Yonas, H., Johnson, D.W., & Pindzola, R.R. (1995). Xenon-enhanced CT of cerebral blood flow. Scientific Amer.

4 Pethany, S.L., “Patient Considerations”, Cerebral Blood Flow Measurement with Stable Xenon-Enhanced Computed Tomography edited by Howard Yonas (1992).

5 Gur D., Yonas H., Jackson D. L., et al. Simultaneous measurements of cerebral blood flow by Xenon/CT method and the microsphere method: A comparison. Invest. Radiol. 1985; 20:672-677.

6 Gur D., Yonas H., Jackson D.L., et al. Measurements of cerebral blood flow during inhalation as measured by the microspheres method. Stroke 1985; 16:871-874.

7 DeWitt D.S., Fatouros P.P., Wist A.O., et al. Stable Xenon versus radio labeled microspheres cerebral blood flow measurements in baboons. Stroke 1989; 20:1716-1723.

8 Wolfson S.K. Jr., Clark J., Greenberg J. H., et al. Xenon enhanced tomography compared with [14C] Iodoantipyrine for normal and low cerebral blood flow states in baboons. Stroke 1990; 21:751-757.

9 Bouma G. J., Muizelaar J. P. Evaluation of regional cerebral blood flow in acute head injury by stable Xenon-enhanced computerized tomography. Acta Neurochir (Wien) (Suppl) 1993, 59:34-40.

10 Yonas H., Obrist W., Gus D., et al. Cross correlation of CBF derived by 133Xe and Xenon/CT in normal volunteers. J. Cerebral Blood Flow Metab. 9 (Suppl. 1) 1989, S409.

11 Nariai T., Suzuki R., et al. (Tomonaga M., Tanaka A., Yonas H. (eds.)) Testing for cerebral blood flow reserve in chronic ischemic diseases: Comparison of data obtained with Xenon/Computed Tomography Acetazolamide Challenge Test and Position Emissions Tomography in Quantitative Blood Flow Measurement Using Stable Xenon/CT: Clinical Applications. New York: Futura, 1995, 157-163.

12 Fick A: Ueber die Mesrung des Blutquantums in den Herznentrikeln. Sitz Physik – Med Ges Wurzburg 1870; 2:16-28.

13 Kety S.S., Schmidt CF: The Nitrous Oxide Method For The Quantitative Determination Of Cerebral Blood Flow In Many: Theory, Procedure And Normal Values. J. Clin Inveset 1948; 27:476-483.

14 Kety S.S.: The Theory And Applications Of The Exchange Of Inert Gas At The Lungs And Tissues. Pharmacol Rev 1951 3:1-41.

15 Neumann-Haefelin T., Kastrup A., deCrospigny A., Yenari M., Ringer T., Sun G., Moseley M.: Serial MRI After Transient Focal Ischemia in Rats, Dynamics of Tissue Imaging, Blood Brain Barrier Damage and Edema Formation. Stroke 2000 31:1965-73.