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RANZCR Rad Onc Anatomy study materials
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RANZCR Rad Onc Anatomy practice questions

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Question 1Anatomy (as applied to radiation oncology practice)

Which vertebral level most commonly marks the inferior extent of the spinal cord (conus medullaris) in adults?

  1. S2
  2. C7
  3. T8
  4. L1-L2 Correct answer.

Explanation

In adults the spinal cord typically terminates as the conus medullaris at the level of the first or second lumbar vertebra. Because the cord ends here, lumbar puncture is performed at L3-L4 or below to avoid needle injury to the cord. This landmark is also used when defining the inferior border of craniospinal irradiation fields.

Question 2Anatomy (as applied to radiation oncology practice)

The pituitary fossa (sella turcica) lies within which bone?

  1. Occipital
  2. Frontal
  3. Ethmoid
  4. Sphenoid Correct answer.

Explanation

The sella turcica is a depression on the superior surface of the body of the sphenoid bone. It houses the pituitary gland and is bounded anteriorly by the tuberculum sellae and posteriorly by the dorsum sellae. Recognising this relationship is important when outlining pituitary targets and avoiding the optic chiasm.

Question 3Anatomy (as applied to radiation oncology practice)

Which lymph node station is the primary draining basin for the upper third of the thoracic oesophagus?

  1. Superficial inguinal nodes
  2. Coeliac nodes
  3. Cervical and upper mediastinal nodes Correct answer.
  4. Axillary nodes

Explanation

The upper thoracic oesophagus drains predominantly to cervical and upper mediastinal (paratracheal) nodes. This explains why cervical nodal relapse can occur with upper oesophageal tumours. Lower oesophageal tumours instead drain toward coeliac and gastrohepatic nodes.

Question 4Anatomy (as applied to radiation oncology practice)

The prostate gland lies immediately inferior to which structure?

  1. Right kidney
  2. Sigmoid colon
  3. Urinary bladder Correct answer.
  4. Diaphragm

Explanation

The prostate sits in the pelvic cavity directly below the urinary bladder, surrounding the proximal urethra. This relationship underlies urinary symptoms after prostate irradiation and guides avoidance of the bladder neck. The rectum lies posteriorly and is also a key organ at risk.

Question 5Anatomy (as applied to radiation oncology practice)

In the TNM system, the T category for most solid tumours describes which feature?

  1. Presence of distant metastasis
  2. Histological grade of the tumour
  3. Size and local extent of the primary tumour Correct answer.
  4. Number of involved regional nodes

Explanation

The T category reflects the size and local invasion of the primary tumour. N describes regional nodal involvement and M describes distant metastases. Grade is a separate histological descriptor and is not part of TNM.

Question 6Anatomy (as applied to radiation oncology practice)

Which structure forms the anterior boundary of the female pelvic radiation target volume containing the uterus and cervix?

  1. Rectum
  2. Pubic symphysis
  3. Posterior wall of the bladder Correct answer.
  4. Sacrum

Explanation

The bladder lies anterior to the uterus and cervix, so its posterior wall forms the anterior border of the target. The rectum lies posteriorly and the sacrum more posteriorly still. Correct identification helps spare bladder dose during intracavitary brachytherapy.

Question 7Anatomy (as applied to radiation oncology practice)

The brachial plexus is most at risk of radiation injury when treating which region?

  1. Prostate
  2. Pelvis
  3. Lumbar spine
  4. Supraclavicular and axillary nodes Correct answer.

Explanation

The brachial plexus passes through the supraclavicular and axillary regions, so nodal irradiation there can exceed its tolerance. Dose constraints are applied to limit the risk of plexopathy. Pelvic and lumbar treatments are remote from this structure.

Question 8Anatomy (as applied to radiation oncology practice)

Which cranial nerve is most closely related to the medial aspect of the cavernous sinus and at risk during pituitary irradiation?

  1. Abducens nerve (CN VI) Correct answer.
  2. Hypoglossal nerve (CN XII)
  3. Optic nerve (CN II)
  4. Facial nerve (CN VII)

Explanation

The abducens nerve runs within the cavernous sinus, close to the internal carotid artery, unlike the other ocular motor nerves which lie in its lateral wall. The optic nerve lies anteriorly near the chiasm, not medially within the sinus. Sparing the cavernous sinus reduces cranial neuropathy risk.

Question 9Anatomy (as applied to radiation oncology practice)

A patient with a T2 glottic carcinoma is treated with definitive radiotherapy. Which nodal region is typically excluded from the clinical target volume because of the low risk of spread?

  1. Level I nodes bilaterally
  2. Bilateral retropharyngeal nodes routinely
  3. Contralateral neck routinely
  4. Level II-IV ipsilateral nodes only when nodes are clinically involved Correct answer.

Explanation

Early glottic cancers have sparse lymphatic supply and low rates of occult nodal disease, so elective nodal irradiation is generally omitted unless nodes are clinically involved. Supraglottic and advanced tumours, by contrast, require elective neck treatment. This distinction reflects differing lymphatic anatomy of the larynx.

Question 10Anatomy (as applied to radiation oncology practice)

During whole breast radiotherapy, which structure is most commonly used to define the posterior field border at the chest wall?

  1. The lung-chest wall interface (CTV to pectoralis/rib interface) Correct answer.
  2. The trachea
  3. The oesophagus
  4. The anterior surface of the scapula

Explanation

The posterior border of the breast target is defined by the interface between breast tissue and the pectoralis muscle or chest wall, limiting lung dose. The scapula and trachea are not used as posterior borders. This anatomy underpins tangent field placement and lung constraints.

Question 11Anatomy (as applied to radiation oncology practice)

The presacral space (space of Retzius is anterior; the retrorectal space lies posterior) contains which structure relevant to rectal cancer staging?

  1. The bladder
  2. The mesorectum with its lymphovascular bundle Correct answer.
  3. The ureters only
  4. The femoral vessels

Explanation

The mesorectum is the fatty envelope posterior to the rectum containing vessels and lymphatics, and its integrity determines local recurrence risk. It lies within the presacral/retrorectal compartment bounded by the sacrum posteriorly. This is why total mesorectal excision and precise posterior field coverage matter.

Question 12Anatomy (as applied to radiation oncology practice)

Which anatomical feature explains the risk of radiation-induced optic neuropathy when treating lesions near the optic chiasm?

  1. The chiasm lies close to the pituitary and receives dose from nearby targets Correct answer.
  2. The chiasm regenerates rapidly
  3. The chiasm is encased in bone
  4. The chiasm has a rich lymphatic supply

Explanation

The optic chiasm sits immediately above the pituitary fossa, so pituitary and skull-base targets can deliver substantial dose to it. The optic apparatus is a serial structure with a relatively low tolerance, and exceeding it risks blindness. This proximity drives strict chiasm constraints in treatment planning.

Question 13Anatomy (as applied to radiation oncology practice)

Which of the following best describes the anatomical boundary between the nasopharynx and the oropharynx?

  1. The plane of the hard palate Correct answer.
  2. The hyoid bone
  3. The angle of the mandible
  4. The cricoid cartilage

Explanation

The nasopharynx lies above the plane of the hard palate and the oropharynx below it. This boundary determines nodal drainage patterns used to design elective neck volumes. The hyoid and cricoid relate to lower pharyngeal and laryngeal levels.

Question 14Anatomy (as applied to radiation oncology practice)

A tumour in the left upper lobe of the lung with ipsilateral hilar and mediastinal nodal involvement is being staged. Which nodal station is most likely involved first given typical lymphatic drainage?

  1. Ipsilateral hilar (station 10) nodes Correct answer.
  2. Coeliac nodes
  3. Contralateral supraclavicular nodes
  4. Inguinal nodes

Explanation

Lymph from the lung drains first to the hilar nodes and then to the mediastinum. Contralateral supraclavicular disease would represent more advanced, often N3, spread. Coeliac and inguinal nodes are not part of thoracic drainage.

Question 15Anatomy (as applied to radiation oncology practice)

Which structure must be carefully contoured when treating a cervical oesophageal tumour to limit dose to the spinal cord?

  1. The thyroid gland
  2. The spinal canal with cord as a serial organ at risk Correct answer.
  3. The clavicle
  4. The sternum

Explanation

The spinal cord is a serial organ at risk, and a high dose to any segment can cause myelopathy. In cervical and upper thoracic oesophageal plans the cord lies immediately posterior to the target. Constraining the maximum cord dose is therefore essential.

Question 16Anatomy (as applied to radiation oncology practice)

The kidneys are considered parallel organs in radiobiology. What does this imply for dose constraints?

  1. Mean dose and volume of functioning parenchyma preserved matter more than a small maximum dose Correct answer.
  2. Dose to the renal artery determines function
  3. Only maximum point dose matters
  4. The kidneys are serial organs requiring strict maximum dose

Explanation

Parallel organs can tolerate high dose to a portion of their volume provided enough functional subunits remain. For kidneys, mean dose and the volume receiving threshold dose predict nephropathy better than a single maximum point. This is why bilateral renal dose is carefully summed in abdominal plans.

Question 17Anatomy (as applied to radiation oncology practice)

Which anatomical landmark is used to define the superior border of a whole pelvic radiotherapy field for gynaecological malignancy?

  1. The T12-L1 junction
  2. The pubic symphysis
  3. The ischial tuberosities
  4. The L4-L5 interspace or sacral promontory Correct answer.

Explanation

The superior border of a whole pelvic field is conventionally placed at the L4-L5 interspace, corresponding to the sacral promontory, to cover the common iliac nodes. The pubic symphysis and ischial tuberosities are inferior landmarks. The T12-L1 junction would be far too high for a standard pelvis field.

Question 18Anatomy (as applied to radiation oncology practice)

Which nerve is at risk during irradiation of the parotid bed, potentially causing facial weakness if the tumour invades?

  1. Glossopharyngeal nerve (CN IX)
  2. Facial nerve (CN VII) Correct answer.
  3. Accessory nerve (CN XI)
  4. Trigeminal nerve (CN V)

Explanation

The facial nerve exits the stylomastoid foramen and passes through the parotid gland, dividing into branches within it. Parotid tumours can therefore involve CN VII, and its preservation is a key surgical and radiotherapeutic consideration. The trigeminal and lower cranial nerves lie elsewhere.

Question 19Anatomy (as applied to radiation oncology practice)

Which vascular structure defines the medial border of the axillary nodal region at level I?

  1. The clavicle
  2. The medial border of the latissimus dorsi
  3. The humeral head
  4. The lateral border of the pectoralis minor muscle Correct answer.

Explanation

Axillary level I nodes lie lateral to the lateral border of pectoralis minor, level II behind it, and level III medial to its medial border. This surgical-anatomical division guides breast nodal target delineation. The clavicle and humeral head are bony landmarks not used for this medial boundary.

Question 20Anatomy (as applied to radiation oncology practice)

A patient receives craniospinal irradiation. Which anatomical consideration determines where the spinal field begins relative to the cranial field?

  1. Matching at the level of the C1-C2 junction to avoid overlap at the cord Correct answer.
  2. Matching at the foramen magnum only
  3. Matching at T12
  4. Matching at the sacrum

Explanation

The spinal field typically begins around the C1-C2 level, and the junction with the cranial field must be moved between fractions or feathered to avoid cord overdose. The cervical cord is a serial structure with low tolerance. Matching at T12 or the sacrum would leave the upper cord untreated.

Question 21Anatomy (as applied to radiation oncology practice)

Which structure lies in the posterior mediastinum and is a key organ at risk during thoracic radiotherapy for oesophageal cancer?

  1. The trachea
  2. The descending thoracic aorta Correct answer.
  3. The right atrium
  4. The thymus

Explanation

The descending thoracic aorta runs through the posterior mediastinum alongside the oesophagus and can receive high dose during oesophageal radiotherapy. The thymus lies anteriorly, the right atrium is in the middle mediastinum, and the trachea is more anterior. Aortic dose is increasingly recognised as a cardiac risk factor.

Question 22Anatomy (as applied to radiation oncology practice)

When delineating the elective nodal volume for a tonsillar squamous cell carcinoma, which level is commonly included because of the pattern of lymphatic spread?

  1. Level VI nodes
  2. Level II and III ipsilateral nodes Correct answer.
  3. Level V contralateral nodes only
  4. Level I ipsilateral nodes only

Explanation

Tonsillar tumours drain first to levels II and III, with level IV and contralateral neck considered depending on tumour extent and nodal status. Level VI is a central compartment node group more relevant to thyroid and laryngeal disease. Level I is not the primary echelon for tonsillar primaries.

Question 23Anatomy (as applied to radiation oncology practice)

Which anatomical relationship explains why the left testis drains to para-aortic nodes while the right testis drains to nodes near the IVC?

  1. Embryological descent from the gonadal ridge determines lymphatic drainage along gonadal vessels Correct answer.
  2. The scrotum drains to para-aortic nodes
  3. Lymphatic drainage follows the pampiniform plexus only
  4. The testes have somatic drainage to inguinal nodes

Explanation

The testes arise from the gonadal ridge and descend, carrying their lymphatic drainage with the gonadal vessels to para-aortic nodes. The left drains near the aorta and the right near the IVC. The scrotal skin, by contrast, drains to inguinal nodes.

Question 24Anatomy (as applied to radiation oncology practice)

Which landmark defines the inferior border of the larynx relevant to glottic target delineation?

  1. The arytenoid cartilages
  2. The lower border of the cricoid cartilage Correct answer.
  3. The thyroid notch
  4. The hyoid bone

Explanation

The larynx extends from the epiglottis to the lower border of the cricoid cartilage, which marks the tracheal inlet. The hyoid and thyroid notch are superior landmarks. The arytenoids lie within the larynx and do not define its inferior extent.

Question 25Anatomy (as applied to radiation oncology practice)

In whole brain radiotherapy, which structure is shielded or constrained to limit dose to the hippocampus while maintaining target coverage?

  1. The thalamus
  2. The hippocampal formation within the temporal horn of the lateral ventricle Correct answer.
  3. The caudate nucleus
  4. The amygdala

Explanation

Hippocampal avoidance whole brain radiotherapy aims to spare the hippocampal formation, which lies medially in the temporal lobe adjacent to the temporal horn. Sparing it may preserve memory function. The amygdala, caudate, and thalamus are not the primary avoidance structures in this technique.

Question 26Anatomy (as applied to radiation oncology practice)

Which vertebral level most commonly marks the inferior extent of the spinal cord (conus medullaris) in an adult?

  1. L1-L2 Correct answer.
  2. S1
  3. C7
  4. T10

Explanation

In adults the cord normally terminates as the conus medullaris at approximately the L1-L2 disc space, though it can range from T12 to L3. This landmark matters when planning craniospinal irradiation because the spinal field must cover the cord down to the thecal sac, which extends lower, to about S2.

Question 27Anatomy (as applied to radiation oncology practice)

Which paranasal sinus lies immediately superior to the orbit and is often involved by tumours extending from the ethmoid region?

  1. Frontal sinus Correct answer.
  2. Sphenoid sinus
  3. Maxillary sinus
  4. Ethmoid sinus

Explanation

The frontal sinus sits in the frontal bone above the orbital roof and drains into the middle meatus. Tumours of the ethmoid roof can extend superiorly into the frontal sinus, which is why its relationship to the orbit and anterior cranial fossa guides target delineation.

Question 28Anatomy (as applied to radiation oncology practice)

Which artery is the principal blood supply to the thyroid gland and is at risk during dissection or irradiation near the superior pole?

  1. Thyroidea ima artery
  2. Inferior thyroid artery
  3. Superior thyroid artery Correct answer.
  4. Superficial temporal artery

Explanation

The superior thyroid artery, a branch of the external carotid, supplies the upper pole of the thyroid and runs close to the external branch of the superior laryngeal nerve. The inferior thyroid artery supplies the lower pole and is related to the recurrent laryngeal nerve.

Question 29Anatomy (as applied to radiation oncology practice)

In the TNM system for most solid tumours, what does the 'N' category describe?

  1. Primary tumour size and invasion
  2. Histological grade
  3. Distant metastatic spread
  4. Regional lymph node involvement Correct answer.

Explanation

The N category records the presence, number, and location of involved regional lymph nodes, which differs from distant metastases (M) and primary tumour extent (T). Accurate nodal assessment depends on knowing the regional drainage basins for each site.

Question 30Anatomy (as applied to radiation oncology practice)

Which bony structure forms the anterior wall of the middle cranial fossa and separates it from the orbit?

  1. Petrous temporal bone
  2. Greater wing of the sphenoid Correct answer.
  3. Clivus
  4. Occipital squama

Explanation

The greater wing of the sphenoid forms the anterior wall of the middle cranial fossa and the posterior wall of the orbit. This relationship explains how orbital tumours can extend intracranially through the superior orbital fissure and adjacent bone.

Question 31Anatomy (as applied to radiation oncology practice)

Which lymph node group is the primary drainage site for a tumour of the tip of the tongue?

  1. Superior deep cervical nodes
  2. Retropharyngeal nodes
  3. Submental nodes Correct answer.
  4. Supraclavicular nodes

Explanation

The lingual tip drains first to the submental nodes (level Ia) because of its midline anterior location. More posterior tongue tumours drain to submandibular and deep cervical nodes, so the primary site within the tongue changes the elective neck volume.

Question 32Anatomy (as applied to radiation oncology practice)

Which structure lies immediately anterior to the lower thoracic vertebral bodies and is a key landmark when contouring the oesophagus?

  1. Descending thoracic aorta Correct answer.
  2. Azygos vein
  3. Left atrium
  4. Trachea

Explanation

The descending thoracic aorta runs along the left anterolateral aspect of the lower thoracic vertebrae, and the oesophagus lies just anterior to it in the lower mediastinum. Recognising this relationship helps distinguish oesophageal tumour from aortic invasion on planning imaging.

Question 33Anatomy (as applied to radiation oncology practice)

Which anatomical region does the prostate gland directly abut anteriorly?

  1. Levator ani
  2. Seminal vesicles
  3. Rectum
  4. Retropubic space Correct answer.

Explanation

The prostate lies behind the pubic symphysis and its anterior surface is separated from the pubic bone by the retropubic space of Retzius. The rectum lies posteriorly, and the seminal vesicles are posterolateral and superior.

Question 34Anatomy (as applied to radiation oncology practice)

Which of the following is the most likely late complication of irradiating the region of the brachial plexus at high dose?

  1. Painless weakness and sensory loss in the arm Correct answer.
  2. Unilateral hearing loss
  3. Loss of smell
  4. Immediate laryngeal oedema

Explanation

Brachial plexopathy typically presents months to years after radiotherapy with progressive weakness, sensory change, and often pain in the shoulder and arm. The risk rises with higher total dose and larger fraction size, so plexus contours are constrained in apical lung and supraclavicular treatments.

Question 35Anatomy (as applied to radiation oncology practice)

A tumour arising in the pyriform fossa is being planned. Into which nodal level does it most commonly metastasise first?

  1. Level II Correct answer.
  2. Level VII
  3. Level I
  4. Level VI

Explanation

Pyriform fossa cancers drain primarily to level II and III jugular chain nodes, with level II being the most frequent first echelon. Level VI is more relevant to thyroid and subglottic disease, while level I is not a typical first site for hypopharyngeal primaries.

Question 36Anatomy (as applied to radiation oncology practice)

During radiotherapy to the left breast, which cardiac structure lies immediately deep to the left anterior descending artery and is also at risk of incidental dose?

  1. Right atrium
  2. Superior vena cava
  3. Pulmonary trunk
  4. Left ventricle myocardium Correct answer.

Explanation

The left anterior descending artery runs in the anterior interventricular groove on the surface of the left ventricle, so the underlying myocardium receives dose whenever the LAD is in the tangent fields. Cardiac substructure contouring helps quantify this risk in left-sided breast plans.

Question 37Anatomy (as applied to radiation oncology practice)

A patient with a mid-oesophageal tumour is planned. Which lymph node region is most likely to require elective coverage above the tumour?

  1. Coeliac nodes Correct answer.
  2. Inguinal nodes
  3. Axillary nodes
  4. Supraclavicular nodes

Explanation

Mid-thoracic oesophageal cancers drain both cranially to mediastinal and supraclavicular nodes and caudally along the para-oesophageal chain toward the coeliac axis. Because subdiaphragmatic spread is common with mid and distal lesions, coeliac nodes are often electively included, while the more cranial coverage depends on tumour height.

Question 38Anatomy (as applied to radiation oncology practice)

Which of the following best explains why the optic chiasm is a critical organ at risk when treating a pituitary adenoma?

  1. It is supplied by the middle meningeal artery
  2. It sits inferior to the sphenoid sinus
  3. It lies immediately superior to the sella and its fibres cross there Correct answer.
  4. It lies within the cavernous sinus laterally

Explanation

The chiasm lies above the diaphragma sellae, so a pituitary tumour abuts it directly and dose escalation risks optic neuropathy. Because nasal retinal fibres cross in the chiasm, a lesion compressing it classically produces bitemporal hemianopia.

Question 39Anatomy (as applied to radiation oncology practice)

In planning radiotherapy for a prostate cancer with a high risk of seminal vesicle involvement, which landmark best defines the posterosuperior extent of the seminal vesicles?

  1. The ischial spine
  2. The obturator foramen
  3. The pubic symphysis
  4. The rectovesical pouch Correct answer.

Explanation

The seminal vesicles extend posterosuperiorly from the prostate base toward the rectovesical pouch, where they lie just above the bladder base and anterior to the rectum. This relationship defines how far the seminal vesicle target extends on axial and sagittal imaging.

Question 40Anatomy (as applied to radiation oncology practice)

Which anatomical feature explains the risk of radiation myelopathy when a spinal field junction is placed poorly during craniospinal irradiation?

  1. Overlapping fields can create a local dose hotspot in the cord Correct answer.
  2. The thecal sac ends above the conus
  3. The cord is a parallel organ with large reserve
  4. Cerebrospinal fluid shields the cord

Explanation

Poor field matching can produce a narrow region of dose overlap where the cord receives more than the prescribed dose per fraction. Because the cord is a serial structure with a low tolerance, even a small hotspot can raise myelopathy risk, so junctions are moved or feathered.

Question 41Anatomy (as applied to radiation oncology practice)

A tumour of the nasopharynx is being planned. Which parapharyngeal space involvement pattern most influences coverage of the ipsilateral level II nodes?

  1. Posterolateral extension through the sinus of Morgagni Correct answer.
  2. Inferior extension to the soft palate
  3. Superior extension to the sphenoid sinus
  4. Anterior extension into the nasal cavity

Explanation

Nasopharyngeal carcinoma commonly spreads posterolaterally through the pharyngobasilar fascia at the sinus of Morgagni into the parapharyngeal space, which sits adjacent to the upper jugular chain. This route explains the high rate of level II nodal involvement and the need to cover the parapharyngeal space in the target.

Question 42Anatomy (as applied to radiation oncology practice)

Which structure forms the lateral boundary of the retropharyngeal nodal space?

  1. Carotid sheath Correct answer.
  2. Buccopharyngeal fascia
  3. Longus capitis muscle
  4. Prevertebral fascia

Explanation

The retropharyngeal space lies between the buccopharyngeal fascia anteriorly and the prevertebral fascia posteriorly, bounded laterally by the carotid sheaths. Retropharyngeal nodes within this space are a common site of occult disease in nasopharyngeal and oropharyngeal cancers.

Question 43Anatomy (as applied to radiation oncology practice)

Which anatomical consideration most influences the choice of beam arrangement for a tumour of the anal canal?

  1. The proximity of the thyroid gland
  2. The depth of the parotid glands
  3. The need to spare the small bowel and femoral heads while covering inguinal nodes Correct answer.
  4. The position of the brachial plexus

Explanation

Anal cancer targets include the primary, mesorectum, and bilateral inguinal nodes, so plans must balance coverage of these regions against small bowel and femoral head dose. This is why techniques such as VMAT with careful inferior field design are used.

Question 44Anatomy (as applied to radiation oncology practice)

Which vessel lies immediately posterior to the head of the pancreas and is at risk during irradiation of pancreatic tumours?

  1. Superior mesenteric artery Correct answer.
  2. Portal vein
  3. Splenic vein
  4. Inferior vena cava

Explanation

The superior mesenteric artery arises from the aorta behind the pancreatic neck and runs just posterior to the pancreatic head. Its proximity means pancreatic head tumours can encase it, which affects both resectability and target delineation.

Question 45Anatomy (as applied to radiation oncology practice)

Which structure is the most important organ at risk immediately medial to the tonsillar fossa?

  1. Parapharyngeal space and carotid sheath Correct answer.
  2. Temporalis muscle
  3. External auditory canal
  4. Masseter muscle

Explanation

The tonsillar fossa is bounded laterally by the superior constrictor and the parapharyngeal space, with the carotid sheath just deep to it. Tumour extension or high-dose coverage here risks the internal carotid artery and lower cranial nerves.

Question 46Anatomy (as applied to radiation oncology practice)

In whole pelvic radiotherapy for cervical cancer, which bony landmark best marks the inferior border of the obturator nodal region?

  1. Ischial tuberosity
  2. Sacral promontory
  3. Pubic crest
  4. Superior margin of the obturator foramen Correct answer.

Explanation

The obturator nodes lie along the obturator internus and the obturator vessels, and the region is bounded inferiorly near the superior margin of the obturator foramen. This helps set the lower extent of the pelvic nodal volume while sparing the femoral heads.

Question 47Anatomy (as applied to radiation oncology practice)

Which structure separates the anterior and posterior triangles of the neck?

  1. Clavicle
  2. Sternocleidomastoid muscle Correct answer.
  3. Platysma
  4. Trapezius muscle

Explanation

The sternocleidomastoid divides the neck into the anterior triangle, bounded by the midline, mandible, and muscle, and the posterior triangle behind it. This division helps localise nodal levels during clinical examination and target delineation.

Question 48Anatomy (as applied to radiation oncology practice)

Which of the following best describes the anatomical relationship of the left recurrent laryngeal nerve to the aortic arch?

  1. It runs within the pericardium
  2. It passes through the aortic valve
  3. It loops under the arch lateral to the ligamentum arteriosum Correct answer.
  4. It crosses anterior to the arch

Explanation

The left recurrent laryngeal nerve hooks beneath the aortic arch just lateral to the ligamentum arteriosum before ascending in the tracheo-oesophageal groove. This long course explains why mediastinal nodal disease or radiotherapy near the aortopulmonary window can cause left vocal cord palsy.

Question 49Anatomy (as applied to radiation oncology practice)

Which anatomical boundary separates the true pelvis from the false pelvis?

  1. Pelvic floor (levator ani)
  2. Sacral promontory alone
  3. Pelvic brim (linea terminalis) Correct answer.
  4. Obturator membrane

Explanation

The pelvic brim, formed by the linea terminalis, separates the greater (false) pelvis above from the lesser (true) pelvis below. This boundary is relevant when deciding whether a pelvic nodal target volume extends above the brim into the common iliac region.

Question 50Anatomy (as applied to radiation oncology practice)

When contouring the axilla for a patient with a high axillary burden, which muscle forms the medial boundary of level II axillary nodes?

  1. Latissimus dorsi
  2. Subscapularis
  3. Serratus anterior
  4. Pectoralis minor Correct answer.

Explanation

Level II nodes lie behind pectoralis minor, bounded medially by the muscle's lateral border and the chest wall, which is why pectoralis minor defines the level I to II transition. Recognising this helps ensure adequate coverage of high axillary disease.