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J. M. Ryan and S. Dawson
made, and considerable clinical experience has been
gained. Presently, fluoroscopic placement of gastrostomy
tubes is a well-recognized, clinically important technique.
In many institutions, it has become the method of choice
for placement of gastrostomy feeding tubes as a result of
its low complication rate and low cost compared with
other available methods.
■ Indications for Gastrostomy
Tube Placement
The most common indication for gastrostomy tube
placement is to provide nutritional support for patients
with dysphagia. For most patients, the dysphagia is a
result of a debilitating neurological disorder, such as
cerebrovascular accident, trauma, dysmyelinating and
demyelinating disease, or postsurgical sequelae, such as
a neurological deficit following resection of an intracranial neoplasm. A second important group of patients are
those with swallowing disorders secondary to oropharyngeal or esophageal tumors. An infrequent but important indication is small bowel disease, such as Crohn’s
disease, short bowel syndrome, or radiation enteropathy.
Because patients with small bowel disease cannot tolerate
a normal diet, nutrition must be presented in a form that
can be absorbed, which is achieved by providing an elemental diet through a gastrostomy or gastrojejunostomy
tube.
Other less common indications for gastrostomy tube
placement include decompression of the upper gastrointestinal tract in a patient with advanced malignant obstruction, chronic adynamic gastroparesis, or ileus, and
anorexia with underlying psychiatric or malignant illness. Percutaneous gastrostomy also has been used for
the removal of intragastric foreign bodies, such as displaced esophageal stents, and for transgastric drainage
of pancreatic pseudocyst fluid collections.
■ Contraindications to Percutaneous
Gastrostomy
Relative contraindications for radiologic gastrostomy
tube placement include portal hypertension with gastric
varices, severe gastritis, and massive ascites, which can
increase the tendency for leakage of gastric contents from
the stomach after tube placement. Many radiologists consider large ascites to be an absolute contraindication;
however, this is not the case in our practice. We perform
decompression gastrostomy in patients with chronic
bowel obstruction and ascites, most commonly secondary
to intraperitoneal metastatic spread of ovarian carcinoma. For these patients, we perform preprocedural
paracentesis, and we routinely use the radiologic T-fas-
tener gastropexy to reduce the incidence of intraperitoneal leakage of gastric contents. We also perform serial
paracentesis after gastrostomy tube placement to prevent
massive ascites buildup, which can cause necrosis of the
gastropexy.
Percutaneous placement of a gastrostomy tube requires a safe percutaneous access to the stomach. Occasionally, a patient’s stomach is overlaid by transverse colon or the left lobe of the liver. The stomach may have a
high subcostal position in some patients as an anatomic
variant or in patients who have had a previous partial
gastrectomy. These problems are usually surmountable
by performing the initial gastric puncture under computed tomography (CT) guidance, after which the patient is transferred to the interventional fluoroscopy
suite for track dilation and tube placement.
Encasement of the stomach by tumor is also a relative
contraindication for several reasons. One reason is that
healing does not occur normally, and a fistulous track
therefore does not readily form between the stomach
and the skin. A second reason is that tumor tissue is
abnormally vascularized by neovessels that have an increased propensity to bleed if they are transgressed. Lack
of distensibility of a tumor-encased stomach also may
make tube placement extremely difficult. The symptoms
of anorexia and nausea that patients with tumor encasement of the stomach experience often remain unrelieved by gastrostomy tube placement because the symptoms are due largely to effects of the tumor on the
autonomic ner vous system.
Gastrostomy tube placement is relatively contraindicated in patients who are taking long-term corticosteriod
treatment because they may have a higher complication
rate of gastric perforation as a result of stomach wall
atrophy and poor healing, leading to increased risk for
gastric perforation and leakage of gastric contents. Patients with active or chronic duodenal ulcers should have
a gastrostomy tube placed rather than undergo a transgastric jejunostomy or gastrojejunostomy tube because
the mechanical irritation from a tube passing through
the duodenal bulb may cause serious bleeding.
In some patients, the presence of a tube through the
pylorus can cause a partial or complete gastric outlet
obstruction syndrome, which may be overcome by placement of either a single gastrojejunostomy tube, which
incorporates both a draining gastrostomy port and a
feeding jejunal port, or by a two-tube technique, in
which both a gastrostomy and a transgastric jejunostomy
are placed through separate tracks. Our experience
leads us to favor the two-tube approach because better
gastric drainage may be achieved by using this approach.
To achieve optimum gastric drainage, the drainage tube
should be situated at the most dependent portion of the
stomach, which in most patients requiring gastrostomy
is the fundus because of the patient’s supine position.
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The two-tube approach allows a tube to be placed directly in the fundus, whereas the use of a single gastrojejunostomy catheter allows only for the gastrostomy
drainage port to be placed in the antrum, resulting in
suboptimal drainage. The two-tube approach also allows
a large 14 Fr catheter to be used for drainage and a
separate 14 Fr tube to be used for jejunal feeding. We
routinely use gastrostomy tubes that are 30 cm working
length and transgastric jejunostomy tubes that are 53 cm
working length.
■ Preprocedural Assessment
and Preparation
Informed written consent is necessary before the procedure is performed. Because many patients who require a
gastrostomy tube cannot give consent themselves, consent should be obtained in advance from the next of kin.
Preprocedural blood workup, such as prothrombin time,
partial thromboplastin time, and platelet count, although
not routinely performed on every patient, should be requested for patients in whom a coagulopathy may preexist, such as patients who have been treated with anticoagulants or who are malnourished. The patient’s medical
records are reviewed with particular attention to previous
gastric surgery or medical conditions that preclude the
use of hypotonic agents, sedation, or narcotics. Patients
with a coagulopathy should receive treatment to correct
clotting parameters before the procedure is done.
In our institution the patient is given a cupful of barium by mouth or through nasogastric tube the evening
before the procedure. By the time the procedure commences, the barium will opacify the transverse colon,
thus preventing inadvertent colonic puncture. If the patient is unable to take barium orally, a limited barium
enema may be performed immediately before the procedure in the general fluoroscopy suite to opacify the
transverse colon. An alternative approach, which we favor, is to perform the initial stomach puncture under
CT guidance with subsequent transfer of the patient to
the interventional fluoroscopy suite for completion of
the procedure.
The patient’s fast begins at midnight the night preceding the procedure. When the patient arrives in the fluoroscopy suite, a nasogastric tube and intravenous access
should be in position to expedite the procedure. If problems are encountered in inserting the nasogastric tube,
placement can be done under fluoroscopic guidance before the procedure. An enteroclysis catheter or an angled
angiographic catheter usually can be inserted successfully
under fluoroscopic guidance, even in the presence of
high-grade esophageal obstruction.
Intravenous sedation is administered to patients who
are anxious or restless. A combination of midazolam
(Versed, Roche) and fentanyl (Sublimaze, Janssen) is
used in our institution. A nurse experienced in the administration of sedation monitors the patient’s vital signs
throughout the procedure using an automatic blood pressure cuff, continuous electrocardiographic (ECG) monitoring, and continuous transcutaneous pulse oximetry.
Supplemental oxygen is administered through nasal
prongs during the procedure. It is important to have a
suction apparatus available so that any spontaneous reflux
into the esophagus can be removed before aspiration occurs. We do not routinely administer antibiotics to the
patient before the gastrostomy procedure, although some
institutions prefer to do so.
■ Technique and Modifications
Traditional method of tube placement
The gastropexy technique, which is the traditional
method of tube placement, is illustrated in Figure 11-1.
Initial access to the stomach
The patient is positioned supine on the fluoroscopic table
for a left-sided approach to the abdomen. The margin of
the left lobe of the liver is noted, as is the position of the
transverse colon, which is opacified by the barium administered the preceding evening. Air is insufflated through
the nasogastric tube to distend the stomach. Some
authors have described the use of ultrasound as an additional guidance modality.
water instead of air. No complications occurred in 27 patients for whom this method was used.
venous glucagon, 0.5–1 mg) is used to maintain gastric
distention, and fluoroscopy is performed to select a site of
entry. The preferred entry site is just distal to the incisura
in a plane equidistant from the greater and lesser curves
of the stomach, thus avoiding both gastric and gastroepiploic vessels. The puncture site is also ideally located lateral to the rectus muscle to avoid damage to the
superior epigastric artery.
The skin is infiltrated using 20 mL of 1% lidocaine, and
a small skin incision is made with a no. 11 scalpel blade.
Using an 18-gauge sheathed needle angled toward the
pylorus, a quick thrust is made to introduce the needle
into the stomach. Aspiration of air into a syringe containing 4 mL of saline is usually sufficient evidence of gastric
puncture; however,iodinated contrastmedium or a guidewire may be introduced iffurther confirmation of position
is required. The Teflon sheath then is advanced over the
needle while ensuring that the sheath is in optimal position in the stomach. In patients undergoing gastrostomy
placement for gastric decompression, the sheath is directed toward thefundus of the stomach. Theneedle then
is withdrawn, and a straight tip 0.038-inch guidewire is
6,7
The stomach is filled with
6
Hypotonia (intra-
126 J. M. Ryan and S. Dawson
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A
C D
FIGURE 11-1. Gastrojejunostomy insertion (using the gastropexy technique). A: The stomach is distended with air insufflated
through the nasogastric tube (
insertion. A guidewire is passed through the insertion needle in order to release the T-fastener. C: The four T-fasteners in position
in the midantrum. D: Eighteen-gauge sheathed needle (
T-fasteners and is angled toward the pylorus. A 0.38-inch guidewire has been inserted through the sheathed needle into the
prepyloric region.
white arrow
). Note the presence of barium in the transverse colon (
arrow
) is inserted through the center of the square bordered by the four
curved arrow
). B: T-fastener
B
introduced through the sheath into the stomach. The
sheath then is withdrawn and serial dilatation is performed.
Cannulation of pylorus and duodenum
Cannulation of the pyloric canal is required for transgastric jejunal feeding and for gastrojejunostomy tube
placement, because positioning of the tube in the jejunum greatly reduces the risk of esophageal reflux with
aspiration following feeding (Fig. 11-2). Aspiration pneumonia has caused several deaths in patients after gastros-
8
tomy tube placement.
After the initial needle puncture,
the needle is angled toward the antrum so that the
guidewire advances in the direction of the pylorus. Occasionally, pyloric cannulation can be achieved at this stage
simply by advancing the wire along the greater curve of
the stomach. If the guidewire does not enter the pylorus,
a dilator or a torquable catheter can be used to assist
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127
A
C D
FIGURE 11-2. Gastrojejunostomy insertion. A: The guidewire has been manipulated beyond the ligament of Treitz using an
angiographic catheter. B: Track is serially dilated using 6, 10, and 12 Fr dilators. C: Gastrojejunostomy catheter is inserted over
the guidewire so that its tip position is beyond the ligament of Treitz. D: Catheter is locked in position. Contrast has been injected
to demonstrate mucosal folds in the proximal jejunum.
B
cannulation. Most often, an angled angiographic catheter is required to pass through the pylorus; once this step
is achieved, the wire tip is advanced to the ligament of
Treitz. During cannulation of the pylorus, care must be
taken to avoid looping the guidewire in the fundus of the
stomach, which can occur when the catheter or
guidewire is advanced against resistance and will prevent
correct tube position from being achieved.
Dilatation of the track
With the tip of the guidewire at the ligament of Treitz, the
transgastric jejunostomy (or gastrojejunostomy) track is
serially dilated to 9 and 12 Fr. The dilator must be inserted
with controlled force because the stomach wall is thick
and will indent easily. A rotational action aids the dilatation. The dilator should advance smoothly along the
course of the guidewire to avoid kinking or buckling of
the guidewire into the peritoneal cavity. Overdilatation of
the track is to be avoided. A snug fit between the tube and
the stomach wall usually is achieved by using the percutaneous fluoroscopic technique, thus reducing the potential of intraperitoneal leakage and peritonitis.
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After dilatation has been achieved and a sheath placed,
the transgastric jejunal feeding (or gastrojejunostomy)
catheter is introduced over the guidewire and advanced
with its inner stiffener in position to the level of the pylorus. After the stiffener has been advanced distal to the
pylorus, the catheter is advanced off the stiffener into the
duodenum and out to the ligament of Treitz, where it is
locked in position (Fig. 11-3). This maneuver avoids buckling of the catheter into either the peritoneum or the
fundus of the stomach.
Technical modifications
Nylon T-fasteners
Unlike endoscopic or surgical gastrostomies, the percutaneous technique described herein does not appose the
anterior gastric wall to the anterior abdominal wall, which
may lead to an increased incidence of intraperitoneal
leakage of gastric contents with resultant peritonitis.
Brown and colleagues at Massachusetts General Hospital
FIGURE 11-3. Gastrostomy catheter with locking device. The
collar of the tube is retracted to activate the locking device
(
arrow
).
described a percutaneous method to simulate surgical
9
gastropexy by means of nylon T-fasteners (Fig. 11-4),
and
Coleman et al. also described a percutaneous radiologic
gastropexy technique.
10
The necessity for the use of gastropexy with radiologic gastrostomy remains controversial.
The T-fastener technique closely simulates the Stamm
surgical gastropexy and is the method we use routinely in
our institution. We have reported a study of 316 patients
in whom radiologic gastrostomy with T-fastener gastropexy was performed, which supported the opinion that a
low rate of pericatheteral leakage, low catheter displacement rates, and the ability to perform gastrostomy on
small postsurgical gastric remnants and in patients with
ascites were the principal benefits of the gastropexy tech-
11,12
nique.
In that study, successful catheter placement was
achieved in 99.4% of patients, with a major complication
rate of 1.9% and a minor complication of 3.2%. These
results compare favorably with those in the literature, despite a large number of patients (n ⫽ 43) in the study who
had ascites and tumor encasement of the stomach.
13–16.
The technique for performing a radiologic gastropexy
is easily learned and adds only a short additional duration
to a procedure. A specially designed 18-gauge needle with
a 5-mm longitudinal side-slot cut from the heel of the
bevel to load the fastener (Brown-Mueller T-fastener kit,
Medi-tech, Natick, MA) is used to introduce the T-fastener
into the stomach. Four fasteners are introduced, one at
each corner of a 2.5 cm square, the central point of which
has been selected for the entry of the gastrostomy catheter. The needle with a syringe containing 4 mL of saline is
inserted through the abdominal and gastric walls in a single motion. Aspiration of air into the syringe confirms
intragastric position. The T-fastener is dislodged from the
shaft of the needle by inserting a guidewire through the
needle. This stepis repeated for each of thefour fasteners.
The fasteners then are pulled taut, and the metallic lock-
A B
FIGURE 11-4. A: T-fastener and specially adapted needle with a groove cut for T-fastener insertion. B: Insertion needle with
T-fastener in situ.
Radiologic Gastrostomy and Gastrojejunostomy 129
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ing device on each fastener is cinched with a metal forceps.
The anterior gastric wall and the abdominal wall are now
apposed, simulatinga surgical gastropexy. Overtightening
of the T-fasteners is to be avoided because this can potentially cause necrosis around the gastropexy site. The gastrostomy catheter then can be introduced by either the
Seldinger or the trocar technique.
Intragastric balloon support
Direct puncture of the stomach with a large trocar catheter (12 Fr) is possible with the stomach supported from
within by a fluid-filled balloon. A commercially available
balloon, sutured into a 12 Fr feeding tube to cover the
most proximal side hole and the tube, is passed into the
stomach. The balloon then is distended with air or dilute
contrast medium to aid in gastric wall puncture. The
passage of such a balloon can be difficult and sometimes
impossible in patients with obstructing esophageal lesions, and it may not be well tolerated by these patients.
This technique is not used commonly.
Transgastric jejunostomy feeding tubes
Placement of a transgastric jejunostomy tube may be preferred to a simple gastrostomy in patients with esophageal
reflux because positioning of the catheter in the jejunum
provides protection against regurgitation and aspiration.
Patients with poor gastric emptying also benefit from the
delivery of feeding materials into the jejunum. Patients
with feeding gastrostomy tubes may require later conversion to a transgastric jejunostomy feeding tube as a result
of problems with esophageal reflux or delayed gastric
emptying with a resultant risk of aspiration pneumonia.
The gastric puncture site and the method used for
transgastric jejunostomy feeding tube placement are similar to those for a simple gastrostomy tube, except that
cannulation of the pylorus is required for the former technique. An angled gastric puncture with the needle tip
pointing toward the pylorus is useful when performing
transgastric jejunostomy or gastrojejunostomy, because
this facilitates maneuvers required to pass the guidewire
and catheter from stomach into jejunum.
■ Complications
Complications encountered in patients undergoing surgical gastrostomy have been categorized by Shellito and
1
Malt.
This classification is used for assessment of complications for all methods of gastrostomy placement, with
some modifications, because it allows valid comparisons
to be made between the different methods of gastrostomy tube placement.
Major complications, according to this classification, in-
clude severe wound infection, tube displacement requir-
ing a repeat of the procedure,significant leakage ofgastric
contents requiring intervention, gastric hemorrhage requiring transfusion or surgery,
17
aspiration pneumonia
associated with feeding, profound procedure-related gastroparesis, persistent gastrocutaneous fistula after tube removal, and deep venous thrombosis. Saini et al. added
emergency exploratory laparotomy and the formation of
a gastrocolic fistulato the original classification to account
for complications specific to the radiologic percutaneous
gastrostomy technique.
12
Shellito andMalt classified minor complications as tube
migration that produces bowel obstruction, functional
failure of the tube due to kinking or blockage, inadvertent
premature removal of the tube, abscess formation, and
self-limiting peritonitis not necessitating laparotomy.
Catheter displacement and blockage have been reported with varying frequencies in different studies. If a
gastrostomy tube without a gastropexy becomes dislodged
within a week of insertion, the stomach must be decompressed rapidly using a nasogastric tube to prevent gastric
leakage from the immature gastrostomy into the peritoneal cavity. This procedure is not necessary for patients
who have a gastropexy because gastric leakage is prevented by the apposed stomach and anterior abdominal
wall. It also may be possible to replace the tube immediately in patients with gastropexy by probing the track with
a feeding tube and a guidewire.
If the catheter has been present for more than several
weeks, a mature gastrocutaneous fistula will have formed,
and if the catheter becomes displaced, it usually can be
replaced easily if done within 24 to 48 hours. To do so,
the gastrostomy is probed with a straight guidewire or
infant feeding tube to enter the stomach. Once the stomach is entered, a catheter is passed over the guidewire and
the stomach is reinsufflated with air. If a mature gastrocutaneous fistula has not formed or if the gastrostomy has
closed completely, a new primary procedure is necessary.
Long-term complications of gastrostomy tube placement can include gastric outlet obstruction or migration
of the tube into the esophagus or peritoneal cavity. Catheter blockage is often the result of the administration of
incompletely crushed pills via the gastrostomy tube. The
catheter should be flushed well after each feed or administration of tablets. The morbidity and mortality rates of
the percutaneous method compare favorably with those
of both endoscopic and surgical gastrostomy.
2
■ Immediate and Long-Term Management
of Percutaneous Feeding Tubes
Immediate management of a patient involves monitoring
the patient’s postprocedural recovery from the sedation
130 J. M. Ryan and S. Dawson
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and the detection of early complications such as hemorrhage. Nasogastric suction is continued for 24 hours and
then is discontinued if the patient is free of pain or signs
of peritoneal irritation. Enteral feeding may be commenced as soon as the patient’s bowel sounds return. The
patient should be monitored carefully during the initial
feedings for evidence of aspiration or obstruction.
The long-term care of percutaneous feeding tubes
should be the responsibility of the radiologist who placed
the tube. Therefore, the patient should have direct access
to the interventional radiologist to report problems that
may arise. The skin around the tube should be cleaned
and dried daily, and protective hydrophobic creams
should be applied for any skin irritation. Granulation
tissue around the skin entry site can be treated with
topical silver nitrate sticks. Bacterial, candidal, or fungal
skin infections around the tube are treated with topical
antibiotics, although more severe infections require oral
antibiotic medication. Reflux of gastric contents onto the
skin may cause cutaneous erosion which must be treated
promptly with wet skin dressings soaked in antacids that
will neutralize the acid pH of the gastric fluid. H
-blocker
2
therapy also may be required.
For patients who have undergone a gastropexy, the
T-fasteners are cut after 3 weeks. The gastrostomy tube is
changed routinely after 6 months for all patients.
■ Summary
In summary, percutaneous radiologic gastrostomy is a
safe and inexpensive technique for providing enteral
feeding.
18
Recent studies have shown it to be a safer and
more cost-effective technique than either the endoscopic
or surgical methods of gastrostomy tube placement. The
addition of a gastropexy appears to decrease the incidence of leakage of gastric contents and also makes tube
displacement less of a problem should it occur. For these
reasons, in many institutions radiologic gastrostomy has
become the method of choice for gastrostomy placement.
REFERENCES
1. Shellito PC, Malt RA. Tube gastrostomy: techniques and complications. Ann Surg 1985;201:180–185.
2. Wollman B, D’Agostino HB, Walus-Wigle JR, et al. Radiologic, endoscopic, and surgical gastrostomy: an institutional evaluation and
metanalysis of the literature. Radiology 1995;197: 699–704.
3. Gauderer MWL, Ponsky JL, Izant RJ. Gastrostomy without laparotomy: a percutaneous endoscopic technique. J Pediatr Surg 1980;
15:872–875.
4. Ho CS. Percutaneous gastrostomy for jejunal feeding. Radiology
1983;149:595–596.
5. Tao HH, Gillies RR. Percutaneous feeding gastrostomy. AJR Am J
Roentgenol 1983;141:793–794.
6. Lorentzen T, Skjoldbye S, Nolsoe C, et al. Percutaneous gastrostomy
guided by ultrasound and fluoroscopy. Acta Radiol 1995;369:159–
162.
7. Pugash RA, Brady AP, Isaacson S. Ultrasound guidance in percutaneous gastrostomy and gastrojejunostomy. Can Assoc Radiol J
1995;46:196–198.
8. Laing B, Smithers M, Harper J. Percutaneous fluoroscopic gastrostomy: a safe option? Med J Aust 1994;161:308–310.
9. Brown AS, Mueller PR, Ferrucci JT. Controlled percutaneous gastrostomy: nylon T-fastener for fixation of the anterior wall. Radiology
1986;158:543–545.
10. Coleman CC, Coons HG, Cope C, et al. Percutaneous enterostomy
with the Cope suture anchor. Radiology 1990;174:889–891.
11. Ryan JM, Hahn PF, Boland GW, et al. Percutaneous gastrostomy
with T-fastener gastropexy: results in 316 consecutive patients. Ra-
diology 1997;203:496–500.
12. Saini S, Mueller PR, Gaa J, et al. Percutaneous gastrostomy with
gastropexy: experience in 125 patients. AJR Am J Roentgenol
1990;154: 1003–1006.
13. Halkier B, McGloughlin MJ, Ho CS. Percutaneous gastrostomy and
cystogastrostomy. Semin Inter vent Radiol 1988;3:223–229.
14. Wasiljew BK, Ujiki GT, Beal JM. Feeding gastrostomy: complications
and mortality. Am J Surg 1982;143:194–195.
15. Larson DE, Burton DD, Schroeder KW, et al. Percutaneous endoscopic gastrostomy: indications, success, complications, and mortality in 314 consecutive patients. Gastroenterology 1987;93: 48–52.
16. Bell SD, Carmody EA, Yeung EY, et al. Percutaneous gastrostomy
and gastrojejunostomy: additional experience in 519 procedures.
Radiology 1995;194:817–820.
17. Rose DB, Wolman SL, Ho CS. Gastric hemorrhage complicating
percutaneous transgastric jejunostomy. Radiology 1986;161:835–
836.
18. Bodley R, Banerjee S. Radiologicalpercutaneous gastrostomyplacement for enteral feeding. Paraplegia 1995;33:153–155.
A.H. SchoenfeldRadiation Protection
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12
■■■
Radiation Protection
ALAN H. SCHOENFELD
Persons who work in the interventional radiology suite
have the potential for receiving a relatively high radiation
dose as a result of diagnostic and interventional procedures that may require relatively long fluoroscopy exposure times. This section reviews the principles of radiation protection specific to the angiosuite that will
minimize the exposure to the patient and the radiologist.
With careful attention to technology and the use of
proper fluoroscopy and personal protective equipment,
radiation exposure can be kept to well within accepted
limits.
■ Radiation Units and Dose Limits
The measurement of radiation is based on its ability to
ionize air. The units used to measure radiation are numerous and usually are expressed in both the older, more
familiar “conventional” system and the newer International System of Units (SI). For diagnostic x-rays, the units
used most often are the roentgen (R), radiation absorbed
dose (rad), Gray (Gy), and Sievert (Sv). For absorption of
x-rays in soft tissue, a rule of thumb is
1R⬇ 1 rad ⫽ 10 mGy ⫽ 10 mSv
The National Council on Radiation Protection and
Measurements (NCRP),
tered by the U.S. Congress in 1964 to provide expertise
and guidance with regard to radiation, currently recommends an annual dose limit for occupational exposure of
50 mSv (5 rem) and a cumulative dose limit, in mSv, of 10
⫻ the person’s age (in years)(Table 12-1).
The annual dose limit recommended by the NCRP as-
1
a nonprofit corporation char-
sumes a uniform irradiation of the individual person’s
body. In situations where this is not the case, the concept
of the effective dose (E) is introduced, which has associated with it the same probability of the occurrence of
cancer and genetic effects whether received by the whole
body by uniform irradiation or by partial body or individual organ irradiation. In the case of partial body irradiation, if the dose received by different organs is known, the
effective dose can be calculated by multiplying each organ
dose by the appropriate weighting factor and then summing these values:
(organ dose)I⫻ (weighting factor)I,
E ⫽ R
I
with I, irradiation (Table 12-2). Note that there is no
longer a separate dose limit for the thyroid because it is
incorporated into the effective dose.
Occupational doses are measured by personnel monitors such as film badges or thermoluminescent detectors.
At a minimum, a single monitor should be worn outside
the lead apron at collar level to monitor the thyroid and
eye lens doses. The use of a second monitor, worn under
the apron at waist level, is recommended for a more
accurate determination of the effective dose and should
be mandatory for pregnant personnel. A finger dosimeter should be worn if the individual’s hands will be exposed to the primary x-ray beam.
It should be noted that a relatively high reading of the
dosimeter worn outside the apron at the neck does not
represent the effective dose. The NCRP recommends
that the effective dose E can be estimated by the formulas, E ⫽ 0.5 H
and by E ⫽ (H
⫹ 0.025 HNwhen two monitors are worn
W
/21) for a single monitor,2where HWand
N
131
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TABLE 12-1.
Exposures mSv (rem)
Occupational
Effective dose limits
Annual 50 (5)
Cumulative 10 ⫻ Age (yrs) [1 ⫻ Age (yrs)]
Equivalent dose annual limits for tissues and organs
Lens of eye 150 (15)
Skin, hands, and feet 500 (50)
Members of the Public (annual)
1. Effective dose limit, continuous or frequent exposure 1.0 (0.1)
2. Effective dose limit, infrequent exposure 5.0 (0.5)
3. Equivalent dose limits for tissues and organs
Lens of eye 15 (1.5)
Skin, hands, and feet 50 (5)
Embryo-fetus (monthly)
Equivalent dose limit 0.5 (0.05)
Recommended dose limits (1)
HNare the recorded values of the monitors under the
apron and outside the apron at the neck, respectively.
One study, which involved 28 interventional radiologists from 17 institutions who performed an average of
972 interventional procedures per year, calculated the
effective dose from the personnel dosimetry readings of
these persons using tables of weighting factors, organ
doses, and depth dose charts.
3
The average yearly estimate of the collar and under apron badges for this group
was 48.0 mSv (4.80 rem) and 0.88 mSv (88 mrem), respectively. Conversion of these badge readings to mean
annual effective dose resulted in a value of 3.16 mSv (316
mrem), substantially less than the annual limit of 50 mSv.
The authors also found that Webster’s formula for effective dose from two personnel monitors, H
0.04 H
, overestimates the effective dose by 70% for those
N
⫽ 1.5 HW⫹
E
who wear a thyroid shield but underestimates the value
by 21% for those who do not wear a shield.
Personnel dosimeters always should be kept in a radiation-free area when not in use. If film badges are left on
a lead apron hanging inside the room, they may be exposed to scatter during interventional cases, or they may
accidentally be worn by another staff member.
TABLE 12-2.
Tissue or Organ Factor
Bone surface, skin 0.01
Bladder, breast, liver, esophagus, thyroid, remainder
Bone marrow, colon, lung, stomach 0.12
Gonads 0.20
a
The remainder includes adrenals, brain, small intestine, large intestine,
kidney, muscle, pancreas, spleen, thymus, and uterus.
Weighting factors used in calculation of
effective dose during partial body
irradiation
a
Weighting
a
0.05
Dose Limit
■ Basic Principles of Radiation Protection
The often quoted basic principles of radiation protection
used techniques associated withtime, distance,and shielding. All fluoroscopic examinations clearly should be performed with the lowest exposure time possible. Fluoroscopic units are designed to meet the U.S. Food and Drug
Administration (FDA) limits for entrance exposure rate to
the patient, which for units with automatic exposure
control are 5 R/min for the average patient, with a maximum limit of 10 R/min. Some units have a “high-level
control,” which allows entrance exposure rates in excess
of 10 R/min as long as an audible signal is present to
indicate that the high-level mode is activated. Under highlevel control, the entrance exposure rate may reach levels
as high as 20 to 40R/min although a recent FDA performance standard limits the valueto 20 R/min. The amountof
scatter radiation that exposes the radiologist is directly
proportional to the patient exposure. A rule of thumb is
that the radiation exposurerate at a 90-degree angle measured at 1 m (⬇ 40 inches) from the central ray is approximately 0.1% of the entrance exposure to the patient; thus,
limiting the total exposure time will reduce both the patient and the radiologist dose.
The distance factor in radiation protection refers to
the inverse square law. The radiation intensity of the x-ray
beam decreases with distance from the x-ray tube and is
inversely proportional to the square of the distance. The
same relationship is approximately true regarding the
intensity of the scattered radiation beam and the distance
between the radiologist and the scattering medium (i.e.,
the patient). Thus, whenever possible, persons in the
radiology suite should remain as far away as possible from
the patient.
Because the interventional radiologist is usually standing close to the patient and cannot take advantage of the
Radiation Protection 133
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inverse square law, shielding materials must be used to
intercept the scattered beam. These shielding materials
include aprons made of lead rubber (Z ⫽ 82) or composites consisting of lead and other high-atomic-number
elements, thyroid shields, and leaded eyeglasses. Lead
aprons come in thickness of 0.25, 0.50, and 1.00 mm. The
4
NCRP
recommends protective aprons of at least 0.5 mm
lead equivalent for every person (except the patient) in
the fluoroscopy room, which provides an attenuation factor of approximately 95% at 70 kVp. Persons who must
move around the room during the procedure should
wear a wraparound protective garment, which usually has
0.5 mm of lead in the front panels and 0.25 mm in the
back section.
The NCRP also recommends lead gloves of at least 0.25
mm lead equivalent for the fluoroscopist if the hand is
placed in the useful beam (after attenuation by the patient). Conventional lead gloves are too thick and heavy
to be used by interventionalists, but several manufacturers produce flexible surgical gloves that have some degree of radiation attenuation. A recent study of these
gloves found that the protection they provide varied
widely among manufacturers, ranging from 2 to 35%
reduction at 90 kVp,
5
and their cost effectiveness may not
be adequate. The authors suggested that the most effective way to reduce exposure of the hands is to keep them
out of the primary beam.
Protection for the lens of the eye can be accomplished
by using ceiling-mounted lead glass panels, leaded eyeglasses, and even regular prescription glass lenses. Ceilingmounted lead glass shields secured to a concentric balland-socket joint with spring loaded extension arms can be
rotated and tilted in all directions for flexibility of positioning. Leaded eyeglasses are available with wraparound
side shields with 0.5-mm lead equivalence. At the least, for
84-kVp x-rays conventional white crown glass lenses provide 44% attenuation;photochromic lenses that turn dark
in sunlight result in 70% attenuation.
6
Plastic lenses, how-
ever, offer little protection.
Other protective highly recommended devices include
thyroid shields and lead rubber drapes that can hang
along the side of the table, shielding the lower body of
the operator from leakage and scatter.
■ Factors That Affect Patient Dose
The major factors that affect patient dose rate (roentgen
per minute) during fluoroscopy are the automatic brightness-control system, filtration in the beam, geometry of
the x-ray tube and image intensifier, diameter of the x-ray
beam (image intensifier magnification mode), and patient size. Keeping the patient dose low ultimately reduces the dose to the operator.
Fluoroscopy is almost always conducted under auto-
matic brightness control, during which the kVp and tube
current (mA) are established automatically by the generator, depending on the patient’s size and the entrance
exposure requirements of the image intensifier. In some
units, however, the minimum fluoroscopic kVp can be set
by the radiologist. The use of a higher kVp results in a
more penetrating x-ray beam and lower patient dose, but
the image contrast will be reduced.
Some systems also provide a low-dose and a high-dose
selection. When the low-dose mode is selected, the television gain is increased with a subsequent reduction of the
tube current or kVp, resulting in a lower patient dose.
The resulting image, however, will have increased noise.
When a heavy patient is examined, the high-dose mode
will increase the technique factors and patient dose to
improve the image.
Pulsed fluoroscopy also may be available; this procedure allows the radiologist to produce the fluoroscopic
image at rates of 7.5, 15, or 30 pulses per second instead of
the continuous mode. This option, along with the lastimage hold feature, can result in reductions in entrance
exposure rates to the patient and scatter to the physician
by as much as 75%.
7
The NCRP (4) recommends a minimum total filtration
of 2.5 mm of aluminum for x-ray tubes operating above 70
kVp. Some fluoroscopic units, however, allow the radiologist to vary the amount of filtration, usually specified in
millimeters of aluminum or copper, in the x-ray beam. As
in the case of kVp, an increase in added filtration will result
in a lower dose and reduced contrast. One study applied a
supplemental filter of 0.5 mm aluminum and 0.076 mm
copper for use in neurointerventional procedures, resulting in a dose reduction of 36%.
8
In addition, when the
positions of the x-ray tube and image intensifier were rotated every 5 min and the techniques were monitored
carefully, the maximum skin dose was reduced by 63%.
The distance of the patient from the x-ray tube usually
is set at a minimum of 15 inches in a conventional fluoroscopic unit with an undertable x-ray tube. With a c-arm
type of unit, which is used in the special procedures suite,
the distance can be varied as the table and image intensifier are repositioned. The minimum distance that the
table can be placed above the x-ray tube is usually 12 to
15 inches. Under automatic brightness control, the exposure rate will increase if the image intensifier is moved
away from the patient, which also will increase the magnification factor and decrease the field of view. For these
reasons, the image intensifier should be placed as close
to the patient as possible.
Most special procedure units contain image intensifiers whose diameters are 14 to 16 inches with three to five
magnification modes of operation. If one of the magnification modes is chosen, the minification gain is reduced
and the system compensates by increasing the exposure
rate. The smaller diameter chosen with the magnification
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