Customizing Contrast Injection for Body MDCT:

Algorithmic Approach

Customizing Contrast Injection for Body MDCT:

Algorithmic Approach

Lincoln L. Berland, M.D., F.A.C.R.Lincoln L. Berland, M.D., F.A.C.R.Lincoln L. Berland, M.D., F.A.C.R.

University of Alabamaat Birmingham

University of AlabamaUniversity of Alabamaatat BirminghamBirmingham

Before Contrast

Prep and Hydration

• Hydration single most important factor:To get adequate collecting system fillingTo limit nephrotoxicity

• Don't keep patient NPO (clear liquids in am)• Lots of water prior to scan

Intravenous Contrast Parameters

• Contrast or not?• Route - IV arm, central line, hand, foot• Concentration• Volume• Rate• Saline chaser• Fixed, bolus tracking, test bolus

Principles of Intravenous Contrast Dynamics

General - Iodine Dose

• If increase dose of Iodine, but inject within same duration:

Increases peak enhancementDoes not change time at which peak occurs

• How to achieve this:Increase contrast concentration, orIncrease injection rate, maintain injection duration (more contrast volume)

Iodine Concentration Selection

• Higher concentration: can inject more Iodine for a specific volume/second

Equivalent to increasing injection rate if you don’t increase concentration

• With higher concentration, can decrease the volume injection rate for given Iodineinjection rate

• Therefore, 350-400 mg I/mL preferred over 300 mg I/mL

Aorta, Liver by Rate

• If increase injection rate, but keep Iodine dose constant:

Aortic enhancement peak increases continuously with rateLiver enhancement peak levels off above 1.5 mL/sec

Aorta, Liver Enhancement

• MYTH:Can decrease contrast dose for liver scan by increasing injection rate

• TRUTH:Can decrease contrast dose for CTA by increasing injection rate

Injection Duration

• TIME to peak aortic and liver enhancement depends most strongly on injection duration

• Peak enhancement usually occurs shortly after injection completed

Injection Duration

• MYTH:For body scans, can use fixed scan delay regardless of injection rate

• TRUTH:Enhancement curves vary greatly by patientUse bolus tracking for arterial studiesFixed delay (by duration) usually OK for liver,etc.

Scan Delay

• MYTH: Faster scanner (e.g. 64 vs. 4-slice), shorter delay to scanning

• TRUTH: Faster scanner, longer delay to begin scanning

Peak doesn’t change, but more likely to finish scan before peak occursDownslope of enhancement not as fast as upslope, so better to scan a little late rather than early

Patient-Specific Factors

Patient Weight - Enhancement

• Hepatic and arterial enhancement are proportional to Iodine dose administered and inversely proportional to weight

• Time to the enhancement peak is affected little by weight

• Therefore, Iodine dose should be increased proportional to weight

Cardiac Output - Aorta

• As cardiac output decreases, delay to peak increases

• MYTH: As cardiac output decreases, enhancement decreases

• TRUTH: Decreased cardiac output increases enhancement

• Therefore, decrease Iodine dose with decreased cardiac function

Cardiac Output - Hepatic

• As cardiac output decreases, delay to hepatic enhancement increases

60% decrease in cardiac output can delay peak from baseline 60 seconds to 150 seconds

• MYTH: Decreased cardiac output affects peak hepatic enhancement

• TRUTH: Hepatic enhancement won’t change, but later peak

Phase by Application

• Consequence of these effects is that you must consider the target organ(s) to best design protocols, e.g.:

Earlier scan for aortaSlower scan for runoffLater scan for liver

Contrast - From Theory to Practice

Iodine Dose Selection

• Patient weight• Renal and cardiac function• Brand and concentration of

contrast available• Organ and body region

Iodine Dose Selection

• Base dose varies from 30-60 gm Iodine• Should select based on Iodine dose, not

volume• We recommend standard dose based of

42 gm Iodine for average weight patient• Select by patient weight, other factors

Iodine Dose Selection

• Some select: mL/kg• If vary continuously by weight:

Should be: gm I/kg• We prefer weight categories for

the average patient

Contrast Injection Rate Selection

• Route of injection• Adequacy of line• Injector - Dual Head with saline

chaser better uses contrast injected• Speed of scanner

Scan Timing Selection

• Specific application (e.g. 3-phase, routine, etc.)

• Speed of scanner

Algorithm

• Weight +concentration of agent + application:Volume

• Volume + application + adequacy of IV:Injection rate

• Injection rate + volume:Injection duration

• Injection duration + application + scanner:Scan timing

Contrast Dose Selection

Contrast Volume85 mL

120 mL150 mL180 mL

Contrast Volume56 mL80 mL

100 mL

45-60 kg (100-130 lb)

Select Contrast DoseBody CT

Based on 42 gI for average patient

350 mg/mLWeight

65-90 kg (140-200 lbs)90-110 kg (200-240 lb)

>110 kg (>240 lb)

>90 kg (>200 lb)65-90 kg (140-200 lbs)45-60 kg (100-130 lb)

350 mg/mL Š Renal insufficiencyWeight

Contrast Volume85 mL115 mL140 mL175 mL

Contrast Volume55 mL75 mL90 mL

90-110 kg (200-240 lb)>110 kg (>240 lb)

>90 kg (>200 lb)65-90 kg (140-200 lbs)45-60 kg (100-130 lb)

370 mg/mL Š Renal insufficiencyWeight

Body CT

Based on 42 gI for average patient

370 mg/mL

60-90 kg (130-200 lbs)

Weight45-60 kg (100-130 lb)

Select Contrast Dose

Contrast Dose Selection

Contrast Volume104 mL148 mL185 mL200 mL*

Contrast Volume56 mL80 mL

100 mL

350 mg/mL Š Renal insufficiencyWeight

Select Contrast DoseBody CT

Based on 52 gI for average patient

350 mg/mL

Notes:

Weight45-60 kg (100-130 lb)65-90 kg (140-200 lbs)90-110 kg (200-240 lb)

>110 kg (>240 lb)

>90 kg (>200 lb)65-90 kg (140-200 lbs)45-60 kg (100-130 lb)

*Calculated volume for high weight exceeds 200 mL capacity of injector.Renal insufficiency dose based on 42 gI chart rather than 52 gI chart.

Contrast Volume98 mL

140 mL175 mL200 mL*

Contrast Volume55 mL75 mL90 mL

Weight

Body CT

Based on 52 gI for average patient

370 mg/mLWeight

45-60 kg (100-130 lb)

Select Contrast Dose

Notes:*Calculated volume for high weight exceeds 200 mL capacity of injector.Renal insufficiency dose based on 42 gI chart rather than 52 gI chart.

60-90 kg (130-200 lbs)90-110 kg (200-240 lb)

>110 kg (>240 lb)

>90 kg (>200 lb)65-90 kg (140-200 lbs)45-60 kg (100-130 lb)

370 mg/mL Š Renal insufficiency

Contrast Injection Rate

Injection Volume Injection Rate Injection Duration46-50 mL 1.6 mL/sec 30 seconds51-55 mL 1.8 mL/sec 30 seconds56-60 mL 2.0 mL/sec 30 seconds61-65 mL 2.1 mL/sec 30 seconds66-70 mL 2.3 mL/sec 30 seconds71-75 mL 2.5 mL/sec 30 seconds76-80 mL 2.6 mL/sec 30 seconds81-85 mL 2.8 mL/sec 30 seconds86-90 mL 3.0 mL/sec 30 seconds91-95 mL 3.1 mL/sec 30 seconds96-100 mL 3.3 mL/sec 30 seconds101-105 mL 3.5 mL/sec 30 seconds106-110 mL 3.6 mL/sec 30 seconds111-115 mL 3.8 mL/sec 30 seconds116-120 mL 4.0 mL/sec 35 seconds136-140 mL 4.6 mL/sec 30 seconds141-145 mL 4.8 mL/sec 30 seconds146-150mL 5.0 mL/sec 30 seconds

175 mL 5.8 mL/sec 30 seconds180 mL 6.0 mL/sec 30 seconds185 mL 6.0 mL/sec 31 seconds200 mL 6.0 mL/sec 33 seconds

Body CT (excluding CTAs)

All contrast agents

Routine injection duration

Select Injection Rate

Contrast Injection Rate

Injection Volume Injection Rate Injection Duration46-50 mL 1.6 mL/sec 30 seconds51-55 mL 1.8 mL/sec 30 seconds56-60 mL 2.0 mL/sec 30 seconds61-65 mL 2.0 mL/sec 32 seconds66-70 mL 2.0 mL/sec 35 seconds71-75 mL 2.0 mL/sec 37 seconds76-80 mL 2.0 mL/sec 40 seconds81-85 mL 2.0 mL/sec 42 seconds86-90 mL 2.0 mL/sec 45 seconds91-95 mL 2.0 mL/sec 47 seconds96-100 mL 2.0 mL/sec 50 seconds101-105 mL 2.0 mL/sec 52 seconds106-110 mL 2.0 mL/sec 55 seconds111-115 mL 2.0 mL/sec 57 seconds116-120 mL 2.0 mL/sec 60 seconds136-140 mL 2.0 mL/sec 70 seconds141-145 mL 2.0 mL/sec 72 seconds146-150mL 2.0 mL/sec 75 seconds

175 mL 2.0 mL/sec 87 seconds180 mL 2.0 mL/sec 90 seconds185 mL 2.0 mL/sec 92 seconds200 mL 2.0 mL/sec 100 seconds

If IV cannot accept > 2.0 mL/sec

Body CT (excluding CTAs)

All contrast agents

Select Injection Rate

Delay70 seconds71 seconds72 seconds73 seconds75 seconds77 seconds80 seconds82 seconds85 seconds87 seconds90 seconds92 seconds95 seconds97 seconds100 seconds110 seconds112 seconds115 seconds127 seconds130 seconds131 seconds140 seconds

Routine Scans

All delays from the beginning of injection

31 seconds32 seconds

60 seconds

90 seconds

70 seconds72 seconds75 seconds87 seconds

37 seconds

100 seconds92 seconds

Body CT (excluding CTAs)

All scanners

Portal phase routine scan

Select Scanning Delay

Injection Duration30 seconds

57 seconds

33 seconds35 seconds

40 seconds42 seconds45 seconds

55 seconds52 seconds50 seconds47 seconds

Implementing Algorithm

• Loose leaf handbooks (cookbooks) created• One customized cookbook placed at each

scanner• Each cookbook is specific for scanner type

and concentration of contrast material used• Master reference cookbooks placed in

radiology reading room

Indications:Cirrhosis: evaluating for HCC and portal hypertension.Pre-Intervention planning: for TIPS, chemoembolization, embolization, ablation.Cholangiocarcinoma.Characterize unknown liver lesion.Notes, modifications:Should be done on 40 or 64-slice scanners, if possible, because 3D rendering is usually needed and these provide better image qualityPelvis should be performed if concern about pelvic metastasis or if known prior important pelvic abnormalityIf following up vascular metastases that are known to be seen best on portal venous phase, perform routine abdomen protocol.

Contrast Unenhanced Phase (UP)Hepatic Arterial Phase

(HAP)Portal Venous Phase (PVP) Delayed Phase (DP) Comments

Oral contrast No NoRectal contrast No NoIV contrast Š iodine conc. (mgI/mL) 350-370

Iodine dose (gI), Volume and Flow Rate

52 gI for 60-90 kg patient. Adjust proportionally for weight. See

"Contrast Cookbook"This is a higher dose than routine protocols to optimize post-

processing and segmentationSaline flush - volume (mL) 50 If no dual injector, increase contrast dose by 10 mLSaline flush - flow rate (mL/s) Same as contrast injection rate

Scan delayTrigger at 150 HU in aorta plus 15

seconds 45 seconds post-trigger 3 minutes post-triggerHAP slightly later than routine AP. Change delay to 10 minute for

cholangiocarcinomaAcquisition Parameters

Scout PALateral scanogram can help see spinal compressions; post-scan

scanogram serves as a one-shot IVPPatient position Supine, feet first Supine, feet first Supine, feet first Supine, feet first

Scan range Diaphragm to iliac crest Diaphragm to iliac crestDiaphragm to iliac crest or

greater trochanter LiverScanning direction Out Out Out OutAcquisition field of view Full patient width Full patient width Full patient width Full patient widthTube voltage (kVp) 120 120 120 120 Can use 140 kVp for large patientsTube load (mAs) 170 to 200 250 to 300 250 to 300 170 to 200 Consider automated dose modulationGantry rotation time (s) 0.5 0.5 0.5 0.5 Consider 0.75 for obese patients

Detector configuration (mm) 40 x 0.625 or 64 x 0.625 40 x 0.625 or 64 x 0.62540 x 0.625 or 64 x

0.62532 x 1.25 or 64 x 0.625

Pitch 1 1 1 1Scanner automatically assigns optimal pitch based on approximate

selection.Reconstruction ParametersAxial reconstruction (mm) 5.0 x 5.0 5.0 x 5.0 5.0 x 5.0 5.0 x 5.0Thin section axial for 3D/MPR (mm) 1.3 x 0.7 up to 2.0 x 1.0 1.3 x 0.7 up to 2.0 x 1.0

Coronal reconstruction (mm) 3.0 Š 4.0 x 3.0 3.0 Š 4.0 x 3.0

Coronal and sagittal reconstructions should be performed routinely on HAP and PVP. Thick slab MIPs and/or sagittal MIPs may

replace coronal and sagittal MPRs.

Recon filter kernel B or C B or C B or C

Filter A helpful for very obese patients (less noisy images). Filter B if lower mAs chosen (more noise than Filter A, but appropriate for

average patient). Filter C increases spatial resolution, but also increases noise.

Recon field of view Evolving Evolving Evolving

Liver Four-Phase (Abdomen or Abdomen/Pelvis): 40-slice, 64-slice

Indications:Pancreatic mass known or suspected.Pancreatic carcinoma follow-up after treatment (surgery, XRT, chemotherapy) if pancreatic phase needed (see Exclusions, Notes below).Painless jaundice.Chronic pancreatitis vs. pancreatic mass.Acute pancreatitis > age 50 to rule out mass as etiology of pancreatitis.Exclusions:Acute pancreatitis < age 50 (Routine protocol).Known chronic pancreatitis to evaluate complications (Routine protocol).Known pancreatic adenocarcinoma recurrence or metastasis if well seen on PVP (Routine protocol).Pancreatic neuroendocrine tumor follow-up after treatment (RCC, Vascular Cancer FU protocol).Notes, modifications:Should be done on 40 or 64-slice scanners, if possible, because 3D rendering is usually needed and these provide better image quality.Pelvis should be performed if concern about pelvic metastasis or if known prior important pelvic abnormality.If following known unresectable pancreatic carcinoma, including with metastases, a routine abdomen or abdomen/pelvis may suffice.Routine examination may also be done for chronic pancreatitis to evaluate complications, acute pancreatitis < age 50, or pancreatitis reassessment.Contrast Unenhanced Phase (UP) Pancreatic Phase (PP) Portal Venous Phase (PVP) Comments

Oral contrast

Water or VolumenTM 500 mL to tolerance plus 250 mL

water on tableRectal contrast NoIV contrast Š iodine conc. (mgI/mL) 350-370

Iodine dose (gI), Volume and Flow Rate

52 gI for 60-90 kg patient. Adjust proportionally for weight. See

"Contrast Cookbook"

This is a higher dose than routine protocols to optimize post-processing and segmentation.

Prefer higher injection rate, if possible, up to 5 mL/sec.

Saline flush - volume (mL) 30If no dual injector, increase contrast dose by 10

mLSaline flush - flow rate (mL/s) Same as contrast injection rate

Scan delayTrigger at 150 HU in aorta plus 15

seconds 50 seconds post-triggerAcquisition Parameters

Scout PA

Lateral scanogram can help see spinal compressions; post-scan scanogram serves as a

one-shot IVPPatient position Supine, feet first Supine, feet first Supine, feet first

Scan range Diaphragm to iliac crest Diaphragm to iliac crestDiaphragm to iliac crest or greater

trochanterScanning direction Out Out OutAcquisition field of view Full patient width Full patient width Full patient widthTube voltage (kVp) 120 120 120 Can use 140 kVp for large patientsTube load (mAs) 170 to 200 250 to 300 250 to 300 Consider automated dose modulationGantry rotation time (s) 0.5 0.5 0.5 Consider 0.75 for obese patients

Detector configuration (mm) 40 x 0.625 or 64 x 0.625 40 x 0.625 or 64 x 0.62540 x 0.625 or 64 x

0.625

Pitch 1 1 1Scanner automatically assigns optimal pitch

based on approximate selection.Reconstruction ParametersAxial reconstruction (mm) 5.0 x 5.0 2.0 x 2.0 4.0 x 3.0

Thin section axial for 3D/MPR (mm) 1.3 x 0.7 up to 2.0 x 1.0 1.3 x 0.7 up to 2.0 x 1.0

Perform 3D volume and curved planar reformatting. Note: qualifies for additional post-

processing coding

Coronal reconstruction (mm) 3.0 Š 4.0 x 3.0 3.0 Š 4.0 x 3.0

Coronal reconstructions should be performed on both the Pancreatic and Portal Venous phases. Thick slab MIPs and/or sagittal MIPs may be considered as a replacement for coronal and

sagittal MPRs.

Recon filter kernel B or C B or CFilter A helpful for very obese patients. Filter B if

lower mAs chosenRecon field of view Evolving Evolving

Pancreas (Abdomen or Abdomen/Pelvis): 40-slice, 64-slice

Renal Mass Pre-Intervention

Renal Mass Pre-intervention

• Indications:Prepare for nephron-sparing surgery or ablation

• Objectives:Define detailed vascular supplyLocalizationStaging

Scan Phases

• Non-contrastMay delete if have had recent non-contrast

• ArterialThrough mid-pelvis to assure ID of anomalous arteries

• Nephrographic/excretoryEntire abdomen-pelvisSplit-dose

Split-Dose Injection

• Permits multiple purposes in single series, e.g.

Late corticomedullary-early nephrographicNephrographic-excretory

Split-Dose Injection Purpose

• Combine advantages of excretory, nephrographic and portal venous phases

• Use for both renal mass pre-intervention and CT urography protocols

Renal mass includes arterial phaseCT urography does not

Split-Dose Protocol Example

• Example:115 mL Isovue 370 selected for 70 kg patientInject about 1/4 of usual dose (30 mL) by hand

• Wait 10 minutes for excretion• 300 mL saline IV during pause• Inject additional complete dose (115 mL @ 4

mL/sec)• Arterial phase• Scan delay of 100 sec (for nephrographic

phase)

Nephrographic-Excretory

Late CM-Arterial-Excretory

Split-Dose Injection

Lesion margins seen better on nephrographic phase

Renal Mass Visualization

Nephrographic/Excretory depicts vascular-collecting system to lesion relationships

Post-Processing - MIPS

Arterial-Nephrographic Nephrographic-Excretory

Split-Dose Injection

Summary

• CT technology and protocol design is extremely complex.

• First step to tailoring exams is to understand basic principles of contrast dynamics and CT technology.