are Associate Professors of Radiology,
is a Radiology Resident Physician, and
is an Assistant Professor of Radiology in the Department of
Radiology, University of Texas Medical Branch at Galveston.
is an Assistant Professor of Internal Medicine in the Department
of Internal Medicine, University of Texas Medical Branch at
In 2002, radiologists face a sea of new acronyms, including DWI,
HASTE, PRESS, STEAM, GRASS, MRCP, PET, and PACS. This article will
define many new acronyms utilized throughout radiology and their
potential usefulness will be discussed. We will identify and review
major breakthroughs in technology, emphasizing magnetic resonance
(MR) imaging and briefly exploring the new tools available to
diagnose and treat pathology.
Since the discovery and implementation of computed axial
tomography, for which Cormack and Hounsfield shared the Nobel Prize
in Medicine in 1980,
the field of radiology has gained the ability to diagnose and
characterize disease processes that would have been unthinkable
only 50 years ago.
The goal of this discussion is not to cover all pulse sequences
by all manufacturers, but rather to limit the scope to commercially
available MR scanners and equipment in which the authors have
significant experience in clinical use
: GE Medical Systems, Milwaukee, WI; and Siemens Medical, Iselin,
Major new noninvasive or minimally invasive radiologic
examinations and procedures will be highlighted. The authors hope
that the information provided will aid radiology residents and
general radiologists as a quick reference during their educational
and professional pursuits.
Magnetic resonance imaging (MRI) has revolutionized imaging of
the central nervous system (CNS), secondary to superb soft-tissue
contrast and multiplanar capabilities. The various diagnostic pulse
sequences developed sound like an alphabet soup.
FSE T2 (GE) & TSE T2 (Siemens) --
Fast-spin-echo (FSE) and turbo-spin-echo (TSE) imaging. These
T2-weighted images depict cerebrospinal fluid (CSF), edema, and
most pathology as bright signal in the brain and other organs.
GRASS (GE) & FLASH (Siemens)--
Gradient-recalled acquisition in the steady state (GRASS) and fast
low-angle shot (FLASH). These pulse sequences are utilized for
their "myelographic" effect in imaging of the spine and for
depicting blood products in the CNS.
FLAIR (GE and Siemens)--
Fluid-attenuated inversion recovery. A heavily T2-weighted sequence
with suppression of CSF signal, which increases conspicuity of
DWI (GE and Siemens)--
Diffusion-weighted imaging. A pulse sequence utilizing echoplanar
imaging (EPI) that can identify acute stroke (within 3 hours) by
evaluating restricted Brownian motion as the result of edema from
Intravenous or intra-arterial thrombolytic therapy may be
instituted based on the early diagnosis of ischemia.
MRA and MRV--
Magnetic resonance arteriography and magnetic resonance venography.
This noninvasive evaluation of arteries and veins in the head and
neck allows detection of intracerebral aneurysms of >= 3 mm,
stenosis, and dural sinus thrombosis.
Magnetic resonance spectroscopy. This noninvasive examination of
the brain evaluates metabolites in normal and abnormal brain based
on hydrogen content and aids in diagnosing tumor, abscess,
demyelination, and other brain abnormalities. Stimulated-echo
acquisition mode (STEAM) and point-resolved spectroscopy (PRESS)
are the major pulse sequences utilized.
Point-resolved spectroscopy. This is a "single-shot" method of
obtaining MRS spectral data.
Functional magnetic resonance imaging. fMRI evaluates eloquent
regions of the brain and aids in surgical planning for
Guglielmi detachable coils (Target Therapeutics, Freemont, CA).
These coils are used to treat intracerebral aneurysms and
arterial-venous malformations in a nonsurgical fashion deployed by
a minimally invasive catheterization delivery system.
Positron emission tomography. This technology uses a
cyclotron-produced isotope attached to glucose
(fluorodeoxyglucose-18 [FDG-18]) to diagnose tumors, which have a
higher metabolic rate, as well as to monitor tumor response to
therapy. PET with computed tomography (CT) fusion is the next major
cross-sectional imaging product on the horizon.
Electron beam tomography. This extremely fast computed axial
tomographic technique can evaluate very small structures (coronary
artery calcifications) and can scan a large portion of the body
Multidetector helical CT with speeds as fast as 0.5 seconds per
scan. Eight detectors allow 16 slices per second; the resulting
images of the heart rival EBT. Scanners are excellent for CT
angiography, pulmonary angiography, and virtual colonography.
High-resolution computed tomography. HRCT permits detailed
evaluation of the anatomy of the secondary pulmonary lobules, which
is an important tool for the work-up of a variety of lung
Magnetic resonance cholangiopancreatography. MRCP depicts the
biliary tree and the pancreatic duct noninvasively without contrast
replacing traditional endoscopic retrograde
cholangiopancreatography (ERCP) in many instances (Figure 1).
HASTE (Siemens) & SSFSE (GE)--
Half-Fourier acquisition single-shot turbo-spin echo (HASTE) and
single-shot fast-spin echo (SSFSE). HASTE and SSFSE are MR pulse
sequences, used as noninvasive alternatives to excretory
intravenous urograms (IVPs), permitting diagnosis of urinary tract
pathology without contrast injection.
STIR (GE and Siemens)--
Short tau inversion recovery. This MR pulse sequence is heavily
T2-weighted with fat suppression and is extremely useful in
orbital, skull base, and musculoskeletal imaging to detect edema,
tumor, inflammation, and infection (Figure 2).
Highly detailed evaluation of the endometrium by ultrasound
following distension of the uterus by water introduced via
catheterization. This technique is useful for identification of
endometrial cancer and small polyps.
RODEO & SPECIAL (GE)--
Rotating delivery of excitation off resonance (RODEO)
and spectral inversion at lipids (SPECIAL). These fat suppression
sequences, available with the newer GE systems, are specialized
sequences used for MRI of the breast for detection of breast
masses, staging of breast cancer, surgical planning, and response
of tumors to chemotherapy (Figure 3). MRI of the breast is also
useful to detect implant rupture.
Interventional and vascular radiology
Computed tomographic angiography/computed tomographic venography.
Helical or spiral CT technology allows evaluation of the arterial
or venous system in the head and neck, chest, abdomen, and pelvis.
These technologies obviate invasive procedures, such as
conventional arteriograms or venograms, to diagnose carotid
stenosis, pulmonary embolus, abdominal aortic aneurysms and venous
Magnetic resonance angiography. MRA of the aorta and peripheral
vessels can replace invasive aortography and its potentially renal
toxic contrast dose (Figure 4).
Transjugular intrahepatic porto-hepatic systemic shunt. This
procedure treats portal hypertension secondary to cirrhosis by
redirecting portal venous blood flow to the hepatic veins and
bypassing the liver. A metallic stent is placed by the
interventional radiologist via an internal jugular vein approach.
TIPS can abate life-threatening hemorrhage from esophageal varices
or treat refractory ascities.
Minimally invasive treatment of malignant hepatic
Radiofrequency ablation, ethanol ablation, laser ablation,
microwave ablation, cryoablation, and chemoembolization techniques
are currently available to the interventional radiologist to treat
malignant hepatic tumors without surgery.
Endovascular repair of abdominal aortic aneurysm (AAA)--
A bifurcated stent apparatus, covered with graft material, is
placed within an aortic aneurysm from an endovascular approach
(femoral artery cutdowns). This minimally invasive procedure has
lowered morbidity and mortality when compared with the traditional
open repair and allows the patient to return to home and work
within a few days.
Uterine artery embolization. A catheter is placed into both uterine
arteries, and symptomatic uterine fibroids are embolized. This
procedure is >80% effective in the treatment of the bleeding,
pain, and pressure associated with large uterine leiomyomata. This
procedure is performed by interventional radiologists and is sought
by patients who do not desire or are not candidates for
hysterectomy or myomectomy.
Picture archiving and com-munication system. Image acquisition,
transfer, and storage are increasingly being performed
electronically. Tech-nological advances, increased speed, and
decreased cost will rapidly lead to the "filmless" radiology
department and to the "filmless" operating room and hospital.
Access to studies and images is gaining favor via the Web.
Computerized speech recognition. CSR is rapidly replacing
traditional radiology reporting by a transcriptionist. Due to the
advantages of increased accuracy, rapid turnaround time, and lower
CSR will eventually replace most traditional transcription
reporting, thereby reducing full-time employees (FTE) and
Digital Imaging and Communications in Medicine. This interface was
developed by the American College of Radiology (ACR), National
Electrical Manufacturer's Association (NEMA), Mallinckrodt
Institute of Radiology, and the Radiological Society of North
America (RSNA) for transfer of radiology images and medical
information between computers.
Information system. Hospital personnel with expertise in computers
are responsible for helping to install, monitor, and maintain the
radiology CSR systems, PACS, and radiology information system
A nuclear medicine study using technetium with sestamibi, which
complements mammography in detecting and staging breast carcinoma.
Somatostatin receptor (Indium III pentetreotide
radiopharmaceutical) imaging for neuroendocrine tumors. This
imaging can detect tumors with APUD (amine precursor uptake
decarboxylation)-producing capabilities such as carcinoids, islet
cell tumors, medullary thyroid carcinomas, pheochromocytomas,
paragangliomas, and small-cell lung cancer.
This indium-labeled radiopharmaceutical attached to a murine
monoclonal antibody is utilized to detect metastatic prostate
cancer in patients who have biopsy-proven prostate cancer and are
at high risk for pelvic nodal metastasis, or in patients with
equivocal or suspected occult metastatic disease.
The advent and implementation of cross-sectional imaging has
markedly advanced medical care in the last 30 years. The goals of
this manuscript were to identify and describe some of the new major
technological advances in diagnostic imaging equipment and
interventional procedures, and define their acronyms, which are
used in clinical practice. The manuscript is noninclusive for all
acronyms and manufacturers; for additional information, the reader
is referred to the MR abbreviations in the review article by Brown
Radiologists will need to keep abreast of all these new
examinations and procedures to determine their cost-effectiveness,
positive and negative predictive values, and their clinical
usefulness. The above-described examinations, procedures, and
acronyms pervade all disciplines. It is hoped that the information
provided will augment the radiologists' armamentarium to guide
better dialogue with ordering clinicians and improve patient care.