Volume 4 Number 2 Summer 1998

Master List Volume 4 Number 2 Summer 1998

IN THIS ISSUE

3-D CT
Techniques and Clinical Applications:
UAB CT takes off its (3-D) classes in the fight against disease.

FAQs

Musculoskeletal Imaging: Current Applications with Emphasis on MRI

Radiology Renewal

Visions Survey

1- Two images of a three dimensional model of the trachea constructed after helical CT scanning of a patient with tracheal stenosis . The focal narrowing in the tracheal column (arrows) can be visualized in multiple degrees of rotation. 2- Complex pelvic fractures involving the acetabulum and hemipelvis can be seen to greater detail after removing the femur and noninvolved pelvic structures by computer postprocessing. 3- CT angiography is a relatively noninvasive technique to image vascular abnormailites. This image shows focal narrowing of the left common carotid artery at its origin (arrows). 4- A 3-D model of the skull shows the relationship of the fracture fragments in this patient with a tripod fracture.

Techniques and clinical applications: UAB CT takes off its (3D) glasses in the fight against disease.

CT is one of the most frequently used diagnostic tools in our radiology department with over 2,000 CT exams performed per month at UAB and The Kirklin Clinic. In spite of its excellent soft tissue contrast and ability to resolve overlapping structures, CT can be difficult to interpret. Due to the limited size of the CT scanner bore, it may be difficult or impossible to position some parts of patients in the ideal orientation for scanning; it can also be very difficult to visualize complex anatomy or appreciate subtle pathology from axial images. In difficult cases Radiologists may perform post processing or 3 dimensional (3D) reconstructions. Post processing cannot add information to the examination, but it can often improve diagnostic ability or confidence by accentuating or isolating structures of interest or presenting the data in another orientation or as an integrated, more easily visualized 3D model

Technical improvements have recently made 3D CT more practical while broadening its application. New high heat capacity X-ray tubes and faster CT scanners improve speed and coverage, or allow for the use of thinner CT slices without excessive noise. Faster scanning decreases problems with patient motion during the scan, often allowing coverage of the area of interest in a single breath. The patient moves through the scanner as the X-ray tube rotates, giving a spiral or helical dataset; overlapping slices may be reconstruction from the helical data without having to physically scan the patient with overlapping X-ray beams, thus dramatically reducing patient X-ray exposure while providing a better data set for 3D or reformatted images.

Helical CT data sets can be processed into 3D models or 2 dimensional "reformatted" images in arbitrary orientations or even along curved planes to best show the anatomy or pathology in question. With the newly acquired 3D workstation in the UAB hospital CT department these formerly tedious and time consuming reconstructions can be performed interactively in real time. Resulting 3D models may be viewed interactively or as a rotating model at the workstation; still images can be filmed in any desired orientation.

Musculoskeletal pathology is still the most common application of 3D CT at UAB. Common indications include the evaluation of complex fractures or lesions in complicated anatomic regions like the pelvis. The 3-D images may help the surgeon to determine the number and orientation of fracture fragments in comminuted fractures. Sagittal, coronal, or obliquely oriented reformatted images are also often helpful, especially in the extremities which can be difficult to position, particularly after trauma.

Tracheal abnormalities are well demonstrated with 3D CT. Tracheal stenoses and masses have traditionally been studied with plain radiographs and linear X-ray tomography; however, as conventional (linear) X-ray tomography has been utilized less often for other diagnostic problems, it has become difficult to train technologists to perform quality tracheal tomography. Fortunately, tracheal pathology is easily and quickly visualized on CT, but complex strictures may be hard to appreciate on axial images alone. 3D presentation allows better visualization of these difficult cases and skeletal structures can be easily superimposed to provide surgical landmarks.

With 3D post processing, CT angiography can often provide angiographic imaging in an inexpensive, non-invasive procedure. Early helical scanning during rapid intravenous contrast administration gives images with high arterial contrast for post processing into angiographic style images. CT angiography does not have as high a spatial resolution as X-ray catheter angiography, but provides sufficient resolution for many common vascular studies such as carotid arteries, aorta and its branches, and proximal extremity arteries.

More recently developed 3D CT software (soon to be available at UAB) can construct interactive models of hollow viscera such as the colon or trachea. These hollow models can give endoscopic style pictures or "virtual endoscopy;" CT colography is currently being clinically tested but shows promise as a screening tool for colonic polyps and cancers.

Clinical applications of these powerful imaging techniques are expanding rapidly as our experience grows. Consultation with UAB radiologists may help to determine if they could be of benefit in addressing a specific clinical concern for your patient.

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FAQS - Frequently Asked Questions - Musculoskeletal Imaging

Q: Current Applications with Emphasis on MRI

The first radiograph ever made was a bone film, specifically an image of Mrs. W.C. Roentgen's left hand in 1895. Mrs. Roentgen had to hold still for the 15 minutes it took for her husband, Dr. Wilhelm Conrad Roentgen, to complete the exposure. Since then, radiographs have been extensively used for imaging osseous disease and injury including but not limited to trauma, neoplasms, arthritis and other connective tissue disorders, infectious processes and metabolic disorders.

Although arthrography can be very helpful in evaluating ligamentous, fibrocartilagenous and capsular injuries of the joints, it is an invasive procedure and has poor sensitivity and specificity for some important injuries, such as anterior cruciate ligament (ACL) tears. MRI, with its high soft tissue contrast and spatial resolution, has revolutionized the non-invasive imaging of musculoskeletal abnormalities. MRI's multiplanar imaging capabilities allow visualization of targeted structures in three orthogonal planes, usually with no need for injection of contrast material. The availability of dedicated receiver coils for the extremities and joints has resulted in improved resolution of intraarticular, periarticular, muscular, and superficial soft tissue images.

Q: When are musculoskeletal MRI exams requested?

Knee and shoulder exams are the most commonly requested studies. Most patients are referred from their orthopedist, rheumatologist or primary care physician with persistent pain or joint instability, unexplained by clinical exam and conventional radiographs. In the shoulder, MRI gives excellent depiction of rotator cuff tears, injuries to the biceps tendon and damage to the glenoid labrum. In the knee, common injuries like meniscal tear and cruciate ligament disruption is well recognized. Other commonly performed musculoskeletal MR exams include: the hip (usually for osteonecrosis or occult fracture), ankles (especially for evaluating talar osteochondral lesions, tendinitis and tendon ruptures), elbows and wrists (for occult fracture, osteonecrosis and tendon or ligament disruptions). TMJ MR examinations can evaluate meniscal dislocations that may require surgical intervention. Muscle fiber tears, tendon disruptions and tendinitis are also well defined by MRI.

Another frequent indication for musculoskeletal MRI is diagnosing and staging of bone tumors and soft tissue masses, many of which are malignant neoplasms. MRI can exquisitely delineate the extent of these masses and demonstrate their proximity to neurovascular structures, as well as characterize their internal matrix {e.g. presence of fat in fatty tumors} to facilitate pre-operative planning. MR can also demonstrate acute fractures that are radiographically impossible to see, (e.g. an elderly osteopenic patient with severe hip pain and negative radiographs).

A positive MRI helps support the clinical suspicion of osteomyelitis or abscess and directs the soft tissue or bone aspiration or biopsy. Invasive procedures are usually necessary to confirm infection and obtain specimens for histologic analysis and culture.

MRI may help in imaging systemic diseases that affect the musculoskeletal system. For example, MR can demonstrate the extent of polymyositis and can help direct a muscle biopsy. MRI may help determine the extent of bone marrow pathology, such as in neoplastic marrow replacement and storage diseases (e.g. leukemia and Gaucher's disease), and is the focus of some current research interests.

Q: When is arthrography requested in conjunction with MRI?

The injection of dilute gadolinium (a paramagnetic contrast agent for MRI) into joints prior to imaging can increase the sensitivity for cartilaginous and ligamentous abnormalities. The most common indication for intraarticular gadolinium at UAB is to aid in diagnosing complex shoulder derangements. In such settings, filling the joint with contrast helps to distinguish partial tears from small complete tears of the rotator cuff.

Gadolininium injection of the elbow prior to MRI helps visualize small tears of the medial (ulnar) collateral ligament. Hip MR arthrography may help demonstrate labral abnormalities (chronically painful hips that click and lock). The acetabular labrum is difficult to image accurately, even after hip injection. MR arthrogram studies are usually ordered after orthopedic consultation, and also in consultation with one of UAB's musculoskeletal radiologists. Such communication is essential to tailor the examination.

Q: What if my patient cannot have an MR?

Some times an MRI cannot be performed. Claustrophobia is common, but usually can be addressed with benzodiazepine premedication. Rarely, patients can be so claustrophobic that only general anaesthesia will suffice. Other contraindications include patients with cardiac pacemakers or with implanted ferromagnetic devices. Some types of aneurysm clips and heart valves contain ferromagnetic material and may either come loose or malfunction inside the magnet. References are kept at UAB's MR sites, which list the ferromagnetic susceptibility of such devices by manufacturer (if the manufacturer is known). Most orthopedic hardware implants are made from high grade steel alloys and are non-ferromagnetic, and therefore MRI is safe. However, they do contribute to significant image degradation, sometimes rendering the entire exam non-diagnostic.

When musculoskeletal MR imaging is not an option, other imaging modalities can usually be substituted. Alternative choices include conventional or CT arthrography, nuclear medicine studies, and ultrasound. Consultation with an orthopedic specialist may better determine the need for an imaging evaluation. Consultation with one of UAB's musculoskeletal radiologists is also encouraged.

Q: When should I request a CT instead of an MRI?

Dense cortical bone or soft tissue calcifications/ossifications create an area of signal void on MR due to their relative lack of mobile hydrogen protons. Little or no information is obtained about heavily calcified structures on MRI. CT can be very helpful in these instances. For instance, osteoid osteomas look very typical on CT. Many fractures, changes of chronic bone remodeling (such as in chronic osteomyelitis), and heterotopic ossification (i.e. myositis ossificans) are better depicted by CT. The speed of acquisition of the CT exam with UAB's helical scanners (two or three minutes total scan time) is a distinct advantage over MRI for patients who cannot hold still or who present with acute trauma.

3-D reconstruction CT software has allowed depicting complex anatomical structures (like the bony pelvis) in multiple planes. This can be helpful in evaluating complex pelvic fractures pre-operatively. Again, consultation with one of the UAB radiologists is encouraged to help determine which imaging method is most likely to be successful.

Q: What is the role of ultrasound in musculoskeletal imaging?

There has been a recent resurgence of interest in musculoskeletal ultrasound due to its easy accessibility and relatively low cost. Early experience was discouraging. However, new high-resolution linear ultrasound transducers have improved the depiction of superficial soft tissues. Ultrasound offers the chief advantage of real time examination of the patient. The examiner can focus on the location of greatest pain or tenderness and can mobilize the area during the study. Scanning in different anatomic positions (i.e. abduction, internal rotation of the humerus) may allow a dynamic process like shoulder impingement syndrome to be imaged. We have recently used ultrasound to localize radiographically occult foreign bodies within the soft tissues, to assess for tendon integrity (most commonly in the Achilles tendon), and to evaluate rotator cuff injuries. As with all ultrasound exams, the accuracy of the test is operator dependent and communication between the referring clinical service, the radiologist and the patient is critical in directing the examination.

Q: How can I schedule a musculoskeletal MRI?

All outpatient MRI examinations are scheduled at the Kirklin Clinic MRI facility at 801-8746. There are two permanent magnets in the basement of Kirklin Clinic as well as a temporary magnet located outside the building at the 5th avenue entrance. Inpatient studies are scheduled through the PIN system. The inpatient magnet is located on the first floor of University Hospital in the West Pavilion.

The musculoskeletal division of UAB radiology consists of Drs. Michael Pitt, Wanda Bernreuter, Nancy Pile, Daniel Moore and Robert Lopez. One of these physicians is always available for questions regarding musculoskeletal imaging and can be reached at 934-5135 or through University paging.

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Radiology Renewal

Radiology continues to undergo major facilites and equipment improvements. Anyone who uses the UABH Radiology Records (formerly Film Library) knows that we have recently moved into completely refurbished quarters. This is part of a continuing effort to improve service, which also includes administrative restructuring and expanding service to 24 hours daily. We also hope that for service you are now calling "4-FILM" (4-3456). We have completely replaced our phone system and have restructured our phone service to improve responsiveness. We would appreciate hearing about any problems you might have (excessive hold time, too many transfers, etc.) so that we can deal with them.

The Radiology faculty office suite is now complete on third floor North Wing. We are particularly proud of our state-of-the-art conference room with a networked computer with built-in video projection.For a schedule of conferences in this room, please look at our intranet site: <vulcan.rad.uab.edu>.

Within the past year, all four of the primary CT scanners at UABH and TKC have been upgraded to state-of-the-art helical technology. Completion of renovations and installation of new equipment in Vascular-Interventional has proceeded slowly. The equipment shortage and cramped quarters have seriously burdened our staff and we appreciate your patience.

Additional projects which are scheduled to begin this year include: 1) renovation of the CT and Ultrasound areas on sixth floor Hillman, 2) build-out of the currently vacant third floor of the General Services Building to consolidate our administrative, physics and service divisions, 3) renovation and expansion of the CT and Ultrasound areas at TKC, 4) renovation of the core general radiology hall at UABH, 5) installation of an additional CT scanning in the Emergency Department, 6) renovation and expansion of the MRI suite at TKC, and 7) addition of a film storage annex in the basement of TKC.

Revolutionary transformation continues in the manner in which images and information are managed at UAB. Over the next two to three years, we hope to be able to substantially replace the routine use of film with computerized image viewing. The savings in film handling and improved efficiencies promise to save the UAB Health System over $40 million in the next 10 years and improve the accessibility of images and the quality of care. Furthermore, we continue to expand our use of electronic communication and information storage within Radiology as we move away from dependence on paper.

Visions Survey

The Department of Radiology has published Visions In UAB Radiology as a means of reaching out to our professional colleagues in other divisions. Our main goal is to keep you informed on the latest developments in Radiology and how they affect you and your practice. In order to assess our progress and to improve in the future, the staff of visions asks that you take a few minutes to fill out the accompanying survey and return it via campus mail. All responses will be kept anonymous.

What department(s) are you affiliated with? ____________________________________

Where is your practice primarily based? ___ Hospital ___ Outpatient

How often do you read Visions? ___ Always ___ Sometimes ___ Never

Would you like to see Visions published more or less frequently (currently we publish 3-4 issues per year)?
___ More ___ About Right ___ Less

Are the articles helpful and informative? ___ Yes ___ No

Is the format of the publication clear and easy to follow? ___ Yes ___ No

What topics would you like to see addressed in future issues? ________________________________________________________________________
________________________________________________________________________
________________________________________________________________________

Comments
________________________________________________________________________
________________________________________________________________________
________________________________________________________________________

Return to:
Pat Moore
UABH- Radiology
JT Room N389

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Vsions is published quarterly by the University of Alabama Hospital, Department of Radiology. Professor and Chairman: Robert J. Stanley, MD, Vice-Chairman for Operations and Academic Affairs: Robert E. Koehler, MD, Vice Chairman for Planning and Administration: Lincoln L. Berland, MD, Director of Outpatient Services: Peter Dempsey, MD. Visions Staff - Managing Editor: Pat Moore. Editors/Writers: Lincoln L. Berland, MD, Rachel Oser, MD, Robert Lopez, MD. Web Master: J. Kevin Smith, MD, PhD. Creative Services Staff - Editor: Jo Lynn Orr. Art Director: Jason Bickell. Please direct questions, comments, and suggestions as follows: Attention Angie French or Lincoln L. Berland, MD. Fax: 975-7213 Address: NHB 623B E-Mail lberland@uabmc.edu UAB Radiology Home Page: www.rad.uab.edu


1- Two images of a three dimensional model of the trachea constructed after helical CT scanning of a patient with tracheal stenosis . The focal narrowing in the tracheal column (arrows) can be visualized in multiple degrees of rotation. 2- Complex pelvic fractures involving the acetabulum and hemipelvis can be seen to greater detail after removing the femur and noninvolved pelvic structures by computer postprocessing. 3- CT angiography is a relatively noninvasive technique to image vascular abnormailites. This image shows focal narrowing of the left common carotid artery at its origin (arrows). 4- A 3-D model of the skull shows the relationship of the fracture fragments in this patient with a tripod fracture.

Q: Current Applications with Emphasis on MRI	The first radiograph ever made was a bone film, specifically an image of Mrs. W.C. Roentgen's left hand in 1895. Mrs. Roentgen had to hold still for the 15 minutes it took for her husband, Dr. Wilhelm Conrad Roentgen, to complete the exposure. Since then, radiographs have been extensively used for imaging osseous disease and injury including but not limited to trauma, neoplasms, arthritis and other connective tissue disorders, infectious processes and metabolic disorders. Although arthrography can be very helpful in evaluating ligamentous, fibrocartilagenous and capsular injuries of the joints, it is an invasive procedure and has poor sensitivity and specificity for some important injuries, such as anterior cruciate ligament (ACL) tears. MRI, with its high soft tissue contrast and spatial resolution, has revolutionized the non-invasive imaging of musculoskeletal abnormalities. MRI's multiplanar imaging capabilities allow visualization of targeted structures in three orthogonal planes, usually with no need for injection of contrast material. The availability of dedicated receiver coils for the extremities and joints has resulted in improved resolution of intraarticular, periarticular, muscular, and superficial soft tissue images.
Q: When are musculoskeletal MRI exams requested?	Knee and shoulder exams are the most commonly requested studies. Most patients are referred from their orthopedist, rheumatologist or primary care physician with persistent pain or joint instability, unexplained by clinical exam and conventional radiographs. In the shoulder, MRI gives excellent depiction of rotator cuff tears, injuries to the biceps tendon and damage to the glenoid labrum. In the knee, common injuries like meniscal tear and cruciate ligament disruption is well recognized. Other commonly performed musculoskeletal MR exams include: the hip (usually for osteonecrosis or occult fracture), ankles (especially for evaluating talar osteochondral lesions, tendinitis and tendon ruptures), elbows and wrists (for occult fracture, osteonecrosis and tendon or ligament disruptions). TMJ MR examinations can evaluate meniscal dislocations that may require surgical intervention. Muscle fiber tears, tendon disruptions and tendinitis are also well defined by MRI. Another frequent indication for musculoskeletal MRI is diagnosing and staging of bone tumors and soft tissue masses, many of which are malignant neoplasms. MRI can exquisitely delineate the extent of these masses and demonstrate their proximity to neurovascular structures, as well as characterize their internal matrix {e.g. presence of fat in fatty tumors} to facilitate pre-operative planning. MR can also demonstrate acute fractures that are radiographically impossible to see, (e.g. an elderly osteopenic patient with severe hip pain and negative radiographs). A positive MRI helps support the clinical suspicion of osteomyelitis or abscess and directs the soft tissue or bone aspiration or biopsy. Invasive procedures are usually necessary to confirm infection and obtain specimens for histologic analysis and culture. MRI may help in imaging systemic diseases that affect the musculoskeletal system. For example, MR can demonstrate the extent of polymyositis and can help direct a muscle biopsy. MRI may help determine the extent of bone marrow pathology, such as in neoplastic marrow replacement and storage diseases (e.g. leukemia and Gaucher's disease), and is the focus of some current research interests.
Q: When is arthrography requested in conjunction with MRI?	The injection of dilute gadolinium (a paramagnetic contrast agent for MRI) into joints prior to imaging can increase the sensitivity for cartilaginous and ligamentous abnormalities. The most common indication for intraarticular gadolinium at UAB is to aid in diagnosing complex shoulder derangements. In such settings, filling the joint with contrast helps to distinguish partial tears from small complete tears of the rotator cuff. Gadolininium injection of the elbow prior to MRI helps visualize small tears of the medial (ulnar) collateral ligament. Hip MR arthrography may help demonstrate labral abnormalities (chronically painful hips that click and lock). The acetabular labrum is difficult to image accurately, even after hip injection. MR arthrogram studies are usually ordered after orthopedic consultation, and also in consultation with one of UAB's musculoskeletal radiologists. Such communication is essential to tailor the examination.
Q: What if my patient cannot have an MR?	Some times an MRI cannot be performed. Claustrophobia is common, but usually can be addressed with benzodiazepine premedication. Rarely, patients can be so claustrophobic that only general anaesthesia will suffice. Other contraindications include patients with cardiac pacemakers or with implanted ferromagnetic devices. Some types of aneurysm clips and heart valves contain ferromagnetic material and may either come loose or malfunction inside the magnet. References are kept at UAB's MR sites, which list the ferromagnetic susceptibility of such devices by manufacturer (if the manufacturer is known). Most orthopedic hardware implants are made from high grade steel alloys and are non-ferromagnetic, and therefore MRI is safe. However, they do contribute to significant image degradation, sometimes rendering the entire exam non-diagnostic. When musculoskeletal MR imaging is not an option, other imaging modalities can usually be substituted. Alternative choices include conventional or CT arthrography, nuclear medicine studies, and ultrasound. Consultation with an orthopedic specialist may better determine the need for an imaging evaluation. Consultation with one of UAB's musculoskeletal radiologists is also encouraged.
Q: When should I request a CT instead of an MRI?	Dense cortical bone or soft tissue calcifications/ossifications create an area of signal void on MR due to their relative lack of mobile hydrogen protons. Little or no information is obtained about heavily calcified structures on MRI. CT can be very helpful in these instances. For instance, osteoid osteomas look very typical on CT. Many fractures, changes of chronic bone remodeling (such as in chronic osteomyelitis), and heterotopic ossification (i.e. myositis ossificans) are better depicted by CT. The speed of acquisition of the CT exam with UAB's helical scanners (two or three minutes total scan time) is a distinct advantage over MRI for patients who cannot hold still or who present with acute trauma. 3-D reconstruction CT software has allowed depicting complex anatomical structures (like the bony pelvis) in multiple planes. This can be helpful in evaluating complex pelvic fractures pre-operatively. Again, consultation with one of the UAB radiologists is encouraged to help determine which imaging method is most likely to be successful.
Q: What is the role of ultrasound in musculoskeletal imaging?	There has been a recent resurgence of interest in musculoskeletal ultrasound due to its easy accessibility and relatively low cost. Early experience was discouraging. However, new high-resolution linear ultrasound transducers have improved the depiction of superficial soft tissues. Ultrasound offers the chief advantage of real time examination of the patient. The examiner can focus on the location of greatest pain or tenderness and can mobilize the area during the study. Scanning in different anatomic positions (i.e. abduction, internal rotation of the humerus) may allow a dynamic process like shoulder impingement syndrome to be imaged. We have recently used ultrasound to localize radiographically occult foreign bodies within the soft tissues, to assess for tendon integrity (most commonly in the Achilles tendon), and to evaluate rotator cuff injuries. As with all ultrasound exams, the accuracy of the test is operator dependent and communication between the referring clinical service, the radiologist and the patient is critical in directing the examination.
Q: How can I schedule a musculoskeletal MRI?	All outpatient MRI examinations are scheduled at the Kirklin Clinic MRI facility at 801-8746. There are two permanent magnets in the basement of Kirklin Clinic as well as a temporary magnet located outside the building at the 5th avenue entrance. Inpatient studies are scheduled through the PIN system. The inpatient magnet is located on the first floor of University Hospital in the West Pavilion. The musculoskeletal division of UAB radiology consists of Drs. Michael Pitt, Wanda Bernreuter, Nancy Pile, Daniel Moore and Robert Lopez. One of these physicians is always available for questions regarding musculoskeletal imaging and can be reached at 934-5135 or through University paging.