Contrast and Radiological Procedures — MCQs

Contrast and Radiological Procedures Indian Medical PG Practice Questions and MCQs

Question 121: Which one of the following contrast media is used for intravenous pyelography (IVP)?

A. Lipiodol
B. Diatrizoate
C. Sodium diatrizoate (Hypaque) (Correct Answer)
D. Iothalamate (Conray-420)

Explanation: **Explanation:** Intravenous Pyelography (IVP), also known as Intravenous Urography (IVU), requires a water-soluble, iodinated contrast medium that is excreted primarily by glomerular filtration in the kidneys. **Why Sodium Diatrizoate (Hypaque) is correct:** Sodium diatrizoate is a high-osmolar ionic contrast medium (HOCM). It is the classic choice for IVP because the sodium salt provides a higher concentration of iodine per molecule compared to meglumine salts. This results in better opacification of the renal parenchyma (nephrogram phase) and the collecting system (pyelogram phase), which is essential for visualizing the anatomy of the ureters and bladder. **Analysis of Incorrect Options:** * **A. Lipiodol:** This is an oil-based contrast medium. It is strictly contraindicated for intravenous use as it can cause fat embolism. It is used for lymphangiography or HSG. * **B. Diatrizoate:** While technically correct as a class, "Sodium diatrizoate" is the specific formulation preferred for urinary tract opacification. * **D. Iothalamate (Conray-420):** While also an ionic contrast, Conray-420 has a very high iodine concentration (420 mg/mL) and is more commonly used for angiography or CT rather than routine IVP, where lower concentrations are often sufficient and safer. **High-Yield Clinical Pearls for NEET-PG:** * **Contrast Type:** Modern practice has shifted toward **Non-Ionic Low-Osmolar Contrast Media (LOCM)** like Iohexol or Iopamidol to reduce the risk of anaphylactoid reactions and Contrast-Induced Nephropathy (CIN). * **Preparation:** Patients must be screened for serum creatinine levels (normal <1.5 mg/dL) before IVP. * **Contraindications:** Absolute contraindications include history of severe reaction to iodine and anuria. * **Sequence:** The **Nephrogram phase** occurs within 1 minute, while the **Pyelogram phase** (filling of calyces) is best seen at 5–10 minutes.

Question 122: Salt and pepper appearance is seen in intraoral periapical radiographs of which condition?

A. Thalassemia (Correct Answer)
B. Sjogren's syndrome
C. Periodontal abscess
D. Osteoporosis

Explanation: **Explanation:** The **"Salt and Pepper" appearance** in intraoral periapical radiographs (IOPA) is a classic radiological sign of **Thalassemia**. **1. Why Thalassemia is correct:** In Thalassemia, chronic hemolytic anemia leads to compensatory **erythroid hyperplasia** of the bone marrow. As the marrow expands to increase red blood cell production, the bony trabeculae in the maxilla and mandible undergo remodeling. This results in a generalized thinning of the trabeculae and an increase in the size of the marrow spaces, creating a granular, mottled radiolucency described as a "salt and pepper" appearance. **2. Why other options are incorrect:** * **Sjogren’s Syndrome:** Characterized radiographically by a **"cherry blossom"** or **"branchless fruit tree"** appearance on sialography due to punctate sialectasis (destruction of salivary acini). * **Periodontal Abscess:** Typically presents as a localized, radiolucent area along the lateral aspect of the root, not a generalized bone pattern. * **Osteoporosis:** While it causes generalized bone thinning, it is characterized by a decrease in the number of trabeculae and cortical thinning (e.g., at the lower border of the mandible), but it is not classically described as "salt and pepper" in a dental context. **3. High-Yield Clinical Pearls for NEET-PG:** * **Skull Radiograph in Thalassemia:** Shows the **"Hair-on-end"** or **"Crew-cut"** appearance due to vertical trabeculations between the inner and outer tables of the skull. * **Facial Features:** Marrow expansion leads to **"Chipmunk Facies"** (prominent cheekbones and protrusion of the maxilla). * **Other "Salt and Pepper" signs:** In general radiology, "Salt and Pepper" appearance on **MRI** is characteristic of **Glomus tumors (Paragangliomas)**, where "pepper" represents flow voids and "salt" represents hemorrhage/slow flow.

Question 123: The facial aspect of an intraoral film is determined by which of the following?

A. Anatomic landmarks
B. Concavity of the embossed dot
C. Convexity of the embossed dot (Correct Answer)
D. Curvature of the arch

Explanation: ### Explanation **Concept Overview:** In intraoral radiography (periapical, bitewing, or occlusal films), a small circular **embossed dot** is present in one corner of the film packet. This dot is a crucial orientation marker used to distinguish between the patient's right and left sides during mounting and interpretation. **Why Option C is Correct:** The dot is embossed such that one side is raised (**convex**) and the other is depressed (**concave**). * **Labial Mounting (Standard):** When the film is placed in the mouth, the **convexity (raised side)** of the dot must face the X-ray tube and the facial/labial aspect of the teeth. * When viewing the processed film, if the convexity is facing the clinician, it is as if the clinician is looking directly at the patient (the patient’s right is the clinician’s left). Therefore, the convexity determines the facial aspect. **Why Other Options are Incorrect:** * **A & D (Anatomic landmarks/Curvature of the arch):** While these help identify whether a film belongs to the maxilla or mandible, they cannot reliably distinguish between the right and left sides of the mouth due to bilateral symmetry. * **B (Concavity of the embossed dot):** The concave side (the "dimple") faces the lingual/palatal aspect (the tongue). Viewing from the concavity is known as **lingual mounting**, which is an outdated method where the clinician views the film as if standing on the patient's tongue. **High-Yield Clinical Pearls for NEET-PG:** * **"Dot in the Slot":** A common clinical mnemonic ensuring the dot is placed toward the occlusal/incisal edge of the film to prevent it from obscuring apical pathology. * **Orientation:** Convexity = Facial/Labial view (Standard). Concavity = Lingual view. * **Film Layers:** Remember the lead foil backing in the film packet is placed on the side away from the tube to prevent backscatter radiation and "herringbone" or "tire-track" artifacts.

Question 124: A patient presents with acute renal failure (ARF) and complete anuria. The ultrasound (USG) is normal. Which of the following investigations will provide the best information regarding renal function?

A. Intravenous Pyelogram
B. Retrograde Pyelography
C. Antegrade Pyelography
D. DTPA scan (Radiorenogram) (Correct Answer)

Explanation: ### Explanation **Correct Answer: D. DTPA scan (Radiorenogram)** **Why it is correct:** In a patient with acute renal failure (ARF) and anuria, the primary clinical goal is to differentiate between **pre-renal/intrinsic renal causes** and **obstructive (post-renal) causes**. While Ultrasound (USG) is the initial screening tool to look for hydronephrosis, it can occasionally be normal in early or hyperacute obstruction. The **DTPA (Diethylenetriaminepentaacetic acid) scan** is a dynamic radionuclide study that measures the **Glomerular Filtration Rate (GFR)** and provides a "Radiorenogram" curve. It is the best investigation here because it assesses **perfusion and functional excretion** even when the kidneys are not producing visible amounts of urine. It can confirm if there is any blood flow to the kidneys (ruling out renal artery embolism) and evaluate the severity of functional impairment. **Why other options are incorrect:** * **A. Intravenous Pyelogram (IVP):** This is **contraindicated** in ARF. Contrast agents are nephrotoxic and require a minimum GFR to be excreted and visualized. In anuria, the contrast will not be filtered, leading to a "non-visualized kidney" and potential worsening of renal failure. * **B & C. Retrograde and Antegrade Pyelography:** These are **morphological/anatomical** studies used to localize the site of a known obstruction. They do not provide information regarding the overall functional status or GFR of the kidney. Since the USG is normal (suggesting no gross obstruction/dilatation), these invasive procedures are not the first choice for functional assessment. **High-Yield Clinical Pearls for NEET-PG:** * **DTPA:** Measures GFR (filtered only). * **MAG3:** Best for pediatric imaging and patients with impaired renal function (secreted by tubules). * **DMSA:** Static scan; best for detecting **renal scars** and ectopic kidneys (binds to proximal tubules). * **Contrast-Induced Nephropathy (CIN):** A major risk in ARF; always prioritize non-contrast or nuclear studies if renal function is compromised.

Question 125: For the diagnosis of Müllerian duct anomalies, between which days of the menstrual cycle is hysterosalpingography typically performed?

A. Days 2-5
B. Days 5-11 (Correct Answer)
C. Days 11-14
D. Days 22-24

Explanation: ### Explanation **Hysterosalpingography (HSG)** is a fluoroscopic procedure used to evaluate the uterine cavity and fallopian tube patency. The timing of the procedure is critical for both diagnostic accuracy and patient safety. **Why Days 5–11 is the Correct Answer:** The ideal window is the **early follicular phase** (post-menstrual but pre-ovulatory). 1. **Endometrial Thickness:** During this period, the endometrium is thinnest. This allows for better visualization of the uterine cavity and prevents "filling defects" caused by a thick, secretory endometrium which could mimic polyps or synechiae. 2. **Prevention of Pregnancy:** Performing it before ovulation (typically Day 14) ensures the patient is not pregnant, avoiding accidental radiation exposure to a developing embryo. 3. **Reduced Risk of Embolization:** The uterine vessels are less friable and less likely to be open compared to the menstrual phase, reducing the risk of contrast intravasation. **Analysis of Incorrect Options:** * **A (Days 2–5):** During menstruation, blood clots can cause false-positive filling defects. There is also a theoretical risk of retrograde menstruation leading to endometriosis or infection. * **C (Days 11–14):** This is too close to ovulation. A thickened endometrium may obstruct the tubal ostia, leading to a false diagnosis of tubal blockage. * **D (Days 22–24):** This is the luteal phase. The risk of an undiagnosed early pregnancy is high, and the secretory endometrium is at its thickest, obscuring anatomical details. **High-Yield Clinical Pearls for NEET-PG:** * **Contrast Used:** Water-soluble iodinated contrast (e.g., Iohexol) is preferred over oil-based contrast to avoid granuloma formation and oil embolism. * **Contraindications:** Pregnancy, active pelvic inflammatory disease (PID), and active uterine bleeding. * **Therapeutic Effect:** HSG can sometimes have a "flushing" effect, slightly increasing pregnancy rates in the following cycles by clearing minor tubal debris. * **Gold Standard:** While HSG is excellent for tubal patency, **MRI** is the gold standard for classifying complex Müllerian duct anomalies (e.g., differentiating septate from bicornuate uterus).

Question 126: While taking the bitewing film, what should be the direction and angulation of the central ray?

A. 10° below the horizontal plane
B. 10° above the horizontal plane (Correct Answer)
C. 10° to the right
D. 10° to the left

Explanation: **Explanation:** The **Bitewing radiograph** is a specialized intraoral technique primarily used to detect interproximal caries and evaluate the height of the alveolar bone crest. **Why 10° above the horizontal plane?** In the bitewing technique, the film is held in place by the patient biting on a "tab." Due to the anatomical curvature of the palate and the slight lingual tilt of the maxillary teeth, the film packet often assumes a slightly slanted position rather than being perfectly vertical. To compensate for this slight palatal inclination and to ensure the X-ray beam passes directly through the interproximal spaces without overlapping the cusps, a **vertical angulation of +10°** (pointing downwards from above the horizontal plane) is required. This "positive" angulation results in a dimensionally accurate representation of both maxillary and mandibular crowns. **Analysis of Incorrect Options:** * **Option A (10° below):** This is "negative" angulation. Using negative angulation would cause elongation of the maxillary teeth and foreshortening of the mandibular teeth, obscuring the interproximal areas. * **Options C & D (10° right/left):** These refer to horizontal angulation. Horizontal angulation must be directed specifically through the contact points of the teeth being imaged (usually perpendicular to the arch) to avoid "overlapping" of proximal surfaces. It is not fixed at 10°. **High-Yield Clinical Pearls for NEET-PG:** * **Vertical Angulation:** +10° is the standard for bitewings. * **Indications:** Best for **Interproximal Caries** (earliest detection) and **Alveolar Crestal Bone** height (periodontal status). * **Common Error:** Incorrect horizontal angulation leads to **overlapping contacts**, making the radiograph non-diagnostic for caries. * **Comparison:** Unlike periapical X-rays, bitewings show the crowns of both upper and lower teeth on a single film.

Question 127: What is the first step in developing a radiographic film?

A. Stirring the developing solution (Correct Answer)
B. Washing the film
C. Immersing the film in the developer solution
D. Immersing the film in the fixer solution

Explanation: ### Explanation **Correct Option: A. Stirring the developing solution** In the manual processing of radiographic films, the **first and most critical step** before immersing the film is stirring the chemicals. This is done to ensure **uniformity in temperature and chemical concentration**. Over time, chemicals in the developer tank settle due to gravity, and temperature gradients form (the solution is often warmer at the top). Stirring ensures that the entire film is exposed to an even strength of developer, preventing uneven development or "streaking" on the radiograph. **Analysis of Incorrect Options:** * **B. Washing the film:** This occurs *after* development to stop the action of the developer and *after* fixing to remove residual chemicals. It is never the first step. * **C. Immersing the film in the developer solution:** While this is the first step of the chemical reaction itself, it must be preceded by stirring. If the film is immersed without stirring, the image quality will be inconsistent. * **D. Immersing the film in the fixer solution:** Fixing is the stage that follows development and rinsing. Its purpose is to remove unexposed silver halide crystals and harden the emulsion. **High-Yield Clinical Pearls for NEET-PG:** 1. **Sequence of Manual Processing:** Stirring → Development → Rinsing (Stop bath) → Fixing → Washing → Drying. 2. **The Developer:** Converts the latent image into a visible black metallic silver image. The primary reducing agents are **Hydroquinone** (builds contrast) and **Phenidone/Elon** (brings out detail). 3. **The Fixer:** Contains **Ammonium/Sodium Thiosulfate** (clearing agent) which removes unexposed silver halide. 4. **Automatic Processing:** In modern practice, automatic processors eliminate the manual stirring step and significantly reduce processing time (90 seconds vs. 1 hour manually).

Question 128: In phlebography, dye is injected into which of the following veins?

A. Anterior tibial vein
B. Great saphenous vein
C. Dorsal metatarsal vein (Correct Answer)
D. Short saphenous vein

Explanation: **Explanation:** **Phlebography (Venography)** is the gold standard (though now largely replaced by Doppler ultrasound) for visualizing the deep venous system of the lower limb to detect Deep Vein Thrombosis (DVT). **Why the Dorsal Metatarsal Vein is Correct:** To visualize the entire deep venous system of the leg, the contrast medium must be injected into a **superficial vein as far distal as possible**. The **dorsal metatarsal vein** (or a vein on the dorsum of the foot) is the preferred site. A tourniquet is applied at the ankle to occlude the superficial veins; this forces the injected contrast from the superficial system into the **deep venous system** via the perforating veins. This ensures the deep veins (popliteal, femoral, and iliac) are opacified against the direction of gravity. **Analysis of Incorrect Options:** * **Anterior Tibial Vein:** This is a deep vein. Injecting directly into a deep vein is technically difficult, invasive, and defeats the purpose of using the physiological flow from superficial to deep systems. * **Great and Short Saphenous Veins:** While these are superficial veins, they are more proximal than the dorsal foot veins. Injecting here might bypass the distal deep veins, leading to an incomplete study of the calf veins where many thrombi originate. **High-Yield Clinical Pearls for NEET-PG:** * **Contrast Agent:** Low-osmolar contrast media (LOCM) are preferred to reduce the risk of post-venographic phlebitis. * **Gold Standard:** While Phlebography is the definitive "Gold Standard" for DVT, **Duplex Ultrasound** is the "Initial Investigation of Choice" due to its non-invasive nature. * **Filling Defect:** The hallmark of DVT on phlebography is a persistent, well-defined **intraluminal filling defect**.

Question 129: Crimp marks on a radiograph are typically due to which of the following?

A. Droplets of fixing solution
B. Droplets of developer
C. Excess application of pressure (Correct Answer)
D. None of the above

Explanation: ### Explanation **Correct Answer: C. Excess application of pressure** **Underlying Concept:** Crimp marks (also known as crinkle marks or pressure marks) are a type of **handling artifact** in conventional radiography. They occur when the radiographic film is bent or kinked, usually during loading or unloading of the cassette or while feeding the film into an automatic processor. The physical bending causes **localized mechanical pressure** on the silver halide crystals within the film emulsion. This pressure sensitizes the crystals in a manner similar to light exposure (the "pressure-sensitization" effect). When the film is developed, these stressed areas appear as distinct, crescent-shaped (half-moon) marks. If the pressure occurs *before* exposure, they usually appear as white (minus-density) marks; if it occurs *after* exposure but before processing, they typically appear as black (plus-density) marks. **Why Other Options are Incorrect:** * **A & B (Droplets of Fixer/Developer):** These result in **chemical stains** or "splash artifacts." Fixer droplets before development cause white spots (as they remove silver halide), while developer droplets cause dark spots. These are irregular in shape and do not produce the characteristic crescentic "crimp" shape. **High-Yield Clinical Pearls for NEET-PG:** * **Static Electricity Artifact:** Appears as "tree-like" or "smudge" black marks, caused by low humidity and rapid removal of film from the folder. * **Grid Cut-off:** Results in an overall decrease in density (underexposure) due to improper alignment of the grid. * **Fogging:** A generalized graying of the film caused by light leaks, outdated film, or excessive heat. * **Guide Shoe Marks:** Parallel lines at the edge of the film caused by rollers in an automatic processor.

Question 130: What is the best diagnostic method for tracheo-oesophageal fistula?

A. Barium sulphate
B. Conray 240
C. Dianosil (Correct Answer)
D. Urograffin

Explanation: **Explanation:** The primary concern when imaging a suspected **Tracheo-Oesophageal Fistula (TOF)** is the risk of contrast aspiration into the lungs. **Why Dianosil is the Correct Answer:** **Dianosil (Propyliodone)** is an oil-based, iodinated contrast medium. It was historically considered the "gold standard" for bronchography and TOF because it is relatively inert in the tracheobronchial tree. Unlike other agents, it does not cause significant pulmonary edema or chemical pneumonitis if aspirated. Its high viscosity also allows for better mucosal coating, making small fistulous tracts easier to visualize. **Analysis of Incorrect Options:** * **A. Barium Sulphate:** Absolutely contraindicated if a fistula is suspected. If aspirated, barium is not absorbed and causes a severe **foreign body granulomatous reaction** and permanent alveolar scarring. * **B. Conray 240 (Iothalamate):** This is an ionic, high-osmolar contrast medium (HOCM). If aspirated, its high osmolality draws fluid into the lungs, leading to severe **pulmonary edema**. * **D. Urograffin (Diatrizoate):** Similar to Conray, this is an ionic HOCM. It is highly irritant to the lungs and can be fatal if aspirated in large quantities. **NEET-PG High-Yield Pearls:** * **Modern Practice:** While Dianosil is the classic textbook answer, it has been largely discontinued in many regions. In modern clinical practice, **Non-ionic Low-Osmolar Contrast Media (LOCM)** like **Iohexol (Omnipaque)** are preferred due to lower toxicity. * **Water-Soluble Contrast:** Always the first choice for suspected perforations (e.g., Gastrografin), *except* when aspiration is a risk. * **TOF Presentation:** Most common type is **Type C** (85%): Proximal esophageal atresia with a distal fistula. * **VACTERL Association:** Always screen for Vertebral, Anal, Cardiac, TOF, Renal, and Limb anomalies.

Practice by Chapter

Iodinated Contrast Media

Practice Questions

MRI Contrast Agents

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Ultrasound Contrast Agents

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Adverse Reactions to Contrast Media

Practice Questions

Management of Contrast Reactions

Practice Questions

Contrast-Induced Nephropathy

Practice Questions

Barium Studies

Practice Questions

Intravenous Urography

Practice Questions

Angiography Techniques

Practice Questions

Lymphangiography

Practice Questions

Contrast Administration Protocols

Practice Questions

Pretesting and Premedication

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