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Patient preparation and coronary CTA techniques Gregory Kicska, M.D. Ph.D. University of Washington, Thoracic Imaging Overview 1. Patient preparation 2. Scanning techniques Patient preparation Preparation related to any contrast CT examination Preparation specific to coronary CTA Exclude contraindications Patient safety Study quality Contraindications: patient saftey Contrast renal insufficiency allergy (anaphylaxis) Radiation pregnancy radiation dose/age Claustrophobia Medically unstable Contraindications: patient saftey Contrast ast media employ a tection of rotoxicity. nction can ne report. high-risk te (GFR). nt due to creatinine f Diet in on is an creatinine renal insufficiency Table 5 Risk of contrast induced nephrotoxicity based on estimated glomerular filtration rate (GFR) GFR (ml/ min/1.73 m2) Risk of contrast induced nephrotoxicity Intravenous iodinated contrast media 60 30–60 Negligible Moderate <30 High Safe Use only if clinically essential prophylaxis required Contraindicated Administration of contrast media to pregnant patients and Contraindications: patient saftey 214 creatinine measurement before intravenous contrast media injection are summarized in Table 4. Most centers employ a serum creatinine threshold of 1.5 mg/dl for detection of patients at high risk for contrast-induced nephrotoxicity. However, considerable derangement of renal function can be masked by a normal appearing serum creatinine report. Hence, the current recommendation is to screen high-risk patients with estimated glomerular filtration rate (GFR). Derangement of GFR can occur in a patient due to undetected chronic renal disease though the creatinine measurements are normal. The Modification of Diet in Renal Disease (MDRD) study group equation is an accurate method for GFR estimation from serum creatinine [27]: Table 5 Risk of contrast induced nephrotoxicity based on estimated glomerular filtration rate (GFR) GFR ¼186 " ðserum creatinineÞ When given in usual clinical doses, iodinated contrast media cross the human placenta and enter the fetus [3]. No adequate and well-controlled teratogenic studies of the effects of these agents in pregnant women have been performed. While it is not possible to conclude that iodinated contrast media present a definite risk to the fetus, there is insufficient evidence to conclude that they pose no risk. The ACR recommends that iodinated contrast media may be given to pregnant patients only when [3]: Contrast renal insufficiency % 1:154 " ðageÞ % 0:203 " k For women, k=0.742; for men, k=1 Multiply by 1.210 if African-American The risk of contrast-induced nephrotoxicity based on estimated GFR is summarized in Table 5. Recently, some vendors are investigating rapid strip-test-based methods for quick measurement of serum creatinine when patients arrive for contrast-enhanced radiological studies [28]. Such methods to estimate serum creatinine can enable efficient detection of patients at risk for contrast-induced nephrotoxicity. GFR (ml/ min/1.73 m2) Risk of contrast induced nephrotoxicity Intravenous iodinated contrast media 60 30–60 Negligible Moderate <30 High Safe Use only if clinically essential prophylaxis required Contraindicated Administration of contrast media to pregnant patients and nursing mothers – – the diagnostic information requested using contrastenhanced study cannot be obtained via other means (such as ultrasound) the information needed affects the care of the patient and fetus during the pregnancy Contraindications: patient saftey Radiation pregnancy radiation dose/age Contraindications: patient saftey Claustrophobia Diazapam 5 mg oral* Medically unstable *Dose adjustment needed specific conditions Contraindications: study quality Motion Breath hold Gating Artifact Inability to raise arms Metal Obesity Contraindications: study quality Motion Breath hold (7-12 sec @ 64 slice) 270 ms acquisition dual source Contraindications: study quality Motion Gating atrial fibrillation or frequent PVCs Contraindications: study quality Artifact Inability to raise arms Metal Obesity The ideal patient HR < 65, sinus Calm Thin Large veins Pearl diver (able to hold breath) Able to follow commands Preparation: 24-1 hr pre-exam No caffeine (24 hrs) No viagra (24 hrs) No “energy supplement” (24 hrs) No food (4 hrs) No liquid (1 hr) Preparation: 24-1 hr pre-exam Cardiac medications should not be suspended! Preparation: 24-1 hr pre-exam Non-anaphylactic contrast reaction • 50 mg prednisone @ 13,7,1 hrs before exam • oral Benadryl 1 hour before exam Preparation: 1 hr pre-exam •IV access •18 - 20 gauge needle •Right arm Preparation: 1 hr pre-exam Satisfactory IV access Contraindications excluded / mitigated Proceed to HR control Preparation: 1 hr pre-exam Satisfactory IV access Contraindications excluded / mitigated Proceed to HR control Preparation: 1 hr pre-exam Oral metoprolol (50 mg tabs) 50-100 mg Wait 90 minutes, check BP/HR Consider additional 50 mg IV metoprolol (5 mg) Give 5 mg IVP Wait 20 minutes, check BP/HR Consider additional 5 mg x 2 Contraindications Metoprolol allergy Bronchospastic disease (asthma) Aortic valve disease Worsening heart failure Heart block Preparation: 1 hr pre-exam Preparation: 1 hr pre-exam Beta blocker contraindication? Consider oral Verapamil Preparation: 1 hr pre-exam HR < 65 bpm Proceed to Ca++ score Examination: patient positioning Center heart in scanner Examination: patient positioning Center heart in scanner = Lowest noise Examination: patient positioning Center heart in scanner = Lowest noise Examination: Ca++ score Ca++ score coverage Examination: Ca++ score Voxels are 3 x 1.3 x 1.3 mm non-overlapping Threshold of 130 H.U. Agatston volume mass score Examination: Ca++ score = 0 - CAD unlikely > 400-1000 - high risk of stenosis Predicting Stenosis Ca++ Score Sensitivity Specificity >1 92% 75% >100 73% 90% >1000 30% 98% Low false negative No false positive Low sensitivity on CTA Examination: Ca++ score 0 < Agatston score < 400-1000 Proceed to CTA planning Examination: gating Retrospective no modulation Retrospective with modulation Prospective Retrospective no modulation Retrospective with modulation Prospective Rate < 70 no function no calcium Age < 40 Rate > 70 function calcium Age > 40 A-fib Prospective Retrospective Modulation Retrospective No modulation Examination: CTA coverage Coronary CTA coverage (retrospective) Ca++ score coverage Top slice with CA Bottom slice with CA Examination: CTA coverage Coronary CTA coverage (prospective) Ca++ score coverage Top slice with CA Bottom slice with CA Examination: dose Set kVp and MAS. Automatic exposure control set desired held soon in its standard deviation set upper and lower limits to avoid spikes in current due to hardware Weight table Examination: dose Examination: dose Participate in dose related QA Examination: contrast 80 ml 5 ml/s 40 ml 4 ml/s 50 ml 4 ml/s 40% 100% 100% 60% Examination: nitroglycerin Contraindications Head trauma/bleed Systolic BP < 100 Nitrate Allergy Phosphodiesterase inhibitors Adverse Headaches - 50% Examination: nitroglycerin 4 minutes Examination: nitroglycerin 4 minutes elapsed Proceed to CTA scanning Examination: scanning Examination: reconstruction Main reconstruction for 3D station Thin section (0.625 mm) axial cardiac kernal < 32cm FOV 50% overlap Examination: reconstruction Additional reconstruction for 2D station •Axial 2.5 mm, lung kernel, lung FOV •Axial 2.5 mm, body kernel, body FOV •Coronal/sagittal, body kernel Conclusions • Exclude contraindications related to patient safety or exam quality • ensure proper patient preparation for contrast exam • control heart rate with beta blocker • calcium scoring is used to plan CTA or terminate exam • scanner gating is one of the most effective ways to reduce dose • utilize automatic exposure control when possible Thank you